maint-5-2/tapestry-core/src/main/java/org/apache/tapestry5/BaseOptimizedSessionPersistedObject.java

// Copyright 2008, 2009 The Apache Software Foundation
//
// 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 org.apache.tapestry5;

import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionBindingListener;

/**
 * Base implementation of
 * {@link org.apache.tapestry5.OptimizedSessionPersistedObject}. Subclasses
 * should invoke {@link #markDirty()} when internal state of the object changes.
 * <p>
 * Note that (due to TAP5-834), the object will receive a spurious
 * <code>valueUnbound()</code> notification when dirty. Tapestry sets dirty
 * session attributes to null, then to the persisted object, to force a
 * <code>valueBound()</code> notification, and that unfortunately also sends the
 * <code>valueUnbound()</code>.
 * 
 * @since 5.1.1.0
 */
public abstract class BaseOptimizedSessionPersistedObject implements
        OptimizedSessionPersistedObject, HttpSessionBindingListener
{
    private transient boolean dirty;

    public final boolean isSessionPersistedObjectDirty()
    {
        return dirty;
    }

    /**
     * Invoked by the servlet container when the value is stored (or re-stored)
     * as an attribute of the session. This
     * clears the dirty flag. Subclasses may override this method, but should
     * invoke this implementation.
     */
    public void valueBound(HttpSessionBindingEvent event)
    {
        dirty = false;
    }

    /**
     * Does nothing.
     */
    public void valueUnbound(HttpSessionBindingEvent event)
    {
    }

    /**
     * Invoked by the subclass whenever the internal state of the object
     * changes. Typically, this is invoked from
     * mutator methods.
     */
    protected final void markDirty()
    {
        dirty = true;
    }
}