B4J Question Standalone Package in B4J

[amir hosein]

Hello everyone
I made a program for communicating to a Arduino Due Board via Serial port .
I want to make a Standalone Package for it . My purpose of making standalone package is to hide my source code . Is that Right ?
If I make a package from my B4J program , My source code will not be accessible to others (users) ?

Please Kindly Answer my Question .

Regards

 

[teddybear]

I want to make a Standalone Package for it . My purpose of making standalone package is to hide my source code . Is that Right ?

No, the compiled jar file also hides your source code.

 

[amir hosein]

T

No, the compiled jar file also hides your source code.

thanks for your answer .
but that's not right because the .jar file (also .apk file) is like a compressed file and can be unpack . when a .jar file unpack then you can see the source but it maybe obfuscated ...
my question is : is there anyway to reach the source code in the Standalone Package ?

 

[aeric]

Your source code compiled to modules and other file after build as Standalone Package.

 

[DonManfred]

when a .jar file unpack then you can see the source but it maybe

there is NO JAR inside an APK

 

[DonManfred]

my question is : is there anyway to reach the source code in the Standalone Package ?

No.

The B4A Source is transpiled to java code which are compiled then into modules.

 

[amir hosein]

No.

The B4A Source is transpiled to java code which are compiled then into modules.

Thanks for your answer .
My program is in B4J language .
I unpacked (decompile) a sample .JAR file and I reached to source code but it was obfuscated ...

According to your answer , No one can reach to source code (using any tools ) and I can publish my program to my users without a concern .
Thank you

Best Regards

 

[teddybear]

What is the source code you are referring to？ java code or b4x code?
If it's Java, even though you make a package, it can still be decompiled.

 

[amir hosein]

What is the source code you are referring to？ java code or b4x code?
If it's Java, even though you make a package, it can still be decompiled.

Of course I mean the Java code .
So , if the code can be accessible by using a tool , the standalone package not suitable for me ...
I want to hide my coding( encryption ) about the data in my source and this is not a solution .

Thanks

 

[aeric]

Please read B4X IDE guide:

https://www.b4x.com/guides/B4XIDE.html#pf27

Answer from DeepSeek: https://chat.deepseek.com/share/gyri8s5zs3p9hn3fxj
The short answer is yes, a program compiled with a B4J Standalone Package can be decompiled, and it is relatively easy to do.
Here’s a detailed explanation of why and how.

The Core Reason: B4J's Compilation Model​

B4J (like other B4X tools) does not compile your source code directly into native machine code (like C or C++ would). Instead, it follows this process:

1. Your B4J Code: You write your code in the B4J IDE.
2. Translation to Java: The B4J compiler translates your code into standard Java source code.
3. Java Compilation: This generated Java code is then compiled by the standard Java compiler (javac) into Java Bytecode (.class files).
4. Packaging: These .class files, along with any necessary libraries, are packaged into a JAR file, which is the executable you distribute.

The critical point is that the final executable (the JAR file) contains Java Bytecode, not native code.

Why Java Bytecode is Vulnerable to Decompilation​

Java Bytecode is a high-level, well-documented intermediate language. It contains a significant amount of symbolic information (like class names, method names, and variable names) that is preserved to enable features like reflection and dynamic linking. This makes it much easier to reverse-engineer than native machine code.
Specialized tools called decompilers can analyze this bytecode and reconstruct surprisingly readable Java source code from it.

How Easy Is It?​

Extremely easy. Anyone with basic technical knowledge can do it in minutes.

1. Get a Decompiler: Popular free tools include JD-GUI, CFR, or Procyon.
2. Open the JAR File: You simply open the JAR file from your B4J standalone package with the decompiler.
3. View the Source: The decompiler will instantly display a tree of packages and classes. You can then browse and save the source code.

The decompiled code will not be identical to your original B4J code—it will be the Java code that B4J generated. However, since the translation from B4J to Java is very straightforward, the logic of your program will be completely exposed. This includes:

• The overall application structure.
• Class and method names.
• Core business logic and algorithms.
• String literals (like database connection strings, API keys if hardcoded, etc.).

Example: What Gets Exposed​

If you have a B4J sub like this:

Sub Process_Globals
    Private const API_KEY As String = "sk_1234567890abcdef"
End Sub

Sub CheckLicense(key As String) As Boolean
    If key = "MY_SECRET_KEY_2024" Then
        Return True
    Else
        Return False
    End If
End Sub

A decompiler will show the Java equivalent, making your secret keys and license-checking logic completely visible.

What Can You Do About It? (Obfuscation)​

While you cannot prevent decompilation, you can make the decompiled code much harder to understand and reverse-engineer. This process is called obfuscation.
An obfuscator tool takes your Java Bytecode and:

• Renames classes, methods, and variables to meaningless names (e.g., a, b, c, func1).
• Removes unused code.
• Alters the control flow to make it confusing.

B4J has built-in support for a powerful obfuscator called B4J Obfuscator, which is based on ProGuard.
How to Obfuscate your B4J App:

1. In the B4J IDE, go to Project > Build Configurations.
2. Create a new configuration (e.g., "Release-Obfuscated").
3. Check the box that says "Obfuscate".
4. When you compile your standalone package using this configuration, the obfuscator will run, making the decompiled output extremely difficult to work with.

