org.hibernate.search.util.impl

Class Closer<E extends Exception>

java.lang.Object

org.hibernate.search.util.impl.Closer<E>

All Implemented Interfaces:

AutoCloseable

public final class Closer<E extends Exception>
extends Object
implements AutoCloseable

A helper for closing multiple resources and re-throwing only one exception, suppressing the others as necessary.

This class is not thread safe.

This helper is mainly useful when implementing AutoCloseable.close() or a similar closing method in your own class, to make sure that all resources are at least given the chance to close, even if closing one of them fails. When creating then closing resources in the scope of a single method call, try-with-resource blocks should be favored.

Warning: In order not to ignore exceptions, you should always call close() once you closed all of your resources. The most straightforward way to do this is to use a try-with-resource block:

 public void myCloseFunction() throws MyException {
   try ( Closer<MyException> closer = new Closer<>() ) {
     closer.push( this.myCloseable::close );
     closer.pushAll( this.myListOfCloseables, MyCloseableType::close );
   }
 }
 

Exception type

Note that the closer has a generic type parameter, allowing it to re-throw a given checked exception. If you don't want to use this feature, you can simply use a Closer<RuntimeException>.

Splitting

If you need to close multiple resources throwing different checked exceptions, and those exceptions don't have a practical common superclass, you can "split" the closer:

 public void myCloseFunction() throws IOException, MyException, MyOtherException {
   try ( Closer<MyException> closer1 = new Closer<>();
       Closer<IOException> closer2 = closer1.split();
       Closer<MyOtherException> closer3 = closer1.split() ) {
     closer2.push( this.someJavaIOCloseable::close );
     closer1.pushAll( this.myListOfCloseables1, MyCloseableTypeThrowingMyException::close );
     closer3.pushAll( this.myListOfCloseables2, MyCloseableTypeThrowingMyOtherException::close );
   }
 }
 

The multiple closers will share the same state, which means the first exception to be caught by any of the closers will be the one to be re-thrown, and all subsequent exceptions caught by any closer will be added as suppressed to this first exception. Be careful though, you will have to close every single closer. Closing just the original one will not be enough.

Author:

Yoann Rodiere

Constructor Summary

Constructors

Constructor and Description
Closer()

Method Summary

Modifier and Type	Method and Description
void	close()
<T> void	push(ClosingOperator<T,? extends E> operator, T objectToClose) Execute the given close operator immediately on the given objectToClose, swallowing any throwable in order to throw it later.
void	push(GenericCloseable<? extends E> closeable) Close the given closeable immediately, swallowing any throwable in order to throw it later.
<T> void	pushAll(ClosingOperator<T,? extends E> operator, Iterable<T> objectsToClose) Execute the given close operator immediately on each element of the given iterable, swallowing any throwable in order to throw them later.
<T> void	pushAll(ClosingOperator<T,? extends E> operator, T... objectsToClose) Execute the given close operator immediately on each element of the given array, swallowing any throwable in order to throw them later.
<E2 extends Exception> Closer<E2>	split()

Methods inherited from class java.lang.Object

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

Constructor Detail

Closer

public Closer()

Method Detail

push

public <T> void push(ClosingOperator<T,? extends E> operator,
                     T objectToClose)

Execute the given close operator immediately on the given objectToClose, swallowing any throwable in order to throw it later.

Parameters:

operator - An operator to close objectToClose. Accepts lambdas such as MyType::close.

objectToClose - An object to close

push

public void push(GenericCloseable<? extends E> closeable)

Close the given closeable immediately, swallowing any throwable in order to throw it later.

Parameters:

closeable - A GenericCloseable to close. Accepts lambdas such as myObject::close.

pushAll

public <T> void pushAll(ClosingOperator<T,? extends E> operator,
                        Iterable<T> objectsToClose)

Execute the given close operator immediately on each element of the given iterable, swallowing any throwable in order to throw them later.

Parameters:

operator - An operator to close each element in objectsToClose. Accepts lambdas such as MyType::close.

objectsToClose - An iterable of objects to close

pushAll

@SafeVarargs
public final <T> void pushAll(ClosingOperator<T,? extends E> operator,
                                           T... objectsToClose)

Execute the given close operator immediately on each element of the given array, swallowing any throwable in order to throw them later.

Parameters:

operator - An operator to close each element in objectsToClose. Accepts lambdas such as MyType::close.

objectsToClose - An array of objects to close

split

public <E2 extends Exception> Closer<E2> split()

Returns:

A closer sharing the same state as this, allowing to handle multiple exception types.

See Also:

splitting

close

public void close()
           throws E extends Exception

Specified by:

close in interface AutoCloseable

Throws:

E - The first throwable caught when executing the push methods, if any. Any throwable caught after the first will have been suppressed.

E extends Exception