SpringCloud学习之Feign 的使用（五）

Feign 是一个声明式的伪RPC的REST客户端，它用了基于接口的注解方式，很方便的客户端配置，刚开始使用时还不习惯，感觉是在客户端写服务端的代码，Spring Cloud 给 Feign 添加了支持Spring MVC注解，并整合Ribbon及Eureka进行支持负载均衡。

Feign的使用很简单，有以下几步：

1、添加依赖

2、启动类添加 @EnableFeignClients 注解支持

3、建立Client接口，并在接口中定义需调用的服务方法

4、使用Client接口。

具体如下首先先添加feign需要的依赖

1、添加 spring-cloud-starter-openfeign 依赖

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

完整的 pom.xml

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<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.2.0.RELEASE</version> <relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.xu</groupId> <artifactId>service-consumer-feign</artifactId> <version>0.0.1-SNAPSHOT</version> <name>service-consumer-feign</name> <description>Demo project for Spring Boot</description> <properties> <java.version>1.8</java.version> <spring-cloud.version>Hoxton.M3</spring-cloud.version> </properties> <dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-hystrix</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-test</artifactId> <scope>test</scope> <exclusions> <exclusion> <groupId>org.junit.vintage</groupId> <artifactId>junit-vintage-engine</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>fastjson</artifactId> <version>1.2.48</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </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> <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> </repository> </repositories> </project>

2、启动类添加 @EnableFeignClients 注解支持

package com.xu.serviceconsumer;

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.openfeign.EnableFeignClients;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ServiceConsumerFeignApplication {

    public static void main(String[] args) {

        SpringApplication.run(ServiceConsumerFeignApplication.class, args);
    }

    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {

        return new RestTemplate();
    }
}

3、建立Client接口，并在接口中定义需调用的服务方法

package com.xu.serviceconsumer.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RequestParam;

@FeignClient(name = "service-hello")
public interface UserFeignClient {

    @RequestMapping(value="/hi",method = RequestMethod.GET)
    String getName(@RequestParam String name);

}

说明：>> name="service-hello"，这里的"service-hello"是注册到Eureka 中的要调用的应用名

>> @GetMapping("/hi") 这里的“/hi”是要调用的应用里的相应的方法（这里需注意，如果service-hello服务下面的访问路径是 /hi/hello ，则这里也要写"/hi/hello"）。

4、使用Client接口

package com.xu.serviceconsumer.controller;

import com.alibaba.fastjson.JSONObject;
import com.fasterxml.jackson.databind.util.JSONPObject;
import com.xu.serviceconsumer.service.HelloService;
import com.xu.serviceconsumer.service.UserFeignClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
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.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import java.util.HashMap;
import java.util.Map;

@RestController
public class HelloControler {

    private static final Logger LOGGER = LoggerFactory.getLogger(HelloControler.class);

    @Autowired
    private HelloService helloService;

    @Autowired
    private LoadBalancerClient loadBalancerClient;

    @Autowired
    private UserFeignClient userFeignClient;

    @RequestMapping(value = "/hi")
    public String hi(@RequestParam String name) {

        return helloService.hiService(name);
    }

    @RequestMapping(value = "/hello")
    public String hello(@RequestParam String name) {

        return userFeignClient.getName(name);
    }

    @RequestMapping(value = "/log-instance")
    public Object logInstance() {
        ServiceInstance serviceInstance = this.loadBalancerClient.choose("SERVICE-HELLO");
        LOGGER.info("{}:{}:{}", serviceInstance.getServiceId(),
                serviceInstance.getHost(),serviceInstance.getPort());

        JSONObject object1 = new JSONObject();
        object1.put("ServiceId",serviceInstance.getServiceId());
        object1.put("Host",serviceInstance.getHost());
        object1.put("Port",serviceInstance.getPort());
        return object1.toJSONString();
    }

}

打开浏览器，访问上面Controller中的RestApi请求http://localhost:8767/hello?name=Ronnie结果如下：

看到这里显然我们的请求响应成功了，成功调用了服务提供者的服务，本节课程到此就结束了，各位如有疑问请再下方留言，我会尽快答复，谢谢观赏！

SpringCloud学习之Feign 的使用（五）

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