一、使用Feign

Feign 提供宣告式REST呼叫。一開始我們還在懊惱，dubbo都已經提供了配置式的服務呼叫了，為什麼SpringCloud沒有相應的解決方案？有SpringCloud提供了Feign宣告式事務，使用Feign有個非常大的好處就是，只要你屬性SpringMVC的annotation配置，Feign就沒有什麼學習成本。

事不宜遲，我們首先將Feign整合到我們的微服務當中：

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

之前的筆記中，使用者服務系統提供了二個介面，第一個介面是查詢使用者、第二個是新增使用者。以下我們就在商品服務中通過Feign整合兩個API

首先我們需要在配置類當中打上@EnableFeignClients 

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ProductsystemApplication {

然後我們建立一個UserFeignClient介面：

@FeignClient(name = "tony-mall-provider-user")
public interface 
 
UserFeignClient {

    @GetMapping("/user/getUserById/{id}")
    User getUserById(@PathVariable("id") int id);
@PutMapping("/user/add")
    User addUser(@RequestParam("username") String username, @RequestParam("password")String password,@RequestParam("balance") long balance);
}

或許你已經注意到，所有的操作跟我們SpringMVC中的annotation一模一樣。不過需要注意的是，方法的引數預設是使用@RequestBody進行交換的，所以如果我們希望使用普通的引數傳參，還需要打上SpringMVC的@RequestParam annotation。

之後在我們呼叫的service層或者是controller層 直接注入UserFeignClient。由於演示我就不劃分業務層和服務層了。

@RestController
public class ProductController {

    @Autowired
private ProductRepository productRepository;@Autowired
private UserFeignClient userFeignClient;
@GetMapping("/getProductByFeign/{productId}/userId/{userId}")
    public Map<String, Object> getProductByFeign(@PathVariable int productId, @PathVariable int userId) {
        Map<String, Object> map = new HashMap<>();
User user = this.userFeignClient.getUserById(userId);
Product product = this.productRepository.getByProductId(productId);
map.put("user", user);
map.put("product", product);
        return map;
}

}

二、Feign壓縮

feign.compression.request.mime-types=text/xml,application/xml,application/json
feign.compression.request.min-request-size=2024

三、Feign日誌

在配置類中配置Feign的日誌級別：

@Bean
public Logger.Level feignLoggerLevel(){
   return Logger.Level.FULL;
}

使用application.properties指定某個介面的日誌級別：

logging.level.com.tony.mall.rest.UserFeignClient=DEBUG

輸出的Feign請求日誌如下：

2017-07-14 15:58:34.044 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] ---> GET http://tony-mall-provider-user/user/getUserById/1 HTTP/1.1
2017-07-14 15:58:34.047 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] ---> END HTTP (0-byte body)
2017-07-14 15:58:34.173 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] <--- HTTP/1.1 200 (125ms)
2017-07-14 15:58:34.174 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] content-type: application/json;charset=UTF-8
2017-07-14 15:58:34.174 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] date: Fri, 14 Jul 2017 07:58:34 GMT
2017-07-14 15:58:34.174 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] transfer-encoding: chunked
2017-07-14 15:58:34.174 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] x-application-context: tony-mall-provider-user:8803
2017-07-14 15:58:34.174 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] 
2017-07-14 15:58:34.176 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] {"userId":1,"username":"TONY","userpwd":"TONYPWD","balance":1000000}
2017-07-14 15:58:34.176 DEBUG 12184 --- [nio-8802-exec-4] com.tony.mall.rest.UserFeignClient       : [UserFeignClient#getUserById] <--- END HTTP (68-byte body)