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Running ant tasks in eclipse with Java 1.8 lead to "JRE version less than 11 is not supported. "

With eclipse I get the following error when I execute an ant task with Java 1.8.

JRE version less than 11 is not supported.

My "external tool configuration" is configured with "Seperate JRE" Eclipse Adoptium jdk-8.0.352.8-hotspot

Anybody knows how to prevent this restriction?

Eclipse IDE for Enterprise Java and Web Developers (includes Incubating components) Version: 2022-12 (4.26.0) Build id: 20221201-1913

Solution

  • Got it running.

    • I only need the classes to end up with Java 8.
    • Ant itself can run with 11 or higher

    Adding source and target with 1.8 did the trick for me in build.xml

      <JAVAC destdir="${build.classes.test}" source="1.8" target="1.8">
        <src path="${src.test}" />

    Afterwards I checked with javap -v MyStuff.class and saw Output major version: 52 which is 1.8

    More background

    Here are bugs describing the situation:

    Further issues

    • java task is not running with 1.8

      • The above method worked for the the ant javac task. But I had also ant java to generate some classes. I ended up with

        [java] Caused by: java.lang.ClassNotFoundException: javax.xml.bind.JAXBException

      • Because Ant is running with Java 17 and JAXB classes like javax.xml.bind.JAXBException are not included in JDK anymore since Java 11.

      • My workaround is to not use Eclipse for these ant tasks but to use a seperate (old=same we use in jenkins build) ant installation and run tasks from command line. See https://ant.apache.org/manual/install.html#getBinary

    • running ant task with 1.8 leads to Error: A JNI error has occurred, please check your installation and try again.

      • "External Tool Configration" -> "JRE" -> "Seperate JRE" switch jdk8 to 17 (or run in the same JRE as the workspace if you have higher jdk there)
      • and because of that this leads to above issues ;-)