Java JAR wrapper for creating Windows native executables
created by LoRd_MuldeR <mulder2@gmx.de>

Introduction

Launch5j is a reimagination of “Launch4j”, with full Unicode support. This is a tool for wrapping Java applications distributed as JARs in lightweight Windows native executables. The executable can be configured to search for a certain JRE version or use a bundled one. The wrapper also provides better user experience through an application icon, a native pre-JRE splash screen, and a Java download page in case the appropriate JRE cannot be found.

Usage

There currently are two different ways to use Launch5j with your application code:

• Use the launcher executable with a separate JAR file

  Simply put the launcher executable (launch5j.exe) and your JAR file into the same directory. Launch5j will automatically detect the path of the JAR file based on the location of the executable file. More specifically, Launch5j detects the full path of the executable file and then replaces the .exe file extension with a .jar file extension. Of course, you can rename the launch5j.exe executable to whatever you prefer.

  For example: If you application's JAR file is called bazinga.jar, pick the Launch5j variant of your choice, rename the Launch5j executable to bazinga.exe, and put these two files (JAR + EXE) into the “install”directory.

• Combine the launcher executable and the JAR file (“wrapping”)

  In order to combine the launcher executable (launch5j_wrapped.exe) and the JAR file to a single file, you can simply concatenate these files. The executable launcher must go before the JAR file content. There are many ways to achieve this, but one method is by running the following copy command-line in the terminal:

  copy /B launch5j_wrapped.exe + bazinga.jar bazinga.exe
  

  If you are building you application with Apache Ant, consider using the concat task like this:

  <concat destfile="bazinga.exe" binary="true">
     <fileset file="launch5j_wrapped.exe"/>
     <fileset file="bazinga.jar"/>
  </concat>
  

  The resulting bazinga.exe will be fully self-contained and is the only file you'll need to ship.

  Warning: Code signing, as with Microsoft®'s SignTool, probably does not work with the “wrapped” executable file! If code signing is a requirement, please use a separate JAR file and just sing the launcher executable.

Variants

Launch5j executables come in a number of variants, allowing you to pick the most suitable one for you project:

• wrapped
  Expects that the JAR file and the executable launcher have been combined to a single file; default variant expects that a separate JAR file is present in the same directory where the executable launcher resides.

• registry
  Tries to automatically detect the install path of the JRE from the Windows registry; default variant expects the JRE to be located in the /runtime path relative to the location of the executable launcher.

• nowait
  Does not keep the launcher executable alive while the application is running; default variant keeps the launcher executable alive until the application terminates and then forwards the application's exit code.

• nosplash
  Does not display a splash screen while the application is launching; default variant does display a splash screen while the application is launching – will be hidden as soon as application window shows up.

• noenc
  Does not apply URL encoding to the given command-line arguments; default variant does apply URL encoding to all given command-line arguments in order to work around a long standing bug in Java.

Platforms

All of the above Launch5j variants are available as x86 (32-Bit) and x64 (64-Bit) executables. The x86 (32-Bit) executables can run on 32-Bit and 64-Bit versions of Microsoft® Windows™, whereas the x64 (64-Bit) executables require a 64-Bit version of Microsoft® Windows™. Consequently, it is generally recommended to distribute the x86 (32-Bit) launcher executable. Please note that this does not restrict the “bitness” of the JRE that can be used. Even the x86 (32-Bit) launcher executable is perfectly able to detect and launch a 64-Bit JRE – if it is available.

Note: Launch5j has been tested to work correctly on Windows XP (Service Pack 2), or a compatible newer version.

Customizations

Launch5j comes with a default executable icon and a default splash screen bitmap. These just server as an example and you probably want to replace them with your own application-specific graphics.

It is not necessary to re-build the executable files for that purpose. Instead, you can simply use a resource editor, such as XN Resource Editor (mirror) or Resource Hacker™, to modify the pre-compiled executable files as needed:

Additional options

Some options can be configured via the launcher executable's STRINGTABLE resource:

• ID_STR_HEADING (#1)
  Specifies a custom application title that will be used, e.g., as the heading of message boxes.

• ID_STR_JVMARGS (#2)
  Specifies additional options JVM options to be passed, such as -Xmx2g or -Dproperty=value.
  See here for a list of available options:
  https://docs.oracle.com/javase/7/docs/technotes/tools/windows/java.html

• ID_STR_CMDARGS (#3)
  Specifies additional fixed command-line parameters to be passed to the Java application.

• ID_STR_JREPATH (#4)
  Specifies the path to the Java runtime (javaw.exe) relative to the launcher executable location. If not specified, then the default runtime path runtime\\bin\\javaw.exe is assumed.

  (This option does not apply to the “registry” variant of Launch5j)

• ID_STR_MUTEXID (#5)
  Specifies the application ID to be used when creating the single-instance mutex.
  The ID must be at least 5 characters in length and should be a unique string for each application!
  If not specified, then no mutex will be created and thus multiple instances will be allowed.

  Hint: If the specified application ID starts with an @ character, then Launch5j will not show a message box when the application is already running; the @ character is not considered a part of the actual ID.

