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Java example source code file (Resource.java)

This example Java source code file (Resource.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

bytebuffered, codesigner, detect, eof, eofexception, inputstream, interruptedioexception, ioexception, jar, manifest, net, network, nio, only, resource, security, string, url, util

The Resource.java Java example source code

/*
 * Copyright (c) 1998, 2009, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code 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 General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.misc;

import java.io.EOFException;
import java.net.URL;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.io.InputStream;
import java.security.CodeSigner;
import java.util.jar.Manifest;
import java.nio.ByteBuffer;
import java.util.Arrays;
import sun.nio.ByteBuffered;

/**
 * This class is used to represent a Resource that has been loaded
 * from the class path.
 *
 * @author  David Connelly
 * @since   1.2
 */
public abstract class Resource {
    /**
     * Returns the name of the Resource.
     */
    public abstract String getName();

    /**
     * Returns the URL of the Resource.
     */
    public abstract URL getURL();

    /**
     * Returns the CodeSource URL for the Resource.
     */
    public abstract URL getCodeSourceURL();

    /**
     * Returns an InputStream for reading the Resource data.
     */
    public abstract InputStream getInputStream() throws IOException;

    /**
     * Returns the length of the Resource data, or -1 if unknown.
     */
    public abstract int getContentLength() throws IOException;

    private InputStream cis;

    /* Cache result in case getBytes is called after getByteBuffer. */
    private synchronized InputStream cachedInputStream() throws IOException {
        if (cis == null) {
            cis = getInputStream();
        }
        return cis;
    }

    /**
     * Returns the Resource data as an array of bytes.
     */
    public byte[] getBytes() throws IOException {
        byte[] b;
        // Get stream before content length so that a FileNotFoundException
        // can propagate upwards without being caught too early
        InputStream in = cachedInputStream();

        // This code has been uglified to protect against interrupts.
        // Even if a thread has been interrupted when loading resources,
        // the IO should not abort, so must carefully retry, failing only
        // if the retry leads to some other IO exception.

        boolean isInterrupted = Thread.interrupted();
        int len;
        for (;;) {
            try {
                len = getContentLength();
                break;
            } catch (InterruptedIOException iioe) {
                Thread.interrupted();
                isInterrupted = true;
            }
        }

        try {
            b = new byte[0];
            if (len == -1) len = Integer.MAX_VALUE;
            int pos = 0;
            while (pos < len) {
                int bytesToRead;
                if (pos >= b.length) { // Only expand when there's no room
                    bytesToRead = Math.min(len - pos, b.length + 1024);
                    if (b.length < pos + bytesToRead) {
                        b = Arrays.copyOf(b, pos + bytesToRead);
                    }
                } else {
                    bytesToRead = b.length - pos;
                }
                int cc = 0;
                try {
                    cc = in.read(b, pos, bytesToRead);
                } catch (InterruptedIOException iioe) {
                    Thread.interrupted();
                    isInterrupted = true;
                }
                if (cc < 0) {
                    if (len != Integer.MAX_VALUE) {
                        throw new EOFException("Detect premature EOF");
                    } else {
                        if (b.length != pos) {
                            b = Arrays.copyOf(b, pos);
                        }
                        break;
                    }
                }
                pos += cc;
            }
        } finally {
            try {
                in.close();
            } catch (InterruptedIOException iioe) {
                isInterrupted = true;
            } catch (IOException ignore) {}

            if (isInterrupted) {
                Thread.currentThread().interrupt();
            }
        }
        return b;
    }

    /**
     * Returns the Resource data as a ByteBuffer, but only if the input stream
     * was implemented on top of a ByteBuffer. Return <tt>null otherwise.
     */
    public ByteBuffer getByteBuffer() throws IOException {
        InputStream in = cachedInputStream();
        if (in instanceof ByteBuffered) {
            return ((ByteBuffered)in).getByteBuffer();
        }
        return null;
    }

    /**
     * Returns the Manifest for the Resource, or null if none.
     */
    public Manifest getManifest() throws IOException {
        return null;
    }

    /**
     * Returns theCertificates for the Resource, or null if none.
     */
    public java.security.cert.Certificate[] getCertificates() {
        return null;
    }

    /**
     * Returns the code signers for the Resource, or null if none.
     */
    public CodeSigner[] getCodeSigners() {
        return null;
    }
}

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