SpringCloud中fegin的使用是非常优雅的，被大多数面向接口编程的程序员喜欢，而且熔断（hystrix）则能在服务不可达时快速给客户端一个默认响应。可以说是很不错的机制，今天我们就来了解一下这两个。

1，准备

①，用idea建立一个空工程

②，添加一个pom类型的父模块

③，给父工程添加子模块即可

④，结构如下

⑤，eclipse就更简单了，直接建立一个pom类型的父工程，右键父工程给其添加子模块即可

2，父工程配置

①，pom.xml

<?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>spc-parent</artifactId><version>0.0.1-SNAPSHOT</version><!--这里一定要是pom，不然公共的api模块会无法install--><packaging>pom</packaging><name>spc-parent</name><description>Demo project for Spring Boot</description><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><maven.compiler.source>1.8</maven.compiler.source><maven.compiler.target>1.8</maven.compiler.target></properties><!-- 父类工程管理机制 --><dependencyManagement><dependencies><!--springcloud 依赖--><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>Dalston.SR1</version><type>pom</type><scope>import</scope></dependency><!--springboot依赖--><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-dependencies</artifactId><version>1.5.12.RELEASE</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><build><resources><resource><directory>src/main/resources</directory><!-- 这个路径下的文件运行访问 --><filtering>true</filtering></resource></resources><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-resources-plugin</artifactId><configuration><delimiters><delimit>$</delimit><!-- 访问被$包围的值 --></delimiters></configuration></plugin></plugins></build></project>

3，api模块

①，pom.xml

<?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><!--保留名字--><artifactId>api</artifactId><!--父工程--><parent><groupId>com.example</groupId><artifactId>spc-parent</artifactId><version>0.0.1-SNAPSHOT</version></parent><dependencies><!-- 依赖fegin --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-feign</artifactId><version>1.3.1.RELEASE</version></dependency></dependencies>
</project>

②，用到的pojo

import java.util.Date;public class Ticket {private Integer id;private String name;private Date buyDate;
}

③，定义接口

import com.example.api.bean.Ticket;
import com.example.api.factory.TickClientServiceFallbackFactory;
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;//必须指定服务名,指定熔断统一处理类
@FeignClient(value = "ticket-provider",fallbackFactory =TickClientServiceFallbackFactory.class)
public interface TicketService {//  以下为暴露的服务，与提供者的映射路径一致@RequestMapping(value = "/ticket/add", method = RequestMethod.POST)public boolean add(Ticket ticket);@RequestMapping(value = "/ticket/get/{id}", method = RequestMethod.GET)public Ticket get(@PathVariable("id") Long id);@RequestMapping(value = "/ticket/list", method = RequestMethod.GET)public List<Ticket> list();}

④，熔断处理类

import com.example.api.bean.Ticket;
import com.example.api.service.TicketService;
import feign.hystrix.FallbackFactory;
import org.springframework.stereotype.Component;import java.util.Date;
import java.util.List;//加入到ioc容器
@Component
public class TickClientServiceFallbackFactory implements FallbackFactory<TicketService> {@Overridepublic TicketService create(Throwable cause) {
//        通过匿名内部类的方式，如果出错默认结果return new TicketService() {@Overridepublic boolean add(Ticket ticket) {System.out.println("添加失败^_^");return false;}@Overridepublic Ticket get(Long id) {Ticket ticket = new Ticket();ticket.setId(1);ticket.setBuyDate(new Date());ticket.setName("请稍后重试");return ticket;}@Overridepublic List<Ticket> list() {return null;}};}
}

4，注册模块

①，pom.xml

 <artifactId>eureka</artifactId><parent><groupId>com.example</groupId><artifactId>spc-parent</artifactId><version>0.0.1-SNAPSHOT</version></parent><dependencies><!--eureka-server服务端 --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka-server</artifactId></dependency></dependencies>

②，application.properties

#eueka 主机名
eureka.instance.hostname=eureka-service
#不注册自己
eureka.client.register-with-eureka=false
#获取服务
eureka.client.fetch-registry=false
#提供者和消费者的注册地址
eureka.client.service-url.defaultZone=http://localhost:8761/eureka/server.port=8761

