Free tool to create Windows installers

Rahul Sah

As a developer one likes to have applications that can be distributed in easy, installable setups. Since the installation setup is the first

interaction of the user with your application, you would like to have all installation tasks be done like a breeze. Nullsoft has come out with a script-based

program, NSIS, that helps you create such an installer (i.e. setup.exe).

Nullsoft Scriptable Install System (NSIS) is an Open Source package that allows programmers to make Windows-based installers for their applications. NSIS has two components-script and a compiler. In order to create an installer for your software, you need to write a script which will decide as to how the installer will behave. For example, the path for installing the software and what all registry changes it needs to have.

Plus, the shortcuts it will create on the desktop.

Once you have written the installer script, you need to compile it in the given compiler, which will give you the final distribution as a 'setup.exe' file. Installer created with NSIS is compatible with all versions of Windows (be it 95 or Vista).

Getting started

We have given the NSIS package installer on this month's PCQ Professional CD. Copy the NSIS package installer on your Windows machine first. After installing the NSIS package, you need to create a script. For this open a Note pad and start writing the installation script for your software. Let's see how a script to build an installer for a JAVA program works.

It makes an installer setup for a simple Java program that does the following tasks:

• Copies all class files into the installer package.
• Creates Start Menu icons for running the demo application.
• Creates a Desktop shortcut for running the demo application.
• Checks whether JRE is present or not.
• Creates registry entries for uninstallability of application through Add/Remove programs.
• Makes the application uninstallable.

The first few instructions of the script define the installer attributes. The attributes that are set here are the window names and the text to be displayed on them. Let's name our application as 'PCQ Application' and its installer as 'PCQAppInstaller.exe.' The following code snippet shows the same:

Name "PCQ Application"

Caption "PCQ Demo Application"

OutFile "PCQAppInstaller.exe"

DirText "Please choose a directory to which you'd like to install PCQ Application."

InstallDir "$PROGRAMFILES\PCQ Application"

The 'OutFile' keyword gives the name to the setup program that will be created after compilation and 'InstallDir' creates default location for the installation process. NSIS has some constants like $PROGRAMFILES, $DESKTOP and $SMPROGRAMS which point to the current user's Program Files folder, desktop and Start Menu respectively.

Each script has at least one section. A section carries the instructions for different segments of installation process. Our script has two sections, namely Install and Uninstall. The Install section will have instructions to copy files into installer package, make their shortcuts and registry entries. The code for this is as follows.

Section "install"

SetOutPath $INSTDIR\

File E:\nsis_scripts\java_app\PCQ_Test.class

...

WriteUninstaller $INSTDIR\Uninstall.exe

CreateDirectory "$SMPROGRAMS\PCQ Application"

CreateShortCut "$DESKTOP\PCQ Application.lnk" "$SYSDIR\javaw.exe" "PCQ_Test"

...

WriteRegStr HKLM "Software\Microsoft\Windows\CurrentVersion\Uninstall\PCQ Application" "DisplayName"\ "PCQ Application (remove only)"

...

SectionEnd

'SetOutPath' sets the location where the files will be copied upon installation and 'File' keyword packs the files into the installer. The Start Menu program setup for the PCQ Application and the registry entries for the same will be done through 'CreateDirectory' and 'WriteRegStr' respectively. Now if we look at the 'CreateShortCut' instruction, we have three parameters. The first will create the desktop shortcut link for the PCQ Application, second will invoke JRE's javaw.exe to execute the class name passed as third parameter i.e. PCQ_Test. Also, we have to check whether JRE is present on users' machine or not as it is needed to execute our Java program. So, we can add the following snippet to 'install' section to do this check.

readRegStr $0 HKLM "SOFTWARE\JavaSoft\Java Runtime Environment" CurrentVersion

StrCmp $0 "" NoFound

...

NoFound:

MessageBox MB_OK "JRE not found. Installation will quit now...

The $0 variable, if blank, shows no JRE is installed otherwise it will store the JRE version. Like other programming languages, conditional checking can be done. 'StrCmp' lets us check for value in $0 variable. If blank, it jumps to NoFound case else it continues with installation. This way the installation setup will be prepared.

Finally to make the application uninstallable, we have to create a section 'uninstall.' In this section we give instructions to delete all shortcuts, files and their directories, and also to remove the registry entries. We put the instruction WriteUninstaller $INSTDIR\Uninstall.exe in the install section. Now NSIS will look for an uninstall section in the script while compiling. The snippet for uninstall script is as follows.

Section "Uninstall"

...

Delete $INSTDIR\PCQ_Test.class ;//delete files

Delete "$DESKTOP\PCQ Application.lnk"

...

SectionEnd

Once you have finished writing the script, save the file with .nsi extension. Now lets also see what's in PCQ_Test. java program. It takes a date instance from the system time and displays the current date and time to the user after formatting it and converting that to a string. The Ccode snippet is as follows:

public PCQ_Test() {

Date today;

DateFormat dateFormatter;

dateFormatter = DateFormat.getDateInstance(DateFormat.DEFAULT);

DateFormat timeFormatter =

DateFormat.getTimeInstance(DateFormat.DEFAULT);

today = new Date();

String showDate = dateFormatter.format(today);

String showTime = timeFormatter.format(today);

String message = "Hello!! Today's Date is "+showDate+" and Time is "+showTime;

...

}

Compilation

Now to open NSIS compiler, launch 'MakeNSISW' from Start>Programs> NSIS. This will open a complier window. To compile the script that you have created above, load the script by clicking File>Load Script option. Alternatively, the script can also be dragged onto the compiler window or by right-clicking the .nsi file and choosing 'Compile NSIS Script.' The compiler compiles the script and if it does not find any errors with the instructions the 'Test Installer' button gets enabled. If script has errors they are shown on the window and the build process is stopped. With the 'Test Installer' button we can test the installer setup that the script has created.

In conclusion

NSIS not only makes installers for Java developers but also for any other application development environment, be it Macromedia Flash or .NET. Thus it's a handy tool for developers to make their applications easy for distribution.

Source: PCQuest