SpringCloud组件之Feign

SpringCloud五大组件之Feign

一、Feign简介（GitHub上的描述）

Feign is a Java to Http client binder inspired by Retrofit, JAXRS-2.0, and WebSocket. Feign’s first goal was reducing the complexity of binding Denominator uniformly to Http APIs regardless of ReSTfulness.
翻译：Feign是受Retrofit，JAXRS-2.0和WebSocket启发的Java到Http客户端绑定程序。 Feign的第一个目标是减少与ReSTfulness无关的将Denominator统一绑定到Http API的复杂性。
Feign是一个声明式的伪HTTP客户端，它使得写HTTP客户端变得更简单。使用Feign，只需要创建一个接口并注解。

二、我们使用上节讲到的User服务，进行服务改造。Pom配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache/POM/4.0.0"
         xmlns:xsi="http://www.w3/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache/POM/4.0.0 http://maven.apache/xsd/maven-4.0.0.xsd">
    <parent>
        <groupId>父GroupId</groupId>
        <artifactId>父ArtifactId</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>member</artifactId>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    </dependencies>
</project>

三、application.yml配置如下：

spring:
  application:
    name: user
server:
  port: 28666
eureka:
  instance:
    #开启IP注册
    prefer-ip-address: true
    #地址名称
    instance-id: ${spring.cloud.client.ip-address}:${server.port}
    #心跳
    lease-renewal-interval-in-seconds: 5
    #无心跳，十秒踢出
    lease-expiration-duration-in-seconds: 10
    #获取此实例的相对健康检查URL路径。 健康检查页面URL，然后构造出主机名和通信的类型 - 安全或不安全，如securePort和nonSecurePort规定。 它通常用于制造基于实例的健康做出明智的决策 - 例如，它可以被用来确定是否进行部署到整个服务器场或停止部署，而不会造成进一步的损害。
    health-check-url-path: /actuator/health
  client:
    #表示的频率（以秒为单位）来从eureka服务器注册表的信息
    registryFetchIntervalSeconds: 5
    service-url:
      defaultZone: ${EUREKA_SERVICE_URL:http://127.0.0.1:28001}/eureka/
### Feign 配置
feign:
  compression:
    request:
      # 开启请求压缩
      enabled: true
      # 配置压缩的 MIME TYPE
      mime-types: text/xml,application/xml,application/json
      # 配置压缩数据大小的下限
      min-request-size: 2048
    response:
      # 开启响应压缩
      enabled: true

五、我们创建一个接口，MemberServiceFeign.java这是Feign客户端，代码如下：

@FeignClient(value = "member",fallback = MemberServiceFeignHystric.class)
public interface MemberServiceFeign {

    /**
     * 远程调用member接口
     *
     * @param name
     * @return
     */
    @GetMapping("/member/sayHiMember")
    String sayHiMember(@RequestParam(value = "name") String name);

    /**
     * 远程调用接口
     *
     * @param name
     * @return
     */
    @GetMapping("/member/port")
    String port(@RequestParam(value = "name") String name);

}

六、我们在User控制器里面调用Feign接口，代码如下：

@RestController
@RequestMapping("/user")
public class UserController {
    @Resource
    private MemberServiceFeign memberServiceFeign;
    @Value("${server.port}")
    String port;

    @GetMapping("/userInfo")
    @ResponseBody
    public String userInfo(@RequestParam String name) {
        return memberServiceFeign.sayHiMember(name);
    }

    @GetMapping("/port")
    @ResponseBody
    public String port(@RequestParam String name) {
        return memberServiceFeign.port(name);
    }
}

七、启动类

@EnableEurekaClient
@SpringBootApplication
@EnableFeignClients
@EnableDiscoveryClient
public class ServiceUserApplication {

    public static void main(String[] args) {
        SpringApplication.run(ServiceUserApplication.class, args);
    }

    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

八、member服务暴露接口，代码如下：

@RestController
@RequestMapping("/member")
public class MemberController {

    @Value("${server.port}")
    String port;

    @GetMapping("/sayHiMember")
    public String sayHiMember(String name) {
        return "SayHi会员:" + name;
    }

    @GetMapping("/port")
    public String port(String name) {
        return "port:" + port + "名称" + name;
    }

}