Feign简介
Feign 是一个声明web服务客户端，这便得编写web服务客户端更容易，使用Feign 创建一个接口并对它进行注解，它具有可插拔的注解支持包括Feign注解与JAX-RS注解，Feign还支持可插拔的编码器与解码器，Spring Cloud 增加了对 Spring MVC的注解，Spring Web 默认使用了HttpMessageConverters, Spring Cloud 集成 Ribbon 和 Eureka 提供的负载均衡的HTTP客户端 Feign.
声明式REST客户端：Feign
先要启动eureka_register_service工程（注册中心）和biz-service-0工程（服务生产者）
创建一个maven工程eureka_feign_client
pom.xml
| 12345678910111213141516171819202122232425262728293031323334353637383940 | <parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>1.4.3.RELEASE</version><relativePath/> <!-- lookup parent from repository --></parent><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><java.version>1.8</java.version></properties><dependencies> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-feign</artifactId> </dependency> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-eureka</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>Brixton.SR5</version> <type>pom</type> <scope>import</scope></dependency> </dependencies></dependencyManagement> |
在应用主类中通过@EnableFeignClients注解开启Feign功能
启动文件FeignApplication.java
| 12345678910 | @SpringBootApplication@EnableDiscoveryClient@EnableFeignClientspublic class FeignApplication { public static void main(String[] args) { SpringApplication.run(FeignApplication.class, args); } } |
定义服务接口类UserClient.java
使用@FeignClient(“biz-service-0”)注解来绑定该接口对应biz-service-0服务
| 12345678910111213 | @FeignClient("biz-service-0")public interface UserClient { @RequestMapping(method = RequestMethod.GET, value = "/getuser") public User getuserinfo(); @RequestMapping(method = RequestMethod.GET, value = "/getuser") public String getuserinfostr(); @RequestMapping(method = RequestMethod.GET, value = "/info") public String info(); } |
在web层中调用上面定义的UserController，具体如下
| 1234567891011121314151617181920212223 | @RestControllerpublic class UserController { @Autowired UserClient userClient; @RequestMapping(value = "/getuserinfo", method = RequestMethod.GET) public User getuserinfo() { return userClient.getuserinfo(); } @RequestMapping(value = "/getuserinfostr", method = RequestMethod.GET) public String getuserinfostr() { return userClient.getuserinfostr(); } @RequestMapping(value = "/info", method = RequestMethod.GET) public String info() { return userClient.info(); } } |
application.properties配置变量
| 123 | spring.application.name=feign-consumerserver.port=8004eureka.client.serviceUrl.defaultZone=http://localhost:8000/eureka/ |
访问 http://127.0.0.1:8004/getuserinfo
总结：
其实通过Feign封装了HTTP调用服务方法，使得客户端像调用本地方法那样直接调用方法，类似Dubbo中暴露远程服务的方式，区别在于Dubbo是基于私有二进制协议，而Feign本质上还是个HTTP客户端
