Spring-Cloud-Finchley | 声明式服务调用 Feign

简介

本篇的 Feign 和上一篇的 Ribbon 都是用于调用其他服务，但是调用的方式不同，Ribbon 需要搭配 RestTemplate 进行 Http 请求，步骤较为繁琐；Feign 是 Ribbon 的改进，整合了 Ribbon 和 Hystrix，不需要构建 Http 请求，并且采用接口的方式声明即可调用。

实例

1、创建 maven 工程

创建 maven 工程，添加核心的父 maven 依赖，所有子 pom 文件继承这个父 pom 文件。

  <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>
    <spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
  </properties>

  <parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.5.RELEASE</version>
    <relativePath/>
  </parent>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </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>${spring-cloud.version}</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>

2、搭建服务注册中心 eureka-server

添加 maven 依赖

	<parent>
		<groupId>com.hly</groupId>
		<artifactId>03-spring-cloud-feign</artifactId>
		<version>1.0-SNAPSHOT</version>
		<relativePath/> <!-- lookup parent from repository -->
	</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-netflix-eureka-server</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
	</dependencies>

application.yml

server:
  port: 8761

eureka:
  instance:
    hostname: localhost
  client:
    registerWithEureka: false
    fetchRegistry: false
    serviceUrl:
      defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/

spring:
  application:
    name: eureka-server

SpringBoot 启动类

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {

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

3、搭建服务提供者 eureka-client

添加 maven 依赖

	<parent>
		<groupId>com.hly</groupId>
		<artifactId>03-spring-cloud-feign</artifactId>
		<version>1.0-SNAPSHOT</version>
		<relativePath/> <!-- lookup parent from repository -->
	</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-netflix-eureka-client</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>
	</dependencies>

添加配置信息 application.yml

server:
  port: 8762

spring:
  application:
    name: eureka-client

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/

SpringBoot 启动类

@SpringBootApplication
@RestController
@EnableEurekaClient
public class EurekaClientApplication {

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

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

	@RequestMapping("/hello")
	public String home(@RequestParam(value = "name", defaultValue = "hly") String name) {
		return "hi " + name + " ,i am from port:" + port;
	}
}

4、搭建服务消费者 feign 客户端

添加 maven 依赖

	<parent>
		<groupId>com.hly</groupId>
		<artifactId>03-spring-cloud-feign</artifactId>
		<version>1.0-SNAPSHOT</version>
		<relativePath/> <!-- lookup parent from repository -->
	</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-netflix-eureka-client</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

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

添加 application.yml 配置

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8761/eureka/
server:
  port: 8765
spring:
  application:
    name: service-feign
    
# 设置feign客户端超时时间
ribbon:
# 建立连接所用的时间，适用于网络状况正常的情况下，两端连接所用的时间。
 ReadTimeout: 5000
# 建立连接后从服务器读取到可用资源所用的时间。
 ConnectTimeout: 5000
 
# feign:
 # hystrix:
    #enabled : true

SpringBoot 启动类

@SpringBootApplication
@EnableEurekaClient
//让注册中心扫描到，EnableEurekaClient只适用于 eureka,@EnableDiscoveryClient 可以是其他注册中心
@EnableDiscoveryClient
@EnableFeignClients
public class EurekaFeignApplication {

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

服务层接口

//服务名指定调用哪个服务
@FeignClient(value = "eureka-client")
public interface ServiceHi {
    //这里的映射名和需要调用的服务的映射名一样
    @RequestMapping(value = "/hello",method = RequestMethod.GET)
    String sayHiFromClientOne(@RequestParam(value = "name") String name);
}

控制层

@RestController
public class HiController {

    @Autowired
    ServiceHi serviceHi;

    /**
     * 消费服务
     * 访问：http://localhost:8765/hi?name=hly 交替输出响应两个服务
     * @param name
     * @return
     */
    @GetMapping(value = "/hi")
    public String sayHi(@RequestParam String name) {
        return serviceHi.sayHiFromClientOne( name );
    }
}

演示

1、依次启动注册中心 eureka-server ，启动两个 eureka-client(启动一个后，修改application.yml 配置文件的端口，再次启动一次)，接着启动 Feign 客户端，访问：
http://localhost:8765/hi?name=hly ，刷新浏览器，实现负载均。