org.anc.resource

Class ResourceManager<T extends Closeable>

java.lang.Object

org.anc.resource.ResourceManager<T>

Type Parameters:

T - a resource type that implements the Closeable interface.

public class ResourceManager<T extends Closeable>
extends Object

Try to provide a RAII (Resource Acquisition Is Initialization) mechanism for Java. Instances of ResourceManager can be used to ensure a group of resources are all closed when one, or more, of them throws an exception. Calling the close() method ensures that all managed resources will have their close() method called. Any exceptions thrown by resources are caught, wrapped in a ResourceManagerCheckedException or a ResourceManagerRuntimeException and re-thrown only after all resources have been closed.

When throwing exceptions runtime exceptions take precedence and a ResourceManagerRuntimeException will be thrown even if some resources threw checked exceptions. If any resources did throw checked exceptions they will be available with ResourceManagerRuntimeException.getCheckedExceptions().

There are three flavors of the close method:

1. close() : will re-throw runtime and checked exceptions.
2. closeQuietly() : will discard any checked exceptions and re-throw runtime exceptions.
3. closeAbruptly() : ignores all exceptions.

All of the close*() methods catch any exceptions thrown and only propagate the exceptions after all resources have had their close() methods called.

EXAMPLE

 ResourceManager manager = new ResourceManager();
 try
 {
    InputStream istream = manager.add(new FileInputStream(...));
    OutputStream ostream = manager.add(new FileOutputStream(...));
    Closeable dbConnection = manager.add(openDatabaseConnection());
    ...
 }
 finally
 {
    manager.closeQuietly();
 }
 

Since:

2.2.0

Author:

Keith Suderman

See Also:

Resource Acquisition Is Initialization

Field Summary

Fields

Modifier and Type	Field and Description
protected LinkedList<T>	resources

Constructor Summary

Constructors

Constructor and Description
ResourceManager()

Method Summary

Modifier and Type	Method and Description
T	add(T resource) Add a resource to the resource manager.
void	close()
void	closeAbruptly() All resources are closed and all exceptions are ignored.
void	closeQuietly() Close all resources.

Methods inherited from class java.lang.Object

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

Field Detail

resources

protected LinkedList<T extends Closeable> resources

Constructor Detail

ResourceManager

public ResourceManager()

Method Detail

add

public T add(T resource)

Add a resource to the resource manager.

close

public void close()
           throws ResourceManagerCheckedException

Throws:

ResourceManagerCheckedException

closeQuietly

public void closeQuietly()

Close all resources. All exceptions are caught here. Checked exceptions are ignored and runtime exceptions are propagated only after all resources have been closed.

closeAbruptly

public void closeAbruptly()

All resources are closed and all exceptions are ignored.