NetBeans Platform Quick Start

Welcome to the NetBeans Platform!

The key benefit of the NetBeans Platform is its modular architecture. Secondary benefits are the NetBeans Platform's reliance on the Swing UI toolkit, which is the official toolkit for creating user interfaces in Java, in combination with the NetBeans IDE's award winning "Matisse" GUI Builder.

In this quick start, you are introduced to the benefits and usages of modularity via a very simple example, contributed by Thomas Würthinger, who is currently a PhD student at the Johannes Kepler University in Linz, Austria. Once you have grasped the concepts introduced in this quick start, you will be ready to step onto the NetBeans Platform Learning Trail, providing a very rich variety of tutorials for many different scenarios relating to the NetBeans Platform.

If you are new to the NetBeans Platform, it is highly recommended to watch the screencast series Top 10 NetBeans APIs.

Note: This document uses the NetBeans IDE 7.0 Release or above. If you are using an earlier version, see the previous version of this document.

Contents

• A Single Module NetBeans Platform Application
• A Modular Application Using Lookup
• LookupListener and InstanceContent

To follow this tutorial, you need the software and resources listed in the following table.

Note: Even though it is a separate product, there is no need to download the NetBeans Platform separately. Typically, you develop the application in NetBeans IDE and then exclude the modules that are specific to the IDE but that are superfluous to your application.

A Single Module NetBeans Platform Application

We start by simply creating a new NetBeans Platform application, containing a single module.

1. Choose File | New Project and then choose NetBeans Modules. Select "NetBeans Platform Application". You should see this:

   

   Click Next.

2. Name your new application "WordApp" and make it the IDE's main project:

   

   The IDE's main project is started when the global project command "Run Project" is invoked.

   Click Finish. The new project appears as follows in the Projects window:

   

3. Right-click the Modules node, shown above, and choose "Add New". Call the new module "WordEditorCore":

   

   Click Next.

4. Specify a unique name for the module, which is its code name base, together with a project display name that will be shown in the Projects window:

   

   Click Finish. The new module is created and its structure is shown in the Projects window:

   

5. Right-click the "Word Editor Core" module and choose New | Other. In the Module Development category, select "Window":

   

   Click Next. You should now see this:

   

6. Select "editor" and "Open on Application Start", as shown below:

   

   Then click Next.

7. Set the class name prefix to "Text" and the package to "org.word.editor.core":

   

   Click Finish. The new window is added to the source structure of your module:

   

8. Now double click on the file "TextTopComponent.java" to open it in the Design view of the "Matisse" GUI Builder. Use the Palette (Ctrl-Shift-8) to drag and drop a button and a text area onto the window:

   

   Do the following to make the new GUI components meaningful:

   • Right-click the text area, choose "Change Variable Name", and then name it "text". That is the name that will enable you to access the component from your code.
   • Right-click the button, choose "Edit Text", and then set the text of the button to "Filter!"
9. Double click on the button, causing an event handling method to automatically be created in the Source editor. The method is called whenever the button is clicked. Change the body of the method to the following code.

   private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
      String s = text.getText();
      s = s.toUpperCase();
      text.setText(s);
   }

10. Right-click the application and choose Run. Doing so will start up your new NetBeans Platform application and install your module. You will have a new window, as well as a new menu item for opening it, as shown below:

    

11. Enter a text in the text area, and click "Filter!". You should see that the text is now shown in uppercase:

    

You have learned how to create a new NetBeans Platform application and how to add new modules to it. In the next section, you will be introduced to the NetBeans Platform's pluggable service infrastructure.

A Modular Application Using Lookup

In this section, you create two additional modules. The first new module, "TextFilterAPI", contains a service provider interface. The second module, "UppercaseFilter", is a service provider for the interface. The GUI module, defined above, will be loosely coupled with the "UppercaseFilter" service provider, since the GUI module will not refer to any code from the "UppercaseFilter" service provider. That will be possible because the "UppercaseFilter" service provider will be registered in the META-INF/services folder and loaded via the NetBeans Lookup class, which is comparable to the JDK 6 ServiceLoader class. You will then create another loosely coupled service provider, named "LowercaseFilter".

1. Expand the new application in the Projects window, right-click the Modules node, and choose "Add New". Name the new module "TextFilterAPI":

   

   Click Next. Use code name base "org.word.editor.api" and complete the wizard, which adds the module to your previously created application, as you did in the previous section:

   

2. Right-click the "TextFilterAPI" module and choose New | Java Interface. Name the Java interface "TextFilter", in the package "org.word.editor.api", and use the editor to define it as follows:

   package org.word.editor.api;
   
   public interface TextFilter {
   
       String process(String s);
   
   }
       

3. Right-click the "TextFilterAPI" module, choose Properties, and use the "API Versioning" tab to specify that the package containing the interface should be available throughout the application:

   

4. Create a third module in your application, name it "UppercaseFilter":

   

5. Click Next. Use "org.word.editor.uppercase" as the code name base:

   

   Click Finish.

6. Right-click the "UppercaseFilter" module, choose Properties, and use the "Libraries" tab to add a dependency on the "TextFilterAPI" module:

   

   

7. In the same way as shown in the previous step, set a dependency on the Lookup API module, which provides the ServiceProvider annotation that you will use in the next step.
8. Because of the Lookup API dependency you defined above, you can now implement the interface defined in the second module. Do so by creating a new class named "UppercaseFilter", in the "org.word.editor.uppercase" package, as shown below:

   package org.word.editor.uppercase;
   
   import org.openide.util.lookup.ServiceProvider;
   import org.word.editor.api.TextFilter;
   
   @ServiceProvider(service=TextFilter.class)
   public class UppercaseFilter implements TextFilter {
   
       public String process(String s) {
           return s.toUpperCase();
       }
   
   }

   At compile time, the @ServiceProvider annotation will create a META-INF/services folder with a file that registers your implementation of the TextFilter interface, following the JDK 6 ServiceLoader mechanism.

