iteratorimpl.java

来自「用Java实现的23个常用设计模式源代码」· Java 代码 · 共 122 行

//$Id: IteratorImpl.java,v 1.5.2.3 2003/11/27 16:09:59 oneovthafew Exp $
package net.sf.hibernate.impl;

import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.NoSuchElementException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import net.sf.hibernate.HibernateException;
import net.sf.hibernate.LazyInitializationException;
import net.sf.hibernate.engine.HibernateIterator;
import net.sf.hibernate.engine.SessionImplementor;
import net.sf.hibernate.type.Type;

/**
 * An implementation of <tt>java.util.Iterator</tt> that is
 * returned by <tt>iterate()</tt> query execution methods.
 * @author Gavin King
 */
public final class IteratorImpl implements HibernateIterator {
	
	private static final Log log = LogFactory.getLog(IteratorImpl.class);
	
	private ResultSet rs;
	private final SessionImplementor sess;
	private final Type[] types;
	private final boolean single;
	private Object[] nextResults;
	private Object currentResult;
	private boolean hasNext;
	private final String[][] names;
	private PreparedStatement ps;
	private Object nextResult;
	
	public IteratorImpl(ResultSet rs, PreparedStatement ps, SessionImplementor sess, Type[] types, String[][] columnNames)
	throws HibernateException, SQLException {
		
		this.rs=rs;
		this.ps=ps;
		this.sess = sess;
		this.types = types;
		this.names = columnNames;
		
		single = types.length==1;
		
		postNext( rs.next() );
	}
	
	public void close() throws SQLException {
		if (ps!=null) {
			log.debug("closing iterator");
			nextResults = null;
			sess.getBatcher().closeQueryStatement(ps, rs);
			ps = null;
			rs = null;
			hasNext = false;
		}
	}
	
	private void postNext(boolean hasNext) throws HibernateException, SQLException {
		this.hasNext = hasNext;
		if (!hasNext) {
			log.debug("exhausted results");
			close();
		}
		else {
			log.debug("retrieving next results");
			if (single) {
				nextResult = types[0].nullSafeGet( rs, names[0], sess, null );
			}
			else {
				nextResults = new Object[types.length];
				for (int i=0; i<types.length; i++) {
					nextResults[i] = types[i].nullSafeGet( rs, names[i], sess, null );
				}
				nextResult = nextResults;
			}
		}
	}
	
	public boolean hasNext() {
		return hasNext;
	}
	
	public Object next() {
		if ( nextResult==null ) throw new NoSuchElementException("No more results");
		try {
			currentResult = nextResult;
			postNext( rs.next() );
			log.debug("returning current results");
			return currentResult;
		}
		catch (Exception sqle) {
			log.error("could not get next result", sqle);
			throw new LazyInitializationException(sqle);
		}
	}
	
	public void remove() {
		if (!single) throw new UnsupportedOperationException("Not a single column hibernate query result set");
		if (currentResult==null) throw new IllegalStateException("Called Iterator.remove() before next()");
		try {
			sess.delete(currentResult);
		}
		catch (Exception sqle) {
			log.error("could not remove", sqle);
			throw new LazyInitializationException(sqle);
		}
	}
	
}