Spring（十）：注解实现自动装配

熊熊出没  金牌会员 | 2022-9-26 11:02:55 | 显示全部楼层 | 阅读模式
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上一篇文章我们已经学习了Bean的自动装配，是在xml文件中配置autowire来实现的，现在我们来学习一下通过注解来实现自动装配。
一、使用注解需要的准备工作
使用注解在xml配置文件中导入约束并配置对注解的支持：
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>
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二、注解的使用
仍然是上一篇文章的三个类，People、Cat、Dog。
xml文件配置如下：
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans><?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans><?xml version="1.0" encoding="UTF-8"?>
  30. <beans xmlns="http://www.springframework.org/schema/beans"
  31.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  32.     xmlns:context="http://www.springframework.org/schema/context"
  33.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  34.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  35.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  36.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  37.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  38.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  39.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  41.     <context:annotation-config/>
  43. </beans><?xml version="1.0" encoding="UTF-8"?>
  44. <beans xmlns="http://www.springframework.org/schema/beans"
  45.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  46.     xmlns:context="http://www.springframework.org/schema/context"
  47.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  48.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  49.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  50.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  51.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  52.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  53.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  55.     <context:annotation-config/>
  57. </beans><?xml version="1.0" encoding="UTF-8"?>
  58. <beans xmlns="http://www.springframework.org/schema/beans"
  59.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  60.     xmlns:context="http://www.springframework.org/schema/context"
  61.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  62.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  63.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  64.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  65.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  66.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  67.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  69.     <context:annotation-config/>
  71. </beans><?xml version="1.0" encoding="UTF-8"?>
  72. <beans xmlns="http://www.springframework.org/schema/beans"
  73.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  74.     xmlns:context="http://www.springframework.org/schema/context"
  75.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  76.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  77.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  78.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  79.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  80.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  81.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  83.     <context:annotation-config/>
  85. </beans><?xml version="1.0" encoding="UTF-8"?>
  86. <beans xmlns="http://www.springframework.org/schema/beans"
  87.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  88.     xmlns:context="http://www.springframework.org/schema/context"
  89.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  90.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  91.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  92.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  93.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  94.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  95.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  97.     <context:annotation-config/>
  99. </beans>
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1.@Autowired
@Autowired注解
@Autowired注解是spring的一个注解，这个注解可以在属性、构造函数、set方法等地方使用，能够实现Bean的自动装配。
（1）在属性上使用
  1. public class People {<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>private String name;<?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans>@Autowired<?xml version="1.0" encoding="UTF-8"?>
  30. <beans xmlns="http://www.springframework.org/schema/beans"
  31.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  32.     xmlns:context="http://www.springframework.org/schema/context"
  33.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  34.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  35.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  36.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  37.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  38.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  39.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  41.     <context:annotation-config/>
  43. </beans>private Dog dog;<?xml version="1.0" encoding="UTF-8"?>
  44. <beans xmlns="http://www.springframework.org/schema/beans"
  45.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  46.     xmlns:context="http://www.springframework.org/schema/context"
  47.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  48.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  49.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  50.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  51.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  52.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  53.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  55.     <context:annotation-config/>
  57. </beans>@Autowired<?xml version="1.0" encoding="UTF-8"?>
  58. <beans xmlns="http://www.springframework.org/schema/beans"
  59.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  60.     xmlns:context="http://www.springframework.org/schema/context"
  61.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  62.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  63.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  64.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  65.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  66.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  67.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  69.     <context:annotation-config/>
  71. </beans>private Cat cat;}
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（2）在构造函数上使用
  1. public class People {<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>private String name;<?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans>private Dog dog;<?xml version="1.0" encoding="UTF-8"?>
  30. <beans xmlns="http://www.springframework.org/schema/beans"
  31.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  32.     xmlns:context="http://www.springframework.org/schema/context"
  33.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  34.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  35.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  36.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  37.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  38.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  39.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  41.     <context:annotation-config/>
  43. </beans>private Cat cat;<?xml version="1.0" encoding="UTF-8"?>
  44. <beans xmlns="http://www.springframework.org/schema/beans"
  45.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  46.     xmlns:context="http://www.springframework.org/schema/context"
  47.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  48.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  49.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  50.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  51.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  52.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  53.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  55.     <context:annotation-config/>
  57. </beans>@Autowired<?xml version="1.0" encoding="UTF-8"?>
  58. <beans xmlns="http://www.springframework.org/schema/beans"
  59.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  60.     xmlns:context="http://www.springframework.org/schema/context"
  61.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  62.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  63.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  64.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  65.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  66.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  67.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  69.     <context:annotation-config/>
  71. </beans>public People(Dog dog, Cat cat) {<?xml version="1.0" encoding="UTF-8"?>
  72. <beans xmlns="http://www.springframework.org/schema/beans"
  73.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  74.     xmlns:context="http://www.springframework.org/schema/context"
  75.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  76.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  77.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  78.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  79.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  80.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  81.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  83.     <context:annotation-config/>
