How can i do a Transactional method in Liferay 7.3?

Question

I create a scheduler that in the same transaction delete rows in DB and insert new rows after delete. But if the adding of rows fails, I lost my data because the delete was correctly. How I can delete and add with the same transaction to avoid losing data in case of errors? I want to do a delete and two different adds in the same table.

Answer 1

There are three cases:

1. If your code were everything starts is in a method a LocalServiceImpl class generated by service builder:

   • Liferay automatically creates a transaction that begins in the first method called in the first LocalServiceImpl and is propagated in the internal calls that that method does to the methods other LocalServiceImpl classes.
   • So the idea is to have a entry point in a LocalServiceImpl method where Liferay will automatically start the transaction, and from that method, call the other LocalServiceImpl methods that must be executed in the same transaction.
   • Note: by default only the methods that change data (add, update, delete) are creating a new transaction.

2. If your code is in a MVCActionCommand, you can use the BaseTransactionalMVCActionCommand as the parent class and implement your code in the doTransactionalCommand method.

   • Your code will be wrapped in a new transaction
   • For more information see: https://github.com/liferay/liferay-portal/blob/master/portal-kernel/src/com/liferay/portal/kernel/portlet/bridges/mvc/BaseTransactionalMVCActionCommand.java

3. If your code is outside of the LocalServiceImpl classes, you can always manually create a transaction using TransactionInvokerUtil:

    import com.liferay.portal.kernel.transaction.*;
    import com.liferay.portal.kernel.service.*;
    import java.util.concurrent.*;
   
    private _invokeTransactionally(Callable callable)
        throws Throwable {
   
        Class<?>[] rollbackForClasses = new Class<?>[1];
   
        rollbackForClasses[0]=Exception.class;
   
        try {
            TransactionInvokerUtil.invoke(
                TransactionConfig.Factory.create(
                    Propagation.REQUIRED, rollbackForClasses), callable);
        }
        catch(Exception e) {
             // handle the exception
        }
    }
   
    Callable callable = new Callable<Void>() {
        Void call() throws Exception {
             // here insert your code
   
             return null;
        }
    }
   

   • Your code should go inside the Callable class.
   • To execute it: _invokeTransactionally(callable);