diff --git a/controller/abstract.go b/controller/abstract.go
new file mode 100644
index 0000000..749244e
--- /dev/null
+++ b/controller/abstract.go
@@ -0,0 +1,20 @@
+package controller
+
+import (
+	"electricity_bill_calc/exceptions"
+	"electricity_bill_calc/model"
+
+	"github.com/gin-gonic/gin"
+)
+
+func _retreiveSession(c *gin.Context) (*model.Session, error) {
+	session, exists := c.Get("session")
+	if !exists {
+		return nil, exceptions.NewUnauthorizedError("用户会话不存在")
+	}
+	userSession, ok := session.(*model.Session)
+	if !ok {
+		return nil, exceptions.NewUnauthorizedError("用户会话格式不正确，需要重新登录")
+	}
+	return userSession, nil
+}
diff --git a/controller/maintenance_fee.go b/controller/maintenance_fee.go
index 5621d56..0e06e22 100644
--- a/controller/maintenance_fee.go
+++ b/controller/maintenance_fee.go
@@ -29,14 +29,9 @@ func InitializeMaintenanceFeeController(router *gin.Engine) {
 
 func listMaintenanceFees(c *gin.Context) {
 	result := response.NewResult(c)
-	session, exists := c.Get("session")
-	if !exists {
-		result.Error(http.StatusUnauthorized, "用户会话无效。")
-		return
-	}
-	userSession, ok := session.(*model.Session)
-	if !ok {
-		result.Failure(http.StatusInternalServerError, "内部缓存错误，需要重新登录。")
+	userSession, err := _retreiveSession(c)
+	if err != nil {
+		result.Failure(http.StatusInternalServerError, err.Error())
 		return
 	}
 	requestPark := c.DefaultQuery("park", "")
@@ -82,14 +77,9 @@ func createMaintenanceFeeRecord(c *gin.Context) {
 	result := response.NewResult(c)
 	formData := new(_FeeCreationFormData)
 	c.BindJSON(formData)
-	session, exists := c.Get("session")
-	if !exists {
-		result.Error(http.StatusUnauthorized, "用户会话无效。")
-		return
-	}
-	userSession, ok := session.(*model.Session)
-	if !ok {
-		result.Failure(http.StatusInternalServerError, "内部缓存错误，需要重新登录。")
+	userSession, err := _retreiveSession(c)
+	if err != nil {
+		result.Failure(http.StatusInternalServerError, err.Error())
 		return
 	}
 	sure, err := service.ParkService.EnsurePark(userSession.Uid, formData.ParkId)
diff --git a/exceptions/auth.go b/exceptions/auth.go
index d3728b8..e452ceb 100644
--- a/exceptions/auth.go
+++ b/exceptions/auth.go
@@ -19,3 +19,17 @@ func NewAuthenticationError(code int16, msg string) *AuthenticationError {
 func (e AuthenticationError) Error() string {
 	return fmt.Sprintf("[%d]%s", e.Code, e.Message)
 }
+
+type UnauthorizedError struct {
+	Message string
+}
+
+func NewUnauthorizedError(msg string) *UnauthorizedError {
+	return &UnauthorizedError{
+		Message: msg,
+	}
+}
+
+func (e UnauthorizedError) Error() string {
+	return fmt.Sprintf("Unauthorized: %s", e.Message)
+}