Getting Started with Diff Viewer from Scratch

Give it a name and store it somewhere:

Create a new module:

Give it a name and store it somewhere:

Give it a unique identifier and display name:

Right-click the application, choose Properties, go to Libraries, and select "Diff" from the "ide" cluster and then click the Resolve button to include the related modules:

Create a new Action:

Let it always be enabled:

Specify the locations where the Action will be invoked:

Provide class name, display name, and icon:

Right-click the module and specify that you want to add a dependency:

Add a dependency on the Diff module:

Do the same as the above for the Window System module.

Define the Action as follows, replacing the hardcoded files with your own:

package org.my.diff;

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.IOException;
import javax.swing.SwingUtilities;
import org.netbeans.api.diff.Diff;
import org.netbeans.api.diff.DiffView;
import org.netbeans.api.diff.StreamSource;
import org.openide.awt.ActionID;
import org.openide.awt.ActionReference;
import org.openide.awt.ActionRegistration;
import org.openide.util.NbBundle.Messages;
import org.openide.windows.TopComponent;

@ActionID(
        category = "Tools",
        id = "org.my.diff.DiffViewerAction")
@ActionRegistration(
        asynchronous = true,
        displayName = "#CTL_DiffViewerAction")
@ActionReference(
        path = "Menu/Tools", 
        position = 0)
@Messages("CTL_DiffViewerAction=Open Diff Viewer")
public final class DiffViewerAction implements ActionListener {

     @Override
    public void actionPerformed(ActionEvent e) {
        StreamSource local = StreamSource.createSource("name1","title1", "text/html", new File("C:/tutorials/nbm-google.html"));
        StreamSource remote = StreamSource.createSource("name2","title2", "text/html", new File("C:/tutorials/72/nbm-google.html"));
        diff(local, remote);
    }

    public void diff(final StreamSource local, final StreamSource remote) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    DiffView view = Diff.getDefault().createDiff(local, remote);
                    TopComponent tc = new TopComponent();
                    tc.setDisplayName("Diff Viewer");
                    tc.setLayout(new BorderLayout());
                    tc.add(view.getComponent(), BorderLayout.CENTER);
                    tc.open();
                    tc.requestActive();
                } catch (IOException ex) {
                }
            }
        });
    }
}

Alternatively, let's assume that the files we want to diff are within the module, for some reason, rather than externally on disk. This is how the "actionPerformed" above would be rewritten:

@Override
public void actionPerformed(ActionEvent e) {
    StreamSource ss1 = null;
    StreamSource ss2 = null;
    InputStreamReader ir1 = null;
    InputStreamReader ir2 = null;
    try {
        ir1 = new InputStreamReader(FileUtil.getConfigFile("files/one").getInputStream());
        ir2 = new InputStreamReader(FileUtil.getConfigFile("files/two").getInputStream());
        ss1 = StreamSource.createSource("name1", "title1", "text/html", ir1);
        ss2 = StreamSource.createSource("name2", "title2", "text/html", ir2);
    } catch (FileNotFoundException ex) {
        Exceptions.printStackTrace(ex);
    }
    diff(ss1, ss2);
}

And here are the related layer elements:

<folder name="files"><file name="one" url="file1.html"/> <file name="two" url="file2.html"/> </folder>

The above assumes the layer.xml is in the same package as the two files "file1.html" and "file2.html".

Run the application and go to the Tools menu to invoke the Action:

You'll see this:

Go back to the Project Properties dialog of the application and include these two modules from the "ide" cluster:

Clean the application. Build the application. Run the application. Invoke the Action. You'll see the Diff Viewer, as below, diffing the two files you passed in: