ClassCastException when trying to insert with Squeryl

问题

This may be due to my misunderstanding of how Squeryl works. My entity is defined as:

case class Wallet(userid: Int, amount: Long) 
    extends KeyedEntity[Int] with Optimistic {  
  def id = userid
}  

My table variable is defined as:

val walletTable = table[Wallet]("wallets")
on(walletTable) {
 w =>
   declare {
     w.userid is (primaryKey)
   }
}

Then I'm just calling a method to try to add money to the wallet:

val requestedWallet = wallet.copy(amount = wallet.amount + amount)
try {
  inTransaction {
    walletTable.update(requestedWallet)
  }

On the line where I call update, an exception is getting thrown: [ClassCastException: java.lang.Integer cannot be cast to org.squeryl.dsl.CompositeKey]

I'm not using composite keys at all, so this is very confusing. Does it have to do with the fact that my id field is not called "id", but instead "userid"?

回答1:

I get the same behavior when I try what you are doing. It seems that for some reason id can't be an alias unless it is a composite key (at least in 0.9.5). You can work around that and get the same result with something like this:

case class Wallet(@Column("userid") id: Int, amount: Long)
  extends KeyedEntity[Int] with Optimistic  {  

  def userid = id

}  

The column annotation will look to the database for the userid field, and id will be a val instead. You can then alias userid for consistency.

来源：https://stackoverflow.com/questions/13939922/classcastexception-when-trying-to-insert-with-squeryl