第八章 SpringCloud之Feign、Hystrix结合使用

#这个章节主要是针对Hystrix的使用，因为Feign的章节在上一节已经实现了，整个代码也是在上一个章节的基础上修改的

##################Hystrix一个简单Demo实现#######################

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>
    <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.test</groupId>
    <artifactId>eureka-client-feign-hystrix</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>eureka-client-feign-hystrix</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Greenwich.SR1</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-server</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</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>

</project>

2、application.yml文件配置

spring:
  application:
    name: eureka-client-feign-hystrix  #应用名
logging:  #logging日志配置
  level:
    root: INFO
    org.hibernate: INFO
server:
  port: 8667   #服务端口

eureka:
  instance:
    hostname: localhost
    prefer-ip-address: true
    instance-id: ${spring.application.name}:${spring.application.instance_id:${server.port}}
  client:
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:8661/eureka

3、启动类加配置

package com.test.eurekaclientfeign;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableFeignClients
@EnableCircuitBreaker
public class EurekaClientFeignHystrixApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaClientFeignHystrixApplication.class, args);
    }

}

4、User.java类

package com.test.eurekaclientfeign.entity;

import java.io.Serializable;
import java.math.BigDecimal;

public class User implements Serializable {
    private  Long id;

    private  String name;

    private  String username;

    private  BigDecimal balance;

    private  short age;

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public BigDecimal getBalance() {
        return balance;
    }

    public void setBalance(BigDecimal balance) {
        this.balance = balance;
    }

    public short getAge() {
        return age;
    }

    public void setAge(short age) {
        this.age = age;
    }
}

5、自定义UserFeignClientConfig.java类,该类的使用，表示不使用Feign的默认配置

package com.test.eurekaclientfeign.feign;

import feign.Logger;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class UserFeignClientConfig {
  /*  @Bean
    public Contract feignContract() {
        return new feign.Contract.Default();
    }*/

    @Bean
    Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL;
    }
}

6、UserFeignClient1.java

package com.test.eurekaclientfeign.feign;

import com.test.eurekaclientfeign.entity.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient(name = "eureka-client-user", configuration = UserFeignClientConfig.class)
public interface UserFeignClient1 {
    @RequestMapping(method = RequestMethod.GET, value = "/user/{id}")
    User findById(@PathVariable("id") Long id);
}

7、MovieController.java类，实现远程调用的类

package com.test.eurekaclientfeign.controller;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.test.eurekaclientfeign.entity.User;
import com.test.eurekaclientfeign.feign.UserFeignClient1;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MovieController {

    @Autowired(required = true)
    private UserFeignClient1 userFeignClient1;

    @GetMapping(value = "/hystrix/{id}")
    @HystrixCommand(fallbackMethod = "defaultMethod")
    //一但无法调用远程的findById()，则会调用Hystrix的默认接口defaultMethod(),其参数要一致，否则无法使用
    public User findById(@PathVariable("id") Long id) {
        return this.userFeignClient1.findById(id);
    }

    public User defaultMethod(@PathVariable("id") Long id){
        User user = new User();
        user.setId(id);
        user.setName("hystrix");
        return user;
    }

}

8、URL访问

http://localhost:8661/  # 服务发现
http://192.168.137.1:8667/hystrix/9  #实现断路，因为数据库没有id=9的数据
http://192.168.137.1:8667/hystrix/1  #可以正常访问

Hystrix访问实现如下：

########Hystrix将调用访问和断路执行方法绑定在一个线程#########

只需在MovieController.java中的HystrixCommand添加一个commandProperties属性即可，如下

package com.test.eurekaclientfeign.controller;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;
import com.netflix.hystrix.contrib.javanica.annotation.HystrixProperty;
import com.test.eurekaclientfeign.entity.User;
import com.test.eurekaclientfeign.feign.UserFeignClient1;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MovieController {

    @Autowired(required = true)
    private UserFeignClient1 userFeignClient1;

    @GetMapping(value = "/hystrix/{id}")
    @HystrixCommand(fallbackMethod = "defaultMethod",
            commandProperties = {
                    @HystrixProperty(name="execution.isolation.strategy", value="SEMAPHORE")
            }
    )
    //一但无法调用远程的findById()，则会调用Hystrix的默认接口defaultMethod(),其参数要一致，否则无法使用
    //添加commandProperties属性，可以使得findById()和defaultMethod()绑定到一个线程中
    public User findById(@PathVariable("id") Long id) {
        return this.userFeignClient1.findById(id);
    }

    public User defaultMethod(@PathVariable("id") Long id){
        User user = new User();
        user.setId(id);
        user.setName("hystrix");
        return user;
    }

}

###########Hystrix健康检查与监控################

1、在pom.xml再添加下面依赖

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

2、在启动类添加一个Bean

package com.test.eurekaclientfeign;

import com.netflix.hystrix.contrib.metrics.eventstream.HystrixMetricsStreamServlet;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.cloud.client.circuitbreaker.EnableCircuitBreaker;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
@EnableFeignClients
@EnableCircuitBreaker
public class EurekaClientFeignHystrixApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaClientFeignHystrixApplication.class, args);
    }

    @Bean
    public ServletRegistrationBean getServlet(){
        HystrixMetricsStreamServlet streamServlet = new HystrixMetricsStreamServlet();
        ServletRegistrationBean registrationBean = new ServletRegistrationBean(streamServlet);
        registrationBean.setLoadOnStartup(1);
        registrationBean.addUrlMappings("/actuator/hystrix.stream");
        registrationBean.setName("HystrixMetricsStreamServlet");
        return registrationBean;
    }
}

3、启动Eureka和服务程序，访问远程调用的服务程序，执行下面的URL

#使用了actuator，所以都必须以这个组件开始
http://localhost:8667/actuator/hystrix.stream

http://localhost:8667/actuator/health