How to modify and rebuild expression.
1. remove a sub-node of an Expression
After removing a sub-node of an expression, the whole expression maybe affected. Take this SQL for example:
d.cntrb_date1 >= '$From_Date$'
remove either d.cntrb_date1 or ‘$From_Date$’, the whole expression will be removed as well.
According to the different kind of expression, the result will be different after removing a sub-node.
- Math expression: +,-,*,/ and other expression with two operands, after removing one operand, the other will be remain unchanged.
- Logical expression: and, or， after removing one operand, the other will be remain unchanged.
- Comparison expression: <, > , after removing one operand, the whole expression will be removed.
- in, between, () expression: after removing one operand, the whole expression will be removed.
- Other kind of expression: after removing one operand, the whole expression will be removed.
After the removal of the sub-node, if the whole parent expression is removed as well, the processing will be executed recursively until the top-level expression.
1.1 API
Call TExpression.removeMe() to remove an expression itself.
1.2 using TParseTreeNodeList.removeItem(int index) to remove the sub-expression in the expression list
(1,2,3,4)
After calling
expressionList.removeItem(0);
The result is:
(2,3,4)
2. Modify the expression
d.cntrb_date1 >= '$From_Date$'
After set ‘$From_Date$’ to 1 , the expression will be
d.cntrb_date1 >= 1
The java code to achieve this:
expression.getRightOperand().setString("1");
assertTrue(expression.toString().equalsIgnoreCase("d.cntrb_date1 >= 1"));
3. Add a new expression
If we like to change
d.cntrb_date1 >= '$From_Date$'
to:
d.cntrb_date1 >= '$From_Date$' + 1
Here is the Java code:
expression.getRightOperand().setString(expression.getRightOperand().toString()+" + 1");
assertTrue(expression.toString().equalsIgnoreCase("d.cntrb_date1 >= '$From_Date$' + 1"));
Reference Java code
- public void testRemove1()
- public void testRemoveExprList()