9. The code that handles a click on the filter button now needs to be changed, so that an implementation of the interface "TextFilter" is located and loaded. When such an implementation is found, it is invoked to filter the text.

   Before we can do this, we need to add a dependency in the Project Properties dialog of the "WordEditorCore" module to the "TextFilterAPI" module:

   

   Now, you can load implementations of the "TextFilter" class, as shown below:

   private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
      String enteredText = text.getText();
      Collection<? extends TextFilter> allFilters = Lookup.getDefault().lookupAll(TextFilter.class);
      StringBuilder sb = new StringBuilder();
      for (TextFilter textFilter : allFilters) {
         String processedText = textFilter.process(enteredText);
         sb.append(processedText).append("\n");
      }
      text.setText(sb.toString());
   }

   The above could be achieved via the JDK 6 "ServiceLoader" class, except that the "Lookup" class can be used in JDK's prior to JDK 6. Aside from that, the "Lookup" class has a number of additional features, as the next section will illustrate.

10. Now you can run the application again and check that everything works just as before. While the functionality is the same, the new modular design offers a clear separation between the GUI and the implementation of the filter. The new application can also be extended quite easily, simply by adding new service providers to the application's classpath.
11. As an exercise, add a new module that provides a "LowercaseFilter" implementation of the API to the application.

You have now used the default Lookup, that is, "Lookup.getDefault()", to load implementations of an interface from the META-INF/services folder.

LookupListener and InstanceContent

In this section, we create a fourth module, which receives texts dynamically whenever we click the "Filter!" button in our first module.

1. In the "Word Editor Core" module, change the constructor of the "TextTopComponent" as follows:

   private InstanceContent content;
   
   private TextTopComponent() {
       initComponents();
       setName(NbBundle.getMessage(TextTopComponent.class, "CTL_TextTopComponent"));
       setToolTipText(NbBundle.getMessage(TextTopComponent.class, "HINT_TextTopComponent"));
   //        setIcon(Utilities.loadImage(ICON_PATH, true));
   
       content = new InstanceContent();
       associateLookup(new AbstractLookup(content));
   
   }

2. Change the code of the filter button so that the old value is added to the InstanceContent object when the button is clicked.

   private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
      String enteredText = text.getText();
      Collection<? extends TextFilter> allFilters = Lookup.getDefault().lookupAll(TextFilter.class);
      StringBuilder sb = new StringBuilder();
      for (TextFilter textFilter : allFilters) {
         String processedText = textFilter.process(enteredText);
         sb.append(processedText).append("\n");
         content.add(enteredText);
      }
      text.setText(sb.toString());
   }

3. Create another module in your application and name it "WordHistory":

   

   Click Next. Use code name base "org.word.editor.history":

   

4. In the WordHistory module, create a new window component:

   

   Use prefix "History", in the "org.word.editor.history" package. Specify that it should appear in the "explorer" position.

   

5. Once you have created the window, add a "JTextArea" to it. Change the variable name of the text area to "historyText".
6. Add code to the constructor of the HistoryTopComponent class so that it listens to the lookup of the String class of the current active window. It displays all retrieved String objects in the text area:

   ...
   ...
   ...
   public final class HistoryTopComponent extends TopComponent implements LookupListener {
   
       private org.openide.util.Lookup.Result<String> result;
   
       public HistoryTopComponent() {
           initComponents();
       }
   
       @Override
       public void componentOpened() {
           result = org.openide.util.Utilities.actionsGlobalContext().lookupResult(String.class);
           result.addLookupListener(this);
       }
   
       @Override
       public void componentClosed() {
           result.removeLookupListener(this);
       }
   
       @Override
       public void resultChanged(LookupEvent le) {
           Collection<? extends String> allStrings = result.allInstances();
           StringBuilder sb = new StringBuilder();
           for (String string : allStrings) {
               sb.append(string).append("\n");
           }
           historyText.setText(sb.toString());
       }
   
       ...
       ...
       ...
   

7. Then you can start the application and experiment with it. The result should look similar to the one shown in the screenshot below:

   

8. As an exercise, redesign the user interface of the "TextTopComponent" in such a way that a "JComboBox" displays the filters, as shown below:

   

   The "Filter!" button should use the currently selected filter to process the text in the "JTextField".

Congratulations! At this stage, with very little coding, you have created a small example of a modular application:

The application consists of 4 modules. Code from one module can only be used by another module if (1) the first module explicitly exposes packages and (2) the second module sets a dependency on the first module. In this way, the NetBeans Platform helps to organize your code in a strict modular architecture, ensuring that code isn't reused randomly but only when there are contracts set between the modules that provide the code.

Secondly, the Lookup class has been introduced as a mechanism for communicating between modules, as an extension of the JDK 6 ServiceLoader approach. Implementations are loaded via their interfaces. Without using any code from an implementation, the "WordEditorCore" module is able to display the service provided by the implementor. Loose coupling is provided to NetBeans Platform applications in this way.

To continue learning about modularity and the NetBeans Platform, head on to the four-part "NetBeans Platform Selection Management" series, which starts here. After that, get started with the NetBeans Platform Learning Trail, choosing the tutorials that are most relevant to your particular business scenario. Also, whenever you have questions about the NetBeans Platform, of any kind, feel free to write to the mailing list, dev@platform.netbeans.org; its related archive is here.

Have fun with the NetBeans Platform and see you on the mailing list!