Class Not Found Exception when Trying to Execute a Java Application with ProcessBuilder

Question

I'm trying to execute the Main method within a class in a jar file by using Java's ProcessBuilder from a servlet. I need to run this in a separate process due to other dependencies.

I'm getting the following exception, so I guess that I am not correctly passing the package and Main method name (com.test.Main) in the arguments array. I am not sure how to do this correctly.

I'd appreciate any suggestions. Thanks.

ERROR -- java.lang.NoClassDefFoundError: com/test/Main ERROR -- Caused by: java.lang.ClassNotFoundException: com.test.Main ERROR -- at java.net.URLClassLoader$1.run(URLClassLoader.java:202) ERROR -- at java.security.AccessController.doPrivileged(Native Method) ERROR -- at java.net.URLClassLoader.findClass(URLClassLoader.java:190) ERROR -- at java.lang.ClassLoader.loadClass(ClassLoader.java:307) ERROR -- at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)

ERROR -- at java.lang.ClassLoader.loadClass(ClassLoader.java:248) ERROR -- Could not find the main class: com.test.Main. Program will exit. ERROR -- Exception in thread "main"

Here's my code.

    public int runProcessBuilder() throws IOException, InterruptedException{
    {
        // Get absolute path
        File dir_location = new File(".");
        String appPath = dir_location.getCanonicalPath() + "\\Tomcat 6.0\\webapps\\TestServer\\WEB-INF";

        // Args to run
        String[] argList = {"java.exe","-Djava.library.path="+appPath+"\\lib","-classpath",appPath+"\\lib\\test.jar","com.test.Main","-pTEST_ARG","123"};           

        // Create ProcessBuilder
        ProcessBuilder builder = new ProcessBuilder(argList);

        // Set Environment variable(s)
        Map<String, String> environ = builder.environment();
        environ.put("TEST_HOME", appPath);

        // Set java directory - TODO: use system property
        String java_exe = "C:\\Program Files\\Java\\jdk1.6.0_18\\bin";
        builder.directory(new File(java_exe));

        // Start Process
        final Process process = builder.start();

        // Read error stream
        StreamReader errorReader = new StreamReader(process
                .getErrorStream(), "ERROR");

        // Read input stream
        StreamReader outputReader = new StreamReader(process
                .getInputStream(), "OUTPUT");

        // Start both reader threads
        errorReader.start();
        outputReader.start();

        // Wait for process end and get Exit Code
        int exitCode = process.waitFor();
        System.out.println("Exit code: " + exitCode);

        return exitCode;
      }
}

It appears that your class path does not contain the class in questions. Are you sure that the class path being dynamically generated is correct? I mean, can you check the file test.jar actually is there? — Edwin Dalorzo
– Edwin Dalorzo, Commented Apr 10, 2011 at 3:19
I bet in your batch file you do not dynamically generate paths to test.jar file. Right? If you are using absolute paths in your batch file and it works, it can only mean that the absolute paths you are generating in code are not the same. Don't you think? — Edwin Dalorzo
– Edwin Dalorzo, Commented Apr 10, 2011 at 3:39
This is the batch file's contents, which is in the WebContent directory. java -classpath ".\WEB-INF\lib\test.jar" com.test.Main -pTEST_ARG "123" — gmtosh
– gmtosh, Commented Apr 10, 2011 at 3:39
You are using a relative path in your batch file, but you are using absolute paths in your code, are you absolutely sure that your code appPath+"\\lib\\test.jar" corresponds to the path where test.jar is located? Why don't you create a File object containing this path and check if the file actually exists. I have the impression that this path is what is incorrect. — Edwin Dalorzo
– Edwin Dalorzo, Commented Apr 10, 2011 at 3:43

Stephen C · Accepted Answer · 2011-04-10 03:26:38Z

1

There is something wrong with either the "-classpath" argument or the JAR file you are trying to use.

Print out the value of the "-classpath" argument, and check that the JAR file is really at that location in the file system, and that it is readable.
Use jar -tvf test.jar | grep ... to check that the Main class is in the JAR file, and has the correct path in the JAR.

(It is not the Manifest that is the issue ... because you are not using "-jar".)

(It is also not an issue with the signature of main entrypoint method ... because that would have resulted in a different exception.)

edited Apr 10, 2011 at 3:26

answered Apr 10, 2011 at 3:20

Stephen C

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1 Comment

Edwin Dalorzo Over a year ago

You could also create a File object using the path and ask if the file exists and log something in Tomcat logs or debug the code.

buruzaemon · Accepted Answer · 2011-04-10 03:19:00Z

0

Have you set the Main-Class value in your jar's manifest file?

That would be something like:

Main-Class: com.test.Main

You might want to review the Running JAR-Packaged Software documentation.

answered Apr 10, 2011 at 3:19

buruzaemon

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3 Comments

Edwin Dalorzo Over a year ago

I do not think this is the problem because in the command line invocation the path to the class containing the main method is being provided.

Stephen C Over a year ago

Nope. He's not using "-jar", so the manifest entry is not relevant.

djangofan Over a year ago

but, still, the .class (which has a main method) that he is trying to run is within the .jar even though the .jar is not a auto-run type of jar.

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