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ActiveMQ example source code file (AbstractStoreCursor.java)

This example ActiveMQ source code file (AbstractStoreCursor.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

abstractstorecursor, exception, exception, failed, failed, id, iterator, logger, messagereference, messagereference, override, prioritizedpendinglist, runtimeexception, runtimeexception, util

The ActiveMQ AbstractStoreCursor.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.activemq.broker.region.cursors;

import java.util.Iterator;
import org.apache.activemq.broker.region.Destination;
import org.apache.activemq.broker.region.MessageReference;
import org.apache.activemq.command.Message;
import org.apache.activemq.command.MessageId;
import org.apache.activemq.store.MessageRecoveryListener;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 *  Store based cursor
 *
 */
public abstract class AbstractStoreCursor extends AbstractPendingMessageCursor implements MessageRecoveryListener {
    private static final Logger LOG = LoggerFactory.getLogger(AbstractStoreCursor.class);
    protected final Destination regionDestination;
    private final PendingList batchList;
    private Iterator<MessageReference> iterator = null;
    protected boolean batchResetNeeded = true;
    private boolean storeHasMessages = false;
    protected int size;
    private MessageId lastCachedId;
    private boolean hadSpace = false;

    protected AbstractStoreCursor(Destination destination) {
        super((destination != null ? destination.isPrioritizedMessages():false));
        this.regionDestination=destination;
        if (this.prioritizedMessages) {
            this.batchList= new PrioritizedPendingList();
        } else {
            this.batchList = new OrderedPendingList();
        }
    }
    
    
    public final synchronized void start() throws Exception{
        if (!isStarted()) {
            clear();
            super.start();      
            resetBatch();
            this.size = getStoreSize();
            this.storeHasMessages=this.size > 0;
            setCacheEnabled(!this.storeHasMessages&&useCache);
        } 
    }
    
    
    public final synchronized void stop() throws Exception {
        resetBatch();
        super.stop();
        gc();
    }

    
    public final boolean recoverMessage(Message message) throws Exception {
        return recoverMessage(message,false);
    }
    
    public synchronized boolean recoverMessage(Message message, boolean cached) throws Exception {
        boolean recovered = false;
        if (recordUniqueId(message.getMessageId())) {
            if (!cached) {
                message.setRegionDestination(regionDestination);
                if( message.getMemoryUsage()==null ) {
                    message.setMemoryUsage(this.getSystemUsage().getMemoryUsage());
                }
            }
            message.incrementReferenceCount();
            batchList.addMessageLast(message);
            clearIterator(true);
            recovered = true;
            storeHasMessages = true;
        } else {
            /*
             * we should expect to get these - as the message is recorded as it before it goes into
             * the cache. If subsequently, we pull out that message from the store (before its deleted)
             * it will be a duplicate - but should be ignored
             */
            if (LOG.isTraceEnabled()) {
                LOG.trace(this + " - cursor got duplicate: " + message.getMessageId() + ", " + message.getPriority());
            }
        }
        return recovered;
    }
    
    
    public final void reset() {
        if (batchList.isEmpty()) {
            try {
                fillBatch();
            } catch (Exception e) {
                LOG.error(this + " - Failed to fill batch", e);
                throw new RuntimeException(e);
            }
        }
        clearIterator(true);
        size();
    }
    
    
    public synchronized void release() {
        clearIterator(false);
    }
    
    private synchronized void clearIterator(boolean ensureIterator) {
        boolean haveIterator = this.iterator != null;
        this.iterator=null;
        if(haveIterator&&ensureIterator) {
            ensureIterator();
        }
    }
    
    private synchronized void ensureIterator() {
        if(this.iterator==null) {
            this.iterator=this.batchList.iterator();
        }
    }


    public final void finished() {
    }
        
    
    public final synchronized boolean hasNext() {
        if (batchList.isEmpty()) {
            try {
                fillBatch();
            } catch (Exception e) {
                LOG.error(this + " - Failed to fill batch", e);
                throw new RuntimeException(e);
            }
        }
        ensureIterator();
        return this.iterator.hasNext();
    }
    
