alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Java example source code file (DatagramDnsQueryEncoder.java)

This example Java source code file (DatagramDnsQueryEncoder.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

addressedenvelope, bytebuf, channelhandlercontext, datagramdnsqueryencoder, datagrampacket, dnsrecordencoder, dnssection, exception, inetsocketaddress, list, messagetomessageencoder, net, network, override, suppresswarnings, unstableapi, util

The DatagramDnsQueryEncoder.java Java example source code

/*
 * Copyright 2015 The Netty Project
 *
 * The Netty Project 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 io.netty.handler.codec.dns;

import io.netty.buffer.ByteBuf;
import io.netty.channel.AddressedEnvelope;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.socket.DatagramPacket;
import io.netty.handler.codec.MessageToMessageEncoder;
import io.netty.util.internal.UnstableApi;

import java.net.InetSocketAddress;
import java.util.List;

import static io.netty.util.internal.ObjectUtil.checkNotNull;

/**
 * Encodes a {@link DatagramDnsQuery} (or an {@link AddressedEnvelope} of {@link DnsQuery}} into a
 * {@link DatagramPacket}.
 */
@UnstableApi
@ChannelHandler.Sharable
public class DatagramDnsQueryEncoder extends MessageToMessageEncoder<AddressedEnvelope {

    private final DnsRecordEncoder recordEncoder;

    /**
     * Creates a new encoder with {@linkplain DnsRecordEncoder#DEFAULT the default record encoder}.
     */
    public DatagramDnsQueryEncoder() {
        this(DnsRecordEncoder.DEFAULT);
    }

    /**
     * Creates a new encoder with the specified {@code recordEncoder}.
     */
    public DatagramDnsQueryEncoder(DnsRecordEncoder recordEncoder) {
        this.recordEncoder = checkNotNull(recordEncoder, "recordEncoder");
    }

    @Override
    protected void encode(
        ChannelHandlerContext ctx,
        AddressedEnvelope<DnsQuery, InetSocketAddress> in, List out) throws Exception {

        final InetSocketAddress recipient = in.recipient();
        final DnsQuery query = in.content();
        final ByteBuf buf = allocateBuffer(ctx, in);

        boolean success = false;
        try {
            encodeHeader(query, buf);
            encodeQuestions(query, buf);
            encodeRecords(query, DnsSection.ADDITIONAL, buf);
            success = true;
        } finally {
            if (!success) {
                buf.release();
            }
        }

        out.add(new DatagramPacket(buf, recipient, null));
    }

    /**
     * Allocate a {@link ByteBuf} which will be used for constructing a datagram packet.
     * Sub-classes may override this method to return a {@link ByteBuf} with a perfect matching initial capacity.
     */
    protected ByteBuf allocateBuffer(
        ChannelHandlerContext ctx,
        @SuppressWarnings("unused") AddressedEnvelope<DnsQuery, InetSocketAddress> msg) throws Exception {
        return ctx.alloc().ioBuffer(1024);
    }

    /**
     * Encodes the header that is always 12 bytes long.
     *
     * @param query the query header being encoded
     * @param buf   the buffer the encoded data should be written to
     */
    private static void encodeHeader(DnsQuery query, ByteBuf buf) {
        buf.writeShort(query.id());
        int flags = 0;
        flags |= (query.opCode().byteValue() & 0xFF) << 14;
        if (query.isRecursionDesired()) {
            flags |= 1 << 8;
        }
        buf.writeShort(flags);
        buf.writeShort(query.count(DnsSection.QUESTION));
        buf.writeShort(0); // answerCount
        buf.writeShort(0); // authorityResourceCount
        buf.writeShort(query.count(DnsSection.ADDITIONAL));
    }

    private void encodeQuestions(DnsQuery query, ByteBuf buf) throws Exception {
        final int count = query.count(DnsSection.QUESTION);
        for (int i = 0; i < count; i++) {
            recordEncoder.encodeQuestion((DnsQuestion) query.recordAt(DnsSection.QUESTION, i), buf);
        }
    }

    private void encodeRecords(DnsQuery query, DnsSection section, ByteBuf buf) throws Exception {
        final int count = query.count(section);
        for (int i = 0; i < count; i++) {
            recordEncoder.encodeRecord(query.recordAt(section, i), buf);
        }
    }
}




Other Java examples (source code examples)


Here is a short list of links related to this Java DatagramDnsQueryEncoder.java source code file:
... this post is sponsored by my books ...

#1 New Release!
FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.