dom4j写入海量数据问题

主要是报内存溢出,我把写的操作放在循环里面的话,就只能把子节点写进去,没有了头和根节点,如果最后把整个document写进去的话,就内存溢出了,请大侠们指点指点啊,小弟在此谢过了
以下是代码:

package hrsys.out;

import org.dom4j.*;
import org.dom4j.io.*;
import org.xml.sax.SAXException;

import hrsys.db.dbcon;
import hrsys.outdata.Friends;

import java.io.*;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Timestamp;
import java.util.*;

public class FriendsViewByTableName
{

private XMLWriter writer = null;

//调用dom4j中的一个类来解决中文问题,在得到writer时把format传进去
OutputFormat format = OutputFormat.createPrettyPrint();

public void viewData(Adm_chgtmp adm)
{
/** 指定XML编码 */
format.setEncoding("GBK");

String tableName = null;
String columnName = null;
String columnValue = null;

Element friendElement = null;
Element ageElement = null;
Document document = null;
String sql = "";
String sql1 = "";

ResultSet rs = null;
ResultSet rs1 = null;
dbcon connect = null;

String TMPID = adm.getTMPID();
String TMPDESC = adm.getTMPDESC();
String ALLROWS = adm.getALLROWS();
String MARKISNEW = adm.getMARKISNEW();
String DELETEON = adm.getDELETEON();
String TMPDATA =adm.getTMPDATA();
String ISNEW = adm.getISNEW();
Timestamp LASTUPDATE = adm.getLASTUPDATE();

List list = stringToken(TMPDATA);
Iterator it = list.iterator();
try
{
document = DocumentHelper.createDocument();

Element friendsElement = document.addElement("DATA");

//document.setRootElement(friendsElement);

// try {
// writer.processingInstruction("xml version=\"1.0\"", "encoding=\"GBK\"");
// } catch (SAXException e1) {
// // TODO Auto-generated catch block
// e1.printStackTrace();
// }
while(it.hasNext())
{
tableName = (String)it.next();
sql ="select * from " + tableName +" where ISNEW = 1 ";
sql1 = "select * from syscolumns where id=object_id('"+ tableName + "')" ;
try{
connect = new dbcon();
rs = connect.executeQuery(sql);
rs1 = connect.executeQuery(sql1);
rs1.last();
int row = rs1.getRow();
String column[] = new String[row];
rs1.beforeFirst();


System.out.println(row);

while(rs1.next())
{
for(int i=0;i<row;i++)
{
column[i] = rs1.getString("name");
rs1.next();
}
}




while(rs.next())
{
friendElement = friendsElement.addElement(tableName);

for(int i = 0;i<column.length;i++)
{
columnName = column[i];

columnValue = rs.getString(columnName);
System.out.println("列名:"+columnName);
System.out.println("值:"+columnValue);
ageElement = friendElement.addElement(columnName);
ageElement.setText((columnValue+"").toString().trim());
}

// writer.write(friendElement);
// friendElement.clearContent();//释放这个Element的空间,不然会导致内存耗尽
//friendsElement.clearContent();
}
//writer.write(friendsElement);

} catch( SQLException e){
e.printStackTrace();

} catch( Exception e){
e.printStackTrace();

}
finally
{
try
{
if(rs!=null)
rs.close();
if(rs1!=null)
rs1.close();
connect.closeConnect();
}
catch(SQLException e)
{
e.printStackTrace();

}

}
writer = new XMLWriter(new FileWriter(new File("C:/exp/friend.xml"),true),format);
writer.write(document);
System.out.println("创建文件成功");

}

} catch (IOException e)
{
e.printStackTrace();
}
finally
{
if(writer != null)
{
try
{
writer.close();
}
catch(Exception err)
{
err.printStackTrace();
}
}
}


}
public List stringToken(String tableName)
{
List list = new ArrayList();
StringTokenizer stok = new StringTokenizer(tableName,",");
while(stok.hasMoreElements())
{
list.add(stok.nextToken());
}
return list;
}

}