Examples of MementoTransaction

org.prevayler.util.memento.MementoTransaction

An atomic transaction to be executed on a PrevalentSystem. Any operation which changes the observable state of a PrevalentSystem must be encapsulated as a Command.

This command adds the capability to create mementos of objects before they get modified. In the event of a failure, these mementos are restored and the system is left in the state it was in before the command got executed.

The execution is split in four parts:

Find the objects: find all the objects needed for checking the precondition, creating the mementos and execution, and store them in transient fields;
Check the precondition: verify that it is safe to execute;
Create the mementos: create a memento for each object that is possibly going to be modified;
Execute: modify the objects.

@author Johan Stuyts @version 2.0


  protected void createMementos(MementoCollector collector) {
  }


  protected Account execute(MementoCollector collector) throws Exception {
    MementoTransaction command = new Withdrawal(sourceNumber, amount);
    command.execute(collector, bank);


    command = new Deposit(destinationNumber, amount);
    command.execute(collector, bank);


    return null;
  }


  public static void run() throws Exception {
    Account account1 = null, account2 = null;


    System.out.println("*** Creating account 1");
    MementoTransaction command = new AccountCreation("Owner 1");
    account1 = execute(command);


    System.out.println("*** Creating account 2");
    command = new AccountCreation("Owner 2");
    account2 = execute(command);

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Examples of MementoTransaction

Examples of org.prevayler.util.memento.MementoTransaction

Examples of org.prevayler.util.memento.MementoTransaction