forupdatefragment.java

介绍了hibernate的入门有一些基本常用的事例

//$Id: ForUpdateFragment.java,v 1.4 2004/10/26 15:41:00 oneovthafew Exp $
package org.hibernate.sql;

import java.util.Iterator;
import java.util.Map;

import org.hibernate.LockMode;
import org.hibernate.QueryException;
import org.hibernate.dialect.Dialect;
import org.hibernate.util.StringHelper;

/**
 * @author Gavin King
 */
public class ForUpdateFragment {
	private final StringBuffer aliases = new StringBuffer();
	private boolean isNowaitEnabled;
	private final Dialect dialect;
	
	public ForUpdateFragment(Dialect dialect) {
		this.dialect = dialect;
	}

	public ForUpdateFragment addTableAlias(String alias) {
		if ( aliases.length()>0 ) aliases.append(", ");
		aliases.append(alias);
		return this;
	}
	
	public String toFragmentString() {
		if ( aliases.length()==0 ) return "";
		return isNowaitEnabled ?
				dialect.getForUpdateNowaitString( aliases.toString() ) :
				dialect.getForUpdateString( aliases.toString() );
	}

	public ForUpdateFragment setNowaitEnabled(boolean nowait) {
		isNowaitEnabled = nowait;
		return this;
	}

	public ForUpdateFragment(Dialect dialect, Map lockModes, Map keyColumnNames) 
	throws QueryException {
		this(dialect);
		LockMode upgradeType = null;
		Iterator iter = lockModes.entrySet().iterator();
		while ( iter.hasNext() ) {
			final Map.Entry me = (Map.Entry) iter.next();
			final LockMode lockMode = (LockMode) me.getValue();
			if ( LockMode.READ.lessThan(lockMode) ) {
				final String tableAlias = (String) me.getKey();
				if ( dialect.forUpdateOfColumns() ) {
					String[] keyColumns = (String[]) keyColumnNames.get(tableAlias); //use the id column alias
					keyColumns = StringHelper.qualify(tableAlias, keyColumns);
					for (int i=0; i<keyColumns.length; i++) addTableAlias( keyColumns[i] );
				}
				else {
					addTableAlias(tableAlias);
				}
				if ( upgradeType!=null && lockMode!=upgradeType ) {
					throw new QueryException("mixed LockModes");
				}
				upgradeType = lockMode;
			}
		}

		if ( upgradeType==LockMode.UPGRADE_NOWAIT ) setNowaitEnabled(true);
	}
}