hirondelle.web4j.database
Class DuplicateException

Object
  Throwable
      Exception
          ServletException
              hirondelle.web4j.model.AppException
                  hirondelle.web4j.database.DAOException
                      hirondelle.web4j.database.DuplicateException

All Implemented Interfaces:

MessageList, Serializable

public final class DuplicateException
extends DAOException

Thrown when a uniqueness problem occurs in the datastore during an ADD or CHANGE operation.

This type of exception is singled out since it is so common. It allows Actions to catch this specific kind of exception.

For relational databases, this exception should be thrown for INSERT and UPDATE operations which may violate a UNIQUE or PRIMARY KEY constraint, or similar item. Db, DbTx, and TxTemplate will throw a DuplicateException exception for SQLExceptions having an error code matching the ErrorCodeForDuplicateKey configured in web.xml. See web.xml for more information.

Typical Use Case

Here, an Action is calling a DAO method which may throw a DuplicateException:

private void addSomething throws DAOException {
  //this try..catch is needed only if the operation 
  //can have a duplicate problem
  try {
    dao.addSomething();
  }
  catch (DuplicateException ex){
    addError("Cannot add. That item already exists.");
  }
}

Note that if the operation cannot have a duplicate problem, then the Action should not attempt to catch DuplicateException.

Here is the DAO operation which may have a duplicate problem.

//It is highly recommended, but optional, to declare 
//DuplicateException in this method header, to bring 
//it to the attention of the caller
public addSomething() throws DAOException, DuplicateException {
  //...elided
}

Again, if the operation cannot have a duplicate problem, then the DAO should not declare a DuplicateException in its throws clause.

The Db.add(SqlId, Object[]) and Db.edit(SqlId, Object[]) methods can throw a DuplicateException.

See Also:

Serialized Form

Constructor Summary

DuplicateException(String aMessage, Throwable aRootCause)
Constructor.

Method Summary

Methods inherited from class hirondelle.web4j.model.AppException

add, add, add, getMessages, isEmpty, isNotEmpty, toString

Methods inherited from class ServletException

getRootCause

Methods inherited from class Throwable

fillInStackTrace, getCause, getLocalizedMessage, getMessage, getStackTrace, initCause, printStackTrace, printStackTrace, printStackTrace, setStackTrace

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

DuplicateException

public DuplicateException(String aMessage,
                          Throwable aRootCause)

Constructor.

Arguments are passed to DAOException.DAOException(String, Throwable).