SpringCloud教程 | 第5篇:之面向接口编程服务消费者（Feign）+熔断器Feign Hystrix

一、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，只需要创建一个接口并注解。它具有可插拔的注解特性，可使用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
Api配置

二、准备工作

继续用上一节的工程，启动eureka-server 集群，启动服务提供者 provider,

第一步，创建Module->microservicecloud-api ，服务提供者省略参考其他章节
api POM.xml配置文件

<?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">
    <parent>
        <artifactId>mall</artifactId>
        <groupId>com.linjia</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>microservicecloud-api</artifactId>
    <packaging>jar</packaging>
    <name>microservicecloud-api</name>
    <dependencies>
        <dependency> <!--小辣椒get set -->
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <!--feign 需要的jar -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
        </dependency>
    </dependencies>
    <build>
        <finalName>${name}</finalName>
    </build>
</project>

2.interface 接口

package com.linjia.springcloud.service;
import com.linjia.springcloud.entity.Dept;
import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import java.util.List;


/**
 * 
 * @Description: 修改microservicecloud-api工程，根据已经有的DeptClientService接口
 * @author
 * @date 2018年4月21日
 */
//@FeignClient(value = "MICROSERVICECLOUD-DEPT")  非熔断
    //熔断器 启动 microservicecloud-consumer-dept-feign 访问
@FeignClient(value = "MICROSERVICECLOUD-DEPT",fallbackFactory=DeptClientServiceFallbackFactory.class)
public interface DeptClientService
{
	@RequestMapping(value = "/dept/get/{id}", method = RequestMethod.GET)
	public Dept get(@PathVariable("id") long id);

	@RequestMapping(value = "/dept/list", method = RequestMethod.GET)
	public List<Dept> list();

	@RequestMapping(value = "/dept/add", method = RequestMethod.POST)
	public boolean add(Dept dept);
}

Feign Hystrix

因为熔断只是作用在服务调用这一端

package com.linjia.springcloud.service;

import com.linjia.springcloud.entity.Dept;
import feign.hystrix.FallbackFactory;
import org.springframework.stereotype.Component;

import java.util.List;

@Component // 不要忘记添加，不要忘记添加
public class DeptClientServiceFallbackFactory implements FallbackFactory<DeptClientService>
{
	@Override
	public DeptClientService create(Throwable throwable)
	{
		return new DeptClientService() {
			@Override
			public Dept get(long id)
			{
                return new Dept(id,"该ID：" + id + "没有没有对应的信息,Consumer客户端提供的降级信息,此刻服务Provider已经关闭","no this database in MySQL");
			}

			@Override
			public List<Dept> list()
			{
				return null;
			}

			@Override
			public boolean add(Dept dept)
			{
				return false;
			}
		};
	}
}

二、创建Module ->microservicecloud-consumer-dept-feign

1.服务消费者POM配置

<?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">
    <parent>
        <artifactId>mall</artifactId>
        <groupId>com.linjia</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>microservicecloud-consumer-dept-feign</artifactId>

    <name>microservicecloud-consumer-dept-feign</name>
    <url>http://www.example.com</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.linjia</groupId>
            <artifactId>microservicecloud-api</artifactId>
            <version>${project.version}</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- feign 相关  -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
        </dependency>


        <!-- eureka相关   eureka与zookeeper区别，zookeeper 高一致性，eureka 高可用-->
        <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>

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

        <!-- 修改后立即生效，热部署 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>springloaded</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>
        <!-- web -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>


    </dependencies>

    <build>
        <finalName>${name}</finalName>
    </build>
</project>

2.服务消费者yml配置

server:
   port: 8089
feign:
  hystrix:
    enabled: true
eureka:
  client:
    register-with-eureka: false
    service-url:
      # defaultZone: http://springCloudEureka7001.com:7001/eureka/
        defaultZone: http://springCloudEureka7001.com:7001/eureka/,http://springCloudEureka7002.com:7002/eureka/,http://springCloudEureka7003.com:7003/eureka/
      #集群模式
#http://localhost:8089/consumer/dept/list  访问

3.服务消费者启动类

package com.linjia;

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;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;

/**
 * Hello world!
 *
 */
@SpringBootApplication
@EnableEurekaClient    //注册中心客户端
@EnableFeignClients(basePackages= {"com.linjia.springcloud"})  //feign 开启 ,server 接口路径
@ComponentScan("com.linjia.springcloud")
public class FeginConsumerApplication
{
    public static void main( String[] args )
    {
      SpringApplication.run(FeginConsumerApplication.class, args);
    }

}

4.服务消费者Controller

package com.linjia.springcloud.web;

import com.linjia.springcloud.entity.Dept;
import com.linjia.springcloud.service.DeptClientService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

/**
 * @author
 * @date 2018/5/14
 */
@RestController
public class DeptController_Consumer {
    @Autowired
    private DeptClientService service;

    @RequestMapping(value = "/consumer/dept/get/{id}")
    public Dept get(@PathVariable("id") Long id)
    {
        return this.service.get(id);
    }

    @RequestMapping(value = "/consumer/dept/list")
    public List<Dept> list()
    {
        return this.service.list();
    }

    @RequestMapping(value = "/consumer/dept/add")
    public Object add(Dept dept)
    {
        //调用过程，服务提供者的Controller->Service->Dao
        return this.service.add(dept);
    }
}

运行：编译Api,分别启动eureka,provider,Consumer,访问：http://localhost:8089/consumer/dept/list查看调用结果（红色部分为新增部分）

SpringCloud教程 | 第5篇:之面向接口编程 服务消费者（Feign）+熔断器Feign Hystrix

一、Feign简介

二、准备工作

Feign Hystrix

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SpringCloud教程 | 第5篇:之面向接口编程服务消费者（Feign）+熔断器Feign Hystrix