错误：行已被另一个事务更新或删除（或未保存值映射不正确）

Question

我有以下动作：

def index() {

  User.withNewTransaction {

   def user = User.get(params.userId)
   user.name = "test"
   user.save(flush:true)

   response.setContentType("image/gif")
   response.outputStream << PIXEL_BYTES_OF_A_GIF_IMAGE
   return
  }
}

运行时，有时会报如下错误：

Message
Executing action [index] of controller [test.TestController] caused exception: Runtime error executing action
Caused by
Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [test.User#1]

为什么会发生这个错误？我认为withNewTransaction 会阻止这个错误。

Answer 1

您可以使用pessimistic locking

用途：

User user = User.lock(params.userId)

或

User user = User.findById(params.userId, [lock: true])