Important: Even obfuscation is not a silver bullet. A determined attacker can still analyze the obfuscated code, but it raises the barrier significantly, protecting your software from casual piracy and intellectual property theft. It also helps hide sensitive strings, though for things like API keys, a server-side solution is always more secure.

Summary​

	Without Obfuscation	With Obfuscation
Can it be decompiled?	Yes, easily.	Yes, but the result is garbled.
Readability of Decompiled Code	Very high. Logic is clear.	Very low. Names are meaningless, logic is tangled.
Protection Level	Very low.	Good protection against casual reverse-engineering.

Conclusion: Always assume that any B4J application you distribute can and will be decompiled. For any serious project, you must use the built-in obfuscator to protect your intellectual property. For maximum security, never hard-code secrets like passwords or API keys; instead, handle sensitive operations on a remote server that you control.
This response is AI-generated, for reference only.

 

[aeric]

Asking further:
but it is packaged by jlink into modules file


Excellent point! You're absolutely right to bring this up. My previous answer was too general. When you use B4J's Standalone Package (jlink) option, the situation becomes more complex and offers significantly better protection against casual decompilation.

Let's dive into the specifics of what happens with jlink and how it changes the decompilation landscape.

What jlink Does Differently​

Instead of creating a simple JAR file, the jlink option:

1. Creates a Custom JRE: It uses the jlink tool from the JDK to create a minimal, customized Java Runtime Environment (JRE) that contains only the Java modules your application actually needs.
2. Packages into a Runtime Image: Your application's code and all its dependencies (libraries, B4J runtime, etc.) are packaged into this custom runtime image.
3. Uses JIMAGE Format: The core of this custom JRE is stored in the lib/modules file. This file is not a simple archive like a JAR; it's a special, highly efficient container format (JIMAGE) used by the Java runtime to store modules.

So, Can It Still Be Decompiled?​

Yes, but it's much harder and requires extra steps compared to a standard JAR file.

The primary obstacle is no longer just the decompiler itself, but first extracting your code from the custom runtime image.

Here’s what an attacker would need to do:

Step 1: Locate and Extract the Application Code from the Runtime Image​

The attacker cannot simply point a decompiler at the modules file. They need specialized tools to unpack the JIMAGE format.

• Tool Needed: The standard JDK includes a tool called jimage for this purpose.
• Process: They would run a command like:
  bash
  jimage extract <path-to-standalone-package>/lib/modules --output ./extracted_modules
  This command extracts the contents of the modules file into a directory.

Step 2: Find the Relevant JAR/Class Files​

After extraction, the attacker will find a folder structure containing the modules of the custom JRE (like java.base) and, crucially, your application code.

• Your application is typically contained in a module or JAR file, often named something identifiable (e.g., b4j/your-app-name.jar or within a module path).
• They need to browse the extracted folders to find the JAR file or the directory containing the .class files for your application, not the standard Java modules.

Step 3: Decompile the Class Files​

Once they have isolated your application's JAR or class files, they can use a standard Java decompiler (like JD-GUI) as described in the previous answer.

Level of Difficulty and Protection​

Aspect	Standard Package (JAR)	Standalone Package (jlink)
Accessing Code	Trivial. Double-click the JAR in a decompiler.	Moderate. Requires knowledge of command-line tools (jimage) and navigating an extracted file structure.
Barrier to Entry	Very low. Any novice can do it.	Higher. Requires someone with Java platform knowledge.
Protection Level	Very Low. Effectively no protection.	Moderate. Protects against casual users and adds significant steps for attackers. It's security through obscurity.

The Role of Obfuscation is Still Critical​

Even with jlink, obfuscation remains your most important defense.

• jlink provides obscurity: It hides your code inside a binary container, deterring casual inspection.
• Obfuscation provides resilience: It makes the code meaningless even after it is extracted and decompiled.

The most secure approach is to combine both:

1. Use the Standalone Package (jlink) to make initial access harder.
2. Enable obfuscation in your B4J build configuration to ensure that if someone does extract your code, the decompiled output is gibberish.

Practical Example for You to Try​

To see the difference yourself:

1. Create a simple B4J app.
2. Compile it twice:
   • Once as a Release Package (creates a JAR).
   • Once as a Standalone Package (jlink).
3. Try to decompile both:
   • The JAR from the Release Package will open directly in JD-GUI.
   • For the Standalone Package, you'll need to first find your app's JAR within the package (often in the app folder or similar—B4J might package it accessibly) or use jimage extract on the lib/modules file to get the core modules.

Conclusion​

You are correct. Using the Standalone Package (jlink) significantly raises the bar compared to a simple JAR file. It moves your application from "trivially decompilable" to "requires specific technical knowledge to extract the code first."

However, it is not a substitute for obfuscation. A determined reverse-engineer with Java platform knowledge can still extract and decompile your code. Therefore, for any project where protecting your intellectual property is important, you should always use obfuscation, regardless of whether you deploy as a JAR or a jlink package.