企业分布式微服务云SpringCloud SpringBoot mybatis （三） 服务消费者（Feign）

1、Feign简介

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，只须要建立一个接口并注解。它具备可插拔的注解特性，可以使用Feign 注解和JAX-RS注解。Feign支持可插拔的编码器和解码器。Feign默认集成了Ribbon，并和Eureka结合，默认实现了负载均衡的效果。

简而言之：

• Feign 采用的是基于接口的注解
• Feign 整合了ribbon

2、准备工做

继续用上一节的工程， 启动eureka-server，端口为8761; 启动service-hi 两次，端口分别为8762 、8773.

3、建立一个feign的服务

新建一个spring-boot工程，取名为serice-feign，在它的pom文件引入Feign的起步依赖spring-cloud-starter-feign、Eureka的起步依赖spring-cloud-starter-eureka、Web的起步依赖spring-boot-starter-web，代码以下：

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<?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.forezp</groupId> <artifactId>service-feign</artifactId> <version> 0.0 . 1 -SNAPSHOT</version> <packaging>jar</packaging> <name>service-feign</name> <description>Demo project for Spring Boot</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version> 1.5 . 2 .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.cloud</groupId> <artifactId>spring-cloud-starter-feign</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> </dependencies> <dependencyManagement> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dependencies</artifactId> <version>Dalston.RC1</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> <repositories> <repository> <id>spring-milestones</id> <name>Spring Milestones</name> <url>https: //repo.spring.io/milestone</url> <snapshots> <enabled> false </enabled> </snapshots> </repository> </repositories> </project>

　　

在工程的配置文件application.yml文件，指定程序名为service-feign，端口号为8765，服务注册地址为http://localhost:8761/eureka/ ，代码以下：
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eureka: client: serviceUrl: defaultZone: http: //localhost:8761/eureka/ server: port: 8765 spring: application: name: service-feign

　　在程序的启动类ServiceFeignApplication ，加上@EnableFeignClients注解开启Feign的功能：

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@SpringBootApplication @EnableDiscoveryClient @EnableFeignClients public class ServiceFeignApplication { public static void main(String[] args) { SpringApplication.run(ServiceFeignApplication. class , args); } }

　　定义一个feign接口，经过@ FeignClient（“服务名”），来指定调用哪一个服务。好比在代码中调用了service-hi服务的“/hi”接口，代码以下：

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/** * Created by fangzhipeng on 2017/4/6. */ @FeignClient (value = "service-hi" ) public interface SchedualServiceHi { @RequestMapping (value = "/hi" ,method = RequestMethod.GET) String sayHiFromClientOne( @RequestParam (value = "name" ) String name); }

　　在Web层的controller层，对外暴露一个”/hi”的API接口，经过上面定义的Feign客户端SchedualServiceHi 来消费服务。代码以下：

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@RestController public class HiController { @Autowired SchedualServiceHi schedualServiceHi; @RequestMapping (value = "/hi" ,method = RequestMethod.GET) public String sayHi( @RequestParam String name){ return schedualServiceHi.sayHiFromClientOne(name); } }

　　架构代码以下:

资料和源码来源地址

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