  85. </beans><?xml version="1.0" encoding="UTF-8"?>
  86. <beans xmlns="http://www.springframework.org/schema/beans"
  87.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  88.     xmlns:context="http://www.springframework.org/schema/context"
  89.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  90.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  91.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  92.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  93.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  94.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  95.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  97.     <context:annotation-config/>
  99. </beans>this.dog = dog;<?xml version="1.0" encoding="UTF-8"?>
  100. <beans xmlns="http://www.springframework.org/schema/beans"
  101.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  102.     xmlns:context="http://www.springframework.org/schema/context"
  103.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  104.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  105.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  106.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  107.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  108.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  109.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  111.     <context:annotation-config/>
  113. </beans><?xml version="1.0" encoding="UTF-8"?>
  114. <beans xmlns="http://www.springframework.org/schema/beans"
  115.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  116.     xmlns:context="http://www.springframework.org/schema/context"
  117.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  118.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  119.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  120.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  121.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  122.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  123.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  125.     <context:annotation-config/>
  127. </beans>this.cat = cat;<?xml version="1.0" encoding="UTF-8"?>
  128. <beans xmlns="http://www.springframework.org/schema/beans"
  129.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  130.     xmlns:context="http://www.springframework.org/schema/context"
  131.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  132.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  133.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  134.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  135.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  136.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  137.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  139.     <context:annotation-config/>
  141. </beans>}
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（3）在set方法上使用
  1. public class People {<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>private String name;<?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans>private Dog dog;<?xml version="1.0" encoding="UTF-8"?>
  30. <beans xmlns="http://www.springframework.org/schema/beans"
  31.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  32.     xmlns:context="http://www.springframework.org/schema/context"
  33.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  34.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  35.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  36.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  37.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  38.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  39.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  41.     <context:annotation-config/>
  43. </beans>private Cat cat;<?xml version="1.0" encoding="UTF-8"?>
  44. <beans xmlns="http://www.springframework.org/schema/beans"
  45.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  46.     xmlns:context="http://www.springframework.org/schema/context"
  47.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  48.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  49.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  50.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  51.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  52.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  53.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  55.     <context:annotation-config/>
  57. </beans>@Autowired<?xml version="1.0" encoding="UTF-8"?>
  58. <beans xmlns="http://www.springframework.org/schema/beans"
  59.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  60.     xmlns:context="http://www.springframework.org/schema/context"
  61.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  62.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  63.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  64.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  65.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  66.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  67.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  69.     <context:annotation-config/>
  71. </beans>public void setDog(Dog dog) {<?xml version="1.0" encoding="UTF-8"?>
  72. <beans xmlns="http://www.springframework.org/schema/beans"
  73.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  74.     xmlns:context="http://www.springframework.org/schema/context"
  75.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  76.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  77.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  78.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  79.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  80.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  81.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  83.     <context:annotation-config/>
  85. </beans><?xml version="1.0" encoding="UTF-8"?>
  86. <beans xmlns="http://www.springframework.org/schema/beans"
  87.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  88.     xmlns:context="http://www.springframework.org/schema/context"
  89.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  90.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  91.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  92.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  93.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  94.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  95.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  97.     <context:annotation-config/>
  99. </beans>this.dog = dog;<?xml version="1.0" encoding="UTF-8"?>
  100. <beans xmlns="http://www.springframework.org/schema/beans"
  101.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  102.     xmlns:context="http://www.springframework.org/schema/context"
  103.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  104.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  105.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  106.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  107.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  108.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  109.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  111.     <context:annotation-config/>
  113. </beans>}<?xml version="1.0" encoding="UTF-8"?>
  114. <beans xmlns="http://www.springframework.org/schema/beans"
  115.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  116.     xmlns:context="http://www.springframework.org/schema/context"
  117.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  118.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  119.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  120.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  121.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  122.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  123.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  125.     <context:annotation-config/>
  127. </beans>@Autowired<?xml version="1.0" encoding="UTF-8"?>
  128. <beans xmlns="http://www.springframework.org/schema/beans"
  129.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  130.     xmlns:context="http://www.springframework.org/schema/context"
  131.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  132.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  133.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  134.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  135.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  136.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  137.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  139.     <context:annotation-config/>
  141. </beans>public void setCat(Cat cat) {<?xml version="1.0" encoding="UTF-8"?>
  142. <beans xmlns="http://www.springframework.org/schema/beans"
  143.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  144.     xmlns:context="http://www.springframework.org/schema/context"
