collectionloader.java

用Java实现的23个常用设计模式源代码

//$Id: CollectionLoader.java,v 1.15.2.12 2003/11/15 09:49:06 oneovthafew Exp $
package net.sf.hibernate.loader;

import java.io.Serializable;
import java.sql.SQLException;
import java.util.List;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.LockMode;
import net.sf.hibernate.MappingException;
import net.sf.hibernate.collection.CollectionPersister;
import net.sf.hibernate.collection.QueryableCollection;
import net.sf.hibernate.engine.SessionFactoryImplementor;
import net.sf.hibernate.engine.SessionImplementor;
import net.sf.hibernate.persister.Loadable;
import net.sf.hibernate.sql.JoinFragment;
import net.sf.hibernate.sql.Select;
import net.sf.hibernate.type.AssociationType;
import net.sf.hibernate.type.Type;
import net.sf.hibernate.util.StringHelper;

/**
 * Loads a collection of values or a many-to-many association.<br>
 * <br>
 * The collection persister must implement <tt>QueryableCOllection<tt>. For
 * other collections, create a customized subclass of <tt>Loader</tt>.
 * 
 * @see OneToManyLoader
 * @author Gavin King
 */
public class CollectionLoader extends OuterJoinLoader implements CollectionInitializer {
	
	private final QueryableCollection collectionPersister;
	private final Type keyType;
	
	public CollectionLoader(QueryableCollection persister, SessionFactoryImplementor session) throws MappingException {
		this(persister, 1, session);
	}
	
	public CollectionLoader(QueryableCollection persister, int batchSize, SessionFactoryImplementor factory) throws MappingException {
		
		super( factory.getDialect() );
		
		keyType = persister.getKeyType();
		
		String alias = generateRootAlias( persister.getTableName() );
		
		List associations = walkCollectionTree(persister, alias, factory);
		
		int joins=associations.size();
		suffixes = generateSuffixes(joins);
		
		sql = renderStatementString(persister, alias, associations, batchSize, factory);
		
		classPersisters = new Loadable[joins];
		lockModeArray = createLockModeArray(joins, LockMode.NONE);
		for ( int i=0; i<joins; i++ ) classPersisters[i] = (Loadable) ( (OuterJoinableAssociation) associations.get(i) ).joinable;
		this.collectionPersister = persister;
		
		postInstantiate();

	}
	
	protected CollectionPersister getCollectionPersister() {
		return collectionPersister;
	}
	
	public void initialize(Serializable id, SessionImplementor session) throws SQLException, HibernateException {
		loadCollection(session, id, keyType);
	}
	
	public final String renderStatementString(QueryableCollection persister, String alias, List associations, int batchSize, SessionFactoryImplementor factory) 
	throws MappingException {
		
		StringBuffer whereString = whereString(alias, persister.getKeyColumnNames(), batchSize);
		if ( persister.hasWhere() ) whereString.append(" and ").append( persister.getSQLWhereString(alias) );
		
		JoinFragment ojf = mergeOuterJoins(associations);
		Select select = new Select()
			.setSelectClause( 
				persister.selectClauseFragment(alias) + 
				selectString(associations, factory)
			)
			.setFromClause( persister.getTableName(), alias )
			.setWhereClause( whereString.toString()	)
			.setOuterJoins(
				ojf.toFromFragmentString(),
				ojf.toWhereFragmentString()
			);
		if ( persister.hasOrdering() ) select.setOrderByClause( persister.getSQLOrderByString(alias) );
		return select.toStatementString();
	}

	protected int getJoinType(
		AssociationType type,
		int config,
		String path,
		String table,
		String[] foreignKeyColumns,
		SessionFactoryImplementor factory) 
		throws MappingException {
		
		int joinType = super.getJoinType(type, config, path, table, foreignKeyColumns, factory);
		//we can use an inner join for the many-to-many
		if ( joinType==JoinFragment.LEFT_OUTER_JOIN && StringHelper.EMPTY_STRING.equals(path) ) joinType=JoinFragment.INNER_JOIN;
		return joinType;
	}

	
}