bakcode/netty/netty-avro-codec/AvroDecoder.java

package net.dnio.codec.avro;

import org.apache.avro.generic.GenericRecord;
import org.apache.avro.io.BinaryDecoder;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.Decoder;
import org.apache.avro.io.DecoderFactory;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.jboss.netty.buffer.ChannelBuffer;
import org.jboss.netty.channel.Channel;
import org.jboss.netty.channel.ChannelHandlerContext;
import org.jboss.netty.handler.codec.oneone.OneToOneDecoder;


/**
 * <pre>
 *
 * Created by IntelliJ IDEA.
 * User: zhenqin
 * Date: 13-8-9
 * Time: 上午9:33
 * To change this template use File | Settings | File Templates.
 *
 * </pre>
 *
 * @author zhenqin
 */
public class AvroDecoder<T> extends OneToOneDecoder {


    /**
     * Avro Data Reader
     */
    private DatumReader<T> datumReader;


    /**
     * Decoder
     */
    private BinaryDecoder reuse;

    /**
     * 日志记录
     */
    private static Log log = LogFactory.getLog(AvroDecoder.class);


    /**
     *
     * @param datumReader Avro Schema Reader
     * @param reuse 可为null
     */
    public AvroDecoder(DatumReader<T> datumReader, BinaryDecoder reuse) {
        this.datumReader = datumReader;
        this.reuse = reuse;
    }

    @Override
    protected Object decode(ChannelHandlerContext ctx, Channel channel, Object msg) throws Exception {
        if (!(msg instanceof ChannelBuffer)) {
            return msg;
        }

        ChannelBuffer buf = (ChannelBuffer) msg;
        final byte[] array;
        final int offset;
        final int length = buf.readableBytes();

        if (buf.hasArray()) {
            array = buf.array();
            offset = buf.arrayOffset() + buf.readerIndex();
        } else {
            array = new byte[length];
            buf.getBytes(buf.readerIndex(), array, 0, length);
            offset = 0;
        }

        Decoder decoder = DecoderFactory.get().binaryDecoder(array, offset, length, reuse);
        GenericRecord result = (GenericRecord) datumReader.read(null, decoder);
        return result;
    }

    public DatumReader<T> getDatumReader() {
        return datumReader;
    }

    public BinaryDecoder getReuse() {
        return reuse;
    }
}