NetBeans Code Snippet Module Tutorial

Creating the Module Project

1. Choose File > New Project (Ctrl-Shift-N). Under Categories, select NetBeans Modules. Under projects, select Module Project and click Next.
2. In the Name and Location panel, type Newhtmlsnippets in Project Name. Change the Project Location to any directory on your computer, such as c:\mymodules. Leave the Standalone Module radiobutton and the Set as Main Project checkbox selected. Click Next.
3. In the Basic Module Configuration panel, replace yourorghere in Code Name Base with org.netbeans.modules, so that the whole code name base is org.netbeans.modules.newhtmlsnippets. Leave the location of the localizing bundle and XML layer, so that they will be stored in a package with the name org/netbeans/modules/newhtmlsnippets. Click Finish.

The IDE creates the Newhtmlsnippets project. The project contains all of your sources and project metadata, such as the project's Ant build script. The project opens in the IDE. You can view its logical structure in the Projects window (Ctrl-1) and its file structure in the Files window (Ctrl-2). For example, the Projects window should now look as follows:

Specifying the Module's Dependencies

You will need to use several classes that belong to the NetBeans APIs. Each has to be declared as a module dependency. Use the Project Properties dialog box for this purpose.

1. In the Projects window, right-click the Newhtmlsnippets project node and choose Properties. In the Project Properties dialog box, click Libraries.

2. For each of "Common Palette", "Text API", and "Utilities API", click "Add...", select the name from the Module list, and then click OK to confirm it:

   

   Click OK to exit the Project Properties dialog box.

3. In the Projects window, expand the Important Files node, double-click the Project Metadata node, and note that the APIs you selected have been declared as Module dependencies.

Creating the Code Snippet

1. Right-click the org.netbeans.modules.newhtmlsnippets node and choose New > Java Class. Type BR in Class Name, make sure that the org.netbeans.modules.newhtmlsnippets package is selected in the Package drop-down list, and click Finish.
2. Replace the default content of the BR.java file with the following:

   package org.netbeans.modules.newhtmlsnippets;
   
   import javax.swing.text.BadLocationException;
   import javax.swing.text.JTextComponent;
   import org.netbeans.modules.newhtmlsnippets.HTMLPaletteUtilities;
   import org.openide.text.ActiveEditorDrop;
   
   public class BR implements ActiveEditorDrop {
       
       public BR() {
       }
       
       private String createBody() {
           String Br = "<br>";
           return Br;
       }
       
       public boolean handleTransfer(JTextComponent targetComponent) {
           String body = createBody();
           try {
               HTMLPaletteUtilities.insert(body, targetComponent);
           } catch (BadLocationException ble) {
               return false;
           }
           return true;
       }
       
   }

   Right-click in the Source Editor and choose Format (Alt-Shift-F).

Defining the Insertion

1. Right-click the org.netbeans.modules.newhtmlsnippets node and choose New > Java Class. Type HTMLPaletteUtilities in Class Name, make sure that the org.netbeans.modules.newhtmlsnippets package is selected in the Package drop-down list, and click Finish.
2. Replace the default content of the HTMLPaletteUtilities.java file with the following:

   package org.netbeans.modules.newhtmlsnippets;
   
   import javax.swing.text.BadLocationException;
   import javax.swing.text.Caret;
   import javax.swing.text.Document;
   import javax.swing.text.JTextComponent;
   import javax.swing.text.StyledDocument;
   import org.openide.text.NbDocument;
   
   public class HTMLPaletteUtilities {
     
       public static void insert(final String s,final JTextComponent target) throws BadLocationException {
           
           final StyledDocument doc = (StyledDocument)target.getDocument();
           
           class AtomicChange implements Runnable {
               
               public void run() {
                   Document value = target.getDocument();
                   if (value == null)
                       return;
                   try {
                       insert(s, target, doc);
                   } catch (BadLocationException e) {}
               }
           }
           
           try {
               NbDocument.runAtomicAsUser(doc, new AtomicChange());
           } catch (BadLocationException ex) {}
           
       }
       
       private static int insert(String s, JTextComponent target, Document doc) throws BadLocationException {
           
           int start = -1;
           
           try {
               
               //firstly, find selected text range:
               Caret caret = target.getCaret();
               int p0 = Math.min(caret.getDot(), caret.getMark());
               int p1 = Math.max(caret.getDot(), caret.getMark());
               doc.remove(p0, p1 - p0);
               
               //then, replace selected text with the inserted one:
               start = caret.getDot();
               doc.insertString(start, s, null);
           
           } catch (BadLocationException ble) {}
           
           return start;
   
       }
   
   }

   Right-click in the Source Editor and choose Format (Alt-Shift-F).

