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http://blog.csdn.net/forezp/article/details/69788938
本文出自方志朋的博客
在上一篇文章，讲了服务的注册和发现。在微服务架构中，业务都会被拆分成一个独立的服务，服务与服务的通讯是基于http restful的。Spring cloud有两种服务调用方式，一种是ribbon+restTemplate，另一种是feign。在这一篇文章首先讲解下基于ribbon+rest。
一、ribbon简介
Ribbon is a client side load balancer which gives you a lot of control over the behaviour of HTTP and TCP clients. Feign already uses Ribbon, so if you are using @FeignClient then this section also applies.
—–摘自官网
ribbon是一个负载均衡客户端，可以很好的控制http和tcp的一些行为。Feign默认集成了ribbon。
ribbon 已经默认实现了这些配置bean：
-
IClientConfig ribbonClientConfig: DefaultClientConfigImpl
-
IRule ribbonRule: ZoneAvoidanceRule
-
IPing ribbonPing: NoOpPing
-
ServerList ribbonServerList: ConfigurationBasedServerList
-
ServerListFilter ribbonServerListFilter: ZonePreferenceServerListFilter
-
ILoadBalancer ribbonLoadBalancer: ZoneAwareLoadBalancer
二、准备工作
这一篇文章基于上一篇文章的工程，启动eureka-server 工程；然后在eureka-client中加入mysql, jpa等依赖:
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
在application.yaml文件中加入数据库的配置:
spring:
application:
name: eureka-client
datasource:
url: jdbc:mysql://192.168.239.234:3306/test
username: root
password: 123456
driver-class-name: com.mysql.jdbc.Driver
新建一个实体:
package com.lying.eurekaclient.orm;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
@Data
@AllArgsConstructor
@NoArgsConstructor
@Builder
@Entity
public class User {
@GeneratedValue
@Id
private Long id;
private String name;
private Integer age;
}
新建一个查询的Service:
package com.lying.eurekaclient.service;
import com.lying.eurekaclient.orm.User;
import org.springframework.data.jpa.repository.JpaRepository;
public interface UserService extends JpaRepository<User, Long> {
User findByName(String name);
}
新建一个controller, 如下:
package com.lying.eurekaclient.controller;
import com.lying.eurekaclient.orm.User;
import com.lying.eurekaclient.service.UserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class UserController {
@Value("${server.port}")
private String port;
@Autowired
private UserService userService;
@RequestMapping(value = "/users/{name}", method = RequestMethod.GET)
public String fetchUserByName(@PathVariable("name") String name) {
return userService.findByName(name).toString() + ": " + port;
}
}
启动eureka-client工程，它的端口为8810；将eureka-client的配置文件的端口改为8811，并启动，这时你会发现：eureka-client在eureka-server注册了2个实例，这就相当于一个小的集群。访问localhost:9999如图所示：数据库和user表自己建
三、建一个服务消费者
重新新建一个spring-boot工程，取名为：service-ribbon;
在它的pom.xml文件分别引入起步依赖spring-cloud-starter-eureka、spring-cloud-starter-ribbon、spring-boot-starter-web，代码如下：
<?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>
<groupId>com.lying</groupId>
<artifactId>ribbon-service</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>ribbon-service</name>
<description>Demo project for Spring Boot</description>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.10.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</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>Edgware.SR2</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-eureka-server</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-ribbon</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>
在工程的配置文件指定服务的注册中心地址为http://localhost:9999/eureka/，程序名称为 ribbon-service，程序端口为9910。配置文件application.yml如下：
server:
port: 9910
spring:
application:
name: ribbon-service
eureka:
client:
service-url:
defaultZone: http://localhost:9999/eureka/
在工程的启动类中,通过@EnableDiscoveryClient向服务中心注册；并且向程序的ioc注入一个bean: restTemplate;并通过@LoadBalanced注解表明这个restRemplate开启负载均衡的功能。
package com.lying.ribbonservice;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
@SpringBootApplication
@EnableDiscoveryClient
public class RibbonServiceApplication {
public static void main(String[] args) {
SpringApplication.run(RibbonServiceApplication.class, args);
}
@Bean
@LoadBalanced
RestTemplate restTemplate() {
return new RestTemplate();
}
}
写一个测试类UserService，通过之前注入ioc容器的restTemplate来消费eureka-client服务的“fetchUserByName”接口，在这里我们直接用的程序名替代了具体的url地址，在ribbon中它会根据服务名来选择具体的服务实例，根据服务实例在请求的时候会用具体的url替换掉服务名，代码如下：
package com.lying.ribbonservice.service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;
@Service
public class UserService {
@Autowired
private RestTemplate restTemplate;
public String getUserInfo(String name) {
return restTemplate.getForObject("http://eureka-client/users/" + name, String.class);
}
}
写一个controller，在controller中用调用UserService 的方法，代码如下：
package com.lying.ribbonservice.controller;
import com.lying.ribbonservice.service.UserService;
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.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class UserController {
@Autowired
private UserService userService;
@RequestMapping(value = "/getUserInfo/{name}", method = RequestMethod.GET)
public String getUserInfo(@PathVariable("name") String name) {
return userService.getUserInfo(name);
}
}
在浏览器上多次访问http://localhost:9910/getUserInfo/Lee，浏览器交替显示：
User(id=2, name=Lee, age=23): 8810
User(id=2, name=Lee, age=23): 8811
这说明当我们通过调用restTemplate.getForObject("http://eureka-client/users/" + name, String.class);方法时，已经做了负载均衡，访问了不同的端口的服务实例。
四、此时的架构
- 一个服务注册中心，eureka server,端口为9999
- eureka-client工程跑了两个实例，端口分别为8810、8811，分别向服务注册中心注册
- sercvice-ribbon端口为9910, 向服务注册中心注册
- 当sercvice-ribbon通过restTemplate调用eureka-client的fetchUserByName接口时，因为用ribbon进行了负载均衡，会轮流的调用eureka-client：8810和8811 两个端口的fetchUserByName接口；
源码下载：https://github.com/lyingfromyou/SpringCloudExample
五、参考资料
本文参考了以下：
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