声明式调用Feign

1、概述

Spring Cloud OpenFeign实现了声明式的http调用，并集成Ribbon,提供负载均衡的功能，整合 Hystrix,提供服务容错能力。

2、环境准备

order-service去调用product-service,

在product-service有一个Controller,order-service去调这个服务

@RestController
@RequestMapping("/api/v1/product")
public class ProductController {


    /**
     * 根据id查找商品详情
     * @param id
     * @return
     */
    @RequestMapping("find")
    public String findById(@RequestParam("id") int id){
        System.out.println("product id: " + id);
        return "iPhone X";

    }
}

现在搭建order-service

3、order-service

3.1、依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

3.2、配置文件

server:
  port: 8090


#指定注册中心地址
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:7001/eureka/

#服务的名称
spring:
  application:
    name: order-service

3.3、启动类

加上@EnableFeignClients 注解

@EnableFeignClients
@SpringBootApplication
public class OrderServiceApplication {

    public static void main(String[] args) {
        SpringApplication.run(OrderServiceApplication.class, args);
    }
}

3.4、ProductClient

@FeignClient(name = "product-service")
public interface ProductClient {

    @GetMapping("/api/v1/product/find")
    String findById(@RequestParam(value = "id") int id);
}

3.5、OrderController

@RestController
@RequestMapping("api/v1/order")
public class OrderController {

    @Autowired
    ProductClient productClient;

    @RequestMapping("save")
    public String save(@RequestParam("product_id") int productId){

        // 调用feign接口
        return productClient.findById(productId);
    }

}

3.6、测试

4、feign的默认配置

FeignClientProperties.java下的FeignClientConfiguration

public static class FeignClientConfiguration {
    // Feign 日志级别。默认为 NONE
    private Level loggerLevel;
    // 请求的连接超时时长，单位：毫秒。默认为 10 * 1000 毫秒
    private Integer connectTimeout;
    // 请求的读取超时时长，单位：毫秒。默认为 60 * 1000 毫秒
    private Integer readTimeout;
    // 重试策略。默认为不重试
    private Class<Retryer> retryer;
    private Class<ErrorDecoder> errorDecoder;
    private List<Class<RequestInterceptor>> requestInterceptors;
    private Boolean decode404;
    private Class<Decoder> decoder;
    private Class<Encoder> encoder;
    private Class<Contract> contract;
    private ExceptionPropagationPolicy exceptionPropagationPolicy;
    ...
}

自定义配置：如

feign:
  client:
    config:
      default:
        connectTimeout: 1000
        readTimeout: 1000

5、单独使用

如果服务的提供者和服务的调用者不在同一个注册中心

@FeignClient(name = "localhost", url="http://localhost:8081")  //name和url的host要相同
public interface ProductClient {

    @GetMapping("/api/v1/product/find")
    String findById(@RequestParam("id") int id);
}