session.java

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//$Id: Session.java,v 1.19.2.18 2004/01/25 03:54:13 oneovthafew Exp $
package net.sf.hibernate;

import net.sf.hibernate.type.Type;
import java.io.Serializable;
import java.sql.Connection;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;

/**
 * The main runtime interface between a Java application and Hibernate. This is the
 * central API class abstracting the notion of a persistence service.<br>
 * <br>
 * The lifecycle of a <tt>Session</tt> is bounded by the beginning and end of a logical
 * transaction. (Long transactions might span several database transactions.)<br>
 * <br>
 * The main function of the <tt>Session</tt> is to offer create, find and delete operations
 * for instances of mapped entity classes. Instances may exist in one of two states:<br>
 * <br>
 * <i>transient:</i> not associated with any <tt>Session</tt><br>
 * <i>persistent:</i> associated with a <tt>Session</tt><br>
 * <br>
 * Transient instances may be made persistent by calling <tt>save()</tt>,
 * <tt>update()</tt> or <tt>saveOrUpdate()</tt>. Persistent instances may be made transient
 * by calling<tt> delete()</tt>. Any instance returned by a <tt>find(), iterate()</tt> or
 * <tt>load()</tt> method is persistent.<br>
 * <br>
 * <tt>save()</tt> results in an SQL <tt>CREATE</tt>, <tt>delete()</tt>
 * in an SQL <tt>DELETE</tt> and <tt>update()</tt> in an SQL <tt>UPDATE</tt>. Changes to
 * <i>persistent</i> instances are detected at flush time and also result in an SQL
 * <tt>UPDATE</tt>.<br>
 * <br>
 * It is not intended that implementors be threadsafe. Instead each thread/transaction
 * should obtain its own instance from a <tt>SessionFactory</tt>.<br>
 * <br>
 * A <tt>Session</tt> instance is serializable if its persistent classes are serializable.<br>
 * <br>
 * A typical transaction should use the following idiom:
 * <pre>
 * Session sess = factory.openSession();
 * Transaction tx;
 * try {
 *     tx = sess.beginTransaction();
 *     //do some work
 *     ...
 *     tx.commit();
 * }
 * catch (Exception e) {
 *     if (tx!=null) tx.rollback();
 *     throw e;
 * }
 * finally {
 *     sess.close();
 * }
 * </pre>
 * <br>
 * If the <tt>Session</tt> throws an exception, the transaction must be rolled back
 * and the session discarded. The internal state of the <tt>Session</tt> might not
 * be consistent with the database after the exception occurs.
 *
 * @see SessionFactory
 * @author Gavin King
 */
public interface Session extends Serializable {
	
	/**
	 * Force the <tt>Session</tt> to flush. Must be called at the end of a
	 * unit of work, before commiting the transaction and closing the
	 * session (<tt>Transaction.commit()</tt> calls this method). <i>Flushing</i>
	 * is the process of synchronising the underlying persistent store with
	 * persistable state held in memory.
	 *
	 * @throws HibernateException
	 */
	public void flush() throws HibernateException;
	
	/**
	 * Set the flush mode. The flush mode determines at which points
	 * Hibernate automatically flushes the session. For a readonly
	 * session, it is reasonable to set the flush mode to
	 * <tt>FlushMode.NEVER</tt> at the start of the session (in
	 * order to achieve some extra performance).
	 *
	 * @see FlushMode
	 * @param flushMode the FlushMode
	 */
	public void setFlushMode(FlushMode flushMode);
	
	/**
	 * Get the current flush mode.
	 *
	 * @return FlushMode
	 */
	public FlushMode getFlushMode();
	
	/**
	 * Get the <tt>SessionFactory</tt> that created this instance.
	 * @see SessionFactory
	 */
	public SessionFactory getSessionFactory();
	
	/**
	 * Get the JDBC connection. Applications are responsible for
	 * calling commit/rollback upon the connection before closing
	 * the <tt>Session</tt>.
	 *
	 * @return the JDBC connection in use by the <tt>Session</tt>
	 * @throws HibernateException if the <tt>Session</tt> is disconnected
	 */
	public Connection connection() throws HibernateException;
	
	/**
	 * Disconnect the <tt>Session</tt> from the current JDBC connection. If
	 * the connection was obtained by Hibernate, close it or return it to the
	 * connection pool. Otherwise return it to the application.<br>
	 * <br>
	 * This is used by applications which require long transactions.
	 *
	 * @return the connection provided by the application or <tt>null</tt>
	 * @throws HibernateException if the <tt>Session</tt> is disconnected
	 * @see Session#reconnect()
	 */
	public Connection disconnect() throws HibernateException;
	
	/**
	 * Obtain a new JDBC connection. This is used by applications which
	 * require long transactions.
	 *
	 * @see Session#disconnect()
	 * @throws HibernateException
	 */
	public void reconnect() throws HibernateException;
	
	/**
	 * Reconnect to the given JDBC connection. This is used by applications
	 * which require long transactions.
	 *
	 * @param connection a JDBC connection
	 * @throws HibernateException if the <tt>Session</tt> is connected
	 * @see Session#disconnect()
	 */
	public void reconnect(Connection connection) throws HibernateException;
	
	/**
	 * End the <tt>Session</tt> by disconnecting from the JDBC connection and
	 * cleaning up. It is not strictly necessary to <tt>close()</tt> the
	 * <tt>Session</tt> but you must at least <tt>disconnect()</tt> it.
	 *
	 * @return the connection provided by the application
	 * or <tt>null</tt>
	 * @throws HibernateException
	 */
	public Connection close() throws HibernateException;
	
	/**
	 * Cancel execution of the current query. May be called from one thread
	 * to stop execution of a query in another thread. Use with care!
	 */
	public void cancelQuery() throws HibernateException;
	
