Spring Cloud 消费服务Feign(踩着坑往前爬)

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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。我们只需要通过创建接口并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来提供均衡负载的HTTP客户端实现。

分布式应用早在十几年前就开始出现,各自的应用运行在各自的tomcat,jboss一类的容器中,他们之间的相互调用变成了一种远程调用,而实现远程调用的方式很多。按照协议划分,可以有RPC,Webservice,http。不同的框架也对他们有了各自的实现,如dubbo(x),motan就都是RPC框架,本文所要讲解的Feign便可以理解为一种http框架,用于分布式服务之间通过Http进行接口交互。说他是框架,有点过了,可以理解为一个http工具,只不过在spring cloud全家桶的体系中,它比httpclient,okhttp,retrofit这些http工具都要强大的多。

Feign 采用的是基于接口的注解

Feign 整合了ribbon

 

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

创建一个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

如果使用idea自己的导入的spring boot节点有可以能引入不了spring-cloud-starter-feign maven,

我的解决方法是换一个版本的spring boot的父节点

具体pom.xml节点如下:

 

技术分享图片
<?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>cn.zhiwei</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>1.5.2.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>
        <spring-cloud.version>Finchley.BUILD-SNAPSHOT</spring-cloud.version>
    </properties>

    <dependencies>
        <!--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-->
        <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版本选择Dalston.RC1负责下载不了feign包-->
    <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-snapshots</id>
            <name>Spring Snapshots</name>
            <url>https://repo.spring.io/snapshot</url>
            <snapshots>
                <enabled>true</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>


</project>
View Code

 

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/ ,代码如下:

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

package cn.zhiwei;

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//注解开启Feign的功能:
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-hi服务的“/hi”接口,代码如下:

package cn.zhiwei.service;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

/**
 * 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-hi服务的“/hi”接口
 * Created by Administrator on 2018/4/6.
 */
@FeignClient(value = "service-hi")
@Component
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,通过上面定义的Feign客户端SchedualServiceHi 来消费服务。代码如下

package cn.zhiwei.controller;

import cn.zhiwei.service.SchedualServiceHi;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

/**
 * 在Web层的controller层,对外暴露一个”/hi”的API接口,
 * 通过上面定义的Feign客户端SchedualServiceHi 来消费服务
 * Created by Administrator on 2018/4/6.
 */
@RestController
public class HiController {
    @Autowired
    SchedualServiceHi schedualServiceHi;
    @RequestMapping(value = "/hi",method = RequestMethod.GET)
    public String sayHi(@RequestParam String name){
        return schedualServiceHi.sayHiFromClientOne(name);
    }
}

  启动程序,多次访问http://localhost:8765/hi?name=威哥,浏览器交替显示:

结果与上篇博客的效果一样

 

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