ioutility.java

采用JAVA开发

/**
 * $RCSfile: IOUtility.java,v $
 * $Revision: 1.1.1.1 $
 * $Date: 2004/01/07 05:06:28 $
 *
 * Copyright (C) 2003 ICSS, Inc. All rights reserved.
 *
 * This software is the proprietary information of ICSS, Inc.
 * Use is subject to license terms.
 */
package com.gctech.misc.util;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;

/**
 * General IO Stream manipulation.
 * <p>
 * This class provides static utility methods for input/output operations, particularly buffered
 * copying between sources (<code>InputStream</code>, <code>Reader</code>, <code>String</code> and
 * <code>byte[]</code>) and destinations (<code>OutputStream</code>, <code>Writer</code>,
 * <code>String</code> and <code>byte[]</code>).
 * </p>
 *
 * <p>Unless otherwise noted, these <code>copy</code> methods do <em>not</em> flush or close the
 * streams. Often, doing so would require making non-portable assumptions about the streams' origin
 * and further use. This means that both streams' <code>close()</code> methods must be called after
 * copying. if one omits this step, then the stream resources (sockets, file descriptors) are
 * released when the associated Stream is garbage-collected. It is not a good idea to rely on this
 * mechanism. For a good overview of the distinction between "memory management" and "resource
 * management", see <a href="http://www.unixreview.com/articles/1998/9804/9804ja/ja.htm">this
 * UnixReview article</a></p>
 *
 * <p>For each <code>copy</code> method, a variant is provided that allows the caller to specify the
 * buffer size (the default is 4k). As the buffer size can have a fairly large impact on speed, this
 * may be worth tweaking. Often "large buffer -&gt; faster" does not hold, even for large data
 * transfers.</p>
 *
 * <p>For byte-to-char methods, a <code>copy</code> variant allows the encoding to be selected
 * (otherwise the platform default is used).</p>
 *
 * <p>The <code>copy</code> methods use an internal buffer when copying. It is therefore advisable
 * <em>not</em> to deliberately wrap the stream arguments to the <code>copy</code> methods in
 * <code>Buffered*</code> streams. For example, don't do the
 * following:</p>
 *
 * <code>copy( new BufferedInputStream( in ), new BufferedOutputStream( out ) );</code>
 *
 * <p>The rationale is as follows:</p>
 *
 * <p>Imagine that an InputStream's read() is a very expensive operation, which would usually suggest
 * wrapping in a BufferedInputStream. The BufferedInputStream works by issuing infrequent
 * {@link java.io.InputStream#read(byte[] b, int off, int len)} requests on the underlying InputStream, to
 * fill an internal buffer, from which further <code>read</code> requests can inexpensively get
 * their data (until the buffer runs out).</p>
 * <p>However, the <code>copy</code> methods do the same thing, keeping an internal buffer,
 * populated by {@link InputStream#read(byte[] b, int off, int len)} requests. Having two buffers
 * (or three if the destination stream is also buffered) is pointless, and the unnecessary buffer
 * management hurts performance slightly (about 3%, according to some simple experiments).</p>
 *
 * @author <a href="mailto:[e-mail]">Peter Donald</a>
 * @author <a href="mailto:[e-mail]">Jeff Turner</a>
 * @version CVS $Revision: 1.1.1.1 $ $Date: 2004/01/07 05:06:28 $
 * @since 4.0
 */

/*
 * Behold, intrepid explorers; a map of this class:
 *
 *       Method      Input               Output          Dependency
 *       ------      -----               ------          -------
 * 1     copy        InputStream         OutputStream    (primitive)
 * 2     copy        Reader              Writer          (primitive)
 *
 * 3     copy        InputStream         Writer          2
 * 4     toString    InputStream         String          3
 * 5     toByteArray InputStream         byte[]          1
 *
 * 6     copy        Reader              OutputStream    2
 * 7     toString    Reader              String          2
 * 8     toByteArray Reader              byte[]          6
 *
 * 9     copy        String              OutputStream    2
 * 10    copy        String              Writer          (trivial)
 * 11    toByteArray String              byte[]          9
 *
 * 12    copy        byte[]              Writer          3
 * 13    toString    byte[]              String          12
 * 14    copy        byte[]              OutputStream    (trivial)
 *
 *
 * Note that only the first two methods shuffle bytes; the rest use these two, or (if possible) copy
 * using native Java copy methods. As there are method variants to specify buffer size and encoding,
 * each row may correspond to up to 4 methods.
 *
 */
public final class IOUtility {
    private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;

    /**
     * Private constructor to prevent instantiation.
     */
    private IOUtility() {}

    /**
     * Unconditionally close an <code>Reader</code>.
         * Equivalent to {@link Reader#close()}, except any exceptions will be ignored.
     *
     * @param output A (possibly null) Reader
     */
    public static void shutdownReader(final Reader input) {
        if (null == input) {
            return;
        }

        try {
            input.close();
        }
        catch (final IOException ioe) {}
    }

    /**
     * Unconditionally close an <code>Writer</code>.
         * Equivalent to {@link Writer#close()}, except any exceptions will be ignored.
     *
     * @param output A (possibly null) Writer
     */
    public static void shutdownWriter(final Writer output) {
        if (null == output) {
            return;
        }

        try {
            output.close();
        }
        catch (final IOException ioe) {}
    }

