diskpagestore.java

Wicket一个开发Java Web应用程序框架。它使得开发web应用程序变得容易而轻松。 Wicket利用一个POJO data beans组件使得它可以与任何持久层技术相结合。

/*
 * 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.wicket.protocol.http.pagestore;


import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.wicket.Application;
import org.apache.wicket.Page;
import org.apache.wicket.WicketRuntimeException;
import org.apache.wicket.protocol.http.WebApplication;
import org.apache.wicket.protocol.http.SecondLevelCacheSessionStore.IPageStore;
import org.apache.wicket.protocol.http.SecondLevelCacheSessionStore.ISerializationAwarePageStore;
import org.apache.wicket.protocol.http.pagestore.PageWindowManager.PageWindow;
import org.apache.wicket.protocol.http.pagestore.SerializedPagesCache.SerializedPageWithSession;
import org.apache.wicket.util.concurrent.ConcurrentHashMap;
import org.apache.wicket.util.lang.Bytes;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * {@link IPageStore} implementation that stores the serialized pages grouped in a single file per
 * pagemap.
 * <p>
 * This store was designed to overcome the problems of {@link FilePageStore} which stores the pages
 * in separate files per page.
 * <p>
 * {@link DiskPageStore} allows to set maximum size for pagemap file and maximum size for session.
 * If the maximum size for session is exceeded, the last recently used pagemap file is removed.
 * 
 * @author Matej Knopp
 */
public class DiskPageStore extends AbstractPageStore implements ISerializationAwarePageStore
{
	/**
	 * Each PageMap is represented by this class.
	 * 
	 * @author Matej Knopp
	 */
	protected static class PageMapEntry implements Serializable
	{
		private static final long serialVersionUID = 1L;

		private String pageMapName;
		private String fileName;
		private PageWindowManager manager;

		/**
		 * @return the name of pagemap
		 */
		public String getPageMapName()
		{
			return pageMapName;
		}

		/**
		 * @return path of file that contains serialized pages in this pagemap
		 */
		public String getFileName()
		{
			return fileName;
		}

		/**
		 * @return manager that maintains information about pages inside the file
		 */
		public PageWindowManager getManager()
		{
			return manager;
		}
	}

	/**
	 * Represents a session,
	 * 
	 * @author Matej Knopp
	 */
	protected static class SessionEntry implements Serializable
	{
		private static final long serialVersionUID = 1L;

		private String sessionId;
		private final List pageMapEntryList = new ArrayList();
		private transient DiskPageStore diskPageStore;

		protected SessionEntry(DiskPageStore diskPageStore)
		{
			this.diskPageStore = diskPageStore;
		}

		/**
		 * @return session id
		 */
		public String getSessionId()
		{
			return sessionId;
		}

		/**
		 * @return summed size of all pagemap files
		 */
		public int getTotalSize()
		{
			int result = 0;
			for (Iterator i = pageMapEntryList.iterator(); i.hasNext();)
			{
				PageMapEntry entry = (PageMapEntry)i.next();
				if (entry.manager != null)
				{
					result += entry.manager.getTotalSize();
				}
			}
			return result;
		}

		/**
		 * @return list of {@link PageMapEntry} for this session
		 */
		public List /* <PageMapEntry> */getPageMapEntryList()
		{
			return Collections.unmodifiableList(pageMapEntryList);
		}

		/**
		 * Returns a {@link PageMapEntry} for specified pagemap. If the create attribute is set and
		 * the pagemap does not exist, new {@link PageMapEntry} will be created.
		 * 
		 * @param pageMapName
		 * @param create
		 * @return
		 */
		public PageMapEntry getPageMapEntry(String pageMapName, boolean create)
		{
			PageMapEntry result = null;
			for (Iterator i = pageMapEntryList.iterator(); i.hasNext();)
			{
				PageMapEntry entry = (PageMapEntry)i.next();
				if (entry.pageMapName == pageMapName ||
					(entry.pageMapName != null && entry.pageMapName.equals(pageMapName)))
				{
					result = entry;
				}

			}
			if (result == null && create)
			{
				result = new PageMapEntry();
				result.pageMapName = pageMapName;
				result.fileName = diskPageStore.getPageMapFileName(sessionId, pageMapName, true);
				result.manager = new PageWindowManager(diskPageStore.getMaxSizePerPageMap());
				pageMapEntryList.add(result);
			}
			return result;
		}

		/**
		 * Removes the pagemap entry and deletes the file.
		 * 
		 * @param entry
		 */
		private void removePageMapEntry(PageMapEntry entry)
		{
			diskPageStore.fileChannelPool.closeAndDeleteFileChannel(entry.fileName);
			pageMapEntryList.remove(entry);
		}

		/**
		 * Removes the specified pagemap and deletes the file.
		 * 
		 * @param pageMapName
		 */
		public synchronized void removePageMap(String pageMapName)
		{
			PageMapEntry entry = getPageMapEntry(pageMapName, false);
			if (entry != null)
			{
				removePageMapEntry(entry);
			}
		}

		/**
		 * Saves the serialized page to appropriate pagemap file.
		 * 
		 * @param page
		 */
		public synchronized void savePage(SerializedPage page)
		{
			// only save page that has some data
			if (page.getData() != null)
			{
				PageMapEntry entry = getPageMapEntry(page.getPageMapName(), true);

