In RESTful API…

HTTP = URL(URI) + HTTP method + Status Code

Showing here, popular status code example of response

Status Code in Layered Pattern

Controller

• http request, http response
• Handle verification, error, exception when data flows User → FrondEnd → BackEnd
• Most representative error : KEY_ERROR (400)
• When user input is wrong, most of them 400

Example

• Key Error : 400

  • If user didn’t input key value (email…)

    const { email, password } = req.body
    
    console.log(email)    // ''
    console.log(password) // 'myPassword''
    
    if (!email) {
        const err = new Error('KEY_ERROR')
        err.statusCode = 400;
        throw err
    }

• Read(Review / Return) value : 200

  const readCart = asyncErrorHandler(async (req, res) => {
    cartList = await cartService.readCart(req.userId);
    return res.status(200).json(cartList);
  });

• Delete : 204

  const deleteCart = asyncErrorHandler(async (req, res) => {
    const { cartId } = req.params;
  
    await cartService.deleteCart(cartId);
    return res.status(204).json({
      message: "DELETE_CART_SUCCESS",
    });
  });

Service

• Business logic (rule)
• Exceptions and errors intended by developer (follows business logic (rule))
• Error can occur on-
  • the layer under service layer
  • service module that called directly on service layer
• User request error : 400
• BackEnd(DB) error : 500

Example

• Conflict : 409

  • Response status code indicates a request conflict with the current state of the target resource.

  • If user password doesn’t follow password creating rule

    const signUp = async (name, email, password, profileImage) => {
        const pwValidation = new RegExp(
          '^(?=.*[A-Za-z])(?=.*[0-9])(?=.*[!@#$%^&*])(?=.{8,20})'
        );
        if (!pwValidation.test(password)) {
            const err = new Error('PASSWORD_IS_NOT_VALID');
            err.statusCode = 409;
            throw err;
        }

Dao

• Database Error
• Other external systems are interlocked (different from Node, Express)
• At this point, asynchronous calls are mainly used. ⇒ We should use suitable method for asynchronous error handling
  

Example

• BackEnd(DB) error : 500

  const createUser = async ( name, email, password, profileImage ) => {
      try {
          return await myDataSource.query(
          `INSERT INTO users(
              name,
              email,
              profile_image,
              password
          ) VALUES (?, ?, ?, ?);
          `,
          [ name, email, password, profileImage ]
        );
      }
      catch (err) {
      const err = new Error('INVALID_DATA_INPUT');
      err.statusCode = 500;
      throw err;
      }