com.google.cloud.spanner

Interface TransactionRunner

public interface TransactionRunner

An interface for executing a body of work in the context of a read-write transaction, with retries for transaction aborts. See TransactionContext for a description of transaction semantics. TransactionRunner instances are obtained by calling DatabaseClient.readWriteTransaction().

A TransactionRunner instance can only be used for a single invocation of run(TransactionCallable).

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	TransactionRunner.TransactionCallable<T> A unit of work to be performed in the context of a transaction.

Method Summary

Modifier and Type	Method and Description
Timestamp	getCommitTimestamp() Returns the timestamp at which the transaction committed.
<T> T	run(TransactionRunner.TransactionCallable<T> callable) Executes a read-write transaction, with retries as necessary.

Method Detail

run

@Nullable
<T> T run(TransactionRunner.TransactionCallable<T> callable)

Executes a read-write transaction, with retries as necessary. The work to perform in each transaction attempt is defined by callable, which may return an object as the result of the work. callable will be retried if a transaction attempt aborts; implementations must be prepared to be called more than once. Any writes buffered by callable will only be applied if the transaction commits successfully. Similarly, the value produced by callable will only be returned by this method if the transaction commits successfully.

callable is allowed to raise an unchecked exception. Typically this prevents further attempts to execute callable, and the exception will propagate from this method call. However, if a read or query in callable detected that the transaction aborted, callable will be retried even if it raised an exception.

getCommitTimestamp

Timestamp getCommitTimestamp()

Returns the timestamp at which the transaction committed. This method may only be called once run(TransactionCallable) has returned normally.