Java tutorial
/** * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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 org.apache.jxtadoop.io; import java.io.*; import java.net.Socket; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.jxtadoop.conf.Configuration; import org.apache.jxtadoop.hdfs.DFSClient; import org.apache.jxtadoop.hdfs.p2p.P2PConstants; import net.jxta.socket.JxtaSocket; /** * An utility class for I/O related functionality. */ @SuppressWarnings({ "unused" }) public class IOUtils { public static final Log LOG = LogFactory.getLog(IOUtils.class); /** * Copies from one stream to another. * @param in InputStrem to read from * @param out OutputStream to write to * @param buffSize the size of the buffer * @param close whether or not close the InputStream and * OutputStream at the end. The streams are closed in the finally clause. */ public static void copyBytes(InputStream in, OutputStream out, int buffSize, boolean close) throws IOException { PrintStream ps = out instanceof PrintStream ? (PrintStream) out : null; byte buf[] = new byte[buffSize]; try { int bytesRead = in.read(buf); while (bytesRead >= 0) { out.write(buf, 0, bytesRead); if ((ps != null) && ps.checkError()) { throw new IOException("Unable to write to output stream."); } bytesRead = in.read(buf); } } finally { if (close) { out.close(); in.close(); out = null; in = null; } } } /** * Copies from one stream to another. <strong>closes the input and output streams * at the end</strong>. * @param in InputStrem to read from * @param out OutputStream to write to * @param conf the Configuration object */ public static void copyBytes(InputStream in, OutputStream out, Configuration conf) throws IOException { copyBytes(in, out, conf.getInt("io.file.buffer.size", P2PConstants.IO_FILE_BUFFER_SIZE), true); } /** * Copies from one stream to another. * @param in InputStrem to read from * @param out OutputStream to write to * @param conf the Configuration object * @param close whether or not close the InputStream and * OutputStream at the end. The streams are closed in the finally clause. */ public static void copyBytes(InputStream in, OutputStream out, Configuration conf, boolean close) throws IOException { copyBytes(in, out, conf.getInt("io.file.buffer.size", P2PConstants.IO_FILE_BUFFER_SIZE), close); } /** Reads len bytes in a loop. * @param in The InputStream to read from * @param buf The buffer to fill * @param off offset from the buffer * @param len the length of bytes to read * @throws IOException if it could not read requested number of bytes * for any reason (including EOF) */ public static void readFully(InputStream in, byte buf[], int off, int len) throws IOException { int toRead = len; while (toRead > 0) { int ret = in.read(buf, off, toRead); if (ret < 0) { throw new IOException("Premeture EOF from inputStream"); } toRead -= ret; off += ret; } } /** Similar to readFully(). Skips bytes in a loop. * @param in The InputStream to skip bytes from * @param len number of bytes to skip. * @throws IOException if it could not skip requested number of bytes * for any reason (including EOF) */ public static void skipFully(InputStream in, long len) throws IOException { while (len > 0) { long ret = in.skip(len); if (ret < 0) { throw new IOException("Premeture EOF from inputStream"); } len -= ret; } } /** * Close the Closeable objects and <b>ignore</b> any {@link IOException} or * null pointers. Must only be used for cleanup in exception handlers. * @param log the log to record problems to at debug level. Can be null. * @param closeables the objects to close */ public static void cleanup(Log log, java.io.Closeable... closeables) { for (java.io.Closeable c : closeables) { if (c != null) { try { c.close(); } catch (IOException e) { LOG.debug("Exception in closing the stream : " + e.getMessage()); if (log != null && log.isDebugEnabled()) { log.debug("Exception in closing " + c, e); } } } } } /** * Closes the stream ignoring {@link IOException}. * Must only be called in cleaning up from exception handlers. * @param stream the Stream to close */ public static void closeStream(java.io.Closeable stream) { LOG.debug("call to IOUtils closeStream()"); cleanup(null, stream); } /** * Closes the socket ignoring {@link IOException} * @param sock the Socket to close */ public static void closeSocket(JxtaSocket jsock) { LOG.debug("call to IOUtils jXtacloseSocket()"); // avoids try { close() } dance if (jsock != null) { try { jsock.shutdownInput(); jsock.shutdownOutput(); LOG.debug("jsock connected : " + jsock.isConnected()); LOG.debug("jsock closed : " + jsock.isClosed()); LOG.debug("jsock bound : " + jsock.isBound()); //jsock.close(); } catch (IOException ignored) { LOG.debug("Error while closing socket : " + ignored.getMessage()); } } jsock = null; } public static void closeSocket(Socket sock) { LOG.debug("call to IOUtils closeSocket()"); // avoids try { close() } dance if (sock != null) { try { sock.close(); } catch (IOException ignored) { LOG.debug("Error while closing socket : " + ignored.getMessage()); } } sock = null; } /** /dev/null of OutputStreams. */ public static class NullOutputStream extends OutputStream { public void write(byte[] b, int off, int len) throws IOException { } public void write(int b) throws IOException { } } }