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Spring Cloud : OpenFeign(远程调用)

java 2025/5/12 13:12:51

RestTemplate虽然比直接用HTTPClient简单的多，但是还是存在着许多的问题，比如url拼接麻烦，容易出错，并且可读性很差

    public OrderDetail selectOrderById(Integer orderId){OrderDetail orderDetail = orderMapper.selectOrderById(orderId);String url="http://product-service/product/"+orderDetail.getProductId();ProductDetail productDetail = restTemplate.getForObject(url, ProductDetail.class);orderDetail.setProductDetail(productDetail);return orderDetail;}

OpenFeign

微服务之间的通信，通常有RPC和HTTP，在SpringCloud中默认使用HTTP来进行微服务的通信，最常用的两种形式：RestTemplate和OpenFeign

OpenFeign是⼀个声明式的WebService客⼾端.它让微服务之间的调⽤变得更简单,类似controller 调⽤service, 只需要创建⼀个接⼝，然后添加注解即可使⽤OpenFeign

OpenFeign的使用

引入依赖

       <dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency>

添加注解@EnableFeignClients

用来开启OpenFeign的功能

@EnableFeignClients
@SpringBootApplication
@MapperScan("org.example1.mapper")
public class OrderServiceApplication {public static void main(String[] args) {SpringApplication.run(OrderServiceApplication.class,args);}
}

写一个关于OpenFeign的客⼾端

用SpringMvc的注解进行调用

@FeignClient(value = "product-service", path = "/product")
public interface ProductApi {@RequestMapping("/{productId}")ProductDetail selectProductById(@RequestParam("productId") Integer productId);@RequestMapping("/p1")String p1(@RequestParam("id") Integer id);@RequestMapping("/p2")String p2(@RequestParam("id") Integer id,@RequestParam("name") String name);@RequestMapping("/p3")String p3(@SpringQueryMap ProductDetail productDetail);@RequestMapping("/p4")String p4(@RequestBody ProductDetail productDetail);
}

远程调用

@Service
public class OrderService {@Autowiredprivate OrderMapper orderMapper;@Autowiredprivate ProductApi productApi;public OrderDetail selectOrderById(Integer orderId){OrderDetail orderDetail = orderMapper.selectOrderById(orderId);
ProductDetail.class);ProductDetail productDetail = productApi.selectProductById(orderDetail.getProductId());orderDetail.setProductDetail(productDetail);return orderDetail;}
}

OpenFeign关于参数的传递

包括一个参数，两个参数，传递对象，传递Json

首先我们在product-service中提供几个接口方法

@RestController
@RequestMapping("/product")
public class ProductController {@Autowiredprivate ProductService productService;@RequestMapping("p1")private String p1(Integer id){return "参数传递："+id;}@RequestMapping("p2")private String p2(Integer id,String name){return "参数传递,id："+id+"name"+name;}@RequestMapping("p3")private String p3(ProductDetail productDetail){return "传递对象"+productDetail;}@RequestMapping("p4")private String p4(@RequestBody ProductDetail productDetail){return "接受Json对象"+productDetail;}}

在Feign客户端

@FeignClient(value = "product-service", path = "/product")
public interface ProductApi {@RequestMapping("/p1")String p1(@RequestParam("id") Integer id);@RequestMapping("/p2")String p2(@RequestParam("id") Integer id,@RequestParam("name") String name);@RequestMapping("/p3")String p3(@SpringQueryMap ProductDetail productDetail);@RequestMapping("/p4")String p4(@RequestBody ProductDetail productDetail);
}

最后通过order-service服务调用

@RequestMapping("/feign")
@RestController
public class FeignController {@Autowiredprivate ProductApi productApi;@RequestMapping("/o1")public String o1(Integer id){return productApi.p1(id);}@RequestMapping("/o2")public String o2(Integer id,String name){return productApi.p2(id,name);}@RequestMapping("/o3")public ProductDetail o3(){ProductDetail productDetail=new ProductDetail();productApi.p3(productDetail);productDetail.setId(1);productDetail.setProductName("zhangsan");return productDetail;}@RequestMapping("/o4")public ProductDetail o4(){ProductDetail productDetail=new ProductDetail();productApi.p3(productDetail);productDetail.setId(1);productDetail.setProductName("zhangsan");return productDetail;}}

我们可以来测试一下

传递一个参数的

传递两个参数的

传递对象的

传递Json对象的

Feign 继承⽅式

Feign支持继承的方式，我们可以把一些常见的操作封装到接口中

创建一个新的服务product-api

将Feign客户端写在这个服务中，这样在调用的时候就不用再重写了

将Feign继承product-api

@FeignClient(value = "product-service", path = "/product")
public interface ProductApi extends org.example.ProductApi {}

注：在product-api服务中记得写入依赖

        <dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</artifactId></dependency>

在写好product-api服务后，将其install到本地

然后再重新测试一下

Feign 抽取⽅式

就是直接将Feign写成一个独立的模块，将product-service中的product-api接口删除

然后重新启动程序，发现报错了

我们需要再启动类中添加

@EnableFeignClients(clients = {ProductApi.class})
@SpringBootApplication
@MapperScan("org.example1.mapper")
public class OrderServiceApplication {public static void main(String[] args) {SpringApplication.run(OrderServiceApplication.class,args);}
}

标明需要加载的Feign客⼾端