  145.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  146.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  147.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  148.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  149.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  150.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  151.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  153.     <context:annotation-config/>
  155. </beans><?xml version="1.0" encoding="UTF-8"?>
  156. <beans xmlns="http://www.springframework.org/schema/beans"
  157.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  158.     xmlns:context="http://www.springframework.org/schema/context"
  159.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  160.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  161.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  162.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  163.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  164.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  165.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  167.     <context:annotation-config/>
  169. </beans>this.cat = cat;<?xml version="1.0" encoding="UTF-8"?>
  170. <beans xmlns="http://www.springframework.org/schema/beans"
  171.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  172.     xmlns:context="http://www.springframework.org/schema/context"
  173.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  174.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  175.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  176.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  177.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  178.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  179.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  181.     <context:annotation-config/>
  183. </beans>}}
复制代码
这三种方法进行测试得到的都可以获得最后的结果，测试如下：
  1. @Test<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>public void test1() {<?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans><?xml version="1.0" encoding="UTF-8"?>
  30. <beans xmlns="http://www.springframework.org/schema/beans"
  31.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  32.     xmlns:context="http://www.springframework.org/schema/context"
  33.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  34.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  35.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  36.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  37.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  38.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  39.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  41.     <context:annotation-config/>
  43. </beans>ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");<?xml version="1.0" encoding="UTF-8"?>
  44. <beans xmlns="http://www.springframework.org/schema/beans"
  45.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  46.     xmlns:context="http://www.springframework.org/schema/context"
  47.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  48.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  49.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  50.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  51.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  52.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  53.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  55.     <context:annotation-config/>
  57. </beans><?xml version="1.0" encoding="UTF-8"?>
  58. <beans xmlns="http://www.springframework.org/schema/beans"
  59.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  60.     xmlns:context="http://www.springframework.org/schema/context"
  61.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  62.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  63.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  64.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  65.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  66.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  67.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  69.     <context:annotation-config/>
  71. </beans>People people = applicationContext.getBean("people", People.class);<?xml version="1.0" encoding="UTF-8"?>
  72. <beans xmlns="http://www.springframework.org/schema/beans"
  73.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  74.     xmlns:context="http://www.springframework.org/schema/context"
  75.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  76.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  77.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  78.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  79.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  80.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  81.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  83.     <context:annotation-config/>
  85. </beans><?xml version="1.0" encoding="UTF-8"?>
  86. <beans xmlns="http://www.springframework.org/schema/beans"
  87.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  88.     xmlns:context="http://www.springframework.org/schema/context"
  89.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  90.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  91.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  92.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  93.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  94.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  95.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  97.     <context:annotation-config/>
  99. </beans>System.out.println(people.getName());<?xml version="1.0" encoding="UTF-8"?>
  100. <beans xmlns="http://www.springframework.org/schema/beans"
  101.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  102.     xmlns:context="http://www.springframework.org/schema/context"
  103.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  104.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  105.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  106.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  107.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  108.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  109.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  111.     <context:annotation-config/>
  113. </beans><?xml version="1.0" encoding="UTF-8"?>
  114. <beans xmlns="http://www.springframework.org/schema/beans"
  115.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  116.     xmlns:context="http://www.springframework.org/schema/context"
  117.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  118.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  119.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  120.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  121.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  122.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  123.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  125.     <context:annotation-config/>
  127. </beans>people.getDog().bark();<?xml version="1.0" encoding="UTF-8"?>
  128. <beans xmlns="http://www.springframework.org/schema/beans"
  129.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  130.     xmlns:context="http://www.springframework.org/schema/context"
  131.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  132.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  133.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  134.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  135.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  136.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  137.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  139.     <context:annotation-config/>
  141. </beans><?xml version="1.0" encoding="UTF-8"?>
  142. <beans xmlns="http://www.springframework.org/schema/beans"
  143.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  144.     xmlns:context="http://www.springframework.org/schema/context"
  145.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  146.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  147.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  148.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  149.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  150.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  151.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  153.     <context:annotation-config/>
  155. </beans>people.getCat().bark();<?xml version="1.0" encoding="UTF-8"?>
  156. <beans xmlns="http://www.springframework.org/schema/beans"
  157.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  158.     xmlns:context="http://www.springframework.org/schema/context"
  159.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  160.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  161.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  162.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  163.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  164.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  165.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  167.     <context:annotation-config/>
  169. </beans>}
复制代码
测试结果：

