Java URL Load load(URL url, boolean allowCache)

Description

Loads and returns data from the specified URL.

License

Open Source License

Declaration


public static byte[] load(URL url, boolean allowCache) throws IOException

Method Source Code

//package com.java2s;
/**//from ww w .ja  v  a 2s . c o  m
 * The utillib library.
 * More information is available at http://www.jinchess.com/.
 * Copyright (C) 2002 Alexander Maryanovsky.
 * All rights reserved.
 *
 * The utillib library is free software; you can redistribute
 * it and/or modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * The utillib library is distributed in the hope that it will
 * be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
 * General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with utillib library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;

import java.io.EOFException;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import java.net.URL;
import java.util.Hashtable;

public class Main {
    /**
     * Maps URLs to byte arrays of the data loaded from them.
     */

    private final static Hashtable urlCache = new Hashtable();

    /**
     * Loads and returns data from the specified URL.
     */

    public static byte[] load(URL url, boolean allowCache) throws IOException {
        InputStream in = inputStreamForURL(url, allowCache);
        try {
            return readToEnd(in);
        } finally {
            try {
                in.close();
            } catch (IOException e) {
            }
        }
    }

    /**
     * Returns an <code>InpuStream</code> for reading the data at the specified
     * URL. If <code>allowCache</code> is <code>true</code>, and the URL is cached,
     * a <code>ByteArrayInpuStream</code> with the cached data is returned.
     */

    public static InputStream inputStreamForURL(URL url, boolean allowCache) throws IOException {
        byte[] cached = null;
        if (allowCache)
            cached = (byte[]) urlCache.get(url);
        return cached == null ? url.openStream() : new ByteArrayInputStream(cached);
    }

    /**
     * Reads from the given InputStream until its end and returns a byte array
     * of the contents. The input stream is not <code>close</code>d by this
     * method.
     */

    public static byte[] readToEnd(InputStream in) throws IOException {
        byte[] buf = new byte[2048];

        int amountRead = 0;
        int count = 0;
        while ((count = in.read(buf, amountRead, buf.length - amountRead)) > 0) {
            amountRead += count;

            if (amountRead == buf.length) {
                byte[] oldBuf = buf;
                buf = new byte[oldBuf.length * 2];
                System.arraycopy(oldBuf, 0, buf, 0, amountRead);
            }
        }

        byte[] arr = new byte[amountRead];
        System.arraycopy(buf, 0, arr, 0, amountRead);
        return arr;
    }

    /**
     * Reads the specified amount of bytes from the specified input stream and
     * returns the resulting array. Throws an <code>EOFException</code> if the
     * stream ends before the specified amount of bytes is read.
     */

    public static byte[] read(InputStream in, int amount) throws IOException {
        ByteArrayOutputStream buf = new ByteArrayOutputStream(amount);
        if (pump(in, buf, amount) != amount)
            throw new EOFException();

        return buf.toByteArray();
    }

    /**
     * Writes the bytes read from the given input stream into the given output
     * stream until the end of the input stream is reached. Returns the amount of
     * bytes actually read/written.
     */

    public static int pump(InputStream in, OutputStream out) throws IOException {
        return pump(in, out, new byte[2048]);
    }

    /**
     * Writes up to the given amount of bytes read from the given input stream 
     * into the given output stream until the end of the input stream is reached.
     * Returns the amount of bytes actually read/written.
     */

    public static int pump(InputStream in, OutputStream out, int amount) throws IOException {
        return pump(in, out, amount, new byte[2048]);
    }

    /**
     * Writes the bytes read from the given input stream into the given output
     * stream until the end of the input stream is reached. Returns the amount of
     * bytes actually read/written. Uses the given byte array as the buffer.
     */

    public static int pump(InputStream in, OutputStream out, byte[] buf) throws IOException {
        if (buf.length == 0)
            throw new IllegalArgumentException("Cannot use a 0 length buffer");

        int count;
        int amountRead = 0;
        while ((count = in.read(buf)) != -1) {
            out.write(buf, 0, count);
            amountRead += count;
        }

        return amountRead;
    }

    /**
     * Writes up to the given amount of bytes read from the given input stream 
     * into the given output stream until the end of the input stream is reached.
     * Returns the amount of bytes actually read/written. Uses the given byte array
     * as the buffer.
     */

    public static int pump(InputStream in, OutputStream out, int amount, byte[] buf) throws IOException {
        if (buf.length == 0)
            throw new IllegalArgumentException("Cannot use a 0 length buffer");

        int amountRead = 0;
        while (amount > 0) {
            int amountToRead = amount > buf.length ? buf.length : amount;
            int count = in.read(buf, 0, amountToRead);
            if (count == -1)
                break;

            out.write(buf, 0, count);
            amount -= count;
            amountRead += count;
        }

        return amountRead;
    }
}

Java URL Load load(URL url, boolean allowCache)

Description

License

Declaration

Method Source Code

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