SpringCloud框架服务消费者-Feign

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1.Feign介绍

Feign是一个声明式的web service客户端，它使得编写web service客户端更为容
易。创建接口，为接口添加注解，即可使用Feign。Feign可以使用Feign注解或者
JAX-RS注解，还支持热插拔的编码器和解码器。Spring Cloud为Feign添加了
Spring MVC的注解支持，并整合了Ribbon和Eureka来为使用Feign时提供负载均衡。

译自：http://projects.spring.io/spring-cloud/docs/1.0.3/springcloud.
html#spring-cloud-feign

2.示例

创建一个Maven项目，并在pom.xml添加如下内容：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="ht
tp://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://m
aven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
	<artifactId>microservice-consumer-movie-feign</artifactId>
	<packaging>jar</packaging>
<parent>
<groupId>com.itmuch.cloud</groupId>
	<artifactId>spring-cloud-microservice-study</artifactId>
	<version>0.0.1-SNAPSHOT</version>
</parent>
<dependencies>
	<dependency>
		<groupId>org.springframework.cloud</groupId>
		<artifactId>spring-cloud-starter-eureka</artifactId>
	</dependency>
	<dependency>
		<groupId>org.springframework.cloud</groupId>
		<artifactId>spring-cloud-starter-feign</artifactId>
	</dependency>
	<dependency>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-actuator</artifactId>
	</dependency>
</dependencies>
</project>

• 启动类：MovieFeignApplication.java

/**
* 使用@EnableFeignClients开启Feign
* @author eacdy
*/
@SpringBootApplication
@EnableFeignClients
@EnableDiscoveryClient
public class MovieFeignApplication {
	public static void main(String[] args) {
		SpringApplication.run(MovieFeignApplication.class, args);
	}
}

• 实体类：User.java

public class User {
	private Long id;
	private String username;
	private Integer age;
	...
	// getters and setters
}

• Feign测试类：UserFeignClient.java

/**
* 使用@FeignClient("microservice-provider-user")注解绑定microserv
ice-provider-user服务，还可以使用url参数指定一个URL。
* @author eacdy
*/
@FeignClient(name = "microservice-provider-user")
public interface UserFeignClient {
	@RequestMapping("/{id}")
	public User findByIdFeign(@RequestParam("id") Long id);
	}
}

• Feign的测试类：FeignController.java

@RestController
public class FeignController {
	@Autowired
	private UserFeignClient userFeignClient;
	@GetMapping("feign/{id}")
		public User findByIdFeign(@PathVariable Long id) {
		User user = this.userFeignClient.findByIdFeign(id);
		return user;
	}
}

• application.yml

server:
	port: 8020
spring:
	application:
		name: microservice-consumer-movie-feign
eureka:
	client:
		serviceUrl:
			defaultZone: http://discovery:8761/eureka/
instance:
	preferIpAddress: true
ribbon:
	eureka:
		enabled: true 
# 默认为true。如果设置为false，Ribbon将不会从Eureka中获得服务列表，
#而是使用静态配置的服务列表。
#静态服务列表可使用：<client>.ribbon.listOfServers来指定。
#参考：http://projects.spring.io/spring-cloud/docs/1.0.3/spring-cloud.html#spring-cloud-ribbonwithout-eureka
### 参考：https://spring.io/guides/gs/client-side-load-balancing/

Feign代码地址：
http://git.oschina.net/itmuch/spring-cloud-study/tree/master/microserviceconsumer-
movie-feign https://github.com/eacdy/spring-cloudstudy/
tree/master/microservice-consumer-movie-feign