如何解决标头已经写好了想要用500覆盖状态码200
这是我的gorilla-websocket网络套接字处理程序：
func wshandler(w http.ResponseWriter,r *http.Request) {
wsupgrader.CheckOrigin = func(r *http.Request) bool {
return true
}
c,err := wsupgrader.Upgrade(w,r,nil)
if err != nil {
fmt.Println(err)
return
}
for {
var m WebsocketGeneralClientMessage
err := c.ReadJSON(&m)
if err != nil {
log.Println(err)
break
}
switch m.Type {
case "register":
err := Register(c,m)
if err != nil {
log.Println(err)
}
}
}
}
根据type，我想对不同类型的消息做出不同的响应。我只有register类型。由于某些原因，Register函数给我以下错误：
Headers were already written. Wanted to override status code 200 with 500
func Register(c *websocket.Conn,m WebsocketGeneralClientMessage) error {
var d RegisterData
json.Unmarshal(m.Data,&d)
if len(d.Email) < 6 || len(d.Email) > 64 {
_error := "The email length must be between 6 and 64 characters"
c.WriteJSON(WebsocketGeneralServerMessage{Type: "register",Status: "error",Data: map[string]interface{}{"text": _error}})
return errors.New(_error)
}
if len(d.Password) < 6 || len(d.Password) > 32 {
_error := "The password length must be between 6 and 64 characters"
c.WriteJSON(WebsocketGeneralServerMessage{Type: "register",Data: map[string]interface{}{"text": "The password length must be between 6 and 64 characters"}})
return errors.New(_error)
}
err := checkmail.ValidateFormat(d.Email)
if err != nil {
_error := "The email format is not correct"
c.WriteJSON(WebsocketGeneralServerMessage{Type: "register",Data: map[string]interface{}{"text": _error}})
return errors.New(_error)
}
var rawUUID pgtype.UUID
var exists bool
err = Pool.QueryRow(context.Background(),`SELECT EXISTS(SELECT "email" FROM "account" WHERE "email"=$1)`,d.Email).Scan(&exists)
if err != nil {
_error := "An error occured while creating the account. Please send a message in #bugs at our Discord."
c.WriteJSON(WebsocketGeneralServerMessage{Type: "register",Data: map[string]interface{}{"text": _error}})
return errors.New(_error)
}
if exists {
_error := "An error occured while creating the account. Please send a message in #bugs at our Discord."
c.WriteJSON(WebsocketGeneralServerMessage{Type: "register",Data: map[string]interface{}{"text": _error}})
return errors.New(_error)
}
err = Pool.QueryRow(context.Background(),`INSERT INTO "account" ("email","password") VALUES($1,$2) RETURNING "uuid"`,d.Email,d.Password).Scan(&rawUUID)
if err != nil {
_error := "An error occured while creating the account. Please send a message in #bugs at our Discord."
c.WriteJSON(WebsocketGeneralServerMessage{Type: "register",Data: map[string]interface{}{"text": _error}})
return errors.New(_error)
}
uuid,err := rawUUID.Value()
if err != nil {
_error := "An error occured while saving the account to the database"
c.WriteJSON(WebsocketGeneralServerMessage{Type: "register",Data: map[string]interface{}{"text": _error}})
return errors.New(_error)
}
c.WriteJSON(WebsocketGeneralServerMessage{Type: "register",Status: "success",Data: map[string]interface{}{"uuid": uuid}})
return nil
}
我知道问题出在var exists bool之后的函数的后半部分，因为我删除了该部分，并且程序未给出错误。可能是什么问题？显然出现错误是因为我应该覆盖响应，但是每个c.WriterJSON都以return结尾，因此不应覆盖任何响应。
这是完整的错误：
2020/09/21 13:58:01 [Recovery] 2020/09/21 - 13:58:01 panic recovered:
GET /ws HTTP/1.1
Host: 192.168.0.41
Accept-Encoding: gzip
Connection: Upgrade
Origin: http://192.168.0.41
Sec-Websocket-Key: 9E7mNgJ4qH4VsbWDJuEaWQ==
Sec-Websocket-Version: 13
Upgrade: websocket
User-Agent: okhttp/3.14.4
runtime error: invalid memory address or nil pointer dereference
/usr/local/Cellar/go/1.15/libexec/src/runtime/panic.go:212 (0x104c992)
panicmem: panic(memoryError)
/usr/local/Cellar/go/1.15/libexec/src/runtime/signal_unix.go:720 (0x104c812)
sigpanic: panicmem()
/Users/virtumonde/go/pkg/mod/github.com/jackc/pgx/v4@v4.8.1/pgxpool/pool.go:355 (0x14c21ba)
(*Pool).Acquire: res,err := p.p.Acquire(ctx)
/Users/virtumonde/go/pkg/mod/github.com/jackc/pgx/v4@v4.8.1/pgxpool/pool.go:419 (0x14c2459)
(*Pool).QueryRow: c,err := p.Acquire(ctx)
/Users/virtumonde/Desktop/dev/terminus/terminus-server/ws_routes.go:46 (0x14cfa0b)
Register: err = Pool.QueryRow(context.Background(),d.Email).Scan(&exists)
/Users/virtumonde/Desktop/dev/terminus/terminus-server/ws.go:34 (0x14cf3e4)
wshandler: err := Register(c,m)
/Users/virtumonde/Desktop/dev/terminus/terminus-server/main.go:44 (0x14d07ea)
main.func1: wshandler(c.Writer,c.Request)
/Users/virtumonde/go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/context.go:161 (0x13a5eba)
(*Context).Next: c.handlers[c.index](c)
/Users/virtumonde/go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/recovery.go:83 (0x13b1cc4)
RecoveryWithWriter.func1: c.Next()
/Users/virtumonde/go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/context.go:161 (0x13a5eba)
(*Context).Next: c.handlers[c.index](c)
/Users/virtumonde/go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/logger.go:241 (0x13b0dc4)
LoggerWithConfig.func1: c.Next()
/Users/virtumonde/go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/context.go:161 (0x13a5eba)
(*Context).Next: c.handlers[c.index](c)
/Users/virtumonde/go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/gin.go:409 (0x13a8c79)
(*Engine).handleHTTPRequest: c.Next()
/Users/virtumonde/go/pkg/mod/github.com/gin-gonic/gin@v1.6.3/gin.go:367 (0x13a84ec)
(*Engine).ServeHTTP: engine.handleHTTPRequest(c)
/usr/local/Cellar/go/1.15/libexec/src/net/http/server.go:2843 (0x12676a2)
serverHandler.ServeHTTP: handler.ServeHTTP(rw,req)
/usr/local/Cellar/go/1.15/libexec/src/net/http/server.go:1925 (0x1263c6c)
(*conn).serve: serverHandler{c.server}.ServeHTTP(w,w.req)
/usr/local/Cellar/go/1.15/libexec/src/runtime/asm_amd64.s:1374 (0x106bb60)
goexit: BYTE $0x90 // NOP
解决方法
我发现了问题。我的Pool变量（用于连接到我的Postgres数据库）
var Pool *pgxpool.Pool
在初始化时被另一个局部变量所遮盖。
Pool,err := pgxpool.Connect(context.Background(),"postgres://postgres:@localhost:5432/database")
所以我将初始化更改为
var err error
Pool,err = pgxpool.Connect(context.Background(),"postgres://postgres:@localhost:5432/database")
显然，因此，数据库代码执行了不止一次。
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