    
    public final synchronized MessageReference next() {
        MessageReference result = null;
        if (!this.batchList.isEmpty()&&this.iterator.hasNext()) {
            result = this.iterator.next();
        }
        last = result;
        if (result != null) {
            result.incrementReferenceCount();
        }
        return result;
    }
    
    
    public final synchronized void addMessageLast(MessageReference node) throws Exception {
        if (hasSpace()) {
            if (!isCacheEnabled() && size==0 && isStarted() && useCache) {
                if (LOG.isTraceEnabled()) {
                    LOG.trace(this + " - enabling cache for empty store " + node.getMessageId());
                }
                setCacheEnabled(true);
            }
            if (isCacheEnabled()) {
                recoverMessage(node.getMessage(),true);
                lastCachedId = node.getMessageId();
            }
        } else if (isCacheEnabled()) {
            setCacheEnabled(false);
            // sync with store on disabling the cache
            if (lastCachedId != null) {
                if (LOG.isTraceEnabled()) {
                    LOG.trace(this + " - disabling cache"
                            + ", lastCachedId: " + lastCachedId
                            + " current node Id: " + node.getMessageId());
                }
                setBatch(lastCachedId);
                lastCachedId = null;
            }
        }
        this.storeHasMessages = true;
        size++;
    }

    protected void setBatch(MessageId messageId) throws Exception {
    }

    
    public final synchronized void addMessageFirst(MessageReference node) throws Exception {
        setCacheEnabled(false);
        size++;
    }

    
    public final synchronized void remove() {
        size--;
        if (iterator!=null) {
            iterator.remove();
        }
        if (last != null) {
            last.decrementReferenceCount();
        }
    }

    
    public final synchronized void remove(MessageReference node) {
        size--;
        setCacheEnabled(false);
        batchList.remove(node);
    }
    
    
    public final synchronized void clear() {
        gc();
    }
    
    
    public synchronized void gc() {
        for (Iterator<MessageReference>i = batchList.iterator();i.hasNext();) {
            MessageReference msg = i.next();
            rollback(msg.getMessageId());
            msg.decrementReferenceCount();
        }
        batchList.clear();
        clearIterator(false);
        batchResetNeeded = true;
        setCacheEnabled(false);
    }

    @Override
    public boolean hasSpace() {
        hadSpace = super.hasSpace();
        return hadSpace;
    }

    protected final synchronized void fillBatch() {
        if (LOG.isTraceEnabled()) {
            LOG.trace(this + " - fillBatch");
        }
        if (batchResetNeeded) {
            resetBatch();
            this.batchResetNeeded = false;
        }
        if (this.batchList.isEmpty() && this.storeHasMessages && this.size >0) {
            this.storeHasMessages = false;
            try {
                doFillBatch();
            } catch (Exception e) {
                LOG.error(this + " - Failed to fill batch", e);
                throw new RuntimeException(e);
            }
            if (!this.batchList.isEmpty() || !hadSpace) {
                this.storeHasMessages=true;
            }
        }
    }
    
    
    public final synchronized boolean isEmpty() {
        // negative means more messages added to store through queue.send since last reset
        return size == 0;
    }

    
    public final synchronized boolean hasMessagesBufferedToDeliver() {
        return !batchList.isEmpty();
    }

    
    public final synchronized int size() {
        if (size < 0) {
            this.size = getStoreSize();
        }
        return size;
    }

    public String toString() {
        return regionDestination.getActiveMQDestination().getPhysicalName() + ",batchResetNeeded=" + batchResetNeeded
                    + ",storeHasMessages=" + this.storeHasMessages + ",size=" + this.size + ",cacheEnabled=" + isCacheEnabled();
    }
    
    protected abstract void doFillBatch() throws Exception;
    
    protected abstract void resetBatch();
    
    protected abstract int getStoreSize();
    
    protected abstract boolean isStoreEmpty();
}

Other ActiveMQ examples (source code examples)

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