NetBeans Code Snippet Module Tutorial

This tutorial demonstrates how to create and add code snippets to the HTML/JSP Component Palette. Code snippets are small pieces of code that can be dragged from a component palette and dropped in the Source Editor. They serve to speed up coding. The HTML/JSP Component Palette has several code snippets already, but you might want to add some additional ones and share them with others.

Note: This is not the latest version of this document. It applies to NetBeans IDE 6.0/6.1 only. Click here to see the most up to date version.

Contents

Content on this page applies to NetBeans IDE 6.1

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

Software or Resource Version Required
NetBeans IDE version version 6.1 or
version 6.0
Java Developer Kit (JDK) version 6 or
version 5

Optionally, for troubleshooting purposes, you can download the completed sample.

Introduction to Code Snippets

To create a code snippet, you use the NetBeans Palette API. A code snippet requires the following files:

  • A Java class that defines the piece of code to be dragged into the Source Editor.
  • A display name for the palette item.
  • A tooltip for the palette item.
  • A 16x16 pixel image for the 'Small Icon' display.
  • A 32x32 pixel image for the 'Big Icon' display.

After you have created or added the above files to the NetBeans module, you declare them in a resource declaration XML file, which you register in the NetBeans System Filesystem by using the layer.xml file.

Setting up the Module Project

Before you start writing the module, you have to make sure you that your project is set up correctly. The IDE provides a wizard that sets up all the basic files needed for a module.

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:

Initial Projects window.

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:

    Project Properties dialog box.

    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.

Coding the Code Snippet

In this section, you create BR.java, which defines a code snippet for an HTML line break. By implementing the ActiveEditorDrop class, you let the NetBeans APIs provide the infrastructure for a palette item for NetBeans editors. You also create HTMLPaletteUtilities.java, which defines the insertion of the tag in the editor.

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:

    customizer in design mode

  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 and Registering the Code Snippet

Code snippets are registered in two phases. Firstly, you declare a code snippet in an XML file that conforms to the NetBeans Editor Palette Item DTD. In this XML file, you declare your ActiveEditorDrop implementation class, a 16x16 pixel icon, a 32x32 pixel icon, a display name, and a tooltip.

Note: Use the 1.0 version of the DTD if you want the display name and tooltip to be defined in a properties file. Use the 1.1 version of the DTD if you want to declare the display name and tooltip witin the XML file itself.

Secondly, you register the XML file in the layer.xml file, in the palette's folder.

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 > Other. 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"
      "https://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"
      "https://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:

    BR32 BR16

  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:

    new bundle keys

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:

    layer in context

    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:

    layer in context

    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.


Building and Installing the Code Snippet

Now we need to think about installation and distribution. In the first section below, we install the code snippet, next we create an NBM file and examine distribution channels.

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:

    new snippet in component palette

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

    customizer in action

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

    dropped line break

    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:

    Shareable NBM.

  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.



Next Steps

For more information about creating and developing NetBeans modules, see the following resources:


Versioning

Version
Date
Changes
Open Issues
1 28 November 2005 Initial version
  • Is it the same for Swing/AWT Components?
  • How could formatting/indentation be different?
  • Need to add explanation for adding own dialog box for predefining values.
  • Need new screenshot of the Component Palette, to show the new snippet under the existing Table snippet.
  • Explanatory text for the use of the NetBeans APIs to be added.
  • Show how to share snippets between palettes via shadow files.
2 2 December 2005
3 8 December 2005
4 1 June 2007
  • Began updating for 6.0

Project Features

Project Links

About this Project

Platform was started in November 2009, is owned by Antonin Nebuzelsky, and has 138 members.
By use of this website, you agree to the NetBeans Policies and Terms of Use (revision 20140418.2d69abc). © 2013, Oracle Corporation and/or its affiliates. Sponsored by Oracle logo
 
 
Close
loading
Please Confirm
Close