spring cloud（服务消费者（利用feign实现服务消费及负载均衡）——初学三）

Feign是一个声明式的Web Service客户端，我们只需要使用Feign来创建一个接口并用注解来配置它既可完成。

它具备可插拔的注解支持，包括Feign注解和JAX-RS注解。Feign也支持可插拔的编码器和解码器。

Spring Cloud为Feign增加了对Spring MVC注解的支持，还整合了Ribbon和Eureka来提供均衡负载的HTTP客户端实现。

一、准备工作

　　启动服务注册中心

　　启动服务提供方　　

　　将服务提供方端口修改后再次启动一个服务

　　访问 localhost:1111

　　

二、创建消费者

　　1、创建spring boot项目（利用idea的Spring Initializr快速创建项目）

　　2、添加feign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.daqsoft</groupId>
    <artifactId>customer_demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

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

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.4.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>Dalston.SR1</spring-cloud.version>
    </properties>

    <dependencies>
        <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>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <!--添加feign依赖-->
        <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>${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>

　　3、启动类中添加注解

　　

package com.daqsoft;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.embedded.LocalServerPort;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
//用来发现注册服务
@EnableDiscoveryClient
@EnableFeignClients
public class CustomerDemoApplication {
    public static void main(String[] args) {
        SpringApplication.run(CustomerDemoApplication.class, args);
    }
}

　　4、定义compute-service服务接口

package com.daqsoft;

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

/**
 * @Description Created by liaoxx on 2017-6-12.
 */
//服务提供方的名称
@FeignClient("compute-service")
public interface ComputerClient {
    @RequestMapping(method = RequestMethod.GET, value = "/add")
    Integer add(@RequestParam(value = "a") Integer a, @RequestParam(value = "b") Integer b);
}

　　5、web端调用

package com.daqsoft;

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;
import org.springframework.web.client.RestTemplate;

/**
 * @Description Created by liaoxx on 2017-6-12.
 */
@RestController
public class CustomController {

    @Autowired
    private ComputerClient client;

    @RequestMapping(value = "/add", method = RequestMethod.GET)
    public Integer add(){
        return client.add(10,20);

    }
}

　　6、配置文件不变

spring.application.name=ribbon-consumer

server.port=3333
#服务注册中心地址
eureka.client.serviceUrl.defaultZone=http://localhost:1111/eureka/

　　7、启动服务，多次访问 localhost:3333

　　　在服务提供方不同端口打印的信息