SpringCloud的学习记录(5)

这一章节讲如何使用ribbon和hystrix.

在我们生成的Demo项目上右键点击New->Module->spring Initializr, 然后next, 填写Group和Artifact等信息，

这里Artifact填写ribbonconsumer, 再次next,

这里选择如下图:

最后在Module Name中填写ribbon-consumer.

生成的pom.xml文件如下:

<?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>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.xum</groupId>
    <artifactId>ribbon-consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>ribbon-consumer</name>
    <description>Demo project for Spring Boot</description>
    <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>Greenwich.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-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>com.netflix.hystrix</groupId>
            <artifactId>hystrix-javanica</artifactId>
            <version>RELEASE</version>
            <scope>compile</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>
    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/milestone</url>
        </repository>
    </repositories>
</project>

在src->main->resources下建立application.yml文件, 内容如下

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8771
spring:
  application:
    name: ribbon-consumer
management:
  endpoint:
    health:
      show-details: always
  endpoints:
    web:
      exposure:
        include: '*'

在RibbonConsumerApplication.java里的内容如下, 要加上@EnableCircuitBreaker @EnableHystrixDashboard @EnableDiscoveryClient这三个注解.

package com.xum.ribbonconsumer;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@EnableCircuitBreaker
@EnableHystrixDashboard
@EnableDiscoveryClient
@SpringBootApplication
public class RibbonConsumerApplication { 

    @Bean
    @LoadBalanced  // 这里是加载平衡, 我这里使用RestTemplate
    RestTemplate restTemplate () {
        return new RestTemplate();
    }

    public static void main(String[] args) {
        SpringApplication.run(RibbonConsumerApplication.class, args);
    }
}

然后在RibbonConsumerApplication.java文件夹同级目录下建立Controller文件夹, 里面写一个RibbonConsumerController.java, 内容如下:

package com.xum.ribbonconsumer.controller;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
@RequestMapping(value = "/ribbonconsumer")
public class RibbonConsumerController {
    private static final Logger LOG = LoggerFactory.getLogger(RibbonConsumerController.class);

    @Autowired
    RestTemplate restTemplate;

    @RequestMapping(value = "/test")
    @HystrixCommand(fallbackMethod = "testConsumer_ribbon")  // 这里是HystrixCommand注解, 如果eureka-client项目没有启动, 那么就会转到本项目的fallbackMethod方法,即testConsumer_ribbon(), 就是下面的方法
    public String testConsumer() { // 这里是通过getForEntity属性来调用eureka-client里的testone/test这条api
        LOG.info("RibbonConsumerController=>testConsumer");
        return restTemplate.getForEntity("http://eureka-client/testone/test",String.class).getBody();
    }

  // 这里就是熔断器(Hystrix)自我保护的方法,其实是自定义的方法.
    public String testConsumer_ribbon() {
        LOG.info("RibbonConsumerController=>testConsumer_ribbon");
        return "testConsumer_ribbon";
    }
}

下面是eureka-client项目下testone/test的api返回内容, 这里是简写了,具体的内容可以回看前面eureka-client项目搭建.

    @RequestMapping(value = "/test")
    public String test(@RequestParam(value = "name", required = false, defaultValue = "testOneClient")String name) {
        String info = "Hi " + name + ", this is EurekaClient, port is " + port;
        return info;
    }

最后顺序启动如下项目:

1. eureka-server

2. config-server

3. eureka-client

4. ribbon-consumer

最后用post man发送api: http://localhost:8771/ribbonconsumer/test

或则浏览器打开这条api.

可以看到返回的内容就好像调用eureka-client下的api: http://localhost:8762/testone/test

如果eureka-client项目里没有启动, 那么Hystrix会实现自我保护, 会调用到(fallbackMethod = "testConsumer_ribbon")方法, 自定义的方法.

测试一下, 把eureka-client项目停止,

在post man或则浏览器中输入http://localhost:8771/ribbonconsumer/test, 内容如下:

可以看到, 会调用到testConsumer_ribbon()的保护方法里去.