package org.hibernate.dialect.lock;
import org.hibernate.persister.entity.Lockable;
import org.hibernate.LockMode;
import org.hibernate.HibernateException;
import org.hibernate.StaleObjectStateException;
import org.hibernate.JDBCException;
import org.hibernate.pretty.MessageHelper;
import org.hibernate.exception.JDBCExceptionHelper;
import org.hibernate.sql.Update;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.engine.SessionFactoryImplementor;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.SQLException;
/**
* A locking strategy where the locks are obtained through update statements.
* <p/>
* This strategy is not valid for read style locks.
*
* @since 3.2
*
* @author Steve Ebersole
*/
public class UpdateLockingStrategy implements LockingStrategy {
private static final Log log = LogFactory.getLog( UpdateLockingStrategy.class );
private final Lockable lockable;
private final LockMode lockMode;
private final String sql;
/**
* Construct a locking strategy based on SQL UPDATE statements.
*
* @param lockable The metadata for the entity to be locked.
* @param lockMode Indictates the type of lock to be acquired. Note that
* read-locks are not valid for this strategy.
*/
public UpdateLockingStrategy(Lockable lockable, LockMode lockMode) {
this.lockable = lockable;
this.lockMode = lockMode;
if ( lockMode.lessThan( LockMode.UPGRADE ) ) {
throw new HibernateException( "[" + lockMode + "] not valid for update statement" );
}
if ( !lockable.isVersioned() ) {
log.warn( "write locks via update not supported for non-versioned entities [" + lockable.getEntityName() + "]" );
this.sql = null;
}
else {
this.sql = generateLockString();
}
}
/**
* @see LockingStrategy#lock
*/
public void lock(
Serializable id,
Object version,
Object object,
SessionImplementor session) throws StaleObjectStateException, JDBCException {
if ( !lockable.isVersioned() ) {
throw new HibernateException( "write locks via update not supported for non-versioned entities [" + lockable.getEntityName() + "]" );
}
// todo : should we additionally check the current isolation mode explicitly?
SessionFactoryImplementor factory = session.getFactory();
try {
PreparedStatement st = session.getBatcher().prepareSelectStatement( sql );
try {
lockable.getVersionType().nullSafeSet( st, version, 1, session );
int offset = 2;
lockable.getIdentifierType().nullSafeSet( st, id, offset, session );
offset += lockable.getIdentifierType().getColumnSpan( factory );
if ( lockable.isVersioned() ) {
lockable.getVersionType().nullSafeSet( st, version, offset, session );
}
int affected = st.executeUpdate();
if ( affected < 0 ) {
factory.getStatisticsImplementor().optimisticFailure( lockable.getEntityName() );
throw new StaleObjectStateException( lockable.getEntityName(), id );
}
}
finally {
session.getBatcher().closeStatement( st );
}
}
catch ( SQLException sqle ) {
throw JDBCExceptionHelper.convert(
session.getFactory().getSQLExceptionConverter(),
sqle,
"could not lock: " + MessageHelper.infoString( lockable, id, session.getFactory() ),
sql
);
}
}
protected String generateLockString() {
SessionFactoryImplementor factory = lockable.getFactory();
Update update = new Update( factory.getDialect() );
update.setTableName( lockable.getRootTableName() );
update.setPrimaryKeyColumnNames( lockable.getRootTableIdentifierColumnNames() );
update.setVersionColumnName( lockable.getVersionColumnName() );
update.addColumn( lockable.getVersionColumnName() );
if ( factory.getSettings().isCommentsEnabled() ) {
update.setComment( lockMode + " lock " + lockable.getEntityName() );
}
return update.toStatementString();
}
protected LockMode getLockMode() {
return lockMode;
}
}
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