001/*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.io;
018
019import com.google.common.annotations.Beta;
020
021import java.io.Closeable;
022import java.io.IOException;
023import java.util.logging.Level;
024import java.util.logging.Logger;
025
026import javax.annotation.Nullable;
027
028/**
029 * Utility methods for working with {@link Closeable} objects.
030 *
031 * @author Michael Lancaster
032 * @since 1
033 */
034@Beta
035public final class Closeables {
036  private static final Logger logger
037      = Logger.getLogger(Closeables.class.getName());
038
039  private Closeables() {}
040
041  /**
042   * Closes a {@link Closeable}, with control over whether an
043   * {@code IOException} may be thrown. This is primarily useful in a
044   * finally block, where a thrown exception needs to be logged but not
045   * propagated (otherwise the original exception will be lost).
046   *
047   * <p>If {@code swallowIOException} is true then we never throw
048   * {@code IOException} but merely log it.
049   *
050   * <p>Example:
051   *
052   * <p><pre>public void useStreamNicely() throws IOException {
053   * SomeStream stream = new SomeStream("foo");
054   * boolean threw = true;
055   * try {
056   *   // Some code which does something with the Stream. May throw a
057   *   // Throwable.
058   *   threw = false; // No throwable thrown.
059   * } finally {
060   *   // Close the stream.
061   *   // If an exception occurs, only rethrow it if (threw==false).
062   *   Closeables.close(stream, threw);
063   * }
064   * </pre>
065   *
066   * @param closeable the {@code Closeable} object to be closed, or null,
067   *     in which case this method does nothing
068   * @param swallowIOException if true, don't propagate IO exceptions
069   *     thrown by the {@code close} methods
070   * @throws IOException if {@code swallowIOException} is false and
071   *     {@code close} throws an {@code IOException}.
072   */
073  public static void close(@Nullable Closeable closeable,
074      boolean swallowIOException) throws IOException {
075    if (closeable == null) {
076      return;
077    }
078    try {
079      closeable.close();
080    } catch (IOException e) {
081      if (swallowIOException) {
082        logger.log(Level.WARNING,
083            "IOException thrown while closing Closeable.", e);
084      } else {
085        throw e;
086      }
087    }
088  }
089
090  /**
091   * Equivalent to calling {@code close(closeable, true)}, but with no
092   * IOException in the signature.
093   * @param closeable the {@code Closeable} object to be closed, or null, in
094   *      which case this method does nothing
095   */
096  public static void closeQuietly(@Nullable Closeable closeable) {
097    try {
098      close(closeable, true);
099    } catch (IOException e) {
100      logger.log(Level.SEVERE, "IOException should not have been thrown.", e);
101    }
102  }
103}