org.hibernate.context.internal.ManagedSessionContext.java Source code

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Here is the source code for org.hibernate.context.internal.ManagedSessionContext.java

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/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.context.internal;

import java.util.HashMap;
import java.util.Map;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.context.spi.AbstractCurrentSessionContext;
import org.hibernate.engine.spi.SessionFactoryImplementor;

/**
 * Represents a {@link org.hibernate.context.spi.CurrentSessionContext} the notion of a contextual session
 * is managed by some external entity (generally some form of interceptor, etc).
 * This external manager is responsible for scoping these contextual sessions
 * appropriately binding/unbinding them here for exposure to the application
 * through {@link SessionFactory#getCurrentSession} calls.
 * <p/>
 *  Basically exposes two interfaces.  <ul>
 * <li>First is the implementation of CurrentSessionContext which is then used
 * by the {@link SessionFactory#getCurrentSession()} calls.  This
 * portion is instance-based specific to the session factory owning the given
 * instance of this impl (there will be one instance of this per each session
 * factory using this strategy).
 * <li>Second is the externally facing methods {@link #hasBind}, {@link #bind},
 * and {@link #unbind} used by the external thing to manage exposure of the
 * current session it is scoping.  This portion is static to allow easy
 * reference from that external thing.
 * </ul>
 * The underlying storage of the current sessions here is a static
 * {@link ThreadLocal}-based map where the sessions are keyed by the
 * the owning session factory.
 *
 * @author Steve Ebersole
 */
public class ManagedSessionContext extends AbstractCurrentSessionContext {
    private static final ThreadLocal<Map<SessionFactory, Session>> CONTEXT_TL = new ThreadLocal<Map<SessionFactory, Session>>();

    /**
     * Constructs a new ManagedSessionContext
     *
     * @param factory The factory this context will service
     */
    public ManagedSessionContext(SessionFactoryImplementor factory) {
        super(factory);
    }

    @Override
    public Session currentSession() {
        final Session current = existingSession(factory());
        if (current == null) {
            throw new HibernateException("No session currently bound to execution context");
        } else {
            validateExistingSession(current);
        }
        return current;
    }

    /**
     * Check to see if there is already a session associated with the current
     * thread for the given session factory.
     *
     * @param factory The factory against which to check for a given session
     * within the current thread.
     * @return True if there is currently a session bound.
     */
    public static boolean hasBind(SessionFactory factory) {
        return existingSession(factory) != null;
    }

    /**
     * Binds the given session to the current context for its session factory.
     *
     * @param session The session to be bound.
     * @return Any previously bound session (should be null in most cases).
     */
    public static Session bind(Session session) {
        return sessionMap(true).put(session.getSessionFactory(), session);
    }

    /**
     * Unbinds the session (if one) current associated with the context for the
     * given session.
     *
     * @param factory The factory for which to unbind the current session.
     * @return The bound session if one, else null.
     */
    public static Session unbind(SessionFactory factory) {
        final Map<SessionFactory, Session> sessionMap = sessionMap();
        Session existing = null;
        if (sessionMap != null) {
            existing = sessionMap.remove(factory);
            doCleanup();
        }
        return existing;
    }

    private static Session existingSession(SessionFactory factory) {
        final Map<SessionFactory, Session> sessionMap = sessionMap();
        if (sessionMap == null) {
            return null;
        } else {
            return sessionMap.get(factory);
        }
    }

    protected static Map<SessionFactory, Session> sessionMap() {
        return sessionMap(false);
    }

    private static Map<SessionFactory, Session> sessionMap(boolean createMap) {
        Map<SessionFactory, Session> sessionMap = CONTEXT_TL.get();
        if (sessionMap == null && createMap) {
            sessionMap = new HashMap<SessionFactory, Session>();
            CONTEXT_TL.set(sessionMap);
        }
        return sessionMap;
    }

    private static void doCleanup() {
        final Map<SessionFactory, Session> sessionMap = sessionMap(false);
        if (sessionMap != null) {
            if (sessionMap.isEmpty()) {
                CONTEXT_TL.remove();
            }
        }
    }
}