Spring Cloud 入门教程3、服务消费者（Feign）

一、前言

1、什么是Feign

Feign是基于Ribbon封装的HTTP Client工具包，Feign的目标是简化HTTP Client。Feign也确实做到了这一点，使用Feign发起HTTP请求只需要定义好接口并且配置好相应的注解即可完成对对应接口的绑定。
Spring Cloud基于Feign封装了Spring Cloud Feign（OpenFeign），同Ribbon一样，主要是方便结合Eureka、Consul等服务治理框架使用。Feign的主要作用是：从服务器端拿到对应服务列表后以负载均衡的方式访问对应服务，比Ribbon使用起来会更加方便。

从这张图上来说，Feign主要是从Eureka拿到服务列表之后，以负载均衡的策略选择其中一台发起调用。
2、本篇环境信息

框架
版本
Spring Boot
2.0.0.RELEASE
Spring Cloud
Finchley.BUILD-SNAPSHOT
JDK
1.8.x

3、准备工作

Eureka服务端搭建
参考：https://ken.io/note/spring-cloud-eureka-quickstart
服务提供者搭建
参考：https://ken.io/note/spring-cloud-eureka-quickstart

项
说明
GroupId
io.ken.springcloud.testservice
ArtifactId
testservice

pom.xml、启动类（App.java）保持不变
二、服务提供者准备

1、配置Eureka地址

application.yml 配置
server:
port: 8602

spring:
application:
name: testservice

eureka:
client:
serviceUrl:
defaultZone: http://localhost:8800/eureka/

app:
ip: localhost
2、DTO准备

创建共用的ResponseDTO：Result.java
package io.ken.springcloud.testservice.model;

public class Result {

private int code;

private String message;

private Object content;

private String serviceName;

private String host;

public int getCode() {
    return code;
}

public void setCode(int code) {
    this.code = code;
}

public String getMessage() {
    return message;
}

public void setMessage(String message) {
    this.message = message;
}

public Object getContent() {
    return content;
}

public void setContent(Object content) {
    this.content = content;
}

public String getServiceName() {
    return serviceName;
}

public void setServiceName(String serviceName) {
    this.serviceName = serviceName;
}

public String getHost() {
    return host;
}

public void setHost(String host) {
    this.host = host;
}

}
创建Plus.java用作加法运算RequestDTO
package io.ken.springcloud.testservice.model;

public class Plus {

private int numA;

private int numB;

public int getNumA() {
    return numA;
}

public void setNumA(int numA) {
    this.numA = numA;
}

public int getNumB() {
    return numB;
}

public void setNumB(int numB) {
    this.numB = numB;
}

}
3、编写服务入口

创建服务入口 TestController.java
package io.ken.springcloud.testservice.controller;

import io.ken.springcloud.testservice.model.Plus;
import io.ken.springcloud.testservice.model.Result;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestController {

@Value("${spring.application.name}")
private String serviceName;

@Value("${app.ip}")
private String address;

@Value("${server.port}")
private String port;

@RequestMapping("/")
public Object index() {
    Result result = new Result();
    result.setServiceName(serviceName);
    result.setHost(String.format("%s:%s", address, port));
    result.setMessage("hello");
    return result;
}

@RequestMapping("/plus")
public Object plus(Plus plus) {
    Result result = new Result();
    result.setServiceName(serviceName);
    result.setHost(String.format("%s:%s", address, port));
    result.setMessage("success");
    result.setContent(plus.getNumA() + plus.getNumB());
    return result;
}

@RequestMapping("/plus2")
public Object plus2(@RequestBody Plus plus) {
    Result result = new Result();
    result.setServiceName(serviceName);
    result.setHost(String.format("%s:%s", address, port));
    result.setMessage("success");
    result.setContent(plus.getNumA() + plus.getNumB());
    return result;
}

}
4、访问测试

启动TestService
分别以端口8602,8603启动testservice。 此时testservice等于是在Eureka Server注册了两个实例

分别访问 http://localhost:8602，http://localhost:8603
将会看到以下信息：

http://localhost:8602

{
"code": 0,
"message": "success",
"content": 0,
"serviceName": "testservice",
"host": "localhost:8062"
}

http://localhost:8603

{
"code": 0,
"message": "success",
"content": 0,
"serviceName": "testservice",
"host": "localhost:8063"
}
三、服务消费者搭建（Feign）

1、创建Feign项目

创建一个Spring Boot工程
使用maven-archtype-quickstart模板创建项目

项
说明
GroupId
io.ken.springcloud.feignclient
ArtifactId
feignclient

在pom.xml加入相关依赖

4.0.0

<groupId>io.ken.springcloud.feignclient</groupId>
<artifactId>feignclient</artifactId>
<version>1.0-SNAPSHOT</version>

