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public class Test01 {
// 测试方法！============
public static void main(String[] args) {
String configFile = "mybatis-config.xml";
try (
// 1. 加载配置文件
InputStream inputStream = Resources.getResourceAsStream(configFile)) {
// 2. 创建 SqlSessionFactory 对象
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 3. 获取 SqlSession 对象
SqlSession sqlSession = sessionFactory.openSession();
// 获取mapper
InventoryMapper inventoryMapper = sqlSession.getMapper(InventoryMapper.class);
// 调用mapper的方法
List<Inventory> allInventory = inventoryMapper.getAllInventory();
for (Inventory inventory : allInventory) {
System.out.println(inventory);
}
// System.out.println(inventoryMapper.getInventoryById(1));
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
// 实体类对象
@AllArgsConstructor
@NoArgsConstructor
@Data
public class Inventory implements Serializable {
private static final long serialVersionUID = 1L;
private Integer goodsId;
private String goodsName;
private Date createTime;
private Date modifyTime;
private Integer inventory;
}

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db.driver=com.mysql.cj.jdbc.Driver
db.url=jdbc:mysql://127.0.0.1:3306/trans_inventory?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=Asia/Shanghai
db.username=root
db.password=123456

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<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
<properties resource="db.properties" />
<settings>
<setting name="mapUnderscoreToCamelCase" value="true"/>
</settings>
<environments default="development">
<environment id="development">
<transactionManager type="jdbc" />
<dataSource type="pooled">
<property name="driver" value="${db.driver}" />
<property name="url" value="${db.url}" />
<property name="username" value="${db.username}" />
<property name="password" value="${db.password}" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="mapper/InventoryMapper.xml" />
</mappers>
</configuration>

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public interface InventoryMapper {
List<Inventory> getAllInventory();
Inventory getInventoryById(@Param("id") Integer id);
}

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<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.feng.mapper.InventoryMapper">
<select id="getAllInventory" resultType="com.feng.entity.Inventory">
select *
from inventory
</select>
<select id="getInventoryById" resultType="com.feng.entity.Inventory">
select *
from inventory
where goods_id = #{id}
</select>
</mapper>

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public class Resources {
// new 了一个ClassLoaderWrapper对象
private static final ClassLoaderWrapper classLoaderWrapper = new ClassLoaderWrapper();
public static InputStream getResourceAsStream(String resource) throws IOException {
return getResourceAsStream(null, resource);
}
// loader = null, resource = "xxxx.xml"
public static InputStream getResourceAsStream(ClassLoader loader, String resource) throws IOException {
// ====================== 这一行
InputStream in = classLoaderWrapper.getResourceAsStream(resource, loader);
if (in == null) {
throw new IOException("Could not find resource " + resource);
}
return in;
}
}
public class ClassLoaderWrapper {
ClassLoader defaultClassLoader;
ClassLoader systemClassLoader;
// --------- 构造函数
ClassLoaderWrapper() {
try {
// jdk的方法，得到系统类加载器
systemClassLoader = ClassLoader.getSystemClassLoader();
} catch (SecurityException ignored) {
// AccessControlException on Google App Engine
}
}
public InputStream getResourceAsStream(String resource, ClassLoader classLoader) {
// getResourceAsStream()方法里面用到了 getClassLoaders(null)
return getResourceAsStream(resource, getClassLoaders(classLoader));
}
// 得到所有的类加载器:::classLoader = null
ClassLoader[] getClassLoaders(ClassLoader classLoader) {
return new ClassLoader[] { classLoader, defaultClassLoader, Thread.currentThread().getContextClassLoader(),
getClass().getClassLoader(), systemClassLoader };
}
// 遍历所有的类加载器，谁加载到了就返回谁的inputStream
InputStream getResourceAsStream(String resource, ClassLoader[] classLoader) {
for (ClassLoader cl : classLoader) {
if (null != cl) {
// try to find the resource as passed
InputStream returnValue = cl.getResourceAsStream(resource);
// now, some class loaders want this leading "/", so we'll add it and try again if we didn't find the resource
if (null == returnValue) {
returnValue = cl.getResourceAsStream("/" + resource);
}
if (null != returnValue) {
return returnValue;
}
}
}
return null;
}
}

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// 2. 创建 SqlSessionFactory 对象
SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

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