con.setFieldType( DataType.TYPE_STRING );
con.setFieldName( "field1" );
con.setOperator( "==" );
con.setValue( "$f1" );
con.setConstraintValueType( SingleFieldConstraint.TYPE_TEMPLATE );
p.addConstraint( con );
SingleFieldConstraint con2 = new SingleFieldConstraint();
con.setFieldType( DataType.TYPE_STRING );
con2.setFieldName( "field2" );
con2.setOperator( "==" );