Talking to the Owl

I've spent another Saturday night hacking on computer.  My wrists won't thank me in the morning.  I'll think I'll dance away the pain.  This time I have no one to blame but myself.  Last weekend I had to stay awake to listen to a conference call while we upgraded systems. 

I seem to have caught the GWT bug.  Developing Javascript in Java brings the fun back into rich thin clients!  In fact, once I started writing JUnit tests external of the *.client package to validate the logic of the client code I think I crossed the line between sceptic and believer.  I'll keep putting snapshots of the source I create here.  The beauty of GWT is that I don't need a server to display my results - it compiles to Javascript.  One caveat is that Mozilla doesn't seem to like to submit on the click.

Consider this code as Javascript:

package com.owlmountain.client;

public class MatrixTextParser {
 
 public Matrix parse ( String values ) throws MatrixTextInvalidException {
  Matrix result = null;
  String[] rows = values.split("\n");
  for ( int i = 0; i < rows.length; i++ ) {
   String[] column = rows[i].split(" ");
   if ( i == 0 ) {
    result = new Matrix(rows.length, column.length);
   }
   for ( int j = 0; j < column.length; j++ ) {
    try {
     result.set(i, j, Double.parseDouble(column[j]));
    }
    catch ( NumberFormatException e ) {
     throw new MatrixTextInvalidException(i, j, column[j], e.getMessage());
    }
   }
  }
  return result;
 }

}

To test it, all I have to do is create (in a package outside of *.client)

package com.owlmountain.gwt.test;

import org.apache.log4j.Logger;

import com.owlmountain.client.Matrix;
import com.owlmountain.client.MatrixTextInvalidException;
import com.owlmountain.client.MatrixTextParser;

import junit.framework.TestCase;

public class MatrixTextParserTest extends TestCase {
 Logger logger = Logger.getLogger(MatMultTest.class);
 MatrixTextParser parser = null;
 
 public MatrixTextParserTest(String name) {
  super(name);
  parser = new MatrixTextParser();
 }
 
 public void testGoodParser() throws MatrixTextInvalidException {
  Matrix values = parser.parse("1 2 3\n4 5 6\n");
  assertEquals(2, values.getRowDimension());
  assertEquals(3, values.getColumnDimension());
  logger.info(values);
 }

 public void testBadValueParser() {
  try {
   parser.parse("1 2 3\n4 6 b\n");
   fail("Expected exception");
  }
  catch (MatrixTextInvalidException e) {
   assertEquals(1, e.getRow());
   assertEquals(2, e.getCol());
   assertEquals("b", e.getValue());
   logger.info(e.getMessage());
  }
 }

}

I converted the Jama matrix class to run on the client side by removing every reference outside of the java.lang.*.  Incidentally, I saw a lot of things I didn't like about Jama, right down to simple mistakes like not implementing "toString()" on the Matrix class.  I'm still trying to decide whether I can forgive them for not having a dynamic matrix class.  I'll have to think about a clean way to do that.  Eventually, I'd like to write some SVG graphing and analysis tools, so having a good fast matrix library is a nice start.  Of course, I want a lot of the matrix processing to occur on the client, because each transformation will be small.