    /**
     * Unconditionally close an <code>OutputStream</code>.
     * Equivalent to {@link OutputStream#close()}, except any exceptions will be ignored.
     * @param output A (possibly null) OutputStream
     */
    public static void shutdownStream(final OutputStream output) {
        if (null == output) {
            return;
        }

        try {
            output.close();
        }
        catch (final IOException ioe) {}
    }

    /**
     * Unconditionally close an <code>InputStream</code>.
     * Equivalent to {@link InputStream#close()}, except any exceptions will be ignored.
     * @param input A (possibly null) InputStream
     */
    public static void shutdownStream(final InputStream input) {
        if (null == input) {
            return;
        }

        try {
            input.close();
        }
        catch (final IOException ioe) {}
    }

    ///////////////////////////////////////////////////////////////
    // Core copy methods
    ///////////////////////////////////////////////////////////////

    /**
     * Copy bytes from an <code>InputStream</code> to an <code>OutputStream</code>.
     */
    public static void copy(final InputStream input, final OutputStream output) throws IOException {
        copy(input, output, DEFAULT_BUFFER_SIZE);
    }

    /**
         * Copy bytes from an <code>InputStream</code> to an <code>OutputStream</code>.
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy(final InputStream input, final OutputStream output, final int bufferSize) throws IOException {
        final byte[] buffer = new byte[bufferSize];
        int n = 0;
        while (-1 != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
        }
    }

    /**
     * Copy chars from a <code>Reader</code> to a <code>Writer</code>.
     */
    public static void copy(final Reader input, final Writer output) throws IOException {
        copy(input, output, DEFAULT_BUFFER_SIZE);
    }

    /**
     * Copy chars from a <code>Reader</code> to a <code>Writer</code>.
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy(final Reader input, final Writer output, final int bufferSize) throws IOException {
        final char[] buffer = new char[bufferSize];
        int n = 0;
        while (-1 != (n = input.read(buffer))) {
            output.write(buffer, 0, n);
        }
    }

    ///////////////////////////////////////////////////////////////
    // Derived copy methods
    // InputStream -> *
    ///////////////////////////////////////////////////////////////

    ///////////////////////////////////////////////////////////////
    // InputStream -> Writer

    /**
     * Copy and convert bytes from an <code>InputStream</code> to chars on a
     * <code>Writer</code>.
     * The platform's default encoding is used for the byte-to-char conversion.
     */
    public static void copy(final InputStream input, final Writer output) throws IOException {
        copy(input, output, DEFAULT_BUFFER_SIZE);
    }

    /**
     * Copy and convert bytes from an <code>InputStream</code> to chars on a
     * <code>Writer</code>.
     * The platform's default encoding is used for the byte-to-char conversion.
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy(final InputStream input, final Writer output, final int bufferSize) throws IOException {
        final InputStreamReader in = new InputStreamReader(input);
        copy(in, output, bufferSize);
    }

    /**
     * Copy and convert bytes from an <code>InputStream</code> to chars on a
     * <code>Writer</code>, using the specified encoding.
     * @param encoding The name of a supported character encoding. See the
     * <a href="http://www.iana.org/assignments/character-sets">IANA
     * Charset Registry</a> for a list of valid encoding types.
     */
    public static void copy(final InputStream input, final Writer output, final String encoding) throws IOException {
        final InputStreamReader in = new InputStreamReader(input, encoding);
        copy(in, output);
    }

    /**
     * Copy and convert bytes from an <code>InputStream</code> to chars on a
     * <code>Writer</code>, using the specified encoding.
     * @param encoding The name of a supported character encoding. See the
     *        <a href="http://www.iana.org/assignments/character-sets">IANA
     *        Charset Registry</a> for a list of valid encoding types.
     * @param bufferSize Size of internal buffer to use.
     */
    public static void copy(final InputStream input, final Writer output, final String encoding, final int bufferSize) throws IOException {
        final InputStreamReader in = new InputStreamReader(input, encoding);
        copy(in, output, bufferSize);
    }

    ///////////////////////////////////////////////////////////////
    // InputStream -> String

    /**
     * Get the contents of an <code>InputStream</code> as a String.
     * The platform's default encoding is used for the byte-to-char conversion.
     */
    public static String toString(final InputStream input) throws IOException {
        return toString(input, DEFAULT_BUFFER_SIZE);
    }

    /**
     * Get the contents of an <code>InputStream</code> as a String.
     * The platform's default encoding is used for the byte-to-char conversion.
     * @param bufferSize Size of internal buffer to use.
     */
    public static String toString(final InputStream input, final int bufferSize) throws IOException {
        final StringWriter sw = new StringWriter();
        copy(input, sw, bufferSize);
        return sw.toString();
    }

    /**
     * Get the contents of an <code>InputStream</code> as a String.
     * @param encoding The name of a supported character encoding. See the
     *    <a href="http://www.iana.org/assignments/character-sets">IANA
     *    Charset Registry</a> for a list of valid encoding types.
     */
    public static String toString(final InputStream input, final String encoding) throws IOException {
        return toString(input, encoding, DEFAULT_BUFFER_SIZE);
    }

    /**
     * Get the contents of an <code>InputStream</code> as a String.
     * @param encoding The name of a supported character encoding. See the
     *   <a href="http://www.iana.org/assignments/character-sets">IANA
     *   Charset Registry</a> for a list of valid encoding types.
     * @param bufferSize Size of internal buffer to use.
     */
    public static String toString(final InputStream input, final String encoding, final int bufferSize) throws IOException {
        final StringWriter sw = new StringWriter();
        copy(input, sw, encoding, bufferSize);
        return sw.toString();
    }