org.apache.beam.runners.portability

Class CloseableResource<T>

java.lang.Object

org.apache.beam.runners.portability.CloseableResource<T>

All Implemented Interfaces:

java.lang.AutoCloseable

public class CloseableResource<T>
extends java.lang.Object
implements java.lang.AutoCloseable

An AutoCloseable that wraps a resource that needs to be cleaned up but does not implement AutoCloseable itself.

Recipients of a CloseableResource are in general responsible for cleanup. Ownership can be transferred from one context to another via transfer(). Transferring relinquishes ownership from the original resource. This allows resources to be safely constructed and transferred within a try-with-resources block. For example:

try (CloseableResource<Foo> resource = CloseableResource.of(...)) { // Do something with resource. ... // Then transfer ownership to some consumer. resourceConsumer(resource.transfer()); }

Not thread-safe.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	CloseableResource.CloseException An exception that wraps errors thrown while a resource is being closed.
static interface	CloseableResource.Closer<T> A function that knows how to clean up after a resource.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the underlying resource.
T	get() Gets the underlying resource.
static <T> CloseableResource<T>	of(T resource, CloseableResource.Closer<T> closer) Creates a CloseableResource with the given resource and closer.
CloseableResource<T>	transfer() Returns a new CloseableResource that owns the underlying resource and relinquishes ownership from this CloseableResource.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

of

public static <T> CloseableResource<T> of(T resource,
                                          CloseableResource.Closer<T> closer)

Creates a CloseableResource with the given resource and closer.

get

public T get()

Gets the underlying resource.

transfer

public CloseableResource<T> transfer()

Returns a new CloseableResource that owns the underlying resource and relinquishes ownership from this CloseableResource. close() on the original instance becomes a no-op.

close

public void close()
           throws CloseableResource.CloseException

Closes the underlying resource. The closer will only be executed on the first call.

Specified by:

close in interface java.lang.AutoCloseable

Throws:

CloseableResource.CloseException - wrapping any exceptions thrown while closing