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Java library with file based DAO handling
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/**
* Copyright (C) 2014-2021 Philip Helger (www.helger.com)
* philip[at]helger[dot]com
*
* Licensed 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 com.helger.dao;
import java.io.File;
import java.util.concurrent.atomic.AtomicBoolean;
import javax.annotation.Nonnull;
import javax.annotation.concurrent.GuardedBy;
import javax.annotation.concurrent.ThreadSafe;
import com.helger.commons.ValueEnforcer;
import com.helger.commons.annotation.ELockType;
import com.helger.commons.annotation.MustBeLocked;
import com.helger.commons.annotation.ReturnsMutableObject;
import com.helger.commons.callback.CallbackList;
import com.helger.commons.collection.NonBlockingStack;
import com.helger.commons.concurrent.SimpleReadWriteLock;
import com.helger.commons.debug.GlobalDebug;
import com.helger.commons.io.file.FileIOError;
import com.helger.commons.io.file.FileOperationManager;
import com.helger.commons.string.ToStringGenerator;
/**
* Base implementation of {@link IDAO}
*
* @author Philip Helger
*/
@ThreadSafe
public abstract class AbstractDAO implements IDAO
{
/** By default auto-save is enabled */
public static final boolean DEFAULT_AUTO_SAVE_ENABLED = true;
/**
* The default extension for an old file that was not yet deleted. Mainly used
* in the WAL DAO
*/
public static final String FILENAME_EXTENSION_PREV = ".prev";
/**
* The default extension for a file that is newly created. Mainly used in the
* WAL DAO
*/
public static final String FILENAME_EXTENSION_NEW = ".new";
private static final CallbackList s_aExceptionHandlersRead = new CallbackList <> ();
private static final CallbackList s_aExceptionHandlersWrite = new CallbackList <> ();
protected static final SimpleReadWriteLock s_aRWLock = new SimpleReadWriteLock ();
private static final AtomicBoolean SILENT_MODE = new AtomicBoolean (GlobalDebug.DEFAULT_SILENT_MODE);
protected final SimpleReadWriteLock m_aRWLock = new SimpleReadWriteLock ();
@GuardedBy ("m_aRWLock")
private final NonBlockingStack m_aAutoSaveStack = new NonBlockingStack <> ();
@GuardedBy ("m_aRWLock")
private boolean m_bPendingChanges = false;
@GuardedBy ("m_aRWLock")
private boolean m_bAutoSaveEnabled = DEFAULT_AUTO_SAVE_ENABLED;
/**
* @return true if logging is disabled, false if it
* is enabled.
* @since 9.2.0
*/
public static boolean isSilentMode ()
{
return SILENT_MODE.get ();
}
/**
* Enable or disable certain regular log messages.
*
* @param bSilentMode
* true to disable logging, false to enable
* logging
* @return The previous value of the silent mode.
* @since 9.2.0
*/
public static boolean setSilentMode (final boolean bSilentMode)
{
return SILENT_MODE.getAndSet (bSilentMode);
}
protected AbstractDAO ()
{}
/**
* @return true if not silent mode
* @deprecated since 9.4.0 Use !isSilentMode () instead
*/
@Deprecated
protected static final boolean isDebugLogging ()
{
return !isSilentMode ();
}
/**
* @return The static mutable exception handler list that is invoked for read
* exceptions. Never null. The list applies to ALL DAOs
* since it is static.
*/
@Nonnull
@ReturnsMutableObject
public static final CallbackList exceptionHandlersRead ()
{
return s_aExceptionHandlersRead;
}
/**
* @return The static mutable exception handler list that is invoked for write
* exceptions. Never null. The list applies to ALL DAOs
* since it is static.
*/
@Nonnull
@ReturnsMutableObject
public static final CallbackList exceptionHandlersWrite ()
{
return s_aExceptionHandlersWrite;
}
/**
* @return true if auto save is enabled, false
* otherwise.
*/
@MustBeLocked (ELockType.READ)
protected final boolean internalIsAutoSaveEnabled ()
{
return m_bAutoSaveEnabled;
}
/**
* @return true if auto save is enabled, false
* otherwise.
*/
public final boolean isAutoSaveEnabled ()
{
return m_aRWLock.readLockedBoolean ( () -> m_bAutoSaveEnabled);
}
@MustBeLocked (ELockType.WRITE)
public final void internalSetPendingChanges (final boolean bPendingChanges)
{
m_bPendingChanges = bPendingChanges;
}
/**
* @return true if unsaved changes are present
*/
@MustBeLocked (ELockType.READ)
public final boolean internalHasPendingChanges ()
{
return m_bPendingChanges;
}
/**
* @return true if unsaved changes are present
*/
public final boolean hasPendingChanges ()
{
return m_aRWLock.readLockedBoolean ( () -> m_bPendingChanges);
}
public final void beginWithoutAutoSave ()
{
m_aRWLock.writeLocked ( () -> {
// Save old auto save state
m_aAutoSaveStack.push (Boolean.valueOf (m_bAutoSaveEnabled));
m_bAutoSaveEnabled = false;
});
}
public final void endWithoutAutoSave ()
{
// Restore previous auto save state
final boolean bPreviouslyAutoSaveEnabled = m_aRWLock.writeLockedBoolean ( () -> {
final boolean bPreviously = m_aAutoSaveStack.pop ().booleanValue ();
m_bAutoSaveEnabled = bPreviously;
return bPreviously;
});
if (bPreviouslyAutoSaveEnabled)
{
// And in case something was changed - writeLocked itself
writeToFileOnPendingChanges ();
}
}
@Override
public String toString ()
{
return new ToStringGenerator (this).append ("autoSaveStack", m_aAutoSaveStack)
.append ("pendingChanges", m_bPendingChanges)
.append ("autoSaveEnabled", m_bAutoSaveEnabled)
.getToString ();
}
/**
* Check the access to the passed file using the specified mode. If the access
* is not provided, a {@link DAOException} is thrown. If everything is good,
* this method returns without a comment.
*
* @param aFile
* The file to check. May not be null.
* @param eMode
* The access mode. May not be null.
* @throws DAOException
* If the requested access mode cannot be provided.
*/
protected static void checkFileAccess (@Nonnull final File aFile, @Nonnull final EMode eMode) throws DAOException
{
ValueEnforcer.notNull (aFile, "File");
ValueEnforcer.notNull (eMode, "Mode");
final String sFilename = aFile.toString ();
if (aFile.exists ())
{
// file exist -> must be a file!
if (!aFile.isFile ())
throw new DAOException ("The passed filename '" +
sFilename +
"' is not a file - maybe a directory or a symlink? Path is '" +
aFile.getAbsolutePath () +
"'");
switch (eMode)
{
case READ:
// Check for read-rights
if (!aFile.canRead ())
throw new DAOException ("Read access rights from '" + aFile.getAbsolutePath () + "' are missing.");
break;
case WRITE:
// Check for write-rights
if (!aFile.canWrite ())
throw new DAOException ("Write access rights to '" + aFile.getAbsolutePath () + "' are missing");
break;
}
}
else
{
// Ensure the parent directory is present
final File aParentDir = aFile.getParentFile ();
if (aParentDir != null)
{
final FileIOError aError = FileOperationManager.INSTANCE.createDirRecursiveIfNotExisting (aParentDir);
if (aError.isFailure ())
throw new DAOException ("Failed to create parent directory '" +
aParentDir +
"' of '" +
aFile.getAbsolutePath () +
"': " +
aError);
}
}
}
}