Java example source code file (JdpPacketReader.java)

This example Java source code file (JdpPacketReader.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

broken, bytearrayinputstream, datainputstream, eofexception, invalid, ioexception, jdp, jdpexception, jdppacketreader, key, map, string, unable, utf\-8, util

The JdpPacketReader.java Java example source code

/*
 * Copyright (c) 2013, 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.management.jdp;

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.EOFException;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;

/**
 * JdpPacketReader responsible for reading a packet <p>This class gets a byte
 * array as it came from a Net, validates it and breaks a part </p>
 */
public final class JdpPacketReader {

    private final DataInputStream pkt;
    private Map<String, String> pmap = null;

    /**
     * Create packet reader, extract and check magic and version
     *
     * @param packet - packet received from a Net
     * @throws JdpException
     */
    public JdpPacketReader(byte[] packet)
            throws JdpException {
        ByteArrayInputStream bais = new ByteArrayInputStream(packet);
        pkt = new DataInputStream(bais);

        try {
            int magic = pkt.readInt();
            JdpGenericPacket.checkMagic(magic);
        } catch (IOException e) {
            throw new JdpException("Invalid JDP packet received, bad magic");
        }

        try {
            short version = pkt.readShort();
            JdpGenericPacket.checkVersion(version);
        } catch (IOException e) {
            throw new JdpException("Invalid JDP packet received, bad protocol version");
        }
    }

    /**
     * Get next entry from packet
     *
     * @return the entry
     * @throws EOFException
     * @throws JdpException
     */
    public String getEntry()
            throws EOFException, JdpException {

        try {
            short len = pkt.readShort();
            // Artificial setting the "len" field to Short.MAX_VALUE may cause a reader to allocate
            // to much memory. Prevent this possible DOS attack.
            if (len < 1 && len > pkt.available()) {
                throw new JdpException("Broken JDP packet. Invalid entry length field.");
            }

            byte[] b = new byte[len];
            if (pkt.read(b) != len) {
                throw new JdpException("Broken JDP packet. Unable to read entry.");
            }
            return new String(b, "UTF-8");

        } catch (EOFException e) {
            throw e;
        } catch (UnsupportedEncodingException ex) {
            throw new JdpException("Broken JDP packet. Unable to decode entry.");
        } catch (IOException e) {
            throw new JdpException("Broken JDP packet. Unable to read entry.");
        }


    }

    /**
     * return packet content as a key/value map
     *
     * @return map containing packet entries pair of entries treated as
     * key,value
     * @throws IOException
     * @throws JdpException
     */
    public Map<String, String> getDiscoveryDataAsMap()
            throws JdpException {
        // return cached map if possible
        if (pmap != null) {
            return pmap;
        }

        String key = null, value = null;

        final Map<String, String> tmpMap = new HashMap<>();
        try {
            while (true) {
                key = getEntry();
                value = getEntry();
                tmpMap.put(key, value);
            }
        } catch (EOFException e) {
            // EOF reached on reading value, report broken packet
            // otherwise ignore it.
            if (value == null) {
                throw new JdpException("Broken JDP packet. Key without value." + key);
            }
        }

        pmap = Collections.unmodifiableMap(tmpMap);
        return pmap;
    }
}