Golang中如何统一处理HTTP错误 设计中间件捕获路由错误

type HandlerFunc func(w http.ResponseWriter, r *http.Request) error

http.HandlerFunc

func ErrorMiddleware(next HandlerFunc) http.HandlerFunc {
    return func(w http.ResponseWriter, r *http.Request) {
        if err := next(w, r); err != nil {
            // 可根据错误类型做不同处理
            var apiError struct {
                Code    int    `json:"code"`
                Message string `json:"message"`
            }

            switch e := err.(type) {
            case *NotFoundError:
                apiError.Code = 404
                apiError.Message = e.Error()
            case *ValidationError:
                apiError.Code = 400
                apiError.Message = e.Error()
            default:
                apiError.Code = 500
                apiError.Message = "Internal server error"
            }

            w.Header().Set("Content-Type", "application/json")
            w.WriteHeader(apiError.Code)
            json.NewEncoder(w).Encode(apiError)
        }
    }
}

type NotFoundError struct{ Message string }
func (e *NotFoundError) Error() string { return e.Message }

type ValidationError struct{ Message string }
func (e *ValidationError) Error() string { return e.Message }

func GetUser(w http.ResponseWriter, r *http.Request) error {
    id := r.URL.Query().Get("id")
    if id == "" {
        return &ValidationError{Message: "missing user id"}
    }

    // 模拟用户不存在
    if id == "999" {
        return &NotFoundError{Message: "user not found"}
    }

    // 正常响应
    w.Header().Set("Content-Type", "application/json")
    json.NewEncoder(w).Encode(map[string]string{"id": id, "name": "Alice"})
    return nil
}

http.HandleFunc("/user", ErrorMiddleware(GetUser))
log.Println("Server starting on :8080")
log.Fatal(http.ListenAndServe(":8080", nil))