Spring Cloud Ribbon 使用示例--RestTemplate

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本文详细介绍了如何在SpringBoot 1.x版本中使用RestTemplate与Eureka服务注册中心配合，实现生产者与消费者之间的服务调用，包括producer-server和consumer-server的配置及Maven依赖。展示了在不同服务间通过Ribbon负载均衡的原理和配置。

版本说明

在Spring Boot 1.X版本中，常用RestTemplate接口实现通讯，而在Spring Boot 2.X版本中，WebFlux提供了异步非阻塞通讯方式，是一种更好的通讯解决方案。

使用`RestTemplate`

在本示例中，实现了一个Eureka服务注册中心eureka-server，两个生产者服务provider-server，一个消费者服务consumer-server。生产者与消费者均注册到Eureka服务上。消费者将通过Eureka服务获取生产者服务清单，并将通过RestTemplate接口访问生产者服务。在通讯过程中，将使用Ribbon实现负载均衡。

服务注册中心`eureka-server`

创建一个Spring Boot 工程，命名为eureka-server，并在pom.xml中引入必要的依赖内容，代码如下：

maven依赖

<!-- Spring Boot Parent -->
<parent>
	<groupId>org.springframework.boot</groupId>
	<artifactId>spring-boot-starter-parent</artifactId>
	<version>1.3.7.RELEASE</version>
	<relativePath/>
</parent>

<dependencies>
	<!-- Spring Cloud Eureka -->
	<dependency>
		<groupId>org.springframework.cloud</groupId>
		<artifactId>spring-cloud-starter-eureka-server</artifactId>
	</dependency>
</dependencies>

<dependencyManagement>
	<dependencies>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-dependencies</artifactId>
			<version>Brixton.SR5</version>
			<type>pom</type>
			<scope>import</scope>
		</dependency>
	</dependencies>
</dependencyManagement>

代码实现

@EnableEurekaServer
@SpringBootApplication
public class EurekaApplication {
	public static void main(String[] args) {
		new SpringApplicationBuilder(EurekaApplication.class).web(true).run(args);
	}
}

配置文件

该项目只有一个配置文件，即application.yml。

server:
	port: 1111

eureka:
	instance:
		hostname: localhost
	client:
		register-with-eureka: false
		fetch-registry: false
		service-url:
			default-zone: http://${eureka.instance.hostname}:${server:port}/eureka/

生产者服务`provider-server`

Maven依赖

<!-- Spring Boot Parent -->
<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.3.7.RELEASE</version>
    <relativePath/>
</parent>

<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</artifactId>
    </dependency>
</dependencies>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Brixton.SR5</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

代码实现

Restful服务接口实现如下：

import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    private final Logger logger = Logger.getLogger(getClass());

    @Autowired
    private DiscoveryClient client;

    @RequestMapping(value = "/hello", method = RequestMethod.GET)
    public String index() {
        ServiceInstance instance = client.getLocalServiceInstance();
        logger.info("/hello, host:" + instance.getHost() + ", service_id :" + instance.getServiceId());
        return "Hello World!";
    }
}

应用主类代码

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

@EnableDiscoveryClient
@SpringBootApplication
public class ProviderApplication {

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

配置文件

application.yml配置如下，运行时通过--spring.profiles.active参数指定使用的profile。示例中启动两个provider-server服务，使其构成集群。

spring:
  application:
    name: provider-server

eureka:
  client:
    service-url:
      defaultZone: http://localhost:1111/eureka/

---
spring:
  profiles: provider1
server:
  port: 8081

---
spring:
  profiles: provider2
server:
  port: 8082

消费者服务`consumer-server`

Maven依赖

<!-- Spring Boot Parent -->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.7.RELEASE</version>
        <relativePath/>
    </parent>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Brixton.SR5</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <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</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-ribbon</artifactId>
        </dependency>
    </dependencies>

代码实现

服务接口实现如下：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

@RestController
public class ConsumerController {

    @Autowired
    private RestTemplate restTemplate;

    @RequestMapping(value = "/ribbon-consumer", method = RequestMethod.GET)
    public String helloConsumer() {
        return restTemplate.getForEntity("http://provider-server/hello", String.class).getBody();
    }
}

应用主类实现如下：

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;

@EnableDiscoveryClient
@SpringBootApplication
public class ConsumerApplication {

    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }

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

配置文件

spring:
  application:
    name: consumer-server

server:
  port: 9000

eureka:
  client:
    service-url:
      defaultZone: http://localhost:1111/eureka/