Chinh's semi-random thoughts on software development, gadgets, and other things.

Learning Java from a .NET Developer’s Perspective

I feel like I am discovering a whole new world. For my latest project, I have to do a lot of stuff in Java (1.6). While I am familiar with Java the language, I am a total newbie when it comes to Java related technologies, frameworks, and tools. Some of the specific Java technologies and tools I am using are JAXB/JAX-WS web services, Spring Framework, WebSphere Application Server, Maven, Rational Software Architect/Eclipse IDE.

Java Learning Resources

Here are some of the resources I found very useful while learning Java and related technologies in the past several weeks:

Portals

  • Java.sun.com – From the creator of Java itself.
  • Dzone – It’s like DotNetKicks but has everything including Java stuff.
  • IBM Redbooks – Tons of reference materials and everything is free.
  • developerWorks: IBM’s version of MSDN. There is a busy community section with forums as well.
  • Safari Books Online offers on-demand digital access to reference books. It’s not free, but it’s a great resource if you can read lots of books in a short time. Subscribe to their unlimited account and read all the books you want for a month. Remember to cancel before the month is over. Also remember that IBM Redbooks are free on the Redbooks site. Don’t waste your Safari points on Redbooks. And even if you have an unlimited Safari account, IBM’s site is still better because it offers PDFs.

Java

Web Services

Spring Framework

Eclipse IDE, Rational Software Developer/Architect

Misc

C# Features I Wish Java Has

I am sure Microsoft was pretty much thinking about Java when they created C#. The Java language itself it very similar to C# in terms of syntax, keywords, and use of punctuations such as semicolons and braces. I have found that most language features in C# have equivalents in Java. However, there are a few notable exceptions which I particularly miss:

  • Code regions – I use code regions extensively in C#. Eclipse does support code outlining but it’s only for existing code structures (methods) and is not nearly as flexible as c# regions.
  • Properties – Java only has fields and methods. “Properties” are implemented as get* and set* methods. I really miss properties, especially after typing 10 getters and setters in a row.
  • var keyword – Another small but very nice feature in C# that helps make code more compact and reduce typing.
  • Verbatim (@) strings – Very handy for regular expressions and other string literals that contain lots of escape characters.

Java is still evolving. Here’s hoping that some of the above features will make it into the next version of the language.

Wrap Your Unit Tests in Transactions

I have found that the key to writing good unit tests that interact with the database is making sure that the data is in a known state before and after the test. System.Transactions makes this very easy. All you have to do is wrap your unit test inside a TransactionScope and rollback at the end.

For example, in the test below, I am testing the update feature of my Customer data access class. To make sure I have a customer to update, I create it myself at the start of test, then I update it. At the end, scope.dispose() rolls back the whole thing. The database should look exactly like it was before my test.

[TestMethod]
public void CanUpdateCustomer()
{
    using (TransactionScope scope = new TransactionScope) {
        Customer customer = CreateTestCustomer();
        customerDac.saveCustomer(customer);
 
        customer.Phone1 = "804-555-1212";
        customerDac.updateCustomer(customer);
 
        // TODO: verify that update works
 
        scope.Dispose(); // roll back
    }
}

Here are a few more tips I have for unit tests that interact with the database:

  • Maintain scripts to create/rebuild a starting-point database. The starting-point database may contain some data such as lookup data, codes, etc. If your unit tests work correctly, the database will stay the same across tests. With the rebuild scripts, you can easily rebuild in the case of other mishaps or a bug in one of the unit tests causing corrupt data.
  • If you need to create a database record that doesn’t have an auto-generated key, use a random key to minimize the chance that your test will collide with another test running somewhere else. Seed your random generator with Environment.TickCount or a hash code of the machine name or user name.
  • With my Transactional File Manager, you can also restore the state of the file system in addition to the database. Transactional File Manager is great at automatically cleaning up any temporary files you create in your unit tests.
  • Don’t assume your code is the only thing that is touching the database. If the count of records in a table is x, it won’t necessarily be x + 1 after you add a new record to the table. Somebody else may have added to or deleted from the table while your test is running.

For Java programmers, try using Spring TestContext Framework. It’s a bit more complicated to use but it works just as well.

My Silverlight 2.0 Hello World Application

This is an update to my original article that was based on Silverlight 1.0 alpha. The code for the old article no longer worked with the current Silverlight runtime.

Instead of the traditional and simple display of a string, this Hello World application uses animation in code to say “hello”.

Pre-requisites

You will need to have the following installed:

Create a New Silverlight Project

  • In Visual Studio 2008, choose File/New/Project and select Visual C#/Silverlight/Silverlight Application. The Silverlight project type is added when you install the Silverlight Tools.
  • Give your project a name and choose OK.

    New Silverlight Project

  • On the next dialog window, accept the default “Add a new ASP.NET Web project…” and choose OK.

