org.neo4j.graphdb

Interface Transaction

All Superinterfaces:

AutoCloseable

public interface Transaction
extends AutoCloseable

A programmatically handled transaction.

All database operations that access the graph, indexes, or the schema must be performed in a transaction.

If you attempt to access the graph outside of a transaction, those operations will throw NotInTransactionException.

Transactions are bound to the thread in which they were created. 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 starting from java 7:

 
 try ( Transaction tx = graphDb.beginTx() )
 {
     // operations on the graph
     // ...

     tx.success();
 }
 
 

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 which has internal state to keep track of whether the current transaction is successful. Then we wrap all operations that modify the graph in a try-finally block with the transaction as resource. 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 transaction will automatically be closed where tx.close() will be called and 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 close() to roll back the transaction. This is very important: unless success() is invoked, the transaction will fail upon close(). 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.

Here's the idiomatic use of programmatic transactions in Neo4j on java 6 or earlier:

 
 Transaction tx = graphDb.beginTx();
 try
 {
     // operations on the graph
     // ...

     tx.success();
 }
 finally
 {
     tx.close();
 }
 
 

All ResourceIterables that where returned from operations executed inside a transaction will be automatically closed when the transaction is committed or rolled back. Note however, that the ResourceIterator should be closed as soon as possible if you don't intend to exhaust the iterator.

Method Summary

Modifier and Type	Method and Description
Lock	acquireReadLock(PropertyContainer entity) Acquires a read lock for entity for this transaction.
Lock	acquireWriteLock(PropertyContainer entity) Acquires a write lock for entity for this transaction.
void	close() Commits or marks this transaction for rollback, depending on whether success() or failure() has been previously invoked.
void	failure() Marks this transaction as failed, which means that it will unconditionally be rolled back when close() is called.
void	success() Marks this transaction as successful, which means that it will be committed upon invocation of close() unless failure() has or will be invoked before then.
void	terminate() Marks this transaction as terminated, which means that it will be, much like in the case of failure, unconditionally rolled back when close() is called.

Method Detail

terminate

void terminate()

Marks this transaction as terminated, which means that it will be, much like in the case of failure, unconditionally rolled back when close() is called. Once this method has been invoked, it doesn't matter if success() is invoked afterwards -- the transaction will still be rolled back. Additionally, terminating a transaction causes all subsequent operations carried out within that transaction to throw a TransactionTerminatedException in the owning thread. Note that, unlike the other transaction operations, this method can be called from threads other than the owning thread of the transaction. When this method is called from a different thread, it signals the owning thread to terminate the transaction and returns immediately. Calling this method on an already closed transaction has no effect.

failure

void failure()

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

success

void success()

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

close

void close()

Commits or marks this transaction for rollback, depending on whether success() or failure() has been previously invoked. All ResourceIterables that where returned from operations executed inside this transaction will be automatically closed by this method. This method comes from AutoCloseable so that a Transaction can participate in try-with-resource statements. It will not throw any declared exception. Invoking this method (which is unnecessary when in try-with-resource statement).

Specified by:

close in interface AutoCloseable

acquireWriteLock

Lock acquireWriteLock(PropertyContainer entity)

Acquires a write lock for entity for this transaction. The lock (returned from this method) can be released manually, but if not it's released automatically when the transaction finishes.

Parameters:

entity - the entity to acquire a lock for. If another transaction currently holds a write lock to that entity this call will wait until it's released.

Returns:

a Lock which optionally can be used to release this lock earlier than when the transaction finishes. If not released (with Lock.release() it's going to be released with the transaction finishes.

acquireReadLock

Lock acquireReadLock(PropertyContainer entity)

Acquires a read lock for entity for this transaction. The lock (returned from this method) can be released manually, but if not it's released automatically when the transaction finishes.

Parameters:

entity - the entity to acquire a lock for. If another transaction currently hold a write lock to that entity this call will wait until it's released.

Returns:

a Lock which optionally can be used to release this lock earlier than when the transaction finishes. If not released (with Lock.release() it's going to be released with the transaction finishes.