Spring Cloud (4) 服务消费者-Feign

Spring Cloud Feign

　　Spring Cloud Feign 是一套基于Netflix Feign实现的声明式服务调用客户端。它使得编写Web服务客户端变得更加简单，我们只需要创建接口并使用注解来配置它既可完成对web服务接口的绑定。它具备可插拔的注解支持，包括Feign注解、JAX-RS注解。它也支持可插拔的编码器和解码器。Spring Cloud Feign还扩展了对Spring MVC注解的支持，同时还整合了Ribbon和Eureka来提供负载均衡的Http客户端实现。

新建com.david.feign项目，并在pom.xml中增加依赖：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.david</groupId>
    <artifactId>feign</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>feign</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Edgware.SR2</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

编辑配置文件application.yml:

spring:
  application:
    name: david-feign
server:
  port: 8765
eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka/

在启动类程序中，加上@EnableFeignClients注解开启Feign功能：

@EnableDiscoveryClient
@EnableFeignClients
@SpringBootApplication
public class FeignApplication {

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

创建一个Feign的客户端接口定义。使用@FeignClient注解来制定这个接口所要调用的服务名称，接口中定义的各个函数使用Spring MVC的注解就可以来绑定服务提供的REST接口，比如下面就是绑定david-eureka服务的/test接口。

@FeignClient("david-eureka-client")
public interface TestFeignService {
    @GetMapping("/test")
    String consumer();
}

新建testController.java 注入feign 完成调用。

@RestController
public class TestController {

    @Autowired
    TestFeignService testFeignService;

    @GetMapping("/test")
    public String test(){
        return testFeignService.consumer();
    }
}

启动项目，访问http://localhost:8765/test

项目目录：