Preprocessor

所有拦截器的Before()方法执行之后，向后端service发送请求之前，会执行Preprocessor。

Preprocessor可以用来执行一些某个API特有的逻辑，比如，参数校验，设置默认值，做类型转换，记录log等等。

下面的例子中，对参数’num’的值做了一些校验:

func RegisterComponents(s *turbo.GrpcServer) {
+       s.RegisterComponent("preEatApple", preEatApple)
}

+var preEatApple turbo.Preprocessor = func (resp http.ResponseWriter, req *http.Request) error {
+      num,err := strconv.Atoi(req.Form["num"][0])
+      if err!=nil {
+              resp.Write([]byte("'num' is not numberic"))
+              return errors.New("invalid num")
+      }
+      if num > 5 {
+              resp.Write([]byte("Too many apples!"))
+              return errors.New("Too many apples")
+      }
+      return nil
+}

编辑 “yourservice/service.yaml”:

+preprocessor:
+  - GET /eat_apple/{num:[0-9]+} preEatApple

重启服务并测试:

$ curl -w "\n" "http://localhost:8081/eat_apple/5"
message:"Good taste! Apple num=5"
$ curl -w "\n" "http://localhost:8081/eat_apple/6"
Too many apples!