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ActiveMQ example source code file (DataFileAccessor.java)

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

Java - ActiveMQ tags/keywords

bytesequence, bytesequence, datafile, datafile, datafileaccessor, invalid, io, ioexception, ioexception, map, randomaccessfile, runtimeexception, util, writecommand, writecommand, writekey

The ActiveMQ DataFileAccessor.java source code

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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 org.apache.kahadb.journal;

import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.Map;

import org.apache.kahadb.journal.DataFileAppender.WriteCommand;
import org.apache.kahadb.journal.DataFileAppender.WriteKey;
import org.apache.kahadb.util.ByteSequence;

/**
 * Optimized Store reader and updater. Single threaded and synchronous. Use in
 * conjunction with the DataFileAccessorPool of concurrent use.
 * 
 * 
 */
final class DataFileAccessor {

    private final DataFile dataFile;
    private final Map<WriteKey, WriteCommand> inflightWrites;
    private final RandomAccessFile file;
    private boolean disposed;

    /**
     * Construct a Store reader
     * 
     * @param fileId
     * @throws IOException
     */
    public DataFileAccessor(Journal dataManager, DataFile dataFile) throws IOException {
        this.dataFile = dataFile;
        this.inflightWrites = dataManager.getInflightWrites();
        this.file = dataFile.openRandomAccessFile();
    }

    public DataFile getDataFile() {
        return dataFile;
    }

    public void dispose() {
        if (disposed) {
            return;
        }
        disposed = true;
        try {
            dataFile.closeRandomAccessFile(file);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public ByteSequence readRecord(Location location) throws IOException {

        if (!location.isValid()) {
            throw new IOException("Invalid location: " + location);
        }

        WriteCommand asyncWrite = (WriteCommand)inflightWrites.get(new WriteKey(location));
        if (asyncWrite != null) {
            return asyncWrite.data;
        }

        try {

            if (location.getSize() == Location.NOT_SET) {
                file.seek(location.getOffset());
                location.setSize(file.readInt());
                location.setType(file.readByte());
            } else {
                file.seek(location.getOffset() + Journal.RECORD_HEAD_SPACE);
            }

            byte[] data = new byte[location.getSize() - Journal.RECORD_HEAD_SPACE];
            file.readFully(data);
            return new ByteSequence(data, 0, data.length);

        } catch (RuntimeException e) {
            throw new IOException("Invalid location: " + location + ", : " + e);
        }
    }
    
    public void readFully(long offset, byte data[]) throws IOException {
       file.seek(offset);
       file.readFully(data);
    }

    public int read(long offset, byte data[]) throws IOException {
       file.seek(offset);
       return file.read(data);
    }

    public void readLocationDetails(Location location) throws IOException {
        WriteCommand asyncWrite = (WriteCommand)inflightWrites.get(new WriteKey(location));
        if (asyncWrite != null) {
            location.setSize(asyncWrite.location.getSize());
            location.setType(asyncWrite.location.getType());
        } else {
            file.seek(location.getOffset());
            location.setSize(file.readInt());
            location.setType(file.readByte());
        }
    }

//    public boolean readLocationDetailsAndValidate(Location location) {
//        try {
//            WriteCommand asyncWrite = (WriteCommand)inflightWrites.get(new WriteKey(location));
//            if (asyncWrite != null) {
//                location.setSize(asyncWrite.location.getSize());
//                location.setType(asyncWrite.location.getType());
//            } else {
//                file.seek(location.getOffset());
//                location.setSize(file.readInt());
//                location.setType(file.readByte());
//
//                byte data[] = new byte[3];
//                file.seek(location.getOffset() + Journal.ITEM_HEAD_OFFSET_TO_SOR);
//                file.readFully(data);
//                if (data[0] != Journal.ITEM_HEAD_SOR[0]
//                    || data[1] != Journal.ITEM_HEAD_SOR[1]
//                    || data[2] != Journal.ITEM_HEAD_SOR[2]) {
//                    return false;
//                }
//                file.seek(location.getOffset() + location.getSize() - Journal.ITEM_FOOT_SPACE);
//                file.readFully(data);
//                if (data[0] != Journal.ITEM_HEAD_EOR[0]
//                    || data[1] != Journal.ITEM_HEAD_EOR[1]
//                    || data[2] != Journal.ITEM_HEAD_EOR[2]) {
//                    return false;
//                }
//            }
//        } catch (IOException e) {
//            return false;
//        }
//        return true;
//    }

    public void updateRecord(Location location, ByteSequence data, boolean sync) throws IOException {

        file.seek(location.getOffset() + Journal.RECORD_HEAD_SPACE);
        int size = Math.min(data.getLength(), location.getSize());
        file.write(data.getData(), data.getOffset(), size);
        if (sync) {
            file.getFD().sync();
        }

    }

}

Other ActiveMQ examples (source code examples)

Here is a short list of links related to this ActiveMQ DataFileAccessor.java source code file:

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