spring cloud 通过 ribbon 实现客户端请求的负载均衡（入门级）

项目结构

环境：

idea：2020.1 版

jdk：8

maven：3.6.2

1. 搭建项目

（ 1 ）父工程：spring_cloud_demo_parent

pom 文件

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <modules>

        <module>miscroservice-eureka-server</module>

        <module>miscroservice-eureka-user</module>

        <module>miscroservice-eureka-order</module>

    </modules>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.3.0.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <groupId>com.kevin.parent</groupId>

    <artifactId>demo_parent</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <name>demo_parent</name>

    <description>Demo project for Spring Boot</description>

    <packaging>pom</packaging>

    <properties>

        <java.version>1.8</java.version>

        <spring-cloud.version>Hoxton.SR4</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>

    <dependencies>

        <dependency>

            <groupId>org.projectlombok</groupId>

            <artifactId>lombok</artifactId>

            <optional>true</optional>

        </dependency>

        <dependency>

            <groupId>com.alibaba</groupId>

            <artifactId>fastjson</artifactId>

            <version>1.2.68</version>

        </dependency>

    </dependencies>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

（ 2 ）注册中心 eureka： miscroservice-eureka-server

pom 文件

<?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">

    <parent>

        <artifactId>demo_parent</artifactId>

        <groupId>com.kevin.parent</groupId>

        <version>0.0.1-SNAPSHOT</version>

    </parent>

    <modelVersion>4.0.0</modelVersion>

    <artifactId>miscroservice-eureka-server</artifactId>

    <dependencies>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-eureka-server</artifactId>

            <version>1.4.7.RELEASE</version>

        </dependency>

    </dependencies>

</project>

application.yml 文件：

server:

  port: 8761

eureka:

  instance:  # 实例

    hostname: localhost

  client:

    register-with-eureka: false # 不需要向自己注册

    fetch-registry: false # 不需要向自己检索

    service-url:  #注册中心访问方式

      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka

（ 3 ）服务提供者：miscroservice-eureka-order

pom 文件

<?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">

    <parent>

        <artifactId>demo_parent</artifactId>

        <groupId>com.kevin.parent</groupId>

        <version>0.0.1-SNAPSHOT</version>

    </parent>

    <modelVersion>4.0.0</modelVersion>

    <artifactId>miscroservice-eureka-order</artifactId>

    <dependencies>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-eureka</artifactId>

            <version>1.4.7.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

    </dependencies>

</project>

　application.yml：

server:

  port: 7900

eureka:

  instance:

    prefer-ip-address: true # 是否显示主机 ip

  client:

    service-url:

      defaultZone: http://localhost:8761/eureka/

spring:

  application:

    name: miscroservice-eureka-order

　（ 4 ）服务消费者：miscroservice-eureka-user

pom 文件

<?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">

    <parent>

        <artifactId>demo_parent</artifactId>

        <groupId>com.kevin.parent</groupId>

        <version>0.0.1-SNAPSHOT</version>

    </parent>

    <modelVersion>4.0.0</modelVersion>

    <artifactId>miscroservice-eureka-user</artifactId>

    <dependencies>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-eureka</artifactId>

            <version>1.4.7.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-commons</artifactId>

        </dependency>

    </dependencies>

</project>

　　application.yml：

server:

  port: 8000

eureka:

  instance:

    prefer-ip-address: false # 是否显示主机的 ip

    instance-id: ${spring.cloud.client.ip-address}:${server.port}  # 将服务实例 id 设置为 ip:端口号形式

  client:

    service-url:

      defaultZone: http://localhost:8761/eureka/  # 指定 eureka 服务地址

spring:

  application:

    name: miscroservice-eureka-user

2. 编写业务代码

（ 1 ）注册中心 eureka 启动类

package com.kevin.eureka.server;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

/**

 * @author kevin

 * @version： EurekaApplication.java v 1.0, 2020年05月21日 12:57

 * @Description

 *

 * @EnableEurekaServer 表明该服务是一个 eureka 注册中心服务

 **/

@SpringBootApplication

@EnableEurekaServer

public class EurekaApplication {

    public static void main(String[] args) {

        SpringApplication.run(EurekaApplication.class, args);

