How to get the number of rows written by CSVPrinter?

Question

My code runs a SELECTstatement, and saves the entire ResultSet into a file with a single call to CSVprinter.printRecords(resultSet).

This works very nicely except, I'd like to know, how many records were written... The method itself does not return anything -- an opportunity to make life easier missed by the developers.

I tried calling resultSet.getRow() after printing -- hoping, it will be at the last one, thus giving me the total -- but that always returns zero.

I tried calling resultSet.last() before getRow(), but that fails, because mine is a "forward only" result-set. The afterLast() fails for the same reason.

I could loop over the result-set myself -- passing individual rows to CSVPrinter and counting them -- but that certainly is not as convenient and concise. Is there any other way?

Update: created the improvement request, for whatever that's worth...

Answer 1

You can also do it with a Proxy:

    public class CountingResultSet implements InvocationHandler {
        private ResultSet original; 
        private int counter;

    public static ResultSet newProxy(final ResultSet original) {
        return (ResultSet) Proxy.newProxyInstance(
                OracleVArrayTests.class.getClassLoader(), 
                  new Class[] { ResultSet.class }, 
                  new CountingResultSet(original)); 
    }
    
    public CountingResultSet(final ResultSet original) {
        this.original = original ;
        this.counter = 0;
    }
    
    @Override
    public Object invoke(Object proxy, Method method, Object[] args) 
      throws Throwable {
        if (method.getName().equals("next")) {
            Boolean res = (Boolean)method.invoke(this.original, args);
            if (res) ++this.counter;
            return res;
        }
        
        return method.invoke(this.original,  args);
    }
    
    int getCounter() { return this.counter; }
}

And getting the count:

    try (final ResultSet rs = CountingResultSet.newProxy((ResultSet) ...)) {
    ...
    ((CountingResultSet)Proxy.getInvocationHandler(rs)).getCounter();
    ...
    }