Spring Cloud (2) 服务消费者-基础

LoadBalancerClient

　　使用Spring Cloud提供的负载均衡器客户端来实现服务的消费。

首先创建一个服务消费者工程，命名为com.david.consumer，并在pom.xml中添加依赖:

<?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.david</groupId>
    <artifactId>consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

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

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.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>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Edgware.SR2</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>

配置application.yml指定eureka注册中心地址：

spring:
  application:
    name: david-eureka-consumer
server:
  port: 8763
eureka:
  client:
    service-url:
      default-zone: http://localhost:8761/eureka/

在工程的启动类中，通过@EnableDiscoverClient向服务中心注册，并向程序的ioc注入一个bean：restTemplate。

//向服务中心注册
@EnableDiscoveryClient
@SpringBootApplication
public class ConsumerApplication {

    //向ioc注入一个bean：restTemplate
    @Bean
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }

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

新建TestController

@RestController
public class TestController {

    @Autowired
    LoadBalancerClient loadBalancerClient;

    @Autowired
    RestTemplate restTemplate;

    @GetMapping("/consumer")
    public String test(){
        ServiceInstance serviceInstance = loadBalancerClient.choose("david-eureka-client");
        String url = "http://" + serviceInstance.getHost() +":" + serviceInstance.getPort() + "/test";
        System.out.println(url);
        return restTemplate.getForObject(url,String.class);
    }

}

我们注入了LoadBalancerClient和RestTemplate，并在/consumer方法中，先通过loadbalancerClient中的choose函数来负载均衡的选出一个david-eureka-client的服务实例，这个服务实例的基本信息存储在ServiceInstance中，然后通过这些对象的信息拼接处访问/test 接口的详细地址，最后再利用RestTemplate对象实现对服务提供者接口的调用。

访问http://localhost:8763/consumer

项目结构：