 
 
 除此之外@Autowired还有一个属性required默认为true，我们可以设置它为false，当我们设置了false时，被注解的值就可以为null，否则不行。

 
 
  1. public class People {<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>private String name;<?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans>@Autowired<?xml version="1.0" encoding="UTF-8"?>
  30. <beans xmlns="http://www.springframework.org/schema/beans"
  31.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  32.     xmlns:context="http://www.springframework.org/schema/context"
  33.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  34.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  35.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  36.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  37.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  38.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  39.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  41.     <context:annotation-config/>
  43. </beans>private Dog dog;<?xml version="1.0" encoding="UTF-8"?>
  44. <beans xmlns="http://www.springframework.org/schema/beans"
  45.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  46.     xmlns:context="http://www.springframework.org/schema/context"
  47.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  48.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  49.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  50.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  51.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  52.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  53.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  55.     <context:annotation-config/>
  57. </beans>@Autowired(required = false)<?xml version="1.0" encoding="UTF-8"?>
  58. <beans xmlns="http://www.springframework.org/schema/beans"
  59.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  60.     xmlns:context="http://www.springframework.org/schema/context"
  61.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  62.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  63.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  64.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  65.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  66.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  67.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  69.     <context:annotation-config/>
  71. </beans>private Cat cat;}
复制代码
删掉xml文件中cat的bean：
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans><?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans><?xml version="1.0" encoding="UTF-8"?>
  30. <beans xmlns="http://www.springframework.org/schema/beans"
  31.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  32.     xmlns:context="http://www.springframework.org/schema/context"
  33.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  34.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  35.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  36.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  37.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  38.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  39.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  41.     <context:annotation-config/>
  43. </beans><?xml version="1.0" encoding="UTF-8"?>
  44. <beans xmlns="http://www.springframework.org/schema/beans"
  45.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  46.     xmlns:context="http://www.springframework.org/schema/context"
  47.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  48.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  49.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  50.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  51.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  52.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  53.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  55.     <context:annotation-config/>
  57. </beans><?xml version="1.0" encoding="UTF-8"?>
  58. <beans xmlns="http://www.springframework.org/schema/beans"
  59.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  60.     xmlns:context="http://www.springframework.org/schema/context"
  61.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  62.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  63.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  64.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  65.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  66.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  67.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  69.     <context:annotation-config/>
  71. </beans><?xml version="1.0" encoding="UTF-8"?>
  72. <beans xmlns="http://www.springframework.org/schema/beans"
  73.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  74.     xmlns:context="http://www.springframework.org/schema/context"
  75.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  76.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  77.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  78.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  79.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  80.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  81.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  83.     <context:annotation-config/>
  85. </beans>
复制代码
测试：
  1. @Test<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>public void test1() {<?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans><?xml version="1.0" encoding="UTF-8"?>
  30. <beans xmlns="http://www.springframework.org/schema/beans"
  31.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  32.     xmlns:context="http://www.springframework.org/schema/context"
  33.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  34.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  35.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  36.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  37.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  38.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  39.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  41.     <context:annotation-config/>
  43. </beans>ApplicationContext applicationContext = new ClassPathXmlApplicationContext("beans.xml");<?xml version="1.0" encoding="UTF-8"?>
  44. <beans xmlns="http://www.springframework.org/schema/beans"
