org.neo4j.api.core
Interface Transaction


public interface Transaction

A programmatically handled transaction. All operations that work with the node space (even read operations) must be wrapped in a transaction. 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 in JTA. Here's the idiomatic use of programmatic transactions in Neo:


 Transaction tx = neo.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 NeoService.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, tx.success() will never be invoked and the internal state of the transaction object will cause tx.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 tx.failure() method.


Method Summary
 void failure()
          Marks this transaction as failed, which means that it will inexplicably be rolled back upon invocation of finish().
 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 inexplicably be rolled back upon invocation of finish(). 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.



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