				// allocate window for page
				PageWindow window = entry.manager.createPageWindow(page.getPageId(),
					page.getVersionNumber(), page.getAjaxVersionNumber(), page.getData().length);

				// remove the entry and add it to the end of entry list (to mark
				// it as last accessed(
				pageMapEntryList.remove(entry);
				pageMapEntryList.add(entry);

				// if we exceeded maximum session size, try to remove as many
				// pagemap as necessary and possible
				while (getTotalSize() > diskPageStore.getMaxSizePerSession() &&
					pageMapEntryList.size() > 1)
				{
					removePageMapEntry((PageMapEntry)pageMapEntryList.get(0));
				}

				// take the filechannel from the pool
				FileChannel channel = diskPageStore.fileChannelPool.getFileChannel(entry.fileName,
					true);
				try
				{
					// write the content
					channel.write(ByteBuffer.wrap(page.getData()), window.getFilePartOffset());
				}
				catch (IOException e)
				{
					log.error("Error writing to a channel " + channel, e);
				}
				finally
				{
					// return the "borrowed" file channel
					diskPageStore.fileChannelPool.returnFileChannel(channel);
				}
			}
		}

		/**
		 * Removes the page from pagemap file.
		 * 
		 * @param pageMapName
		 * @param pageId
		 */
		public synchronized void removePage(String pageMapName, int pageId)
		{
			PageMapEntry entry = getPageMapEntry(pageMapName, false);
			if (entry != null)
			{
				entry.manager.removePage(pageId);
			}
		}

		/**
		 * Loads the part of pagemap file specified by the given PageWindow.
		 * 
		 * @param window
		 * @param pageMapFileName
		 * @return
		 */
		public byte[] loadPage(PageWindow window, String pageMapFileName)
		{
			byte[] result = null;
			FileChannel channel = diskPageStore.fileChannelPool.getFileChannel(pageMapFileName,
				false);
			if (channel != null)
			{
				ByteBuffer buffer = ByteBuffer.allocate(window.getFilePartSize());
				try
				{
					channel.read(buffer, window.getFilePartOffset());
					if (buffer.hasArray())
					{
						result = buffer.array();
					}
				}
				catch (IOException e)
				{
					log.error("Error reading from file channel " + channel, e);
				}
				finally
				{
					diskPageStore.fileChannelPool.returnFileChannel(channel);
				}
			}
			return result;
		}

		/**
		 * Loads the specified page data.
		 * 
		 * @param pageMapName
		 * @param id
		 * @param versionNumber
		 * @param ajaxVersionNumber
		 * @return page data or null if the page is no longer in pagemap file
		 */
		public synchronized byte[] loadPage(String pageMapName, int id, int versionNumber,
			int ajaxVersionNumber)
		{
			byte[] result = null;
			PageMapEntry entry = getPageMapEntry(pageMapName, false);
			if (entry != null)
			{
				PageWindow window = entry.manager.getPageWindow(id, versionNumber,
					ajaxVersionNumber);
				if (window != null)
				{
					result = loadPage(window, entry.fileName);
				}
			}
			return result;
		}

		/**
		 * Deletes all files for this session.
		 */
		public synchronized void unbind()
		{
			while (pageMapEntryList.size() > 0)
			{
				removePageMapEntry((PageMapEntry)pageMapEntryList.get(pageMapEntryList.size() - 1));
			}
			File sessionFolder = diskPageStore.getSessionFolder(sessionId, false);
			if (sessionFolder.exists())
			{
				sessionFolder.delete();
			}
		}

		/**
		 * Returns true if the given page exists for specified pageMap
		 * 
		 * @param pageMapName
		 * @param pageId
		 * @param versionNumber
		 * @return
		 */
		public synchronized boolean exists(String pageMapName, int pageId, int versionNumber)
		{
			PageMapEntry entry = getPageMapEntry(pageMapName, false);
			return entry != null &&
				entry.getManager().getPageWindow(pageId, versionNumber, -1) != null;
		}
	}

	private File getStoreFolder()
	{
		File storeFolder = new File(fileStoreFolder, appName + "-filestore");
		return storeFolder;
	}

	/**
	 * Returns the folder for the specified sessions. If the folder doesn't exist and the create
	 * flag is set, the folder will be created.
	 * 
	 * @param sessionId
	 * @param create
	 * @return
	 */
	private File getSessionFolder(String sessionId, boolean create)
	{
		File storeFolder = getStoreFolder();
		File sessionFolder = new File(storeFolder, sessionId);
		if (create && sessionFolder.exists() == false)
		{
			mkdirs(sessionFolder);
		}
		return sessionFolder;
	}


	/**
	 * Utility method for creating a directory
	 * 
	 * @param file
	 */
	private void mkdirs(File file)
	{
		// for some reason, simple file.mkdirs sometimes fails under heavy load
		for (int j = 0; j < 5; ++j)
		{
			for (int i = 0; i < 10; ++i)
			{
				if (file.mkdirs())
				{
					return;
				}
			}
			try
			{
				Thread.sleep(100);
			}
			catch (InterruptedException ignore)
			{
			}
		}
		log.error("Failed to make directory " + file);
	}