企业分布式微服务云SpringCloud SpringBoot mybatis （三）服务消费者（Feign）-白红宇

一、Feign简介

Feign是一个声明式的伪Http客户端，它使得写Http客户端变得更简单。使用Feign，只需要创建一个接口并注解。它具有可插拔的注解特性，可使用Feign 注解和JAX-RS注解。Feign支持可插拔的编码器和解码器。Feign默认集成了Ribbon，并和Eureka结合，默认实现了负载均衡的效果。

简而言之：

Feign 采用的是基于接口的注解

Feign 整合了ribbon

二、准备工作

继续用上一节的工程，启动eureka-server，端口为8761; 启动service-hi 两次，端口分别为8762 、8773.

三、创建一个feign的服务

新建一个spring-boot工程，取名为serice-feign，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，代码如下：

<?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/xsd/maven-4.0.0.xsd"

>

<modelVersion>

4.0

.

0

</modelVersion>

<groupId>com.forezp</groupId>

<artifactId>service-feign</artifactId>

<version>

0.0

.

1

-SNAPSHOT</version>

<packaging>jar</packaging>

<name>service-feign</name>

<description>Demo project

for

Spring Boot</description>

<parent>

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

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

<version>

1.5

.

2

.RELEASE</version>

<relativePath/> 

</parent>

<properties>

<project.build.sourceEncoding>UTF-

8

</project.build.sourceEncoding>

<project.reporting.outputEncoding>UTF-

8

</project.reporting.outputEncoding>

<java.version>

1.8

</java.version>

</properties>

<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.RC1</version>

<type>pom</type>

<scope>

import

</scope>

</dependency>

</dependencies>

</dependencyManagement>

<build>

<plugins>

<plugin>

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

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

</plugin>

</plugins>

</build>

<repositories>

<repository>

<id>spring-milestones</id>

<name>Spring Milestones</name>

<url>https:

//repo.spring.io/milestone</url>

<snapshots>

<enabled>

false

</enabled>

</snapshots>

</repository>

</repositories>

</project>

在工程的配置文件application.yml文件，指定程序名为service-feign，端口号为8765，服务注册地址为http://localhost:8761/eureka/ ，代码如下：复制代码

eureka:

client:

serviceUrl:

defaultZone: http:

//localhost:8761/eureka/

server:

port:

8765

spring:

application:

name: service-feign

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

@SpringBootApplication

@EnableDiscoveryClient

@EnableFeignClients

public

class

ServiceFeignApplication {

public

static

void

main(String[] args) {

SpringApplication.run(ServiceFeignApplication.

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service-hi服务的“/hi”接口，代码如下：

/**

* Created by fangzhipeng on 2017/4/6.

*/

@FeignClient

(value =

"service-hi"

)

public

interface

SchedualServiceHi {

@RequestMapping

(value =

"/hi"

,method = RequestMethod.GET)

String sayHiFromClientOne(

@RequestParam

(value =

"name"

) String name);

}

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

@RestController

public

class

HiController {

@Autowired

SchedualServiceHi schedualServiceHi;

@RequestMapping

(value =

"/hi"

,method = RequestMethod.GET)

public

String sayHi(

@RequestParam

String name){

return

schedualServiceHi.sayHiFromClientOne(name);

}

　　架构代码如下:

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