SpringCloud学习笔记（6）—— 声明式服务调用：Spring Cloud Feign

最新推荐文章于 2024-03-24 14:54:29 发布

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最新推荐文章于 2024-03-24 14:54:29 发布

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分类专栏： Spring Cloud

本文链接：https://blog.youkuaiyun.com/qq_27868849/article/details/86174834

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Spring Cloud Feign 整合了Spring Cloud Ribbon 与 Spring Cloud Hystrix，除此之外它还提供了一种声明式的Web服务客户端定义方式。 Feign在RestTemplate的基础上对其封装，由它来帮助我们定义和实现依赖服务接口的定义。

快速入门

我们继续使用之前实现的hello-service 服务，这里我们会通过 Spring Cloud Feign 提供的声明式服务绑定功能来实现对该服务接口的调用。

创建工程，取名为 feign-consumer，并在pom.xml里面引入spring-cloud-starter-netflix-eureka-serve 和 spring-cloud-starter-feign依赖。

  <parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.1.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.gildata</groupId>
	<artifactId>feign-consumer</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>feign-consumer</name>
	<description>Demo project for Spring Boot</description>

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

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

	<dependency>
		<groupId>org.springframework.cloud</groupId>
		<artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
		<version>2.0.2.RELEASE</version>
	</dependency>
		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-openfeign</artifactId>
			<version>1.4.6.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

创建应用主类FeignConsumerApplication，并用@EnableFeignClients 注解开启 Spring Cloud Feign 的支持功能。

@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class FeignConsumerApplication {

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

}

定义 HelloService 接口，通过@FeignClient 注解指定服务名来绑定服务，然后再使用Spring MVC的注解来绑定具体该服务提供的 REST 接口.

/**
 * Created by liaock on 2019/1/8.
 */
@FeignClient("hello-service")   
public interface HelloService {
    @RequestMapping("/hello")
    String hello();
}

接着创建一个 ConsumerController 来实现对 Feign 客户端的调用。注入上面定义的 HelloService实例，并在helloConsumer函数中调用这个绑定了 hello-service 服务接口的客户端来向该服务发起 /hello 接口的调用。

/**
 * Created by liaock on 2019/1/9.
 */
@RestController
public class ConsumerController {
    @Autowired
    HelloService helloService;

    public String HelloConsumer(){
        return helloService.hello();
    }
}

最后，同Ribbon实现的消费者一样配置application.properties

server.port=9001
spring.application.name=feign-consumer
eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka/

测试验证

启动服务注册中心以及两个HELLO-SERVICE，然后启动 FEIGN-CONSUMER

发送几次GET请求到 http://localhost:9001/feign-consumer，可以得到如之前 Ribbon 实现时的效果一样，正确返回了“Hello World”。并且根据控制台的输出，我们可以看到Feign实现的消费者，依然是利用Ribbon维护了针对 HELLO-SERVIEC 的服务列表信息，并且通过轮询实现了客户端负载均衡。而与Ribbon 不同的是，通过Feign我们只需要定义服务绑定接口，以声明式的方法，优雅而简单地实现了服务调用。

参数绑定

在介绍参数绑定前，我们先扩展下 hello-service。增加如下接口定义。

package com.gildata.springbootdemo.controller;

import com.gildata.springbootdemo.entity.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.web.bind.annotation.*;

import org.apache.log4j.Logger;

import java.util.Random;

/**
 * Created by liaock on 2018/12/17.
 */
@RestController
public class HelloController {
    private final Logger logger = Logger.getLogger(getClass());
    @RequestMapping("/hello")
    public String index(){
        return "Hello World !";
    }

    @RequestMapping(value = "hello1", method = RequestMethod.GET)
    public String hello(@RequestParam String name){
        return "Hello "+ name;
    }

    @RequestMapping(value = "hello2", method = RequestMethod.GET)
    public User hello(@RequestHeader String name, @RequestHeader Integer age){
        return new User(name,age);
    }

    @RequestMapping(value = "hello3", method = RequestMethod.POST)
    public String hello(@RequestBody User user){
        return "Hello "+ user.getName() + "," + user.getAge();
    }
}

定义User对象

package com.gildata.springbootdemo.entity;

/**
 * Created by liaock on 2019/1/9.
 */
public class User {
    private String name;
    private Integer age;

    public  User(){ }

    public User(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

改造 feign-consumer(修改 HelloService以及ConsumerController)

package com.gildata.feignconsumer.service;

import com.gildata.feignconsumer.entity.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.*;

