org.neo4j.graphdb
Interface Transaction

All Known Implementing Classes:

PlaceboTransaction, TopLevelTransaction

public interface Transaction

A programmatically handled transaction. All modifying operations that work with the node space must be wrapped in a transaction. Transactions are thread confined. Transactions can either be handled programmatically, through this interface, or by a container through the Java Transaction API (JTA). The Transaction interface makes handling programmatic transactions easier than using JTA programmatically. Here's the idiomatic use of programmatic transactions in Neo4j:

 
 Transaction tx = graphDb.beginTx();
 try
 {
        ... // any operation that works with the node space
     tx.success();
 }
 finally
 {
     tx.finish();
 }
 
 

Let's walk through this example line by line. First we retrieve a Transaction object by invoking the GraphDatabaseService.beginTx() factory method. This creates a new Transaction instance which has internal state to keep track of whether the current transaction is successful. Then we wrap all operations that work with the node space in a try-finally block. At the end of the block, we invoke the tx.success() method to indicate that the transaction is successful. As we exit the block, the finally clause will kick in and tx.finish will commit the transaction if the internal state indicates success or else mark it for rollback.

If an exception is raised in the try-block, success() will never be invoked and the internal state of the transaction object will cause finish() to roll back the transaction. This is very important: unless success() is invoked, the transaction will fail upon finish(). A transaction can be explicitly marked for rollback by invoking the failure() method.

Read operations inside of a transaction will also read uncommitted data from the same transaction.

Method Summary

void	failure() Marks this transaction as failed, which means that it will unconditionally be rolled back when finish() is called.
void	finish() Commits or marks this transaction for rollback, depending on whether success() or failure() has been previously invoked.
void	success() Marks this transaction as successful, which means that it will be commited upon invocation of finish() unless failure() has or will be invoked before then.

Method Detail

failure

void failure()

Marks this transaction as failed, which means that it will unconditionally be rolled back when finish() is called. Once this method has been invoked, it doesn't matter how many times success() is invoked -- the transaction will still be rolled back.

success

void success()

Marks this transaction as successful, which means that it will be commited upon invocation of finish() unless failure() has or will be invoked before then.

finish

void finish()

Commits or marks this transaction for rollback, depending on whether success() or failure() has been previously invoked.