Hystrix【入门】

公共依赖配置：

<parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.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>Finchley.RELEASE</spring-cloud.version>
</properties>

<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>

1、创建client-server工程

1.1、client-server工程pom依赖：

<!--加上上面的公共依赖-->    <dependencies>
        <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-hystrix</artifactId>
        </dependency></dependencies>

<build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
</build>

1.2、client-server工程启动类：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;

@SpringBootApplication
@EnableHystrix//开启断路器注解
@EnableDiscoveryClient
public class ClientApplication {
    
    public static void main(String[] args) {
        SpringApplication.run(ClientApplication.class, args);
    }
}

1.3、client-server工程配置文件：client-server\src\main\resources\bootstrap.yml

server:
  port: 8888
spring:
  application:
    name: sc-client-service
eureka:
  client:
    serviceUrl:
      defaultZone: http://${eureka.host:127.0.0.1}:${eureka.port:8761}/eureka/
  instance:
    prefer-ip-address: true

1.4、编写模拟使用hystrix场景代码：

/**
 * 用户接口
 */
public interface IUserService {
    String getUser(String username) throws Exception;

}

import org.springframework.stereotype.Component;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;

import cn.springcloud.book.service.IUserService;

/**
 * 具体用户接口实现类
 */
@Component
public class UserServiceImpl implements IUserService {

    @Override
    @HystrixCommand(fallbackMethod = "defaultUser")//降级
    public String getUser(String username) throws Exception {
        if ("spring".equals(username)) {
            return "This is real user";
        } else {
            throw new Exception();
        }
    }

    /**
     * 出错则调用该方法返回友好错误
     *
     * @param username
     * @return
     */
    public String defaultUser(String username) {
        return "The user does not exist in this system";
    }

}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import cn.springcloud.book.service.IUserService;

/**
 * 测试API
 */
@RestController
public class TestController {

    @Autowired
    private IUserService userService;
    
    @GetMapping("/getUser")
    public String getUser(@RequestParam String username) throws Exception{
        return userService.getUser(username);
    }
}

2、创建eureka-server工程

2.1、eureka-server工程pom文件：

<!--加上上面的公共依赖--><dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
</dependencies>

<build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
</build>

2.2、eureka-server工程启动类：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {

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

2.3、eureka-server工程配置文件：eureka-server\src\main\resources\bootstrap.yml

server:
  port: 8761
eureka:
  instance:
    hostname: localhost
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

3、启动2个工程

访问接口：

第一次传入spring

第二次传入：springcloud 

 说明执行了 fallbackMethod 定义的指定方法！