查了一下 spring cloud中的feign自带负载均衡？

feign

Feign是一个声明式的Web Service客户端，它使得编写Web Serivce客户端变得更加简单。我们只需要使用Feign来创建一个接口并用注解来配置它既可完成。它具备可插拔的注解支持，包括Feign注解和JAX-RS注解。Feign也支持可插拔的编码器和解码器。Spring Cloud为Feign增加了对Spring MVC注解的支持，还整合了Ribbon和Eureka来提供均衡负载的HTTP客户端实现。

下面，通过一个例子来展现Feign如何方便的声明对上述computer-service服务的定义和调用。

创建一个Spring Boot工程，配置pom.xml，将上述的配置中的ribbon依赖替换成feign的依赖即可，具体如下：

<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.3.5.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
 
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
<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-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
 
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>Brixton.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>

<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
<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-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>

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

在应用主类中通过@EnableFeignClients注解开启Feign功能，具体如下：

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class FeignApplication {
 
public static void main(String[] args) {
SpringApplication.run(FeignApplication.class, args);
}
 
}

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

}

定义compute-service服务的接口，具体如下：

@FeignClient("compute-service")//相当于eureka中的注册的ip
public interface ComputeClient {
 
@RequestMapping(method = RequestMethod.GET, value = "/add")
Integer add(@RequestParam(value = "a") Integer a, @RequestParam(value = "b") Integer b);
 
}

@RequestMapping(method = RequestMethod.GET, value = "/add")
Integer add(@RequestParam(value = "a") Integer a, @RequestParam(value = "b") Integer b);

}

使用@FeignClient("compute-service")注解来绑定该接口对应compute-service服务
通过Spring MVC的注解来配置compute-service服务下的具体实现。

在web层中调用上面定义的ComputeClient，具体如下：

@RestController
public class ConsumerController {
 
@Autowired
ComputeClient computeClient;
 
@RequestMapping(value = "/add", method = RequestMethod.GET)
public Integer add() {
return computeClient.add(10, 20);
}
 
}

@Autowired
ComputeClient computeClient;

@RequestMapping(value = "/add", method = RequestMethod.GET)
public Integer add() {
return computeClient.add(10, 20);
}

}

application.properties中不用变，指定eureka服务注册中心即可，如：

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spring.application.name=feign-consumer
server.port=3333
eureka.client.serviceUrl.defaultZone=http://localhost:1111/eureka/,http://localhost:2222/eureka/