  45.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  46.     xmlns:context="http://www.springframework.org/schema/context"
  47.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  48.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  49.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  50.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  51.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  52.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  53.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  55.     <context:annotation-config/>
  57. </beans><?xml version="1.0" encoding="UTF-8"?>
  58. <beans xmlns="http://www.springframework.org/schema/beans"
  59.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  60.     xmlns:context="http://www.springframework.org/schema/context"
  61.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  62.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  63.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  64.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  65.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  66.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  67.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  69.     <context:annotation-config/>
  71. </beans>People people = applicationContext.getBean("people", People.class);<?xml version="1.0" encoding="UTF-8"?>
  72. <beans xmlns="http://www.springframework.org/schema/beans"
  73.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  74.     xmlns:context="http://www.springframework.org/schema/context"
  75.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  76.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  77.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  78.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  79.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  80.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  81.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  83.     <context:annotation-config/>
  85. </beans><?xml version="1.0" encoding="UTF-8"?>
  86. <beans xmlns="http://www.springframework.org/schema/beans"
  87.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  88.     xmlns:context="http://www.springframework.org/schema/context"
  89.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  90.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  91.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  92.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  93.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  94.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  95.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  97.     <context:annotation-config/>
  99. </beans>System.out.println(people.getName());<?xml version="1.0" encoding="UTF-8"?>
  100. <beans xmlns="http://www.springframework.org/schema/beans"
  101.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  102.     xmlns:context="http://www.springframework.org/schema/context"
  103.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  104.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  105.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  106.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  107.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  108.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  109.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  111.     <context:annotation-config/>
  113. </beans><?xml version="1.0" encoding="UTF-8"?>
  114. <beans xmlns="http://www.springframework.org/schema/beans"
  115.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  116.     xmlns:context="http://www.springframework.org/schema/context"
  117.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  118.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  119.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  120.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  121.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  122.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  123.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  125.     <context:annotation-config/>
  127. </beans>people.getDog().bark();<?xml version="1.0" encoding="UTF-8"?>
  128. <beans xmlns="http://www.springframework.org/schema/beans"
  129.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  130.     xmlns:context="http://www.springframework.org/schema/context"
  131.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  132.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  133.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  134.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  135.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  136.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  137.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  139.     <context:annotation-config/>
  141. </beans><?xml version="1.0" encoding="UTF-8"?>
  142. <beans xmlns="http://www.springframework.org/schema/beans"
  143.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  144.     xmlns:context="http://www.springframework.org/schema/context"
  145.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  146.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  147.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  148.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  149.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  150.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  151.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  153.     <context:annotation-config/>
  155. </beans>System.out.println(people.getCat());<?xml version="1.0" encoding="UTF-8"?>
  156. <beans xmlns="http://www.springframework.org/schema/beans"
  157.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  158.     xmlns:context="http://www.springframework.org/schema/context"
  159.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  160.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  161.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  162.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  163.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  164.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  165.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  167.     <context:annotation-config/>
  169. </beans>}
复制代码
测试结果：