Silverlight Project Files

Since we will be drawing objects, we need a Canvas control instead of the default Grid. Change your Page.xaml file to read like this:

<UserControl x:Class="SilverlightHelloWorld.Page"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Width="520" Height="140" Loaded="UserControl_Loaded">
    <Canvas x:Name="MyCanvas"/>
</UserControl>

Press F7 when you have Page.xaml opened to switch to the code-behind file Page.xaml.cs, and replace the code there with this code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Windows.Threading;
namespace SilverlightHelloWorld
{
    public partial class Page : UserControl
    {
        // private Storyboard _timer = new Storyboard();
        private DispatcherTimer _timer;
        private List<Cell> cells = new List<Cell>(); // list of all cells
        private int _xSize = 26; // width of the grid, in number of cells
        private int _ySize = 7; // height of the grid
        private int _numCells; // total number of cells
        private int _cellIdx = 0;
        /// <summary>Represents a cell on the grid</summary>
        private class Cell
        {
            public double X; // x-coordinate of cell
            public double Y; // y-coordinate
            public bool On; // True if cell is "on"
            public double Order; // Display order
        }
        public Page()
        {
            InitializeComponent();
        }
        private void UserControl_Loaded(object sender, RoutedEventArgs e)
        {
            // Assign a random value to each cell 
            Random rnd = new Random(Environment.TickCount);
            _numCells = (int)(_xSize * _ySize);
            string template = "                          "
                + " x  x xxxx x    x     xx  "
                + " x  x x    x    x    x  x "
                + " xxxx xxxx x    x    x  x "
                + " x  x x    x    x    x  x "
                + " x  x xxxx xxxx xxxx  xx  "
                + "                          ";
            for (int y = 0; y < _ySize; y++)
            {
                for (int x = 0; x < _xSize; x++)
                {
                    Cell cell = new Cell();
                    cell.X = x * (this.Width / _xSize);
                    cell.Y = y * (this.Height / _ySize);
                    cell.Order = rnd.NextDouble();
                    cells.Add(cell);
                }
            }
            for (int i = 0; i < template.Length; i++)
            {
                cells[i].On = template[i] == 'x';
            }
            // Sort the cells by the random values
            cells.Sort(
                delegate(Cell c0, Cell c1)
                {
                    return c0.Order.CompareTo(c1.Order);
                }
            );
            _timer = new System.Windows.Threading.DispatcherTimer();
            _timer.Interval = TimeSpan.FromMilliseconds(1);
            _timer.Tick += new EventHandler(timer_Completed);
            _timer.Start();
        }
        void timer_Completed(object sender, EventArgs e)
        {
            if (_cellIdx < _numCells)
            {
                // Get the next cell
                Cell cell = cells[_cellIdx];
                // Draw the cell
                Rectangle r = new Rectangle();
                r.Stroke = new SolidColorBrush(Colors.DarkGray);
                if (cell.On)
                {
                    r.Fill = new SolidColorBrush(Colors.Red);
                }
                else
                {
                    r.Fill = new SolidColorBrush(Colors.LightGray);
                }
                r.Width = this.Width / _xSize;
                r.Height = this.Height / _ySize;
                r.SetValue(Canvas.LeftProperty, cell.X);
                r.SetValue(Canvas.TopProperty, cell.Y);
                MyCanvas.Children.Add(r);
                _cellIdx++;
            }
            else
            {
                _timer.Stop();
            }
        }
    }
}
Save the file. Right click on SilverlightHellowordTestPage.aspx and choose Set As Start Page, then run the app.
Hosting the Application
To host the application on your web site, just copy the following files:
  • Silverlight.js
  • SilverlightHelloWorldTestPage.html
  • ClientBin/SilverlightHelloWorld.xap
Click here to see the application in action.
Bag of Links #1
A while ago I had been posting my Finds of the Weeks series and this is the continuation of that. Instead of weekly though, this series will be more of a “whenever possible” kind of thing.
General Programming
.NET/C# Stuff
Database
Windows
Software, Tools, etc.
  • If you have a Linksys WRT54* router, I highly recommend loading Tomato firmware. I have been using it for about 6 months now and it’s so much better than the built-in Linksys firmware. Tomato’s QOS works great to make sure my Vonage phone line remains usable at all times.Tomato firmware
PowerShell
  • Ben Pierce posted a series of very useful PowerShell command-line demos: Demo1 (Administering Windows), Demo 2 (Administering Servers in bulk), Demo 3 (How do I Know Which Class to Use), Demo 4 (Administering Hyper-V).
Something Different
How to Use VISA Gift Card on Amazon
I googled and didn’t find anything useful so I thought I’d share this. If you have a VISA gift card and want to use it on Amazon.com in conjunction with a credit card (to pay for any amount over the gift card value), the trick is to use the VISA gift card to purchase an Amazon gift card of the same value for yourself (search for “gift card” on Amazon.com).
Once you have the Amazon gift card, you can then use it to pay for part of your order, with the remaining balance being charged to another credit card.
I am sure this trick works with most other online merchants too.
Ordering gift card on Amazon
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