利用OpenFeign+Eureka实现HTTP调用的简单示例

• 由于RPC调用须要利用注册中心，以是首先须要创建eureka服务，创建SpringBoot项目后导入spring-cloud-starter-netflix-eureka-server，留意SpringBoot和SpringCloud版本同等性，然后举行配置，启动类添加注解@EnableEurekaServer
  

1. <dependency>
2.         <groupId>org.springframework.cloud</groupId>
3.         <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
4. </dependency>

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1. server:
2.   port: 8761
4. spring:
5.   application:
6.     name: eureka
8. eureka:
9.   client:
10.     register-with-eureka: false # 不向Eureka注册自己
11.     fetch-registry: false       # 不从Eureka获取注册信息
12.   service-url:
13.     defaultZone: http://localhost:8761/eureka/

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1. @SpringBootApplication
2. @EnableEurekaServer
3. public class EurekaApplication {
5.         public static void main(String[] args) {
6.                 SpringApplication.run(EurekaApplication.class, args);
7.         }
9. }

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• 创建服务提供者SpringBoot应用，关键是导入spring-cloud-starter-netflix-eureka-client依靠，举行eureka的配置，编写controller接入层代码，启动类不须要加@EnableEurekaClient注解，因为在新版本中已经被移除
  

1. <dependency>
2.         <groupId>org.springframework.boot</groupId>
3.         <artifactId>spring-boot-starter-web</artifactId>
4. </dependency>
6. <dependency>
7.         <groupId>org.springframework.cloud</groupId>
8.         <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
9. </dependency>

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1. server:
2.   port: 8082
4. spring:
5.   application:
6.     name: producer
8. eureka:
9.   client:
10.     register-with-eureka: true
11.     fetch-registry: true
12.   service-url:
13.     defaultZone: http://localhost:8761/eureka/

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1. @RestController
2. @RequestMapping("/api")
3. public class DataController {
5.     @GetMapping("/data")
6.     public String getData() {
8.         System.out.println("服务提供者被调用");
9.         return "Hello from Producer!";
10.     }
11. }

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• 创建服务消费者SpringBoot应用，引入如下三个关键依靠，举行eureka配置，编写接口，编写接入层代码调用该接口，启动类须要加上@EnableFeignClients
  

1. <dependency>
2.         <groupId>org.springframework.boot</groupId>
3.         <artifactId>spring-boot-starter-web</artifactId>
4. </dependency>
5. <dependency>
6.         <groupId>org.springframework.cloud</groupId>
7.         <artifactId>spring-cloud-starter-openfeign</artifactId>
8. </dependency>
10. <dependency>
11.         <groupId>org.springframework.cloud</groupId>
12.         <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
13. </dependency>

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1. server:
2.   port: 8083
4. spring:
5.   application:
6.     name: consumer
8. eureka:
9.   client:
10.     register-with-eureka: true
11.     fetch-registry: true
12.   service-url:
13.     defaultZone: http://localhost:8761/eureka/

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1. @FeignClient(name = "producer") // 此处不需要写url = "http://localhost:8082"，因为通过注册中心调用
2. public interface ProducerClient {
4.     @GetMapping("/api/data")
5.     String getData();
6. }

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1. @RestController
2. @RequestMapping("/consumer")
3. public class ConsumerController {
5.     @Autowired
6.     private ProducerClient producerClient;
8.     @GetMapping("/data")
9.     public String getDataFromProducer() {
10.         return producerClient.getData();
11.     }
12. }

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1. @SpringBootApplication
2. @EnableFeignClients
3. public class ConsumerApplication {
5.         public static void main(String[] args) {
6.                 SpringApplication.run(ConsumerApplication.class, args);
7.         }
9. }

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• 总结
  

• 通过引入eureka注册中心后，如果服务提供者有多个节点，那么哀求就会被发送到存活的节点上，实现了动态路由，避免因为固定写url但是该节点宕机导致调用失败的题目
  

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