Question

I tried to compile the groovy quickstart example which comes with gradle (in samples/groovy/quickstart directory). gradle compileGroovy and gradle jar both complete successfuly, but I cannot run any of these:

c:\tmp\quickstart\build\classes\main\org\gradle>java Person
Exception in thread "main" java.lang.NoClassDefFoundError: Person (wrong name: org/gradle/Person)
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(Unknown Source)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$000(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: Person.  Program will exit.

and

c:\tmp\quickstart\build\libs>java -jar quickstart.jar
Failed to load Main-Class manifest attribute from
quickstart.jar

i then added manifest attribute to bulid.gradle:

jar {
    manifest {
        attributes("Main-Class": "org.gradle.Person")
    }
}

and now am getting:

c:\tmp\quickstart\build\libs>java -jar quickstart.jar
Exception in thread "main" java.lang.NoClassDefFoundError: groovy/lang/GroovyObject
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClassCond(Unknown Source)
        at java.lang.ClassLoader.defineClass(Unknown Source)
        at java.security.SecureClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.defineClass(Unknown Source)
        at java.net.URLClassLoader.access$000(Unknown Source)
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Caused by: java.lang.ClassNotFoundException: groovy.lang.GroovyObject
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 12 more
Could not find the main class: org.gradle.Person. Program will exit.

How can I run the jar that was created? (or am I missing the whole point…)

Answer 1

The groovy/quickstart sample in the Gradle distribution is not meant to be executed directly. Among other things, the Person class does not have a main method. Think of it as a library.