> For the complete documentation index, see [llms.txt](https://jen-hsuan-hsieh.gitbook.io/asp-net/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jen-hsuan-hsieh.gitbook.io/asp-net/chapter3rest-api-design-development-and-management/33designing-rest-api/336walkthrough-implementation-of-error-handling-for-post-api.md). # 3.3.6.Walkthrough: Implementation of error handling for POST API * 如果POST失敗, 只回400是不夠的, 為了讓開發找更能addressing issue, Steps to improve POST error handling * 1.Steup the error codes and description for API specific errors * 2.Create the template for the error response body * 3.Code a utility function for creating the error response * 4.Implement the error handling code for POST /vacations * Send back status code for duplicate & vacation errors * 建議使用的status code * code 5000: unknown Error * code 6xxx: Any database error such as duplicate keys * code 7xxx: Validation error * 程式碼解析 * api/v1/vacation * 1.在POST方法中 * 1.建立了useError物件 * 2.在Response中設定Content-Type: "application/json" * 2.宣告[函數表達式](https://jenhsuan.gitbooks.io/javascript-node-js/content/chapter1/1236han-shu-chen-shu-ju-yu-han-shu-biao-shi-shi.html)processMongooseErrors: 回傳error物件 * 3.宣告[函數表達式](https://jenhsuan.gitbooks.io/javascript-node-js/content/chapter1/1236han-shu-chen-shu-ju-yu-han-shu-biao-shi-shi.html)processValidationErrors: 處理Validation Error ``` module.exports = function (router) { 'use strict'; // CREATE new vacation packages router.route(URI).post(function (req, res, next) { console.log("POST Vacations") //1. Get the data var doc = req.body; //2. Call the insert method db.save(doc, function (err, saved) { if (err) { // Creates the error response // EARLIER it was >>> res.status(400).send("err") var userError = processMongooseErrors(apiMessages.errors.API_MESSAGE_CREATE_FAILED, "POST", URI, err,{}); res.setHeader('content-type', 'application/json') res.status(400).send(userError) } else { res.send(saved) } }); }); } /** * Converts the Mongoose validation errors to API specific errors */ var processMongooseErrors = function (message, method, endpoint, err,payload) { var errorList = [] // Check for validation error if (err.name === 'ValidationError'){ errorList = processValidationErrors(err) } else if(err.code == 11000){ // it could be database error - 11000 is for duplicate key errorList.push(apiErrors.errors.PACKAGE_ALREADY_EXISTS) } else { var errUnknown = apiErrors.errors.UNKNOWN_ERROR errUnknown.payload = err errorList = [apiErrors.errors.UNKNOWN_ERROR] } return apiErrors.create(message, method, endpoint, errorList, payload) } /** * Converts Mongoose errors to API specific errors */ var processValidationErrors = function (err) { var errorList = [] // Check if there is an issue with the Num of Nights if (err.errors.numberOfNights) { if (err.errors.numberOfNights.kind === apiErrors.kinds.MIN_ERROR || err.errors.numberOfNights.kind === apiErrors.kinds.MAX_ERROR || err.errors.numberOfNights.kind === apiErrors.kinds.NUMBER_ERROR ) { errorList.push(apiErrors.errors.FORMAT_NUM_OF_NIGHTS) } } // Check if name of the package is missing if (err.errors.name) { if (err.errors.name.kind === apiErrors.kinds.REQUIRED) { errorList.push(apiErrors.errors.MISSING_PACKAGE_NAME) } } // Check if description of the package is missing if (err.errors.description) { if (err.errors.description.kind === apiErrors.kinds.REQUIRED) { errorList.push(apiErrors.errors.MISSING_PACKAGE_DESCRIPTION) } } return errorList; } ``` * util/error * 1.建立error list物件 * 2.create方法會回傳text:message, timestamp, method, endpoint, errors, payload ``` exports.errors = { // This is a catch all error // Ideally this should never be thrown UNKNOWN_ERROR : { code:5000, text:"Unknown error !!!", hints:["Please contact development team wit information on 'how to reproduce this error'. Thank you for your help and support."], info:"http://developer.acme.com/unknownerror" }, PACKAGE_ALREADY_EXISTS :{ code:6000, text:"Vacation package with the provided 'name' already exist", hints:["Please use PUT for update instead of POST"], info:"http://developer.acme.com/errors#6000" }, // All required/missing field errors start with number 7 MISSING_PACKAGE_NAME : { code:7001, text:"Required field vacation 'name' is missing", hints:["Please check that user has provided the non null value for 'name'"], info:"http://developer.acme.com/error#RequiredFields" }, MISSING_PACKAGE_DESCRIPTION : { code:7002, text:"Required field vacation 'description' is missing", hints:["Please check that user has provided the non null value for description"], info:"http://developer.acme.com/error#RequiredFields" } , MISSING_PACKAGE_NUM_OF_NIGHTS : { code:7003, text:"Required field vacation 'number of nights' is missing", hints:["Please check that user has provided a number (between 1 & 31)"], info:"http://developer.acme.com/error#RequiredFields" }, // All format errors begin with 8 FORMAT_NUM_OF_NIGHTS : { code:7004, text:"Number of nights MUST be a number (between 1 & 31)", hints:["Please check that user has provided a numeric value for 'number of nights'"], info:"http://developer.acme.com/error#RequiredFields" } } /** * Utility methods * Creates the error response body to be sent back to the caller */ exports.create = function(message,httpMethod,endpointInformation,errorList,receivedPayload){ return { // Meant for the developer text:message, timestamp:new Date(), // POST, GET .... method:httpMethod, // Endpoint information endpoint:endpointInformation, // An array of all errors errors : errorList, // OPTIONAL - Use only during development payload: receivedPayload } } // Mongoose validation error types exports.kinds = { REQUIRED:"required", NOT_VALID:"notvalid", NUMBER_ERROR:"Number", MIN_ERROR:"min", MAX_ERROR:"max", } ``` * 結果 ![](/files/-M4M0XCr7l9gYxlYKkLG)