package org.hibernate.dialect.lock;
import org.hibernate.persister.entity.Lockable;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.engine.SessionFactoryImplementor;
import org.hibernate.StaleObjectStateException;
import org.hibernate.JDBCException;
import org.hibernate.LockMode;
import org.hibernate.sql.SimpleSelect;
import org.hibernate.pretty.MessageHelper;
import org.hibernate.exception.JDBCExceptionHelper;
import java.io.Serializable;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
/**
* A locking strategy where the locks are obtained through select statements.
* <p/>
* For non-read locks, this is achieved through the Dialect's specific
* SELECT ... FOR UPDATE syntax.
*
* @see org.hibernate.dialect.Dialect#getForUpdateString(org.hibernate.LockMode)
* @see org.hibernate.dialect.Dialect#appendLockHint(org.hibernate.LockMode, String)
* @since 3.2
*
* @author Steve Ebersole
*/
public class SelectLockingStrategy implements LockingStrategy {
private final Lockable lockable;
private final LockMode lockMode;
private final String sql;
/**
* Construct a locking strategy based on SQL SELECT statements.
*
* @param lockable The metadata for the entity to be locked.
* @param lockMode Indictates the type of lock to be acquired.
*/
public SelectLockingStrategy(Lockable lockable, LockMode lockMode) {
this.lockable = lockable;
this.lockMode = lockMode;
this.sql = generateLockString();
}
/**
* @see LockingStrategy#lock
*/
public void lock(
Serializable id,
Object version,
Object object,
SessionImplementor session) throws StaleObjectStateException, JDBCException {
SessionFactoryImplementor factory = session.getFactory();
try {
PreparedStatement st = session.getBatcher().prepareSelectStatement( sql );
try {
lockable.getIdentifierType().nullSafeSet( st, id, 1, session );
if ( lockable.isVersioned() ) {
lockable.getVersionType().nullSafeSet(
st,
version,
lockable.getIdentifierType().getColumnSpan( factory ) + 1,
session
);
}
ResultSet rs = st.executeQuery();
try {
if ( !rs.next() ) {
if ( factory.getStatistics().isStatisticsEnabled() ) {
factory.getStatisticsImplementor()
.optimisticFailure( lockable.getEntityName() );
}
throw new StaleObjectStateException( lockable.getEntityName(), id );
}
}
finally {
rs.close();
}
}
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 LockMode getLockMode() {
return lockMode;
}
protected String generateLockString() {
SessionFactoryImplementor factory = lockable.getFactory();
SimpleSelect select = new SimpleSelect( factory.getDialect() )
.setLockMode( lockMode )
.setTableName( lockable.getRootTableName() )
.addColumn( lockable.getRootTableIdentifierColumnNames()[0] )
.addCondition( lockable.getRootTableIdentifierColumnNames(), "=?" );
if ( lockable.isVersioned() ) {
select.addCondition( lockable.getVersionColumnName(), "=?" );
}
if ( factory.getSettings().isCommentsEnabled() ) {
select.setComment( lockMode + " lock " + lockable.getEntityName() );
}
return select.toStatementString();
}
}
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