Adding a Customizer

Optionally, you can let a JPanel appear when the palette item is dropped. In the JPanel, you can let the user define values for attributes that relate to the tag that is about to be created. However, note that adding such a customizer is optional. In the case of a line break, which is what we are creating in this tutorial, there are no attributes that relate to the BR tag. For that reason, to illustrate the customizer functionality, we will add a comment before the BR tag, by means of a customizer.

Note: If you check out the html module from the NetBeans sources, you will find many examples of customizers in the org/netbeans/modules/html/palette/items package.

1. Create a JPanel and name it BRCustomizer. Drag and drop a JLabel and a JTextField onto the JPanel and arrange the JPanel as follows:

   

2. You will need to declare the following at the top of the BRCustomizer class:

   private Dialog dialog = null;
   private DialogDescriptor descriptor = null;
   private boolean dialogOK = false;
   
   BR br;
   JTextComponent target;

3. Rewrite the BRCustomizer constructor as follows:

   public BRCustomizer(BR br, JTextComponent target) {
       this.br = br;
       this.target = target;
           
       initComponents();
   }

4. Add a dependency on the Dialogs API.
5. In your BRCustomizer class, add this method, so that, in the next steps, you can open the customizer from your ActiveEditorDrop implementation class:

   public boolean showDialog() {
   
       dialogOK = false;
   
       String displayName = "";
       try {
           displayName = NbBundle.getBundle("org.netbeans.modules.newhtmlsnippets.Bundle").getString("NAME_html-BR"); // NOI18N
       } catch (Exception e) {}
   
       descriptor = new DialogDescriptor
               (this, NbBundle.getMessage(BRCustomizer.class, "LBL_Customizer_InsertPrefix") + " " + displayName, true,
               DialogDescriptor.OK_CANCEL_OPTION, DialogDescriptor.OK_OPTION,
               new ActionListener() {
           public void actionPerformed(ActionEvent e) {
               if (descriptor.getValue().equals(DialogDescriptor.OK_OPTION)) {
                   evaluateInput();
                   dialogOK = true;
               }
               dialog.dispose();
           }
       }
       );
   
       dialog = DialogDisplayer.getDefault().createDialog(descriptor);
       dialog.setVisible(true);
       repaint();
   
       return dialogOK;
   
   }

6. Define the evaluateInput() method, which is called in the showDialog() method above, as follows:

   private void evaluateInput() {
           
      String comment = jTextField1.getText();
      br.setComment(comment);
           
   }

7. Add to the Bundle.properties file:

   LBL_Customizer_InsertPrefix=Insert
   NAME_html-BR=Line Break

8. Hook your customizer into the ActiveEditorDrop implementation class as follows (only the lines that are changed are highlighted below):

   package org.netbeans.modules.newhtmlsnippets;
   
   import javax.swing.text.BadLocationException;
   import javax.swing.text.JTextComponent;
   import org.netbeans.modules.newhtmlsnippets.HTMLPaletteUtilities;
   import org.openide.text.ActiveEditorDrop;
   
   public class BR implements ActiveEditorDrop {
       
       private String comment = "";
   
       public BR() {
       }
       
       private String createBody() {
           String comment = getComment();
           String Br = "<!-- " + comment + " -->"
                   + "\n        <br>";
           return Br;
       }
       
       public boolean handleTransfer(JTextComponent targetComponent) {
          
           BRCustomizer c = new BRCustomizer(this, targetComponent);
           boolean accept = c.showDialog();
           if (accept) {
               String body = createBody();
               try {
                   HTMLPaletteUtilities.insert(body, targetComponent);
               } catch (BadLocationException ble) {
                   accept = false;
               }
           }
           return accept;
           
       }
       
       public String getComment() {
           return comment;
       }
       
       public void setComment(String comment) {
           this.comment = comment;
       }
       
   }

Declaring the Code Snippet

The NetBeans Editor Palette Item is used to declare the ActiveEditorDrop class, the icons, the display name, and the tooltip.