  (This option does not apply to the “nowait” variant of Launch5j)

• ID_STR_JAVAMIN (#6)
  Specifies the minimum supported JRE version, in the w.x.y.z format (e.g. 11.0.0.0).
  This values is inclusive, i.e. the specified JRE version or any newer JRE version will be accepted.
  If not specified, then the default minimum supported JRE version 8.0.0.0 applies.

  Hint: Old-style 1.x.y_z Java versions are automatically translated to the new x.y.z format!

  (This option only applies to the “registry” variant of Launch5j)

• ID_STR_JAVAMAX (#7)
  Specifies the maximum supported JRE version, in the w.x.y.z format (e.g. 12.0.0.0).
  This values is exclusive, i.e. only JRE versions older than the specified JRE version will be accepted.
  If not specified, then there is no upper limit on the supported JRE version.

  Hint: Old-style 1.x.y.z Java versions are automatically translated to the x.y.z.0 format!

  (This option only applies to the “registry” variant of Launch5j)

• ID_STR_BITNESS (#8)
  Specifies the required bitness of the JRE. This can be either 32 (x86, aka i586) or 64 (x86-64).
  If not specified, then 32-Bit and 64-Bit JREs are accepted, with a preference to 64-Bit.

  (This option only applies to the “registry” variant of Launch5j)

• ID_STR_JAVAURL (#9)
  The Java download URL that will ne suggested, if no suitable JRE could be detected on the machine.
  If not specified, wes suggest downloading OpenJDK as provided by the AdoptOpenJDK project.

  Hint: The URL must begin with a http:// or https:// prefix; otherwise the URL will be ignored!

  (This option only applies to the “registry” variant of Launch5j)

Note: We use the convention that the default resource string value "?" is used to represent an “undefined” value, because resource strings cannot be empty. You can replace the default value as needed!

Unicode command-line arguments

There is a long-standing bug in Java on the Windows™ platform, which causes Unicode command-line arguments to be “mangled”. Even if the Unicode command-line arguments are properly passed to the Java executable (java.exe), they are not passed trough correctly to the main() method of your Java program! This problem can be reproduced in all Java versions ranging from Java 7 (1.7) up to and including the latest Java 15, as of October 2020.

More specifically, Java replaces any characters in the given command-line arguments that can not be represented in the computer's local ANSI codepage (i.e. pretty much any non-ASCII characters) with ? characters. The cause of the problem apparently is that the “native” C code of the Java executable still uses the legacy main() entry point instead of the wmain() entry point; the latter is the modern Unicode-aware entry point – which should be used by programs written for Windows 2000 or later. Why this has not been fixed in 20 years is beyond my understanding.

As a workaround for the current situation in Java, Launch5j will (by default) convert the given Unicode command-line arguments to the UTF-8 format and then apply the URL encoding scheme. This ensures that only pure ASCII characters need to be passed to the Java executable, thus preventing the command-line arguments from being “mangled”. Still the original Unicode command-line arguments are preserved and can be reconstructed in the Java code.

The only downside is that additional processing is required in the application code:

public class YourMainClass {
  public static void main(final String[] args) {
    initCommandlineArgs(args);
    /* your application code goes here! */
  }

  private static void initCommandlineArgs(final String[] argv) {
    if (System.getProperty("l5j.pid") == null) {
      return; /*nothing to do*/
    }
    final String utf8enc = StandardCharsets.UTF_8.name();
    for (int i = 0; i < argv.length; ++i) {
      try {
        argv[i] = URLDecoder.decode(argv[i], utf8enc);
      } catch (Exception e) { }
    }
  }

  /* ... */
}

The JAR file name

Be aware that the same problem of “mangled” Unicode characters applies when the path of the JAR file is passed to the Java executable. In other words, the Java runtime fails to execute any JAR files whose path – file name or directory name anywhere in the path – contains any Unicode characters that cannot be represented in the computer's local ANSI codepage! Unfortunately, we can not encode the path of the JAR file as we do with the other command-line arguments, because the Jave executable requires the path of the JAR file to be passed in a non-encoded form.

Therefore, it is recommended to only use ASCII characters in the name of your JAR file and in the “install” path !!!

Build instructions

In order to build Launch5j from the sources, it is recommended to use the GNU C Compiler (GCC) for Windows, as provided by the Mingw-w64 project. Other C compilers may work, but are not officially supported.

Probably the most simple way to set up the required build environment is by installing the MSYS2 distribution, which includes GCC (Mingw-w64) as well as all the required build tools, such as Bash and GNU make.

Please make sure that the essential development tools and the MinGW-w64 toolchains are installed:

$ pacman -S base-devel
$ pacman -S mingw-w64-i686-toolchain mingw-w64-x86_64-toolchain

Once the build environment has been set up, just run the provided Makefile:

$ cd /path/to/launch5j
$ make

Note: In order to create 32-Bit or 64-Bit binaries, use the mingw32 or mingw64 sub-system of MSYS2, respectively.

Acknowledgment

This project is partly inspired by the “Launch4j” project, even though it has been re-written from scratch:
https://sourceforge.net/p/launch4j/

License

This work has been released under the MIT license:

Copyright 2020 LoRd_MuldeR <mulder2@gmx.de>

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The above copyright notice and this permission notice shall be included in all
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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∎