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MiniJar

MiniJar is a tool for jar reduction. It takes an executable jar and a set of entrypoints, and outputs a jar where unreachable methods have been removed. Minijar uses static analysis (WALA) to build a call graph in order to determine which methods are reachable. It takes into account class hierarchies, abstract methods/classes, and interfaces.

The system is licensed under the Eclipse Public License, which has been approved by the OSI (Open Source Initiative) as a fully certified open source license.

Installation & Usage

To install MiniJar, clone this project and build:

./gradlew build

To run MiniJar:

./gradlew cmdLineJavaExec -Pargs="-Xmx10000m <jarfile>  -m <mainClass> -d <scopeDataFile> -o <jarFile>"

MiniJar accepts the following arguments:

   -m <mainClass>             Provide one or more mainClasses
   -p <entryPointsFile>       Provide an entrypoint file (optional)
   -i <inclusionsFile>        Provide an inclusion file (optional)
   -o <jarfile>               Path to the output jar file

The scopeDataFile is a required argument and is a path to a file of the form:

Primordial,Java,jrt,java.base
Primordial,Java,jarFile,primordial.jar.model
Application,Java,jarFile,<jarname>

The scopeDataFile and <jarname> must be located on the Java class path.

Example: ./gradlew cmdLineJavaExec -Pargs="-Xmx10000m src/main/resources/Example-0.1.0.jar -m Lshape/Example -d wala.data.example.txt -o out.jar"

The wala.data.example.txt scope data file contains:

Primordial,Java,jrt,java.base
Primordial,Java,jarFile,primordial.jar.model
Application,Java,jarFile,Example-0.1.0.jar

Notice that the mainClass is specified in standard Java descriptor format (e.g., Lshape/Example). Similarly the entrypoint file contains a list of methods specified in this standard format (e.g., Lorg/jboss/logmanager/LogManager#<init>()V).

Entrypoint files can be used to ensure that the call graph algorithm takes these methods into account so that they are guaranteed to be reachable. This can be useful when the algorithm misses methods due to reflection.

The result of running the above .gradlew command is an output jar out.jar that is similar to the input jar Example-0.1.0.jar but with unreachable methods removed. The output jar is also executable and leads to the same ouptut as the original jar when executed (via java -jar out.jar).

Limitations

MiniJar currently accepts a single jar file as input. It also does not handle all usages of reflection.