javabashjavap

Is there a way within a bash script to determine the minimum java version required by a jar file containing class files and jar files?

For a single class - we can work out the version of Java used to compile it:

javap -verbose className

I have a scenario where I need to scale this up to a jar file containing many classes and jar files.

My question is: Is there a way within a bash script to determine the java version required by a jar file containing class files and jar files?

Solution

  • You can extract the JAR file and check the MANIFEST.MF file, which contains information about the JDK used to build the JAR. The "Created-By" or "Build-Jdk" header in the MANIFEST.MF file stores the JDK version used to create the JAR

    replace JarName.jar with your jar

    here is the bash script to find the jdk version:

    #!/bin/bash
jdk_version=$(unzip -p JarName.jar META-INF/MANIFEST.MF | grep "Created-By\|Build-Jdk")
echo $jdk_version