Git源碼: https://github.com/chenhang666/SpringCloud
1、概述
官方文檔:http://projects.spring.io/spring-cloud/spring-cloud.html#spring-cloud-feign
Feign是一個聲明式WebService客戶端。使用Feign能讓編寫Web Service客戶端更加簡單,它的使用方法是定義一個藉口,然後在上面添加註解,同時也支持JAX-RS標準的註解。Feign也支持可拔插式的編碼器和解碼器。Spring Cloud對Feign進行了封裝使其支持了Spring MVC標準註解和HttpMessageConverters。Feign可以與Eureka和Ribbon組合使用以支持負載均衡。
一句話概括:Feign是一個聲明式的Web服務客戶端,使得編寫Web服務客戶端變得非常容易,只需要創建一個接口,然後在上面添加註釋即可。
2、實現Feign
公共模塊新增接口
導入Maven依賴
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
import java.util.List;
import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import com.chen.springcloud.entity.Dept;
@FeignClient(value="MICROSERVICECLOUD-DEPT")
public interface DeptClientService {
@RequestMapping(value="/dept/get/{id}",method=RequestMethod.GET)
public Dept get(@PathVariable("id") long id);
@RequestMapping(value="/dept/list",method=RequestMethod.GET)
public List<Dept> list();
@RequestMapping(value="/dept/add",method=RequestMethod.POST)
public boolean add(Dept dept);
}
微服務項目創建Controller
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.chen.springcloud.entity.Dept;
import com.chen.springcloud.service.DeptClientService;
@RestController
public class DeptController_Consumer {
@Autowired
private DeptClientService service;
@RequestMapping(value="/consumer/dept/get/{id}")
public Dept get(@PathVariable("id") long id) {
return this.service.get(id);
}
@RequestMapping(value="/consumer/dept/list")
public List<Dept> list(){
return this.service.list();
}
@RequestMapping(value="/consumer/dept/add")
public Object add(Dept dept) {
return this.service.add(dept);
}
}
微服務項目主啓動類增加註釋
@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients(basePackages= {"com.chen.springcloud"})
@ComponentScan("com.chen.springcloud")
public class DeptConsumer80_Feign_App {
public static void main(String[] args) {
SpringApplication.run(DeptConsumer80_Feign_App.class, args);
}
}
Feign項目即可搭建成功,默認策略爲輪詢。
3、修改訪問策略
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;
import com.netflix.loadbalancer.IRule;
import com.netflix.loadbalancer.RandomRule;
@Configuration //等同於spring applicationContext.xml
public class ConfigBean {
@Bean
@LoadBalanced //自帶負載均衡 默認輪詢
public RestTemplate geRestTemplate() {
return new RestTemplate();
}
//feign也會生效
@Bean
public IRule myRule() {
return new RandomRule();
//return new RetryRule();
}
}
現封裝好的策略可參考:Ribbon訪問策略
feign定義服務綁定接口且以聲明式的方法,實現了服務調用,Feign直接找到服務接口,由於在進行服務調用的時候融合了Ribbon技術。