1 /* 2 * Copyright (C) 2007 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.io; 18 19 import com.google.common.annotations.Beta; 20 import com.google.common.annotations.VisibleForTesting; 21 22 import java.io.Closeable; 23 import java.io.IOException; 24 import java.util.logging.Level; 25 import java.util.logging.Logger; 26 27 import javax.annotation.Nullable; 28 29 /** 30 * Utility methods for working with {@link Closeable} objects. 31 * 32 * @author Michael Lancaster 33 * @since 1.0 34 */ 35 @Beta 36 public final class Closeables { 37 @VisibleForTesting static final Logger logger 38 = Logger.getLogger(Closeables.class.getName()); 39 40 private Closeables() {} 41 42 /** 43 * Closes a {@link Closeable}, with control over whether an 44 * {@code IOException} may be thrown. This is primarily useful in a 45 * finally block, where a thrown exception needs to be logged but not 46 * propagated (otherwise the original exception will be lost). 47 * 48 * <p>If {@code swallowIOException} is true then we never throw 49 * {@code IOException} but merely log it. 50 * 51 * <p>Example: 52 * 53 * <p><pre>public void useStreamNicely() throws IOException { 54 * SomeStream stream = new SomeStream("foo"); 55 * boolean threw = true; 56 * try { 57 * // Some code which does something with the Stream. May throw a 58 * // Throwable. 59 * threw = false; // No throwable thrown. 60 * } finally { 61 * // Close the stream. 62 * // If an exception occurs, only rethrow it if (threw==false). 63 * Closeables.close(stream, threw); 64 * } 65 * </pre> 66 * 67 * @param closeable the {@code Closeable} object to be closed, or null, 68 * in which case this method does nothing 69 * @param swallowIOException if true, don't propagate IO exceptions 70 * thrown by the {@code close} methods 71 * @throws IOException if {@code swallowIOException} is false and 72 * {@code close} throws an {@code IOException}. 73 */ 74 public static void close(@Nullable Closeable closeable, 75 boolean swallowIOException) throws IOException { 76 if (closeable == null) { 77 return; 78 } 79 try { 80 closeable.close(); 81 } catch (IOException e) { 82 if (swallowIOException) { 83 logger.log(Level.WARNING, 84 "IOException thrown while closing Closeable.", e); 85 } else { 86 throw e; 87 } 88 } 89 } 90 91 /** 92 * Equivalent to calling {@code close(closeable, true)}, but with no 93 * IOException in the signature. 94 * @param closeable the {@code Closeable} object to be closed, or null, in 95 * which case this method does nothing 96 */ 97 public static void closeQuietly(@Nullable Closeable closeable) { 98 try { 99 close(closeable, true); 100 } catch (IOException e) { 101 logger.log(Level.SEVERE, "IOException should not have been thrown.", e); 102 } 103 } 104 } 105