 
 
 从测试结果可以看到，cat变成了null。
此时，我们了解了@Autowired的基本用法，我们来思考一个问题，如果有多个同类型的bean会发生什么呢？此时我们修改Cat类型的bean为两个：
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans><?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans>
复制代码

 
结果报错了，它会让我们去选择bean。上面很明显两个bean的id都和属性名不同，如果让其中一个id与属性名相同能否找到呢？
  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans><?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans>
复制代码
不再报错。
如果属性名与字段名不同，能否将上面的问题解决呢？答案是可以的，我们需要用到@Qualifier(value = "")，我们只需要让value等于bean的id即可。
如下面的示例：
  1. 　　<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>
复制代码
  1. 　　@Autowired<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>@Qualifier(value = "cat1")<?xml version="1.0" encoding="UTF-8"?>
  16. <beans xmlns="http://www.springframework.org/schema/beans"
  17.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  18.     xmlns:context="http://www.springframework.org/schema/context"
  19.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  20.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  21.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  22.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  23.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  24.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  25.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  27.     <context:annotation-config/>
  29. </beans>private Cat cat;
复制代码
总结一下：
@Autowired注解是先去IOC容器中查到对应类型的Bean，如果有多个对应类型的Bean，然后根据Bean的id进行匹配。
@Autowired有一个属性required默认为true，我们可以设置它为false。true意味着我们必须找到Bean，false意味着可以找不到Bean（null）。
@Autowired可以@Qualifier(value = "")配合使用，这样就会去容器中找id与value值匹配的Bean。并且此时即便只有一个相同类型的Bean，如果id不匹配也会报错。
2.@Resource注解
@Resource注解是java中的一个注解，使用它同样可以实现Bean的自动装配。
@Resource有一个name属性，当使用name属性时，会根据name的值匹配Bean的id。
下面是使用的几个例子：
（1）不使用name属性，唯一Bean没有id
  1. @Resource<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>private Dog dog;
复制代码
  1. [/code]没有问题。即使有id且id随意，也是能够找到Bean的，因为类型匹配且唯一。
  2. （2）不使用name属性，Bean不唯一但有能够匹配属性名的id
  3. [code]　　<?xml version="1.0" encoding="UTF-8"?>
  4. <beans xmlns="http://www.springframework.org/schema/beans"
  5.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  6.     xmlns:context="http://www.springframework.org/schema/context"
  7.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  12.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  13.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  15.     <context:annotation-config/>
  17. </beans>
复制代码
这种情况也没有问题，因为id能够与属性名匹配。
（3）使用name属性，Bean不唯一但有能匹配name的id
  1. @Resource(name = "dog1")<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>private Dog dog;
复制代码
  1. 　　<?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:context="http://www.springframework.org/schema/context"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  7.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/beans/spring-beans.xsd
  8.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  9.     <bean id="cat1" class="com.jms.pojo.Cat"/>http://www.springframework.org/schema/context
  10.     <bean id="cat2" class="com.jms.pojo.Cat"/>
  11.     <bean id="cat1" class="com.jms.pojo.Cat"/>https://www.springframework.org/schema/context/spring-context.xsd">
  13.     <context:annotation-config/>
  15. </beans>
复制代码
没有问题，因为name能与Bean的id匹配。
总而言之，@Resource与@Autowried用法基本相同，都是先去容器中匹配类型，如过有多个相同类型则将属性名与id进行匹配；当使用了name或者@Qualifier(value = "")时，会直接去对应类型的Bean中找id能与name或value值相匹配的，如果找不到，即便类型匹配且唯一也会报错。
我们用一个图来更加明了的看一下整个流程（以@Autowried为例）：

 
 
 
（本文仅作个人学习记录用，如有纰漏敬请指正）
 

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