/**
 * Created by liaock on 2019/1/8.
 */
@FeignClient("hello-service")
@Service
public interface HelloService {
    @RequestMapping("/hello")
    String hello();

    @RequestMapping(value = "hello1", method = RequestMethod.GET)
    String hello(@RequestParam("name") String name);

    @RequestMapping(value = "hello2", method = RequestMethod.GET)
    User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);

    @RequestMapping(value = "hello3", method = RequestMethod.GET)
    String hello(@RequestBody User user);
}

package com.gildata.feignconsumer.controller;

import com.gildata.feignconsumer.entity.User;
import com.gildata.feignconsumer.service.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by liaock on 2019/1/9.
 */
@RestController
public class ConsumerController {
    @Autowired
    HelloService helloService;

    @RequestMapping(value = "/feign-consumer",method = RequestMethod.GET)
    public String helloConsumer(){
        return helloService.hello();
    }

    @RequestMapping(value = "/feign-consumer2",method = RequestMethod.GET)
    public String helloConsumer2(){
        StringBuilder sb = new StringBuilder();
        sb.append(helloService.hello()).append("\n");
        sb.append(helloService.hello("DIDI")).append("\n");
        sb.append(helloService.hello("DIDI",30)).append("\n");
        sb.append(helloService.hello(new User("DIDI",30))).append("\n");
        return sb.toString();
    }
}

测试验证：发送请求到 http://localhost:9001/feign-consumer2

得到如下结果：

Hello World ! Hello DIDI User{name='DIDI', age=30} Hello DIDI,30

调用成功！

继承特性

当使用Spring MVC 的注解来绑定服务接口时，我们几乎可以从服务提供方的Controller 中依靠复制操作，构建出相应的服务客户端绑定接口，可以考虑进一步抽象，我们可以通过Spring Cloud Feign的继承特性来实现REST接口定义的复用.

为了能够复用 DTO 与接口定义，我们先创建一个基础的Maven工程，命名为 hello-service-api
由于在hello-service-api 中需要定义可同时复用于服务端与客户端的接口，我们要使用到Spring MVC 的注解，所以需要在 pom.xml里面加入 spring-boot-starter-web 依赖，如下：

<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.1.1.RELEASE</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.gildata</groupId>
	<artifactId>hello-service-api</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>hello-service-api</name>
	<description>Demo project for Spring Boot</description>

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

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

创建 HelloService 并将上面实现的User复制到 hello-service-api

package com.example.service;

import com.example.entity.User;
import org.springframework.web.bind.annotation.*;

/**
 * Created by liaock on 2019/1/9.
 */
@RequestMapping("/refactor")
public interface HelloService {

    @RequestMapping(value = "hello4", method = RequestMethod.GET)
    String hello(@RequestParam("name") String name);

    @RequestMapping(value = "hello5", method = RequestMethod.GET)
    User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);

    @RequestMapping(value = "hello6", method = RequestMethod.POST)
    String hello(@RequestBody User user);

}

将hello-service-api mvn install 到本地仓库，并在hello-service及feign-consumer中引入，下面对hello-service 以及 feign-consumer 重构

hello-service的修改.

package hello.controller;
/**
 * Created by liaock on 2019/1/9.
 */
import com.example.entity.User;
import com.example.service.HelloService;
import org.springframework.web.bind.annotation.*;

@RestController
public class RefactorHelloController implements HelloService {
    @Override
    @RequestMapping(value = "hello4", method = RequestMethod.GET)
    public String hello(@RequestParam("name") String name) {
        return "Hello "+ name;
    }

    @Override
    @RequestMapping(value = "hello5", method = RequestMethod.GET)
    public User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age) {
        return new User(name,age);
    }

    @Override
    @RequestMapping(value = "hello6", method = RequestMethod.POST)
    public String hello(@RequestBody User user) {
        return "Hello "+user.getName() + "," + user.getAge();
    }

}

feign-consumer 的修改

package com.gildata.feignconsumer.service;

import com.example.service.HelloService;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;

/**
 * Created by liaock on 2019/1/9.
 */
@Service
@FeignClient(value = "HELLO-SERVICE")
public interface RefactorHelloService extends HelloService {

}

package com.gildata.feignconsumer.controller;

import com.example.entity.User;
import com.gildata.feignconsumer.service.HelloService;
import com.gildata.feignconsumer.service.RefactorHelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

/**
 * Created by liaock on 2019/1/9.
 */
@RestController
public class ConsumerController {
    @Autowired
    HelloService helloService;

