微服务笔记之Spring Cloud 中使用Feign调用接口服务(Dalston)

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最新推荐文章于 2024-11-22 16:08:57 发布

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分类专栏：分布式服务文章标签： spring-boot spring-cloud Feign 负载均衡

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本文介绍如何使用SpringCloud Feign实现客户端负载均衡，包括集成Ribbon、Eureka，以及服务容错处理。通过具体示例，展示了如何配置Maven项目，定义服务接口，实现服务调用，并配置服务注册与发现。

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Spring Cloud 对 Feign 进行了封装，集成了 Ribbon 并结合 Eureka 可以实现客户端的负载均衡，Spring Cloud 实现的 Feign 客户端类名为 LoadBalancerFeignClient，在该类中，维护着与 SpringClientFactory 相关的实例，通过SpringClientFactory 可以获取负载均衡器，负载均衡器会根据一定的规则来选取处理请求的服务器，最终实现负载均衡功能。

集成了 Hystrix 增加了服务容错处理，并为 Feign 的使用提供了各种默认属性，例如编码器、解码器、日志、注解翻译器、实例创建者和客户端，我们可以简单的使用 Feign，也可以增加自定义的配置。

下面给出基本的使用示例(不包含Hystrix):

1. 创建一个maven项目 servicefeign。

pom.xml文件配置如下，spring-cloud为Dalston版本；

<?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.springcloud.lcl</groupId>
  <artifactId>service-feign</artifactId>
  <version>1.0-SNAPSHOT</version>

  <name>service-feign</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.2.RELEASE</version>
    <relativePath/>
  </parent>

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

  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.springframework.boot</groupId>
          <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

spring-cloud为Finchley版本的pom文件如下:

<?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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.springcloud.lcl.fetgn</groupId>
    <artifactId>servicefeign_f</artifactId>
    <packaging>jar</packaging>
    <version>1.0-SNAPSHOT</version>
    <name>servicefeign_f</name>
    <url>http://www.myorganization.org</url>

    <build>
        <finalName>servicefeign_f</finalName>
    </build>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.7</maven.compiler.source>
        <maven.compiler.target>1.7</maven.compiler.target>
        <spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
        <relativePath/>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </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>
</project>

2. 项目目录结构及代码

启动类ServiceFeignApplication的代码:

package com.springcloud.lcl;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;


/**
 * Hello world!
 *
 */
@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class ServiceFeignApplication
{
    public static void main( String[] args )
    {
        SpringApplication.run(ServiceFeignApplication.class,args);
    }
}

api定义HiController类:

package com.springcloud.lcl.controller;

import com.springcloud.lcl.service.FeignHiService;
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;

/**
 * @author lcl
 * @version 0.1
 * @date 2018/10/15
 **/
@RestController
public class HiController {

    @Autowired
    FeignHiService feignHiService;

    @RequestMapping(value = "/hi",method = RequestMethod.GET)
    public String hi(@RequestParam String name){
        return feignHiService.sayHiService(name);
    }

}

service层接口FeignHiService:

此处使用了FeignClient注解创建了调用service-hi服务的客户端，fallback指定了调用异常时的响应处理.

package com.springcloud.lcl.service;

import com.springcloud.lcl.service.impl.FeignHiServiceImpl;
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(value = "service-hi",fallback = FeignHiServiceImpl.class)
public interface FeignHiService {

    @RequestMapping(value = "/hi",method = RequestMethod.GET)
    String sayHiService(@RequestParam(value = "name") String name);
}

实现类FeignHiServiceImpl:

package com.springcloud.lcl.service.impl;

import com.springcloud.lcl.service.FeignHiService;
import org.springframework.stereotype.Component;

/**
 * @author lcl
 * @version 0.1
 * @date 2018/10/15
 **/
@Component
public class FeignHiServiceImpl implements FeignHiService {
    @Override
    public String sayHiService(String name) {
        return "HHii,"+name+",Sorry,Error....";
    }
}

3. 配置文件application.properties(也可用yml方式) ；

spring.application.name=service-feign
server.port=8765
eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka/

4. 启动及验证

启动eurekaserver，再依次启动servicehi，servicefeign;其中servicehi服务可修改端口号后再起一个实例（例:端口8763）

访问eureka http://localhost:8761/ 可看到如下，预期的几个服务已启动并注册；

访问service-feign提供的服务: http://localhost:8765/hi?name=name1

即可看到查询结果服务。