一、Feign简介
Feign是一个声明式的web服务客户端,它使得写web服务客户端更加容易。使用Feign创建一个接口并对其进行注解。它具有可插拔的注解支持,包括Feign自己的注解以及jax-rs注释。Feign还支持可插拔的的编码器和解码器。Spring Cloud增加了对Spring MVC注解的支持,并使用了在Spring Web中默认使用的相同的HttpMessageConverters。Spring Cloud集成了Ribbon和灵感,在使用时提供了负载均衡的http客户端。
二、项目开始
继续用上一节的工程, 启动eureka-server,端口为8001; 启动service-ls 两次,端口分别为8005、8006
三、创建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,代码如下:
<?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.example</groupId>
<artifactId>serice-feign</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>serice-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>
<spring-cloud.version>Edgware.RELEASE</spring-cloud.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>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
</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8009,服务注册地址为http://localhost:8001/eureka/ ,代码如下:
eureka:
client:
serviceUrl:
defaultZone: http://localhost:8001/eureka/
server:
port: 8009
spring:
application:
name: service-feign
在程序的启动类ServiceFeignApplication ,加上@EnableFeignClients注解开启Feign的功能:
package com.example.sericefeign;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class SericeFeignApplication {
public static void main(String[] args) {
SpringApplication.run(SericeFeignApplication.class, args);
}
}
定义一个feign接口,通过@ FeignClient(“服务名”),来指定调用哪个服务。比如在代码中调用了service-ls服务的“/port”接口,代码如下:
package com.example.sericefeign.service;
import com.example.sericefeign.MyFeignConfiguration;
import feign.RequestLine;
import org.springframework.cloud.netflix.feign.FeignClient;
@FeignClient(value = "service-ls",configuration=MyFeignConfiguration.class)//后面接服务名
public interface TestServiceInter {
// @GetMapping(value = "/port")
@RequestLine("GET /port")
String getPort();
}
这用的是SpringMVC的注解,GetMapping,这里虽然没有报错,但是启动的时候就会报错了。比如java.lang.IllegalStateException: MethodfindById not annotated with HTTP method type (ex. GET, POST)
所以,接口处我们应该替换为Feign自己的注解,MyFeignConfiguration代码如下:
@Configuration
public class MyFeignConfiguration {
@Bean
public Contract feignContract(){
return new feign.Contract.Default();
}
}
在Web层的controller层,对外暴露一个”/port”的API接口,通过上面定义的Feign客户端testService来消费服务。代码如下:
@RestController
public class TestController {
@Autowired
TestServiceInter testService;
@RequestMapping(value = "port",method = RequestMethod.GET)
public String getports(){
return testService.getPort();
}
}
启动程序,多次访问http://localhost:8009/port,浏览器交替显示:
我的端口是:8005
我的端口是:8006