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JavaCard Template project with Gradle

Build Status

This is simple JavaCard project template using Gradle build system.

You can develop your JavaCard applets and build cap files with the Gradle! Moreover the project template enables you to test the applet with JCardSim or on the physical cards.

Gradle project contains one module:

  • applet: contains the javacard applet. Can be used both for testing and building CAP


  • Gradle build (CLI / IntelliJ Idea)
  • Build CAP for applets
  • Test applet code in JCardSim / physical cards
  • IntelliJ Idea: Coverage
  • Travis support


The template contains simple Hello World applet generating random bytes on any APDU message received. There is also implemented very simple test that sends static APDU command to this applet - in JCardSim.

The Gradle project can be opened and run in the IntelliJ Idea.

Running in IntelliJ Idea gives you a nice benefit: Coverage!

How to use

  • Clone this template repository:
git clone --recursive
  • Implement your applet in the applet module.

  • Run Gradle wrapper ./gradlew on Unix-like system or ./gradlew.bat on Windows to build the project for the first time (Gradle will be downloaded if not installed).

Building cap

  • Setup your Applet ID (AID) in the ./applet/build.gradle.

  • Run the buildJavaCard task:

./gradlew buildJavaCard  --info --rerun-tasks

Generates a new cap file ./applet/out/cap/applet.cap

Note: --rerun-tasks is to force re-run the task even though the cached input/output seems to be up to date.

Typical output:

[ant:cap] [ INFO: ] Converter [v3.0.5]
[ant:cap] [ INFO: ]     Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights reserved.
[ant:cap] [ INFO: ] conversion completed with 0 errors and 0 warnings.
[ant:verify] XII 10, 2017 10:45:05 ODP.  
[ant:verify] INFO: Verifier [v3.0.5]
[ant:verify] XII 10, 2017 10:45:05 ODP.  
[ant:verify] INFO:     Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights reserved.
[ant:verify] XII 10, 2017 10:45:05 ODP.  
[ant:verify] INFO: Verifying CAP file /Users/dusanklinec/workspace/jcard/applet/out/cap/applet.cap
[ant:verify] javacard/framework/Applet
[ant:verify] XII 10, 2017 10:45:05 ODP.  
[ant:verify] INFO: Verification completed with 0 warnings and 0 errors.

Installation on a card

./gradlew installJavaCard

Or inspect already installed applets:

./gradlew listJavaCard

Running tests

./gradlew test --info --rerun-tasks


Running test: Test method hello(AppletTest)

Gradle suite > Gradle test > AppletTest.hello STANDARD_OUT
    Connecting to card... Done.
    --> [00C00000080000000000000000] 13
    <-- 51373E8B6FDEC284DB569204CA13D2CAA23BD1D85DCAB02A0E3D50461E73F1BB 9000 (32)
    ResponseAPDU: 34 bytes, SW=9000


This project uses mainly:

Kudos for a great work!

JavaCard support

Thanks to Martin Paljak's ant-javacard and oracle_javacard_sdks we support:

  • JavaCard 2.1.2
  • JavaCard 2.2.1
  • JavaCard 2.2.2
  • JavaCard 3.0.3
  • JavaCard 3.0.4
  • JavaCard 3.0.5u1
  • JavaCard 3.1.0b43

Supported Java versions

Java 8-u271 is the minimal version supported.

Make sure you have up to date java version (-u version) as older java 8 versions have problems with recognizing some certificates as valid.

Only some Java versions are supported by the JavaCard SDKs. Check the following compatibility table for more info:


This is a nice benefit of the IntelliJ Idea - gives you coverage results out of the box.

You can see the test coverage on your applet code.

  • Go to Gradle plugin in IntelliJ Idea
  • Tasks -> verification -> test
  • Right click - run with coverage.

Coverage summary: coverage summary

Coverage code: coverage code


If you experience the following error:

java.lang.VerifyError: Expecting a stackmap frame at branch target 19
    Exception Details:
        javacard/framework/APDU.<init>(Z)V @11: ifeq
        Expected stackmap frame at this location.

Then try running JVM with -noverify option.

In the IntelliJ Idea this can be configured in the top tool bar with run configurations combo box -> click -> Edit Configurations -> VM Options.

However, the com.klinec:jcardsim: should not need the -noverify.

Invalid APDU loaded

You may experience error like this: Invalid APDU loaded. You may have JC API in your classpath before JCardSim. Classpath:

This error is thrown by JCardSim which tries to load APDU class augmented with another methods. The augmented APDU version is contained in the JCardSim JAR. However, if api_class.jar from the JavaCard SDK is on the classpath before the JCardSim, this problem occurs. The classpath ordering causes non-augmented version is loaded which prevents JCardSim from correct function.

gradle-javacard-plugin v1.7.4 should fix this error.

If you still experience this in IntelliJ Idea try: open project structure settings -> modules -> applet_test and move JCardSim to the top so it appears first on the classpath. This has to be done with each project reload from the Gradle.


TODOs for this project:

  • Polish Gradle build scripts
  • Add basic libraries as maven dependency.


Community feedback is highly appreciated - pull requests are welcome!