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