Out of memory error with XML datasource

vlpe

I generate a report using Birt Report Engine API using XML datasource with about 800 rows in a web application running on Tomcat server. I get an out of memory exception when creating datasource object, see code :
StringBuilder xpath = new StringBuilder();
xpath.append("table0#-TNAME-#table0#:#[/root/row]#:#");
for (int i = 1; i <= meta.getColumnCount(); i++) {
String colName = meta.getColumnName(i);
xpath.append(String.format("{%s;STRING;/%s},", colName, colName));
}

xpath.deleteCharAt(xpath.length() - 1);
return xpath.toString();

OdaDataSourceHandle dataSourceHandle =
efactory.newOdaDataSource("Data Source",
"org.eclipse.birt.report.data.oda.xml");
dataSourceHandle.setProperty("FILELIST", xmlPath);

OdaDataSetHandle dataSetHandle = efactory.newOdaDataSet("Data Set",
"org.eclipse.birt.report.data.oda.xml.dataSet");
dataSetHandle.setDataSource("Data Source");
dataSetHandle.setQueryText(generateXPathExpr(meta));