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客户端负载均衡Feign之一:申明式服务调用Feign入门示例

Spring Cloud提供了Ribbon和Feign作为客户端的负载均衡。

前面使用了Ribbon做客户端负载均衡,使用Hystrix做容错保护,这两者被作为基础工具类框架被广泛地应用在各个微服务的实现中。SpringCloudFeign是将两者做了更高层次的封装以简化开发。它基于Netfix Feign实现,整合了SpringCloud Ribbon和SpringCloud Hystrix,除了提供这两者的强大功能外,还提供了一种声明是的Web服务客户端定义的方式。SpringCloud Feign在NetFixFeign的基础上扩展了对SpringMVC注解的支持,在其实现下,我们只需创建一个接口并用注解的方式来配置它,即可完成对服务提供方的接口绑定。简化了SpringCloud Ribbon自行封装服务调用客户端的开发量。

在Spring Cloud下,使用Ribbon直接注入一个RestTemplate对象即可,此RestTemplate已做好负载均衡的配置;而使用Feign只需定义个注解,有@FeignClient注解的接口,然后使用@RequestMapping注解在方法上映射远程的REST服务,此方法也是做好了负载均衡配置。

示例一:在Spring cloud Feign中客户端负载均衡是通过Spring cloud Ribbon实现的,下面演示通过Feign实现负载均衡。

新建一个spring-boot工程,取名为feign-consumer,在它的pom文件引入Feign的起步依赖spring-cloud-starter-feign、Eureka的起步依赖spring-cloud-starter-eureka、Web的起步依赖spring-boot-starter-web,pom代码如下:

<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.dxz</groupId>
    <artifactId>feign-consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.5.RELEASE</version>   <!--配合spring cloud版本 -->
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <properties>
        <!--设置字符编码及java版本 -->
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <!--增加eureka-server的依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-eureka-server</artifactId>
        </dependency>
        <!--增加feign的依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
        </dependency>
        <!--用于测试的,本例可省略 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <!--依赖管理,用于管理spring-cloud的依赖 -->
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-starter-parent</artifactId>
                <version>Brixton.SR3</version>   <!--官网为Angel.SR4版本,但是我使用的时候总是报错 -->
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <!--使用该插件打包 -->
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

在工程的配置文件application.yml文件,指定程序名、端口号、服务注册地址,代码如下:

spring.application.name=compute-consume-feign
server.port=2231
eureka.client.serviceUrl.defaultZone=http://localhost:1111/eureka/

在程序的启动类,加上@EnableFeignClients注解开启Feign的功能:

package com.dxz.feign;

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

@SpringBootApplication
@EnableFeignClients
@EnableDiscoveryClient
public class ConsumerApplication {

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

定义一个feign接口,通过@ FeignClient(“服务名”),来指定调用哪个服务。比如在代码中调用了远程服务的接口,代码如下:

package com.dxz.feign.remote;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient("compute-service")
public interface HelloService {
    
    @RequestMapping(value="/add", method = RequestMethod.GET)
    String hello(@RequestParam("a") Integer a, @RequestParam("b") Integer b, @RequestParam("sn") Integer sn);

}

在Web层的controller层,对外暴露一个的API接口,通过上面定义的Feign客户端来消费服务。代码如下:

package com.dxz.feign.service;

import java.util.concurrent.atomic.AtomicInteger;

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.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.dxz.feign.remote.HelloService;

@RestController
public class AddConsumerController {

    @Autowired
    HelloService helloService;
    
    private AtomicInteger sn = new AtomicInteger(0);
    
    @RequestMapping(value="/feign-consumer", method = RequestMethod.GET)
    public String helloConsumer(@RequestParam Integer a, @RequestParam Integer b) {
        return helloService.hello(a, b, sn.incrementAndGet());
    }
}

启动程序,多次访问http://127.0.0.1:2231/feign-consumer?a=1&b=3,浏览器显示:

 

 再观察日志,可以得到之前使用Ribbon时一样的结果,对服务提供方实现了均衡负载。

二、在Spring cloud Feign同时融合了Spring Cloud Hystrix,下面演示通过Feign实现熔断功能。

新增一个服务降级处理类:

复制代码
package com.dxz.feign.remote;

import org.springframework.stereotype.Service;

@Service
public class HelloServiceFallback implements HelloService {

    @Override
    public String hello(Integer a, Integer b, Integer sn) {
        System.out.println("HelloServiceFallback");
        return "fallback";
    }

}
复制代码

在服务绑定接口HelloService中,通过@FeignClient注解的fallback属性来指定服务降级处理类:

复制代码
package com.dxz.feign.remote;

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

import com.dxz.feign.DisableHystrixConfiguration;

@FeignClient(name="compute-service", fallback=HelloServiceFallback.class)
//@FeignClient(name="compute-service",configuration=DisableHystrixConfiguration.class)
public interface HelloService {
    
    @RequestMapping(value="/add", method = RequestMethod.GET)
    String hello(@RequestParam("a") Integer a, @RequestParam("b") Integer b, @RequestParam("sn") Integer sn);

}
复制代码

测试:

posted on 2017-09-13 18:34  duanxz  阅读(...)  评论(...编辑  收藏