7.Spring-Cloud服务容错保护之Hystrix初探

<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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>6.spring-cloud-hystrix-consumer</groupId>
<artifactId>hystrix-consumer</artifactId>
<packaging>jar</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>spring-cloud Maven Webapp</name>
<url>http://maven.apache.org</url>
<!--springboot采用1.5.x 对应springcloud版本为 Dalston -->
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.2.RELEASE</version>
<relativePath />
</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.RELEASE</spring-cloud.version>
</properties>
<dependencies>

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>


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


<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>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<!--引入ribbon 负载均衡 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-ribbon</artifactId>
<!-- 搞了好久踩的坑，就是在复制上面代码的时候 顺手把scope test复制了，其意思为紧参与junit类似的测试工作，所以一直报找不到服务或者或者拒绝连接 -->
<!-- <scope>test</scope> -->
</dependency>
<!--引入hystrix熔断器 -->
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</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>
<!-- 这样变成可执行的jar -->
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>

package com.niugang;


import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.web.client.RestTemplate;


/**
 * 负责服务的发现与消费
 * 
 * @author niugang
 *
 */
@SpringBootApplication
@EnableDiscoveryClient
@EnableHystrix//这个注解就@EnableCircuitBreaker的代替
/*
 * @SpringCloudApplication
 * 包含了
 * @SpringBootApplication
 * @EnableDiscoveryClient
 * @EnableCircuitBreaker
 * 着三个注解
 */
@ComponentScan
public class Application {

   //负载均衡
@LoadBalanced
@Bean
public RestTemplate restTemplate() {
return new RestTemplate();
}
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}

package com.niugang.controller;
import org.slf4j.Logger;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import com.niugang.service.HelloService;
@RestController
public class HelloController {
private final Logger logger = org.slf4j.LoggerFactory.getLogger(HelloController.class);

        @Resource

private HelloService helloService;
@RequestMapping(value = "/ribbon-consumer", method = RequestMethod.GET)
public String ribbon() {
return helloService.helloService();
}
}

package com.niugang.service;


import org.slf4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
@Service
public class HelloService {
private final Logger logger = org.slf4j.LoggerFactory.getLogger(HelloService.class);
@Autowired
    private RestTemplate restTemplate;
    /**
     * @HystrixCommand:指定一些方法，这些方法应该是作为hystrix命令的进程
     * fallbackMethod:指定回退方法，降级处理，此方法应该和@HystrixCommand在一个类中，用来实现服务降级处理逻辑
     * 
     */

      @HystrixCommand(fallbackMethod="helloBackMethodFirst")
public String  helloService() {
logger.info("start invoke service");
//URI需要使用虚拟主机名（即服务名称，而不是主机名)
return restTemplate.getForEntity("http://service-provide/hello", String.class).getBody();
}
/**
* 通用降级函数
* @return
*/
@HystrixCommand(fallbackMethod="helloBackMethodSecond")
public  String  helloBackMethodFirst(){
//此处可能是另外一个网络请求，所以也可能出现错误
return  "error1";
}
/**
* 二次降级
* @return
*/
@HystrixCommand(fallbackMethod="helloBackMethodSecond")
public  String  helloBackMethodSecond(){
return  "error2";
}
}