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/*
* Copyright (C) 2007 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.io;
import com.google.common.annotations.Beta;
import com.google.common.annotations.VisibleForTesting;
import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.annotation.Nullable;
/**
* Utility methods for working with {@link Closeable} objects.
*
* @author Michael Lancaster
* @since 1.0
*/
@Beta
public final class Closeables {
@VisibleForTesting static final Logger logger
= Logger.getLogger(Closeables.class.getName());
private Closeables() {}
/**
* Closes a {@link Closeable}, with control over whether an {@code IOException} may be thrown.
* This is primarily useful in a finally block, where a thrown exception needs to be logged but
* not propagated (otherwise the original exception will be lost).
*
* If {@code swallowIOException} is true then we never throw {@code IOException} but merely log
* it.
*
*
Example:
{@code
*
* public void useStreamNicely() throws IOException {
* SomeStream stream = new SomeStream("foo");
* boolean threw = true;
* try {
* // ... code which does something with the stream ...
* threw = false;
* } finally {
* // If an exception occurs, rethrow it only if threw==false:
* Closeables.close(stream, threw);
* }
* }}
*
* @param closeable the {@code Closeable} object to be closed, or null, in which case this method
* does nothing
* @param swallowIOException if true, don't propagate IO exceptions thrown by the {@code close}
* methods
* @throws IOException if {@code swallowIOException} is false and {@code close} throws an
* {@code IOException}.
*/
public static void close(@Nullable Closeable closeable,
boolean swallowIOException) throws IOException {
if (closeable == null) {
return;
}
try {
closeable.close();
} catch (IOException e) {
if (swallowIOException) {
logger.log(Level.WARNING,
"IOException thrown while closing Closeable.", e);
} else {
throw e;
}
}
}
/**
* Closes the given {@link InputStream}, logging any {@code IOException} that's thrown rather
* than propagating it.
*
* While it's not safe in the general case to ignore exceptions that are thrown when closing
* an I/O resource, it should generally be safe in the case of a resource that's being used only
* for reading, such as an {@code InputStream}. Unlike with writable resources, there's no
* chance that a failure that occurs when closing the stream indicates a meaningful problem such
* as a failure to flush all bytes to the underlying resource.
*
* @param inputStream the input stream to be closed, or {@code null} in which case this method
* does nothing
* @since 17.0
*/
public static void closeQuietly(@Nullable InputStream inputStream) {
try {
close(inputStream, true);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
/**
* Closes the given {@link Reader}, logging any {@code IOException} that's thrown rather than
* propagating it.
*
*
While it's not safe in the general case to ignore exceptions that are thrown when closing
* an I/O resource, it should generally be safe in the case of a resource that's being used only
* for reading, such as a {@code Reader}. Unlike with writable resources, there's no chance that
* a failure that occurs when closing the reader indicates a meaningful problem such as a failure
* to flush all bytes to the underlying resource.
*
* @param reader the reader to be closed, or {@code null} in which case this method does nothing
* @since 17.0
*/
public static void closeQuietly(@Nullable Reader reader) {
try {
close(reader, true);
} catch (IOException impossible) {
throw new AssertionError(impossible);
}
}
}