    @Autowired
    RefactorHelloService refactorHelloService;

    @RequestMapping(value = "/feign-consumer",method = RequestMethod.GET)
    public String helloConsumer(){
        return helloService.hello();
    }

    @RequestMapping(value = "/feign-consumer2",method = RequestMethod.GET)
    public String helloConsumer2(){
        StringBuilder sb = new StringBuilder();
        sb.append(helloService.hello()).append("\n");
        sb.append(helloService.hello("DIDI")).append("\n");
        sb.append(helloService.hello("DIDI",30)).append("\n");
        sb.append(helloService.hello(new com.gildata.feignconsumer.entity.User("DIDI",30))).append("\n");
        return sb.toString();
    }

    @RequestMapping(value = "/feign-consumer3",method = RequestMethod.GET)
    public String helloConsumer3(){
        StringBuilder sb = new StringBuilder();
        sb.append(refactorHelloService.hello("MIMI")).append("\n");
        sb.append(refactorHelloService.hello("MIMI",30)).append("\n");
        sb.append(refactorHelloService.hello(new User("MIMI",30))).append("\n");
        return sb.toString();
    }
}

测试验证

访问 http://localhost:9001/feign-consumer3

提示

Hello MIMI User{name='MIMI', age=30} Hello MIMI,30

测试成功！

Ribbon 配置

全局配置

可以使用ribbon.=的方式来设置ribbon的各项参数。比如：

ribbon.ConnectTimeOut=500
ribbon.ReadTimeout=5000

指定服务配置

比如：

HELLO-SERVICE.ribbon.ConnectTimeOut=500
HELLO-SERVICE.ribbon.ReadTimeout=2000

重试机制

Hystrix 配置

下面我们将介绍如何在Spring Cloud Feign中配置Hystrix 属性以及如何实现服务降级.

全局配置

hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=5000

禁用 Hystrix

feign.hystrix.enabled=false

针对某个客户端关闭 Hystrix ，通过使用 @Scope(“prototype”) 注解为指定的客户端配置 Feign.Builder 实例
构建一个关闭 Hystrix 的配置类

@Configuration
public class DisableHystrixConfiguration {

    @Bean
    @Scope("prototype")
    public Feign.Builder feignBuilder(){
        return Feign.builder();
    }

}

@FeignClient(value = "SERIVCE-USER",configuration = DisableHystrixConfiguration.class)
@Service
public interface HelloService {
	···
}

指定命令配置

采用hystrix.command. 作为前缀。针对上一节介绍的尝试机制中对/hello接口的熔断超时时间的配置如下：

hystrix.command.hello.execution.isolation.thread.timeoutInMilliseconds=5000

服务降级配置

我们对全面创建的 feign-consumer 工程进行改造。

服务降级逻辑的实现需要问Feign客户端的定义接口编写一个具体的接口实现类。具体如下：

package com.gildata.feignconsumer.service;

import com.gildata.feignconsumer.entity.User;

/**
 * Created by liaock on 2019/1/9.
 */
public class HelloServiceFallback implements HelloService {
    @Override
    public String hello() {
        return "error";
    }

    @Override
    public String hello(String name) {
        return "error";
    }

    @Override
    public User hello(String name, Integer age) {
        return new User("未知",0);
    }

    @Override
    public String hello(User user) {
        return "error";
    }
}

在服务绑定接口的 HelloService 中，通过@FeignClient 注解的fallback 属性来制定对应的服务降级实现类。

package com.gildata.feignconsumer.service;

import com.gildata.feignconsumer.entity.User;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.*;

/**
 * Created by liaock on 2019/1/8.
 */
@FeignClient(name="hello-service",fallback = HelloServiceFallback.class)
@Service
public interface HelloService {
    @RequestMapping("/hello")
    String hello();

    @RequestMapping(value = "hello1", method = RequestMethod.GET)
    String hello(@RequestParam("name") String name);

    @RequestMapping(value = "hello2", method = RequestMethod.GET)
    User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);

    @RequestMapping(value = "hello3", method = RequestMethod.GET)
    String hello(@RequestBody User user);
}

测试验证

启动服务注册中心和feign-consumer，但是不启动 hello-service 服务，发送get请求到http://localhost:9001/feign-consumer2，该接口会分别调用 HelloService 中的4个绑定接口，但因为 hello-service 服务没有启动，会直接出发服务降级，输出如下：

error
error
name=未知， age=0
error

测试成功！