SpringCloud系列研究---Eureka服务消费Feign

时间：2018-01-26 14:11:57 阅读：2181 评论：0 收藏：0 [点我收藏+]

标签：int 环境 class reporting 多次 eureka .net pid led

一、Feign简介

Feign是一种声明式、模板化的HTTP客户端。这使得Web服务客户端的写入更加方便要使用Feign创建一个界面并对其进行注释。它具有可插入注释支持，包括Feign注释和JAX-RS注释。Feign还支持可插拔编码器和解码器。Spring Cloud增加了对Spring MVC注释的支持，并使用Spring Web中默认使用的HttpMessageConverters。Spring Cloud集成Ribbon和Eureka以在使用Feign时提供负载均衡的http客户端。这段话来源于官方文档，说白了就是通过Feign来调用Rest接口，而无需使用其他HTTP访问组件，并且同时还提供了负载均衡、编解码等功能，使用起来很方便。

二、环境介绍

首先在A服务器上启动Eureka服务，然后在B、C两台服务器上分别启动ms-demo-provider服务，这里也可以部署在一台服务器上采用不同的端口。访问Eureka界面查看服务注册状态，之后在本地新建客户端调用工程进行测试。此时A为注册中心，B、C分别为服务提供者（提供相同的接口），本地工程为服务消费者。

技术分享图片

三、项目代码

在Idea中创建maven工程，ms-eurekaclient-demo工程代码结构如下：

技术分享图片

1：pom.xml中的依赖如下：

<?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.cloud.microservice</groupId>
    <artifactId>ms-eurekaclient-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>ms-eurekaclient-demo</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.SR1</spring-cloud.version>
    </properties>

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

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
        </dependency>
        <!-- 加入断路器依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-hystrix</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>${spring-cloud.version}</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>

2：application.properties中的配置信息如下：

spring.application.name=ms-eurekaclient-demo
server.port=9800

# 注册中心地址
eureka.client.serviceUrl.defaultZone=http://xx.xx.xx.xx:9000/eureka/

# Indicates whether this client should fetch eureka registry information from eureka server
# 客户端是否要从eureka server获取注册信息，默认为true
eureka.client.fetchRegistry=true

# Indicates how often(in seconds) to fetch the registry information from the eureka server
# 从eureka server获取注册信息的频率，默认为30秒，缩短配置时间可以缓解服务上线时间过长的问题
eureka.client.registryFetchIntervalSeconds=10

3：在入口类Application中增加@EnableEurekaClient和@EnableFeignClients的注解

@EnableEurekaClient：注解用来标识开启服务发现功能，据说也可使用@EnableDiscoveryClient，网上有人说@EnableEurekaClient本身就是用@EnableDiscoveryClient来实现的，这点没仔细研究过
@EnableFeignClients：注解用来开启Feign功能

package com.cloud.microservice.eurekaclientdemo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;

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

4：创建IUserFeignServiceClient接口类，代码如下：

package com.cloud.microservice.eurekaclientdemo.FeignClient;

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

@FeignClient("ms-demo-provider")
public interface IUserFeignServiceClient {
    //Feign定义服务提供者接口
    @RequestMapping(value = "/demo/user/1.0/findAll", method = RequestMethod.GET, produces = {"application/json;charset=UTF-8"})
    String findAll();
}

5：创建IUserService接口类和UserServiceImp实现类，代码如下：

IUserService接口类如下：

package com.cloud.microservice.eurekaclientdemo.FeignClient;

public interface  IUserService {
    String findAll();
}

UserServiceImp实现类如下：

package com.cloud.microservice.eurekaclientdemo.FeignClient;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;


@Service
public class UserServiceImp implements  IUserService{
    @Autowired
    private IUserFeignServiceClient userFeignServiceClient;

    public String findAll() {
        return "Feign: " + userFeignServiceClient.findAll();
    }
}

6：Rest接口定义，代码如下：

package com.cloud.microservice.eurekaclientdemo.FeignClient;

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.RestController;

@RestController
public class FeignDemoController {
    @Autowired
    private IUserService userService;

    @RequestMapping(value = "/feigndemo/findAll", method = RequestMethod.GET, produces = {"application/json;charset=UTF-8"})
    public String feignDemo() {
        return userService.findAll();
    }
}