Programmatically creating Runnable JAR that has external JARs from a GUI?

Question

I have a simple test program that has one button. When a user clicks the button, the program is supposed to create a Runnable JAR. The Runnable JAR is a simple program that opens google.com in Firefox. The program has three classes.

---

1) Main.java

 package test;

    public class Main {

        public static void main(String[] args) {

            Selenium.getGoogle();

        }

    } 

---

2) Selenium.Java

package test;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;

public class Selenium {

    public static void getGoogle () {
        WebDriver driver = new FirefoxDriver();
        driver.get("http://google.com");
    }

}

---

3) TestGUI.java

package test;

import javax.swing.*;
import javax.tools.JavaCompiler;
import javax.tools.ToolProvider;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;


public class TestGUI extends JFrame implements ActionListener {

    private static final long serialVersionUID = 1L;

    public TestGUI() {

        setSize(200, 100);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setVisible(true);
        /*
         * JButton.
         */
        JButton startButton = new JButton("Create Runnable JAR file ! ");
        add(startButton);
        startButton.addActionListener(this);
    }


    public static void main(String[] args) {
        new TestGUI();
    }


    public void actionPerformed(ActionEvent e) {
        System.out.println("The Button Works");
        String file1ToCompile = "test" + java.io.File.separator + "Main.java";

        String file2ToCompile = "test" + java.io.File.separator + "Selenium.java";

        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();

        int compilationResult = compiler.run(null, null, null, file1ToCompile, file2ToCompile);

        if (compilationResult == 0) {

            System.out.println("Compilation is successful");

        } else {
            System.out.println("Compilation Failed");
        }
    }
}

I have two main classes . I added TestGUI.java to the manifest so the GUI will show up . Once a user clicks the button, I want my program to create a Runnable JAR that consists of Main.java and Selenium.java.

However, I get an error null pointer exception for int compilationResult = compiler.run(null, null, null, file1ToCompile, file2ToCompile);

How can I do this?

Answer 1

Here is the answer O.o finally found it!! you just have to see this way the last part of the code:

File folder = new File("C://Users//YourUser//YourWorkspace//YourProject//bin");
File[] files = folder.listFiles();
File file=new File("C://Users//YourUser//Desktop//Examples.jar");

Answer 2

You are getting the NullPointerException most likely because you are using a JRE and not a JDK. Download a JDK and add it to the buildpath.

Secondly, you are just compiling the files. You then need to create a jar file and add the .class files to it. it is important that they have the same package structure in the jar. In the jar you will also need:

Manifest file

Dependant jars

Classloader

The manifest file describes which class contains the main method and info on the classpath. Dependant jars(selenium) also need to be present for obvious reasons. a classloader is needed to load the classes in the dependant jar. below is my implementation:

public void actionPerformed(ActionEvent e){
        System.out.println("The Button Works");
        String file1ToCompile = "src" + java.io.File.separator + "test" + java.io.File.separator + "Main.java";
        String file2ToCompile = "src" + java.io.File.separator + "test" + java.io.File.separator + "Selenium.java";
        JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
        int compilationResult = compiler.run(null, null, null, file1ToCompile, file2ToCompile);
        if (compilationResult == 0) {
            System.out.println("Compilation is successful");
        } else {
            System.out.println("Compilation Failed");
        }

        Manifest manifest = new Manifest();
        manifest.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
        manifest.getMainAttributes().put(new Name("Rsrc-Class-Path"), "./ selenium-server-standalone-2.39.0.jar");
        manifest.getMainAttributes().put(Attributes.Name.CLASS_PATH, ".");
        manifest.getMainAttributes().put(new Name("Rsrc-Main-Class"), "test.Main");
        manifest.getMainAttributes().put(Attributes.Name.MAIN_CLASS, "org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader");
        try{
            JarOutputStream target = new JarOutputStream(new FileOutputStream("output.jar"), manifest);
            add(new File("src" + java.io.File.separator + "test" + java.io.File.separator + "Main.class"), target);
            add(new File("src" + java.io.File.separator + "test" + java.io.File.separator + "Selenium.class"), target);
            add(new File("org"), target);
            add(new File("selenium-server-standalone-2.39.0.jar"), target);
            target.close();
        }catch(Exception ex){
            ex.printStackTrace();
        }
    }

    private void add(File source, JarOutputStream target) throws IOException
    {
        BufferedInputStream in = null;
        try
        {
            if (source.isDirectory())
            {
                String name = source.getPath().replace("\\", "/");
                if (!name.isEmpty())
                {
                    if (!name.endsWith("/"))
                        name += "/";
                    JarEntry entry = new JarEntry(name);
                    entry.setTime(source.lastModified());
                    target.putNextEntry(entry);
                    target.closeEntry();
                }
                for (File nestedFile: source.listFiles())
                    add(nestedFile, target);
                return;
            }

            JarEntry entry = null;

            if(source.getPath().contains("jarinjarloader")){
                entry = new JarEntry(source.getPath());
            }
            else if(source.getName().endsWith(".class")){
                entry = new JarEntry("test/"+source.getName());
            }else if(source.getName().endsWith(".classpath")){
                entry = new JarEntry(source.getName());
            }else if(source.getName().endsWith(".jar")){
                entry = new JarEntry(source.getName());
            }
            entry.setTime(source.lastModified());
            target.putNextEntry(entry);
            in = new BufferedInputStream(new FileInputStream(source));

            byte[] buffer = new byte[1024];
            while (true)
            {
                int count = in.read(buffer);
                if (count == -1)
                    break;
                target.write(buffer, 0, count);
            }
            target.closeEntry();
        }
        finally
        {
            if (in != null)
                in.close();
        }
    }

I used Eclipse's jarinjarloader for my classloader which I obtained by creating a runnable jar in eclipse and extracting the org folder and copying it into my project directory.

There is a slight problem with this but i suspect i am missing something small. output.jar will run fine if the classloader files are in the same directory as the jar. I am currently trying to fix this so that it can find the classloader from within the jar.