<name>feignclient</name>
<url>http://ken.io</url>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
</properties>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.0.RELEASE</version>
</parent>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Finchley.BUILD-SNAPSHOT</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

<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>

    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.11</version>
        <scope>test</scope>
    </dependency>

</dependencies>

<repositories>
    <repository>
        <id>spring-snapshots</id>
        <name>Spring Snapshots</name>
        <url>https://repo.spring.io/libs-snapshot</url>
        <snapshots>
            <enabled>true</enabled>
        </snapshots>
    </repository>
</repositories>

<build>
    <finalName>feignclient</finalName>
</build>

2、配置Fegin启动类

配置启动类
修改srcmainjavaiokenspringcloudeurekaserverApp.java 基于Spring Boot创建启动类，添加上 @EnableDiscoveryClient 注解
另外也需要增加 @EnableFeignClients 注解
package io.ken.springcloud.feignclient;

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

@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class App {

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

}
3、DTO准备

创建共用的ResponseDTO：Result.java
package io.ken.springcloud.feignclient.model;

public class Result {

private int code;

private String message;

private Object content;

private String serviceName;

private String host;

public int getCode() {
    return code;
}

public void setCode(int code) {
    this.code = code;
}

public String getMessage() {
    return message;
}

public void setMessage(String message) {
    this.message = message;
}

public Object getContent() {
    return content;
}

public void setContent(Object content) {
    this.content = content;
}

public String getServiceName() {
    return serviceName;
}

public void setServiceName(String serviceName) {
    this.serviceName = serviceName;
}

public String getHost() {
    return host;
}

public void setHost(String host) {
    this.host = host;
}

}
创建Plus.java作为加法运算RequestDTO
package io.ken.springcloud.feignclient.model;

public class Plus {

private int numA;

private int numB;

public int getNumA() {
    return numA;
}

public void setNumA(int numA) {
    this.numA = numA;
}

public int getNumB() {
    return numB;
}

public void setNumB(int numB) {
    this.numB = numB;
}

}
4、编写Eureka服务访问

创建TestService.java
package io.ken.springcloud.feignclient.service;

import io.ken.springcloud.feignclient.model.Plus;
import io.ken.springcloud.feignclient.model.Result;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(value = "testservice")
public interface TestService {

@RequestMapping(value = "/", method = RequestMethod.GET)
String indexService();

@RequestMapping(value = "/plus", method = RequestMethod.GET)
Result plusService(@RequestParam(name = "numA") int numA, @RequestParam(name = "numB") int numB);

@RequestMapping(value = "/plus", method = RequestMethod.POST, consumes = "application/json")
Result plusabService(Plus plus);

@RequestMapping(value = "/plus2", method = RequestMethod.POST)
Result plus2Service(@RequestBody Plus plus);

}
5、编写服务入口

创建 TestController.java 作为访问testservice的入口
package io.ken.springcloud.feignclient.controller;

import io.ken.springcloud.feignclient.model.Plus;
import io.ken.springcloud.feignclient.service.TestService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class TestController {

@Autowired
private TestService testService;

@RequestMapping("/")
public Object index() {
    return "feign client";
}

@RequestMapping("/ti")
public Object ti() {
    return testService.indexService();
}

@RequestMapping("/plus")
public Object plus(@RequestParam("numa") int numA, @RequestParam("numb") int numB) {
    return testService.plusService(numA, numB);
}

@RequestMapping("/plusab")
public Object plusA(@RequestParam("numa") int numA, @RequestParam("numb") int numB) {
    Plus plus = new Plus();
    plus.setNumA(numA);
    plus.setNumB(numB);
    return testService.plusabService(plus);
}

@RequestMapping("/plus2")
public Object plus2(Plus plus) {
    return testService.plus2Service(plus);
}

}
6、配置Eureka Client

在srcmain下创建文件夹resources文件夹并设置为Resources Root
在resources文件夹下创建application.yml文件并配置Eureka Client
server:
port: 8605

spring:
application:
name: feignclient

eureka:
client:
serviceUrl:
defaultZone: http://localhost:8800/eureka/
7、服务消费/访问测试

FeignClient项目启动后，访问 http://localhost:8605/ti 会交替显示以下内容
{
"code": 0,
"message": "hello",
"content": null,
"serviceName": "testservice",
"host": "localhost:8602"
}

{
"code": 0,
"message": "hello",
"content": null,
"serviceName": "testservice",
"host": "localhost:8603"
}
也可以分别访问 http://localhost:8605/plus?numa=1&numb=2 http://localhost:8605/plusab?numa=1&numb=2 http://localhost:8605/plus2?numA=1&numB=2
测试不同的传参方式
四、备注

本篇示例代码
https://github.com/ken-io/springcloud-course/tree/master/chapter-03