Feign【入门】
feign简介:
feign是一种声明式,模板化的HTTP客户端,spring cloud对feign进行了增强,使其支持SpringMvc的相关注解,并整合了ribbon做负载均衡。在spring cloud中使用feign做HTTP远程服务请求,可以做到就像调用本地方法一样,完全感知不到是在调用远程方法,具体特性如下:
- 可插拔的注解支持,包括feign注解和Jax-rs注解、
- 支持可插拔的HTTP编码器和解码器、
- 支持hystrix和它的fallback、
- 支持ribbon负载均衡、
- 支持HTTP请求和响应的压缩、
1、创建feign-demo工程
1.1、工程依赖
<parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.3.RELEASE</version> <relativePath/> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> <spring-cloud.version>Finchley.RELEASE</spring-cloud.version> </properties> <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>
<dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!-- Spring Cloud OpenFeign的Starter的依赖 --> <dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-openfeign</artifactId> </dependency> </dependencies>
<build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build>
1.2、工程启动类:
import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.cloud.openfeign.EnableFeignClients; @SpringBootApplication @EnableFeignClients public class SpringCloudFeignApplication { public static void main(String[] args) { SpringApplication.run(SpringCloudFeignApplication.class, args); } }
可以看到启动类上加了 @EnableFeignClients 注解,意思是当该工程在启动的时候,会进行包扫描,扫描该启动类包以下,子包中所有带 @FeignClient 注解的类(包括启动类所在包),并进行处理。
1.3、编写相关代码
HelloFeignService接口:
import cn.springcloud.book.feign.config.HelloFeignServiceConfig; import org.springframework.cloud.openfeign.FeignClient; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; //https://api.caiyunapp.com/v2/TAkhjf8d1nlSlspN/121.6544,25.1552/forecast.json 彩云天气API @FeignClient(name = "caiyunapp", url = "https://api.caiyunapp.com/v2/TAkhjf8d1nlSlspN/121.6544,25.1552", configuration = HelloFeignServiceConfig.class) public interface HelloFeignService { @RequestMapping(value = "/forecast.json", method = RequestMethod.GET) String searchRepo(); }
如上所示,@FeignClient注解手动指定了URL,最终会根据指定的URL和@RequestMapping对应的方法转换成完整的请求地址。如下:https://api.caiyunapp.com/v2/TAkhjf8d1nlSlspN/121.6544,25.1552/forecast.json
HelloFeignServiceConfig配置类:
import feign.Logger; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; @Configuration public class HelloFeignServiceConfig { /** * Logger.Level 的具体级别如下: * NONE:不记录任何信息 * BASIC:仅记录请求方法、URL以及响应状态码和执行时间 * HEADERS:除了记录 BASIC级别的信息外,还会记录请求和响应的头信息 * FULL:记录所有请求与响应的明细,包括头信息、请求体、元数据 * * @return */ @Bean Logger.Level feignLoggerLevel() { return Logger.Level.FULL; } }
controller类:
import cn.springcloud.book.feign.service.HelloFeignService; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.ResponseEntity; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.RestController; @RestController public class HelloFeignController { @Autowired private HelloFeignService helloFeignService; // 服务消费者对位提供的服务 @GetMapping(value = "/search") public String searchGithubRepoByStr(@RequestParam("str") String queryStr) { return helloFeignService.searchRepo(queryStr); } }
如上所示,controller类中注入了上面编写的接口类,直接调用了相关方法。
2、启动工程
2.1、执行命令:
mvn spring-boot:run
2.2、访问:losthost:8080/search/
说明访问成功!