	/**
	 * Check if the <tt>Session</tt> is still open.
	 *
	 * @return boolean
	 */
	public boolean isOpen();
	
	/**
	 * Check if the <tt>Session</tt> is currently connected.
	 *
	 * @return boolean
	 */
	public boolean isConnected();
	
	/**
	 * Does this <tt>Session</tt> contain any changes which must be
	 * synchronized with the database? Would any SQL be executed if
	 * we flushed this session?
	 * 
	 * @return boolean
	 */
	public boolean isDirty() throws HibernateException;
	
	/**
	 * Return the identifier of an entity instance cached by the <tt>Session</tt>, or
	 * throw an exception if the instance is transient or associated with a different
	 * <tt>Session</tt>.
	 *
	 * @param object a persistent instance
	 * @return the identifier
	 * @throws HibernateException if the <tt>Session</tt> is connected
	 */
	public Serializable getIdentifier(Object object) throws HibernateException;
	/**
	 * Check if this instance is associated with this <tt>Session</tt>.
	 * 
	 * @param object an instance of a persistent class
	 * @return true if the given instance is associated with this <tt>Session</tt>
	 */
	public boolean contains(Object object);
	/**
	 * Remove this instance from the session cache. Changes to the instance will
	 * not be synchronized with the database.
	 * 
	 * @param object a persistent instance
	 * @throws HibernateException
	 */
	public void evict(Object object) throws HibernateException;
	
	/**
	 * Return the persistent instance of the given entity class with the given identifier,
	 * obtaining the specified lock mode, assuming the instance exists.
	 *
	 * @param theClass a persistent class
	 * @param id a valid identifier of an existing persistent instance of the class
	 * @param lockMode the lock level
	 * @return the persistent instance or proxy
	 * @throws HibernateException
	 */
	public Object load(Class theClass, Serializable id, LockMode lockMode) throws HibernateException;
	
	/**
	 * Return the persistent instance of the given entity class with the given identifier,
	 * assuming that the instance exists.
	 * <br><br>
	 * You should not use this method to determine if an instance exists (use <tt>find()</tt>
	 * instead). Use this only to retrieve an instance that you assume exists, where non-existence
	 * would be an actual error.
	 *
	 * @param theClass a persistent class
	 * @param id a valid identifier of an existing persistent instance of the class
	 * @return the persistent instance or proxy
	 * @throws HibernateException
	 */
	public Object load(Class theClass, Serializable id) throws HibernateException;
	
	/**
	 * Read the persistent state associated with the given identifier into the given transient 
	 * instance.
	 *
	 * @param object an "empty" instance of the persistent class
	 * @param id a valid identifier of an existing persistent instance of the class
	 * @throws HibernateException
	 */
	public void load(Object object, Serializable id) throws HibernateException;
	
	/**
	 * Persist all reachable transient objects, reusing the current identifier 
	 * values.
	 * 
	 * @param object a transient instance of a persistent class
	 */
	public void replicate(Object object, ReplicationMode replicationMode) throws HibernateException;
	
	/**
	 * Persist the given transient instance, first assigning a generated identifier. (Or
	 * using the current value of the identifier property if the <tt>assigned</tt>
	 * generator is used.)
	 *
	 * @param object a transient instance of a persistent class
	 * @return the generated identifier
	 * @throws HibernateException
	 */
	public Serializable save(Object object) throws HibernateException;
	
	/**
	 * Persist the given transient instance, using the given identifier.
	 *
	 * @param object a transient instance of a persistent class
	 * @param id an unused valid identifier
	 * @throws HibernateException
	 */
	public void save(Object object, Serializable id) throws HibernateException;
	
	/**
	 * Either <tt>save()</tt> or <tt>update()</tt> the given instance, depending upon the value of
	 * its identifier property. By default the instance is always saved. This behaviour may be
	 * adjusted by specifying an <tt>unsaved-value</tt> attribute of the identifier property
	 * mapping.
	 *
	 * @see Session#save(java.lang.Object)
	 * @see Session#update(Object object, Serializable id)
	 * @param object a transient instance containing new or updated state
	 * @throws HibernateException
	 */
	public void saveOrUpdate(Object object) throws HibernateException;
	
	/**
	 * Update the persistent instance with the identifier of the given transient
	 * instance. If there is a persistent instance with the same identifier,
	 * an exception is thrown.<br>
	 * <br>
	 * If the given transient instance has a <tt>null</tt> identifier, an exception
	 * will be thrown.<br>
	 * <br>
	 *
	 * @param object a transient instance containing updated state
	 * @throws HibernateException
	 */
	public void update(Object object) throws HibernateException;
	
	/**
	 * Update the persistent state associated with the given identifier. An exception
	 * is thrown if there is a persistent instance with the same identifier in the
	 * current session.<br>
	 * <br>
	 *
	 * @param object a transient instance containing updated state
	 * @param id identifier of persistent instance
	 * @throws HibernateException
	 */
	public void update(Object object, Serializable id) throws HibernateException;
	
	/**
	 * Copy the state of the given object onto the persistent object with the same
	 * identifier. If there is no persistent instance currently associated with 
	 * the session, it will be loaded. Return the persistent instance. If the 
	 * given instance is unsaved or does not exist in the database, save it and 
	 * return it as a newly persistent instance. Otherwise, the given instance
	 * does not become associated with the session.
	 * 
	 * @param object a transient instance with state to be copied
	 * @return an updated persistent instance
	 */
	public Object saveOrUpdateCopy(Object object) throws HibernateException;
	
	/**
	 * Copy the state of the given object onto the persistent object with the 
	 * given identifier. If there is no persistent instance currently associated 
	 * with the session, it will be loaded. Return the persistent instance. If
	 * there is no database row with the given identifier, save the given instance