1. Right-click the org.netbeans.modules.newhtmlsnippets package node and choose New > File/Folder. Select XML Document in the XML folder and click Next. Type BR in File Name. Type \resources at the end of src\org\netbeans\modules\newhtmlsnippets in Folder. Click Finish.
2. Replace the default content of the BR.xml file with the following:

   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE editor_palette_item PUBLIC "-//NetBeans//Editor Palette Item 1.0//EN"
     "http://www.netbeans.org/dtds/editor-palette-item-1_0.dtd">
   
   <editor_palette_item version="1.0">
   
       <class name="org.netbeans.modules.newhtmlsnippets.BR" />
   
       <icon16 urlvalue="org/netbeans/modules/newhtmlsnippets/resources/BR16.png" />
       <icon32 urlvalue="org/netbeans/modules/newhtmlsnippets/resources/BR32.png" />
      
       <description localizing-bundle="org.netbeans.modules.newhtmlsnippets.Bundle"
                  display-name-key="NAME_html-BR"
                  tooltip-key="HINT_html-BR" />
                  
   </editor_palette_item>

   In the 1.1 DTD, you can define the display name and tooltip without using a properties file. Below, only the difference with the previous XML file definition is highlighted:

   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE editor_palette_item PUBLIC "-//NetBeans//Editor Palette Item 1.1//EN"
     "http://www.netbeans.org/dtds/editor-palette-item-1_1.dtd">
   
   <editor_palette_item version="1.0">
   
       <class name="org.netbeans.modules.newhtmlsnippets.BR" />
   
       <icon16 urlvalue="org/netbeans/modules/newhtmlsnippets/resources/BR16.png" />
       <icon32 urlvalue="org/netbeans/modules/newhtmlsnippets/resources/BR32.png" />
      
       <inline-description>
          <display-name>New Line</display-name>
          <tooltip>
              <b>
                 br
              </b>
          </tooltip>
       </inline-description>
                  
   </editor_palette_item>

3. Add a 16x16 pixel icon and a 32x32 pixel icon to the new resources folder. Name them BR16.png and BR32.png. They can also be in other icon formats, such as GIF or JPG. Make sure that the resource is correctly declared in the BR.xml file. You can right-click them here and then save them to your module's source structure:

   

4. If you want to use a properties file for declaring the palette item's display name and tooltip, add the following to the Bundle.properties file:

   

Registering the Code Snippet

The layer.xml file registers the user interface elements of your module in your application, which in this case is the IDE. Here, we need to register the palette item in the layer.xml file so that the item will appear in the HTML Palette.

1. Add the following tags to the layer.xml file, between the <filesystem> tags:

   <folder name="HTMLPalette">
      <folder name="HTML">
         <file name="BR.xml" url="resources/BR.xml"/>
      </folder>
   </folder>

2. Optionally, you can reorder the items in the palette. When you do so, you can use the user interface provided for this purpose to do so. Expand the Important Files node, expand the XML Layer node, and wait for the subnodes to be displayed. Next, expand <this layer in context>. A folder appears for every folder declared by every layer.xml file of every module registered in the IDE. Notice that the HTMLPalette folder is marked in bold. This matches the name of the folder you created in your own layer.xml file. Expand the folder and notice that its subfolder, HTML, is also in bold. Expand the HTML folder and notice that the BR.xml resource declaration file that you declared has been added to the resource declaration files provided by other modules:

   

   When you right-click on the node, several options are available, such as "Delete" and "Copy".

   As an experiment, drag the BR.xml node and drop it right below the TABLE.xml node. Double-click the Layer XML node in the Important Files node, notice that two new tags have been added, one before and one after the <file name="BR.xml" url="resources/BR.xml"/> line:

   

   When you dragged and dropped the BR.xml node in the <this layer in context> node, the IDE created <attr> tags for positioning the new component snippet between the existing component snippets.

Trying Out the Code Snippet

Install and try out the code snippet, by following the steps below.

1. In the Projects window, right-click the Newhtmlsnippets project and choose Install/Reload in Target Platform.

   The module is built and installed in the target platform. The target platform opens so that you can try out your new module. The default target platform is the installation used by the current instance of the development IDE.

2. Create a new HTML file in the IDE. When the HTML file opens, it displays the Component Palette (Ctrl-Shift-8) with one additional code snippet, called "New Line", with a tooltip that displays the result of dragging-and-dropping the item:

   

3. Drag the 'New Line' item into the Source Editor:

   

4. Type a comment, click OK, and notice that a new <br> tag is inserted at the cursor, together with an HTML comment:

   

   Note: Above, the text "breaking up the paragraph with a line break" was typed into the customizer.

Creating a Shareable Module Binary

An NBM file is the binary version of the module that provides the code snippet. Below, using one menu item, we create the NBM file.

1. In the Projects window, right-click the newhtmlsnippet project and choose Create NBM.

   The NBM file is created and you can view it in the Files window (Ctrl-2), as shown below:

   

2. Make the module available to others via, for example, the Plugin Portal.
3. The recipient can install the module by using their IDE's Plugin Manager. They would choose Tools > Plugins from the main menu.