SpringCloud组件之Feign(Hoxton版本)

女爷i 2023-02-21 09:27 13阅读 0赞

# 1.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，具有负载均衡的能力;
 *  整合了Hystrix，具有熔断的能力.

# 2.创建Feign调用演示工程 #

## 2.1 准备工作 ##

启动上篇中Eureka演示工程中Eureka Server与Eureka Client Provider服务 并在Eureka Client Provider中Controller增加一个接口用于Feign调用测试

@RestController
    @RequestMapping("/demo")
    public class DemoController {
    
        @Value("${server.port:#{null}}")
        private String serverPort;
    
        @GetMapping("/hello")
        public String hello() {
            return "Hello " + serverPort;
        }
    
        @GetMapping("/feign")
        public String feignTest(@RequestParam(value = "name") String name){
            return "Hello Feign "+ name;
        }
    
    }

![format_png][]

## 2.2 创建一个服务消费者 ##

新建一个maven工程，取名为：spring-cloud-feign-demo,添加如下依赖pom.xml中

<?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">
        <parent>
            <artifactId>spring-cloud-demo</artifactId>
            <groupId>com.hxmec</groupId>
            <version>1.0-SNAPSHOT</version>
        </parent>
        <modelVersion>4.0.0</modelVersion>
    
        <artifactId>spring-cloud-feign-demo</artifactId>
    
        <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>
    </project>

新建application.yml，增加下面的配置

server:
      port: 9003
    spring:
      application:
        name: feign-demo
    logging:
      pattern:
        console: '%d{yyyy-MM-dd HH:mm:ss.SSS} %-5level [%thread] %logger{15} - %msg%n'
    eureka:
      client:
        service-url:
          defaultZone: http://localhost:8888/eureka/

创建一个启动类 FeignDemoApplication，添加Feign相关注解

@SpringBootApplication
    @EnableEurekaClient
    @EnableDiscoveryClient
    @EnableFeignClients
    public class FeignDemoApplication {
    
        public static void main(String[] args) {
            SpringApplication.run(FeignDemoApplication.class, args );
        }
    }

编写Feign接口服务

@FeignClient(value = "eureka-client-provider")//此名称为消费提供者注册的服务名称
    public interface FeignService {
    
        @RequestMapping(value = "/demo/feign",method = RequestMethod.GET)
        String feignTest(@RequestParam(value = "name") String name);
    }

编写Controller层调用Feign接口实例

@RestController
    @RequestMapping("/feign")
    @AllArgsConstructor
    public class FeignClientController {
    
        private final FeignService feignService;
    
        @GetMapping(value = "/test1")
        public String feign(@RequestParam String name) {
            return feignService.feignTest(name);
        }
    
    }

启动项目，打开http://localhost:8888/ 可以看到应用已经注册到Eureka注册中心![format_png 1][]

请求http://localhost:9003/feign/test1?name=Trazen 验证是否成功调用服务提供者接口![format_png 2][]

# 3.项目git地址 #

[https://github.com/ty1972873004/spring-cloud-demo][https_github.com_ty1972873004_spring-cloud-demo]

# 4.参考 #

【官方文档】https://cloud.spring.io/spring-cloud-netflix/multi/multi\_spring-cloud-ribbon.html

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[https_github.com_ty1972873004_spring-cloud-demo]: https://github.com/ty1972873004/spring-cloud-demo