001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.io.input; 018 019 import java.io.IOException; 020 import java.io.InputStream; 021 022 /** 023 * Proxy stream that closes and discards the underlying stream as soon as the 024 * end of input has been reached or when the stream is explicitly closed. 025 * Not even a reference to the underlying stream is kept after it has been 026 * closed, so any allocated in-memory buffers can be freed even if the 027 * client application still keeps a reference to the proxy stream. 028 * <p> 029 * This class is typically used to release any resources related to an open 030 * stream as soon as possible even if the client application (by not explicitly 031 * closing the stream when no longer needed) or the underlying stream (by not 032 * releasing resources once the last byte has been read) do not do that. 033 * 034 * @version $Id: AutoCloseInputStream.java 610010 2008-01-08 14:50:59Z niallp $ 035 * @since Commons IO 1.4 036 */ 037 public class AutoCloseInputStream extends ProxyInputStream { 038 039 /** 040 * Creates an automatically closing proxy for the given input stream. 041 * 042 * @param in underlying input stream 043 */ 044 public AutoCloseInputStream(InputStream in) { 045 super(in); 046 } 047 048 /** 049 * Closes the underlying input stream and replaces the reference to it 050 * with a {@link ClosedInputStream} instance. 051 * <p> 052 * This method is automatically called by the read methods when the end 053 * of input has been reached. 054 * <p> 055 * Note that it is safe to call this method any number of times. The original 056 * underlying input stream is closed and discarded only once when this 057 * method is first called. 058 * 059 * @throws IOException if the underlying input stream can not be closed 060 */ 061 public void close() throws IOException { 062 in.close(); 063 in = new ClosedInputStream(); 064 } 065 066 /** 067 * Reads and returns a single byte from the underlying input stream. 068 * If the underlying stream returns -1, the {@link #close()} method is 069 * called to automatically close and discard the stream. 070 * 071 * @return next byte in the stream, or -1 if no more bytes are available 072 * @throws IOException if the stream could not be read or closed 073 */ 074 public int read() throws IOException { 075 int n = in.read(); 076 if (n == -1) { 077 close(); 078 } 079 return n; 080 } 081 082 /** 083 * Reads and returns bytes from the underlying input stream to the given 084 * buffer. If the underlying stream returns -1, the {@link #close()} method 085 * i called to automatically close and discard the stream. 086 * 087 * @param b buffer to which bytes from the stream are written 088 * @return number of bytes read, or -1 if no more bytes are available 089 * @throws IOException if the stream could not be read or closed 090 */ 091 public int read(byte[] b) throws IOException { 092 int n = in.read(b); 093 if (n == -1) { 094 close(); 095 } 096 return n; 097 } 098 099 /** 100 * Reads and returns bytes from the underlying input stream to the given 101 * buffer. If the underlying stream returns -1, the {@link #close()} method 102 * i called to automatically close and discard the stream. 103 * 104 * @param b buffer to which bytes from the stream are written 105 * @param off start offset within the buffer 106 * @param len maximum number of bytes to read 107 * @return number of bytes read, or -1 if no more bytes are available 108 * @throws IOException if the stream could not be read or closed 109 */ 110 public int read(byte[] b, int off, int len) throws IOException { 111 int n = in.read(b, off, len); 112 if (n == -1) { 113 close(); 114 } 115 return n; 116 } 117 118 /** 119 * Ensures that the stream is closed before it gets garbage-collected. 120 * As mentioned in {@link #close()}, this is a no-op if the stream has 121 * already been closed. 122 * @throws Throwable if an error occurs 123 */ 124 protected void finalize() throws Throwable { 125 close(); 126 super.finalize(); 127 } 128 129 }