    }

}

（ 2 ）服务提供者

A. 启动类：

package com.kevin.eureka.order;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

/**

 * @author kevin

 * @version： OrderApplication.java v 1.0, 2020年05月21日 21:43

 * @Description

 **/

@SpringBootApplication

@EnableEurekaClient

public class OrderApplication {

    public static void main(String[] args) {

        SpringApplication.run(OrderApplication.class, args);

    }

}

B. po：

package com.kevin.eureka.order.po;

import lombok.Data;

import lombok.ToString;

import java.io.Serializable;

/**

 * @author kevin

 * @version： Order.java v 1.0, 2020年05月21日 21:48

 * @Description

 **/

@Data

@ToString

public class Order implements Serializable {

    private String id;

    private Double price;

    private String receiverName;

    private String receiverAddress;

    private String receiverPhone;

}

C. controller

package com.kevin.eureka.order.controller;

import com.alibaba.fastjson.JSON;

import com.kevin.eureka.order.po.Order;

import com.kevin.eureka.order.service.ServiceInfoManager;

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;

/**

 * @author kevin

 * @version： OrderController.java v 1.0, 2020年05月21日 21:51

 * @Description

 **/

@RestController

public class OrderController {

    @Autowired

    private ServiceInfoManager manager;

    /**

     * 通过 id 查询订单

     *

     * @param id

     * @return

     */

    @RequestMapping("/order/{id}")

    public String findOrderById(@PathVariable String id) {

        int port = manager.getPort();

        System.out.println("port = " + port);

        Order order = new Order();

        order.setId("123");

        order.setPrice(20.00);

        order.setReceiverName("小李");

        order.setReceiverAddress("北京市昌平区");

        order.setReceiverPhone("123456");

        return JSON.toJSONString(order);

    }

}

D. 获取服务端口号

package com.kevin.eureka.order.service;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.core.env.Environment;

import org.springframework.stereotype.Component;

/**

 * @author kevin

 * @version： ServiceInfoManager.java v 1.0, 2020年05月22日 10:48

 * @Description

 **/

@Component

public class ServiceInfoManager {

    @Autowired

    private Environment env;

    /**

     * 获取端口号

     *

     * @return

     */

    public int getPort() {

        String s = env.getProperty("server.port");

        return Integer.parseInt(s);

    }

}

（ 3 ）服务消费者：

A. 启动类

package com.kevin.eureka.user;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

/**

 * @author kevin

 * @version： UserApplication.java v 1.0, 2020年05月21日 13:09

 * @Description

 **/

@SpringBootApplication

@EnableEurekaClient

public class UserApplication {

    public static void main(String[] args) {

        SpringApplication.run(UserApplication.class, args);

    }

}

B. controller：

package com.kevin.eureka.user.com.kevin.eureka.controller;

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 org.springframework.web.client.RestTemplate;

/**

 * @author kevin

 * @version： UserController.java v 1.0, 2020年05月22日 10:15

 * @Description

 **/

@RestController

public class UserController {

    public static final String ORD_URL = "http://miscroservice-eureka-order/order/";

    @Autowired

    private RestTemplate restTemplate;

    @RequestMapping("/findOrdersByUser/{id}")

    public String findOrdersByUser(@PathVariable String id) {

        String oId = "123";

        return restTemplate.getForObject(ORD_URL + oId, String.class);

    }

}

C. 配置类

package com.kevin.eureka.user.com.kevin.eureka.config;

import org.springframework.cloud.client.loadbalancer.LoadBalanced;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import org.springframework.web.client.RestTemplate;

/**

 * @author kevin

 * @version： UserConfig.java v 1.0, 2020年05月22日 10:13

 * @Description

 **/

@Configuration

public class UserConfig {

    @Bean

    @LoadBalanced   // 通过 ribbon 实现客户端请求的负载均衡

    public RestTemplate createResTemp(){

        return new RestTemplate();

    }

}

3. 分别启动 eureka、order、user 服务

浏览器中打开 http://localhost:8761/ ，可以看到 order、user 服务都已经注册进来