Error Handling

Error handling is an indispensable part of services. Normally, if a http status code is not in the 2xx series, it can be considered as an http request error.

The error message of a response is returned in plain text. In addition, some other types of errors were defined and retured. Common practice is to pass two fields: code and msg that are used to describe the business processing results, and the response body can be formatted as json.

Business error response format#

  • Normal business processing

    "code": 0,
    "msg": "successful",
    "data": {
  • An error occurred in the business processing

    "code": 10001,
    "msg": "something wrong"

Login of the user APIs#

Previously, when we handled the login logic if the username did not exist, an error was directly returned. Let's try the login and pass a username that does not exist to see the result.

curl -X POST \ \
-H 'content-type: application/json' \
-d '{
HTTP/1.1 400 Bad Request
Content-Type: text/plain; charset=utf-8
X-Content-Type-Options: nosniff
Date: Tue, 09 Feb 2021 06:38:42 GMT
Content-Length: 19
Username does not exist

Next we will return it in json format

Custom error#

  • First add a baseerror.go file in common and fill in the code

    $ cd common
    $ mkdir errorx&&cd errorx
    $ vim baseerror.go
    package errorx
    const defaultCode = 1001
    type CodeError struct {
    Code int `json:"code"`
    Msg string `json:"msg"`
    type CodeErrorResponse struct {
    Code int `json:"code"`
    Msg string `json:"msg"`
    func NewCodeError(code int, msg string) error {
    return &CodeError{Code: code, Msg: msg}
    func NewDefaultError(msg string) error {
    return NewCodeError(defaultCode, msg)
    func (e *CodeError) Error() string {
    return e.Msg
    func (e *CodeError) Data() *CodeErrorResponse {
    return &CodeErrorResponse{
    Code: e.Code,
    Msg: e.Msg,
  • Replace errors in login logic with CodeError custom errors

    if len(strings.TrimSpace(req.Username)) == 0 || len(strings.TrimSpace(req.Password)) == 0 {
    return nil, errorx.NewDefaultError("Invalid parameter")
    userInfo, err := l.svcCtx.UserModel.FindOneByNumber(req.Username)
    switch err {
    case nil:
    case model.ErrNotFound:
    return nil, errorx.NewDefaultError("Username does not exist")
    return nil, err
    if userInfo.Password != req.Password {
    return nil, errorx.NewDefaultError("User password is incorrect")
    now := time.Now().Unix()
    accessExpire := l.svcCtx.Config.Auth.AccessExpire
    jwtToken, err := l.getJwtToken(l.svcCtx.Config.Auth.AccessSecret, now, l.svcCtx.Config.Auth.AccessExpire, userInfo.Id)
    if err != nil {
    return nil, err
    return &types.LoginReply{
    Id: userInfo.Id,
    Name: userInfo.Name,
    Gender: userInfo.Gender,
    AccessToken: jwtToken,
    AccessExpire: now + accessExpire,
    RefreshAfter: now + accessExpire/2,
    }, nil
  • Use custom errors

    $ vim service/user/api/user.go
    func main() {
    var c config.Config
    conf.MustLoad(*configFile, &c)
    ctx := svc.NewServiceContext(c)
    server := rest.MustNewServer(c.RestConf)
    defer server.Stop()
    handler.RegisterHandlers(server, ctx)
    // Custom error
    httpx.SetErrorHandler(func(err error) (int, interface{}) {
    switch e := err.(type) {
    case *errorx.CodeError:
    return http.StatusOK, e.Data()
    return http.StatusInternalServerError, nil
    fmt.Printf("Starting server at %s:%d...\n", c.Host, c.Port)
  • Restart service verification

    $ curl -i -X POST \ \
    -H 'content-type: application/json' \
    -d '{
    HTTP/1.1 200 OK
    Content-Type: application/json
    Date: Tue, 09 Feb 2021 06:47:29 GMT
    Content-Length: 40
    {"code":1001,"msg":"Username does not exist"}
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