SpringCloud-聲明式Rest調用Feign（四）

本文轉載自查看原文 2018-06-19 18:35 1190 JAVA/ SpringCloud學習筆記/ 原創/ SpringCloud/ Feign

前言：一般情況下我們通常使用RestTemplate來實現聲明式遠程調用，但是當參數過多，那么效率就會變得很低，並且難以維護，所以在微服務當中也有聲明式Rest調用的組件Feign

一、Feign簡介

　　Feign是Netflix開發的聲明式、模板化的http客戶端，Feign可以幫我們更加便捷、優雅地調用HTTP API。在SpringCloud中使用Feign非常簡單，創建一個接口，並在接口上加上注解，就完成了聲明式調用；

二、Feign與SpringCloud的整合簡單使用

　　注：本次學習記錄是基於之前的Eureka介紹和Ribbon介紹之上實踐，這里只展示關鍵代碼，其余代碼可在代碼示例中查看；

　　1、創建基於Eureka和Ribbon的服務端和兩個客戶端生產者、消費者：

　　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：這兩個配置eureka默認為true，要改成false，否則會報錯，connot connect server
#表示是否將自己注冊在EurekaServer上
eureka.client.register-with-eureka=false
#表示是否從EurekaServer獲取注冊信息
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: 啟動類
 * @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生產者：

<?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("獲取用戶成功");
        return "{\"username\":\"張三\",\"age\":\"10\"}";
    }

}

ClientController.java

　　2、在消費者module中的maven依賴中添加相關依賴庫，創建Feign訪問接口，並注解，通過識別Eureka提供的應用名稱，來找對應的請求路徑：

　　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啟動類中加入@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、分別啟動Server、Client生產者、Client消費者，並調用訪問http://localhost:8761、http://localhost:8762/getUser，如圖：

調用成功！

參考書籍：《SpringCloud與Docker微服務架構實戰》周力著

代碼示例：https://gitee.com/lfalex/springcloud-example（ eureka-feign-client、 eureka-ribbon-server、 eureka-ribbon-client2這三個module）

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