Convert SISX to JAR

A Symbian phone requires a .sisx installer, while a Java ME phone requires a .jar MIDlet archive. The conversion is usually requested when replacing an old Symbian application with a Java ME version, but the existing executable cannot be directly transformed.

What the SISX format is

SISX is the Symbian Installation System package format used by Symbian OS and S60 devices, including many Nokia smartphones. Developers used tools such as makesis to build SIS packages and signsis to apply certificates and signatures; distributors commonly delivered signed applications with the .sisx extension.

A SISX package contains Symbian executables, resources, configuration data, certificates, and installation instructions. It is an installer for the Symbian runtime, not a generic archive and not Java bytecode. Symbian phone owners and developers are the main users of this format.

What the JAR format is

In the Mobile platforms category, JAR means a Java Archive used to distribute Java ME applications, also called MIDlets. A Java ME JAR normally contains compiled Java class files, images, sounds, other resources, and a manifest identifying the application.

Java ME installations commonly use a matching Java Application Descriptor file, .jad. The JAD records metadata such as the MIDlet name, version, vendor, JAR size, and download URL. A JAR must also contain a valid MIDlet entry and bytecode compatible with the target CLDC and MIDP profiles; changing the extension or repacking unrelated files does not satisfy those requirements.

Why direct conversion does not work

There is no reliable SISX-to-JAR executable conversion. A Symbian package contains binaries compiled for Symbian APIs and hardware, whereas a Java ME JAR contains Java classes compiled for a CLDC/MIDP runtime. A file converter, archive utility, or extension rename cannot translate native Symbian machine code, user-interface code, permissions, and operating-system services into a working MIDlet.

No reputable online converter can perform this translation. Online services that claim to convert SISX to JAR can at most rename, extract, or repackage data, and uploading signed commercial software or proprietary code creates a security and licensing risk.

Practical ways to obtain a JAR

1. Find an existing Java ME release. Check the original developer, an authorized software archive, or a preservation archive for a separate .jar and matching .jad. If the application was released for both Symbian and Java ME, the Java version is a separate build rather than a conversion.
2. Install the SISX directly. If the target is a compatible Symbian device, transfer the package and install it using the phone's file manager or application installer. The device may reject packages with invalid signatures, expired certificates, or unsupported platform requirements.
3. Port the application from source code. Obtain the original Java ME project, or rewrite the application for the target Java ME profile. Replace Symbian APIs, native libraries, UI components, permissions, and device-specific services with CLDC/MIDP-compatible code. A SISX file alone does not provide the source required for an automatic port.

How to inspect or rebuild files

1. Use SISContents on Windows to inspect or extract package contents when available. 7-Zip may open some SISX files, but it does not interpret Symbian installation instructions and may not extract every component correctly.
2. Open the Java ME source in a compatible Java ME SDK, such as Oracle Java ME SDK 8.3 where its supported profiles match the target device, or use the older Java ME Wireless Toolkit for legacy MIDP projects. These tools compile source into device-compatible classes and perform the required preverification.
3. Build the MIDlet with a manifest containing entries such as MIDlet-Name, MIDlet-Version, MIDlet-Vendor, and at least one MIDlet-1 entry identifying the MIDlet class, icon, and name.
4. Package the compiled and preverified output with the SDK. A generic command such as jar cfm app.jar manifest.mf -C build/classes . creates an archive, but it does not compile or preverify Java ME code; the SDK packaging process is safer for a real device.
5. Create the JAD and set MIDlet-Jar-Size to the exact byte size of the final JAR. Test installation on the target phone or a matching emulator. Sign the JAR and JAD with Java ME certificates if the application requests protected APIs; a Symbian SISX signature cannot be reused.

If extracted resources must be stored in a JAR for archival purposes, a command such as jar cf resources.jar -C extracted-files . creates an archive only. It does not create an installable Java ME application.

Compatibility limitations

A source-level port may need separate builds for different CLDC and MIDP versions, screen sizes, input methods, graphics capabilities, network stacks, and security policies. Symbian applications that depend on native hardware, background services, telephony functions, or Symbian-specific UI frameworks may have no equivalent Java ME implementation.

Renaming .sisx to .jar, opening SISX contents with an archive program, or placing Symbian binaries inside a JAR does not change the executable format. Use a separate Java ME release, install the original package on compatible Symbian hardware, or rebuild the application from suitable source code.