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Feign是一个声明式WebService客户端,使用方法时定义一个接口并在上面添加注解即可。Feign支持可拔插式的编码器和解码器。Spring Cloud对Feign进行了封装,使其支持SpringMVC和HttpMessageConverters。Feign可以与Eureka和Ribbon组合使用以支持负载均衡。
Feign源码
使用案例
- 新建Feign模块,加入依赖(其实跟80消费者差不多,主要是多了Feign依赖)
<dependencies>
<dependency>
<groupId>com.XXX</groupId>
<artifactId>microservice-api</artifactId>
<version>${project.version}</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<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.cloud</groupId>
<artifactId>spring-cloud-starter-ribbon</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-config</artifactId>
</dependency>
<!--热部署-->
<dependency>
<groupId>org.springframework</groupId>
<artifactId>springloaded</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-devtools</artifactId>
</dependency>
</dependencies>
- 因为Feign开发其实是面向接口编程,所以Feign接口可以放在api模块中供各模块使用,所以要在api模块中添加Feign依赖
- 在api中编写接口,接口上添加@FeignClient注解,并通过value指定作用的微服务名
@FeignClient(value = "MICROSERVICECLOUD-DEPT")
public interface DeptClientService {
@PostMapping("/dept")
public boolean addDept(Dept dept);
@GetMapping("/dept")
public List<Dept> findAll();
@GetMapping("/dept/{id}")
public Dept findById(@PathVariable("id")Integer id);
}
- 在Feign模块中编写Controller,并注入FeignClient接口,直接调用service接口中的方法即可(因为声明Feign接口时已经指定过微服务,所以访问时会正确地找到微服务)
@RestController
@RequestMapping("/consumer")
public class ConsumerDeptController {
@Autowired
private DeptClientService service;
@PostMapping("/dept")
public boolean addDept(Dept dept){
return service.addDept(dept);
}
@GetMapping("/dept")
public List<Dept> findAll(){
return service.findAll();
}
@GetMapping("/dept/{id}")
public Dept findById(@PathVariable("id")Integer id){
return service.findById(id);
}
}
- 修改Feign模块的主启动类,加入@EnableFeignClients注解和@ComponentScan注解(主要是扫描api中声明的接口)
@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients(basePackages = {"com.XXX"})
@ComponentScan("com.XXX")
public class Consumer80Feign_APP {
public static void main(String[] args) {
SpringApplication.run(Consumer80Feign_APP.class,args);
}
}
- 启动后访问,即会按照轮询的方式调用provider集群
总结
- Feign通过接口方法调用REST服务,在Eureka中查找对应的服务
- Feign集成了Ribbon技术,所以也支持负载均衡(轮询)