③，主配置类

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;
//开启eureka
@EnableEurekaServer
@SpringBootApplication
public class EurekaApplication {public static void main(String[] args) {SpringApplication.run(EurekaApplication.class, args);}
}

5，消费者配置

①，pom.xml

 <artifactId>customer</artifactId><parent><groupId>com.example</groupId><artifactId>spc-parent</artifactId><version>0.0.1-SNAPSHOT</version></parent><dependencies><!-- hystrix --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-hystrix</artifactId></dependency><dependency><groupId>com.springcloud</groupId><artifactId>microservicecloud-api</artifactId><version>${project.version}</version></dependency><!-- Feign相关 --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-feign</artifactId></dependency><!-- eureka相关 --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka</artifactId></dependency></dependencies>

②，application.properties

server.port=8201spring.application.name=ticket-customer-fegin
eureka.instance.prefer-ip-address=true
#注册地址
eureka.client.service-url.defaultZone=http://localhost:8761/eureka/
#开启熔断
feign.hystrix.enabled=true

③，主配置类

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;
//注册到eureka
@EnableEurekaClient
@SpringBootApplication
//指定fegin扫描的包，需要即扫描api工程中熔断配置类
@EnableFeignClients(basePackages= {"com.example.api"})
//需要扫描api工程及本工程注册的bean
@ComponentScan("com.example")
public class CustomerApplication {public static void main(String[] args) {SpringApplication.run(CustomerApplication.class, args);}
}

④，controller层代码编写

import com.example.api.bean.Ticket;
import com.example.api.service.TicketService;
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;@RestController
public class CustomerController {@Autowiredprivate TicketService ticketService;@RequestMapping(value = "/fegin/add")public boolean add(Ticket ticket) {return ticketService.add(ticket);}@RequestMapping(value = "/fegin/get/{id}")public Ticket get(@PathVariable("id") Long id) {return ticketService.get(id);}@RequestMapping(value = "/fegin/list")public List<Ticket> list() {return ticketService.list();}
}

6，提供者配置

①，pom.xml

<artifactId>provider</artifactId><parent><groupId>com.example</groupId><artifactId>spc-parent</artifactId><version>0.0.1-SNAPSHOT</version></parent><dependencies><!-- 引入自己定义的api通用包，可以使用Dept部门Entity --><dependency><groupId>com.example</groupId><artifactId>api</artifactId><version>${project.version}</version></dependency><!-- 将微服务provider侧注册进eureka --><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-eureka</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-test</artifactId></dependency></dependencies>

②，application.properties

server.port=8002
#服务名
spring.application.name=ticket-provider
#使用ip进行注册
eureka.instance.prefer-ip-address=true
eureka.client.service-url.defaultZone=http://localhost:8761/eureka/

③，主配置类

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;@EnableEurekaClient //启动后注册到eureka
@SpringBootApplication
public class ProviderApplication {public static void main(String[] args) {SpringApplication.run(ProviderApplication.class, args);}
}

④，controller层代码

import com.example.api.bean.Ticket;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;import java.util.Collections;
import java.util.Date;
import java.util.List;@RestController
public class TicketController {@RequestMapping(value = "/ticket/add", method = RequestMethod.POST)public boolean add(Ticket ticket) {System.out.println("添加成功");return true;}@RequestMapping(value = "/ticket/get/{id}", method = RequestMethod.GET)public Ticket get(@PathVariable("id")Long id) {Ticket ticket = new Ticket();ticket.setId(1);ticket.setBuyDate(new Date());ticket.setName("《男儿当自强》");return ticket;}@RequestMapping(value = "/ticket/list", method = RequestMethod.GET)public List<Ticket> list() {System.out.println("找到了好多数据。。。。");return Collections.emptyList();}
}

7，测试

①，启动注册工程（eureka）

②，启动消费者工程，此时已经可以看到效果

③，访问消费者接口，看到如下信息，说明熔断起效果了

④，启动提供者工程，等几秒后，便能正常访问提供者