@Beta public final class Closer extends Object implements Closeable
A Closeable that collects Closeable resources and closes them all when it is closed. This is intended to approximately emulate the behavior of Java 7’s try-with-resources statement in JDK6-compatible code. Running on Java 7, code using this should be approximately equivalent in behavior to the same code written with try-with-resources. Running on Java 6, exceptions that cannot be thrown must be logged rather than being added to the thrown exception as a suppressed exception.
This class is intended to be used in the following pattern:
Closer closer = Closer.create();
try {
InputStream in = closer.register(openInputStream());
OutputStream out = closer.register(openOutputStream());
// do stuff
} catch (Throwable e) {
// ensure that any checked exception types other than IOException that could be thrown are
// provided here, e.g. throw closer.rethrow(e, CheckedException.class);
throw closer.rethrow(e);
} finally {
closer.close();
}
Note that this try-catch-finally block is not equivalent to a try-catch-finally block using try-with-resources. To get the equivalent of that, you must wrap the above code in another try block in order to catch any exception that may be thrown (including from the call to close()).
This pattern ensures the following:
Closeable resource that is successfully registered will be closed later.Throwable is thrown in the try block, no exceptions that occur when attempting
to close resources will be thrown from the finally block. The throwable from the try block will
be thrown.An exception that is suppressed is not thrown. The method of suppression used depends on the version of Java the code is running on:
Throwable.addSuppressed(Throwable).| Modifier and Type | Method and Description |
|---|---|
void |
close()
Closes all
Closeable instances that have been added to this Closer. |
static Closer |
create()
Creates a new
Closer. |
<C extends Closeable> |
register(C closeable)
|
RuntimeException |
rethrow(Throwable e)
Stores the given throwable and rethrows it.
|
<X extends Exception> |
rethrow(Throwable e,
Class<X> declaredType)
Stores the given throwable and rethrows it.
|
<X1 extends Exception,X2 extends Exception> |
rethrow(Throwable e,
Class<X1> declaredType1,
Class<X2> declaredType2)
Stores the given throwable and rethrows it.
|
public <C extends Closeable> C register(@Nullable C closeable)
Registers the given closeable to be closed when this Closer is closed.
closeablepublic RuntimeException rethrow(Throwable e) throws IOException
Stores the given throwable and rethrows it. It will be rethrown as is if it is an IOException, RuntimeException or Error. Otherwise, it will be rethrown wrapped in a RuntimeException. Note: Be sure to declare all of the checked exception types your try block can throw when calling an overload of this method so as to avoid losing the original exception type.
This method always throws, and as such should be called as throw closer.rethrow(e); to ensure the compiler knows that it will throw.
IOException - when the given throwable is an IOExceptionpublic <X extends Exception> RuntimeException rethrow(Throwable e, Class<X> declaredType) throws IOException, X extends Exception
Stores the given throwable and rethrows it. It will be rethrown as is if it is an IOException, RuntimeException, Error or a checked exception of the given type. Otherwise, it will be rethrown wrapped in a RuntimeException. Note: Be sure to declare all of the checked exception types your try block can throw when calling an overload of this method so as to avoid losing the original exception type.
This method always throws, and as such should be called as throw closer.rethrow(e, ...); to ensure the compiler knows that it will throw.
IOException - when the given throwable is an IOExceptionX - when the given throwable is of the declared type XX extends Exceptionpublic <X1 extends Exception,X2 extends Exception> RuntimeException rethrow(Throwable e, Class<X1> declaredType1, Class<X2> declaredType2) throws IOException, X1 extends Exception, X2 extends Exception
Stores the given throwable and rethrows it. It will be rethrown as is if it is an IOException, RuntimeException, Error or a checked exception of either of the given types. Otherwise, it will be rethrown wrapped in a RuntimeException. Note: Be sure to declare all of the checked exception types your try block can throw when calling an overload of this method so as to avoid losing the original exception type.
This method always throws, and as such should be called as throw closer.rethrow(e, ...); to ensure the compiler knows that it will throw.
IOException - when the given throwable is an IOExceptionX1 - when the given throwable is of the declared type X1X2 - when the given throwable is of the declared type X2X1 extends Exceptionpublic void close()
throws IOException
Closes all Closeable instances that have been added to this Closer. If an exception was thrown in the try block and passed to one of the exceptionThrown methods, any exceptions thrown when attempting to close a closeable will be suppressed. Otherwise, the first exception to be thrown from an attempt to close a closeable will be thrown and any additional exceptions that are thrown after that will be suppressed.
close in interface Closeableclose in interface AutoCloseableIOException