ActiveMQ example source code file (ReadOnlyJournal.java)

This example ActiveMQ source code file (ReadOnlyJournal.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

arraylist, arraylist, datafile, file, file, illegalstateexception, io, ioexception, ioexception, location, override, readonlydatafile, readonlyjournal, string, string, util

The ActiveMQ ReadOnlyJournal.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.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * An AsyncDataManager that works in read only mode against multiple data directories.
 * Useful for reading back archived data files.
 */
public class ReadOnlyJournal extends Journal {
    
    private final ArrayList<File> dirs;

    public ReadOnlyJournal(final ArrayList<File> dirs) {
        this.dirs = dirs;
    }

    public synchronized void start() throws IOException {
        if (started) {
            return;
        }

        started = true;
                
        ArrayList<File> files = new ArrayList();
        for (File directory : dirs) {
            final File d = directory;
            File[] f = d.listFiles(new FilenameFilter() {
                public boolean accept(File dir, String n) {
                    return dir.equals(d) && n.startsWith(filePrefix);
                }
            });
            for (int i = 0; i < f.length; i++) {
                files.add(f[i]);
            }
        }
       
        for (File file : files) {
            try {
                String n = file.getName();
                String numStr = n.substring(filePrefix.length(), n.length());
                int num = Integer.parseInt(numStr);
                DataFile dataFile = new ReadOnlyDataFile(file, num, preferedFileLength);
                fileMap.put(dataFile.getDataFileId(), dataFile);
                totalLength.addAndGet(dataFile.getLength());
            } catch (NumberFormatException e) {
                // Ignore file that do not match the pattern.
            }
        }

        // Sort the list so that we can link the DataFiles together in the
        // right order.
        List<DataFile> list = new ArrayList(fileMap.values());
        Collections.sort(list);
        for (DataFile df : list) {
            dataFiles.addLast(df);
            fileByFileMap.put(df.getFile(), df);
        }
        
//        // Need to check the current Write File to see if there was a partial
//        // write to it.
//        if (!dataFiles.isEmpty()) {
//
//            // See if the lastSyncedLocation is valid..
//            Location l = lastAppendLocation.get();
//            if (l != null && l.getDataFileId() != dataFiles.getTail().getDataFileId().intValue()) {
//                l = null;
//            }
//            
//            // If we know the last location that was ok.. then we can skip lots
//            // of checking
//            try {
//                l = recoveryCheck(dataFiles.getTail(), l);
//                lastAppendLocation.set(l);
//            } catch (IOException e) {
//                LOG.warn("recovery check failed", e);
//            }
//        }
    }
    
    public synchronized void close() throws IOException {
        if (!started) {
            return;
        }
        accessorPool.close();
        fileMap.clear();
        fileByFileMap.clear();
        started = false;
    }

    
    public Location getFirstLocation() throws IllegalStateException, IOException {
        if( dataFiles.isEmpty() ) {
            return null;
        }
        
        DataFile first = dataFiles.getHead();
        Location cur = new Location();
        cur.setDataFileId(first.getDataFileId());
        cur.setOffset(0);
        cur.setSize(0);
        return getNextLocation(cur);
    }
    
    @Override
    public synchronized boolean delete() throws IOException {
        throw new RuntimeException("Cannot delete a ReadOnlyAsyncDataManager");
    }    
}