Conditional writing to CSV file with Scriptella - export-to-csv

Question

I'am working on an ETL script that reads data from an DB, manipulates it using Java and finally writes it to a CSV file. My script looks like this:
<query connection-id="db">
SELECT COLUMN_A AS A, COLUMN_B AS B
FROM DATABASE_TABLE
<script connection-id="java">
System.setProperty("a",String.valueOf(get("A")));
System.setProperty("b",String.valueOf(get("B")));
</script>
<script connection-id="csv_out">
$a,$b
</script>
</query>
The scripts is working in a way that I get one row written to the CSV file for each row in the query result. But what I need is a way to create more or less rows than the query result has delivered. Therefore I want a conditional output to the CSV file, based on values set in the Java part:
<script connection-id="java">
System.setProperty("a",String.valueOf(get("A")));
System.setProperty("b",String.valueOf(get("B")));
</script>
// only create line when 'a' has specific value, e.g. '1'
<script connection-id="csv_out" if="$a == 1">
$a,$b
</script>
This approach does not work. It writes nothing to the CSV, even if I set the value of 'a' explicitely to 1. So what is the right way to do conditional script execution in Scriptella? Or is there an even better solution?

Answer 1

Got it. You just have to use the name of the varibale, without the '$' symbol.
// only create line when 'a' has specific value, e.g. 1
<script connection-id="csv_out" if="a == 1">
$a,$b
</script>
For String values you have to use quotes around the comparison String.
// only create line when 'a' has specific value, e.g. 'ok'
<script connection-id="csv_out" if="a == 'ok'">
$a,$b
</script>