SpringCloud-声明式Rest调用Feign（四）

2022-01-11 10:29:11

前言：一般情况下我们通常使用RestTemplate来实现声明式远程调用，但是当参数过多，那么效率就会变得很低，并且难以维护，所以在微服务当中也有声明式Rest调用的组件Feign

一、Feign简介

　　Feign是Netflix开发的声明式、模板化的http客户端，Feign可以帮我们更加便捷、优雅地调用HTTP API。在SpringCloud中使用Feign非常简单，创建一个接口，并在接口上加上注解，就完成了声明式调用；

二、Feign与SpringCloud的整合简单使用

　　注：本次学习记录是基于之前的Eureka介绍和Ribbon介绍之上实践，这里只展示关键代码，其余代码可在代码示例中查看；

　　1、创建基于Eureka和Ribbon的服务端和两个客户端生产者、消费者：

　　Server：

<?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.cn</groupId>

  <artifactId>eureka-ribbon-server</artifactId>

  <version>1.0-SNAPSHOT</version>

  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <java.version>1.8</java.version>

  </properties>

  <parent>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-parent</artifactId>

    <version>1.5.13.RELEASE</version>

  </parent>

  <dependencies>

    <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>Edgware.SR3</version>

        <type>pom</type>

        <scope>import</scope>

      </dependency>

    </dependencies>

  </dependencyManagement>

  <!-- 添加spring-boot的maven插件 -->

  <build>

    <plugins>

      <plugin>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-maven-plugin</artifactId>

      </plugin>

    </plugins>

  </build>

</project>

pom.xml

server.port=8761

#注意：这两个配置eureka默认为true，要改成false，否则会报错，connot connect server

#表示是否将自己注册在EurekaServer上

eureka.client.register-with-eureka=false

#表示是否从EurekaServer获取注册信息

eureka.client.fetch-registry=false

eureka.client.service-url.defaultZone=http://localhost:8761/eureka/

application.properties

package com.cn;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

/**

 * @program: springcloud-example

 * @description: 启动类

 * @author:

 * @create: 2018-06-15 15:43

 **/

@SpringBootApplication

@EnableEurekaServer

public class ServerApplication {

    public static void main(String[] args) {

        SpringApplication.run(ServerApplication.class,args);

    }

}

ServerApplication.java

　　Client生产者：

<?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.cn</groupId>

  <artifactId>eureka-ribbon-client2</artifactId>

  <version>1.0-SNAPSHOT</version>

  <properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <java.version>1.8</java.version>

  </properties>

  <parent>

    <groupId>org.springframework.boot</groupId>

    <artifactId>spring-boot-starter-parent</artifactId>

    <version>1.5.13.RELEASE</version>

  </parent>

  <dependencies>

    <dependency>

      <groupId>org.springframework.cloud</groupId>

      <artifactId>spring-cloud-starter-ribbon</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>Edgware.SR3</version>

        <type>pom</type>

        <scope>import</scope>

      </dependency>

    </dependencies>

  </dependencyManagement>

  <!-- 添加spring-boot的maven插件 -->

  <build>

    <plugins>

      <plugin>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-maven-plugin</artifactId>

      </plugin>

    </plugins>

  </build>

</project>

pom.xml

server.port=8763

spring.application.name=client-87

eureka.client.service-url.defaultZone=http://localhost:8761/eureka

application.properties

package com.cn;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

/**

 * @program: springcloud-example

 * @description:

 * @author:

 * @create: 2018-06-15 16:05

 **/

@SpringBootApplication

@EnableDiscoveryClient

public class ClientApplication {

    public static void main(String[] args) {

        SpringApplication.run(ClientApplication.class, args);

    }

}

ClientApplication.java

package com.cn.contorller;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.ResponseBody;

/**

 * @program: springcloud-example

 * @description:

 * @author:

 * @create: 2018-06-15 16:12

 **/

@Controller

public class ClientController {

    @GetMapping("/getUser")

    @ResponseBody

    public String getUser() {

        System.out.println("获取用户成功");

        return "{\"username\":\"张三\",\"age\":\"10\"}";

    }

}

ClientController.java

　　2、在消费者module中的maven依赖中添加相关依赖库，创建Feign访问接口，并注解，通过识别Eureka提供的应用名称，来找对应的请求路径：

　　pom.xml：

<?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.cn</groupId>
  <artifactId>eureka-feign-client</artifactId>
  <version>1.0-SNAPSHOT</version>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <java.version>1.8</java.version>
  </properties>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.13.RELEASE</version>
  </parent>

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

  </dependencies>
  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-dependencies</artifactId>
        <version>Edgware.SR3</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>
  <!-- 添加spring-boot的maven插件 -->
  <build>
    <plugins>
      <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>

　　application.properties:

server.port=8762

spring.application.name=client-8762

eureka.client.service-url.defaultZone=http://localhost:8761/eureka/

　　Feign接口：

import org.springframework.cloud.netflix.feign.FeignClient;

import org.springframework.web.bind.annotation.RequestMapping;

@FeignClient(name = "CLIENT-87")

public interface UserFeign {

    @RequestMapping("/getUser")

    public String getUser();

}
FeignController：
package com.cn.controller;

import com.cn.feign.UserFeign;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * @program: springcloud-example
 * @description:
 * @author:
 * @create: 2018-06-15 15:55
 **/
@RestController
public class FeignController {
    @Autowired
    private LoadBalancerClient loadBalancerClient;

    @Autowired
    private RestTemplate restTemplate;

    @Autowired
    private UserFeign userFeign;

    @RequestMapping("/getUser")
    public String getUser() {
        return userFeign.getUser();
    }

    @GetMapping("/loadInstance")
    public String loadInstance() {
        ServiceInstance choose = this.loadBalancerClient.choose("client-87");
        System.out.println(choose.getServiceId()+":"+choose.getHost()+":"+choose.getPort());
        return choose.getServiceId() + ":" + choose.getHost() + ":" + choose.getPort();
    }

}

　　在ClientApplication.java启动类中加入@EnableFeignClients注解：

package com.cn;

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.cloud.netflix.feign.EnableFeignClients;

import org.springframework.context.annotation.Bean;

import org.springframework.web.client.RestTemplate;

/**

 * @program: springcloud-example

 * @description:

 * @author:

 * @create: 2018-06-15 15:51

 **/

@SpringBootApplication

@EnableDiscoveryClient

@EnableFeignClients

public class ClientApplication {

    public static void main(String[] args) {

        SpringApplication.run(ClientApplication.class, args);

    }

    /**

     * @Description:

     * @Param:

     * @return:

     * @Author:

     * @Date: 2018/6/15

     */

    @Bean

    @LoadBalanced

    public RestTemplate getRestTemplate() {

        return new RestTemplate();

    }

}

　　3、分别启动Server、Client生产者、Client消费者，并调用访问http://localhost:8761、http://localhost:8762/getUser，如图：

SpringCloud-声明式Rest调用Feign（四）

SpringCloud-声明式Rest调用Feign（四）

调用成功！

参考书籍：《SpringCloud与Docker微服务架构实战》周力著

代码示例：https://gitee.com/lfalex/springcloud-example（ eureka-feign-client、 eureka-ribbon-server、 eureka-ribbon-client2这三个module）

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