org.polymap.core.runtime.DefaultSessionContext.java Source code

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Here is the source code for org.polymap.core.runtime.DefaultSessionContext.java

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/* 
 * polymap.org
 * Copyright 2011, Polymap GmbH. All rights reserved.
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 */
package org.polymap.core.runtime;

import java.util.concurrent.Callable;
import java.util.concurrent.ConcurrentHashMap;
import java.lang.reflect.Constructor;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

/**
 * 
 *
 * @author <a href="http://www.polymap.de">Falko Brutigam</a>
 */
public class DefaultSessionContext extends SessionContext {

    private static Log log = LogFactory.getLog(DefaultSessionContext.class);

    private String sessionKey;

    private ConcurrentHashMap<String, Object> attributes = new ConcurrentHashMap(32, 0.75f, 4);

    //private ReentrantReadWriteLock  attributesLock = new ReentrantReadWriteLock();

    private ListenerList<ISessionListener> listeners = new ListenerList();

    public DefaultSessionContext(String sessionKey) {
        assert sessionKey != null;
        this.sessionKey = sessionKey;
    }

    @Override
    public int hashCode() {
        return sessionKey.hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj instanceof DefaultSessionContext) {
            DefaultSessionContext other = (DefaultSessionContext) obj;
            return sessionKey.equals(other.sessionKey);
        }
        return false;
    }

    protected void destroy() {
        log.debug("destroy(): ...");
        checkDestroyed();
        for (ISessionListener l : listeners.getListeners()) {
            try {
                l.beforeDestroy();
            } catch (Exception e) {
                log.warn("", e);
            }
        }
        listeners = null;
        attributes = null;
        // keep sessionKey for debugging/logging
        //sessionKey = null;
    }

    public boolean isDestroyed() {
        return attributes == null;
    }

    private void checkDestroyed() {
        if (isDestroyed()) {
            throw new IllegalStateException("Session context is destroyed: " + sessionKey);
        }
    }

    public String getSessionKey() {
        checkDestroyed();
        return sessionKey;
    }

    public final <T> T sessionSingleton(final Class<T> type) {
        assert type != null;
        checkDestroyed();
        try {
            T result = (T) attributes.get(type.getName());
            if (result == null) {

                // create an instance (without write lock)
                Constructor constructor = type.getDeclaredConstructor(new Class[] {});
                if (constructor.isAccessible()) {
                    result = type.newInstance();
                } else {
                    constructor.setAccessible(true);
                    result = (T) constructor.newInstance(new Object[] {});
                }

                Object old = attributes.putIfAbsent(type.getName(), result);
                // as there is no lock we have to check after put what object was added actually
                result = old != null ? (T) old : result;
            }
            return result;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    public <T> T execute(final Callable<T> task) throws Exception {
        checkDestroyed();
        SessionContext current = DefaultSessionContextProvider.currentContext.get();
        if (current != null) {
            if (current.getSessionKey().equals(sessionKey)) {
                return task.call();
                // throw new IllegalStateException( "Un/mapping same session context more than once is not supported yet." );
            } else {
                throw new IllegalStateException(
                        "Another context is mapped to this thread: " + current.getSessionKey());
            }
        }

        try {
            DefaultSessionContextProvider.currentContext.set(this);
            return task.call();
        } finally {
            DefaultSessionContextProvider.currentContext.set(null);
        }
    }

    public void execute(final Runnable task) {
        checkDestroyed();
        try {
            execute(new Callable() {
                public Object call() throws Exception {
                    task.run();
                    return null;
                }
            });
        } catch (RuntimeException e) {
            throw e;
        } catch (Exception e) {
            throw new RuntimeException("Should never happen.", e);
        }
    }

    public boolean addSessionListener(ISessionListener l) {
        log.debug("addListener(): " + l);
        checkDestroyed();
        return listeners.add(l);
    }

    public boolean removeSessionListener(ISessionListener l) {
        checkDestroyed();
        return listeners.remove(l);
    }

    public Object getAttribute(String key) {
        checkDestroyed();
        return attributes.get(key);
    }

    public void setAttribute(String key, Object value) {
        checkDestroyed();
        attributes.put(key, value);
    }

    @Override
    public String toString() {
        return "DefaultSessionContext[sessionKey=" + sessionKey + ", attributes=" + attributes + "]";
    }

}