**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.
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.
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:
**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.
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.
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.
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.
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.
Does **not** apply [URL encoding](https://en.wikipedia.org/wiki/Percent-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.
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.
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**](https://web.archive.org/web/20100419201225/http://www.wilsonc.demon.co.uk/d10resourceeditor.htm) ([mirror](https://stefansundin.github.io/xn_resource_editor/)) or [**Resource Hacker™**](http://www.angusj.com/resourcehacker/), to *modify* the pre-compiled executable files as needed:
Some options can be configured via the launcher executable's [STRINGTABLE](https://docs.microsoft.com/en-us/windows/win32/menurc/stringtable-resource) resource:
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*](http://www.bcbjournal.org/articles/vol3/9911/Single-instance_applications.htm) 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)
*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!
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()`](https://docs.microsoft.com/en-us/cpp/c-language/using-wmain?view=vs-2015) 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](https://en.wikipedia.org/wiki/UTF-8) format and then apply the [URL encoding](https://en.wikipedia.org/wiki/Percent-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.
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 any directory name 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 Java executable requires the path of the JAR file to be passed in a non-encoded form.
In order to build **Launch5j** from the sources, it is recommended to use the [*GNU C Compiler* (GCC)](https://gcc.gnu.org/) for Windows, as provided by the [*Mingw-w64*](http://mingw-w64.org/) 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**](https://www.msys2.org/) distribution, which includes *GCC* (Mingw-w64) as well as all the required build tools, such as *Bash*, *GNU make* and *Git*.