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<title>NetBeans Hyperlink Navigation Tutorial for NetBeans Platform 6.0</title>
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<h1>NetBeans Hyperlink Navigation Tutorial</h1>

<p>In this tutorial, you learn how to create hyperlinks in HTML files, programmatically. 

  <p><b>Contents</b></p>
   
      <img  src="../../images/articles/60/netbeans-stamp60-61.gif" class="stamp" width="114" height="114" alt="Content on this page applies to NetBeans IDE 6.1" title="Content on this page applies to NetBeans IDE 6.1"> </p>
      <ul class="toc">
  <li><a href="#intro">Introduction to Hyperlinks</a></li>
  <li><a href="#creating">Creating the Module Project</a></li>
  <li><a href="#hyperlinkprovider">Implementing the HyperlinkProvider Class</a></li>
  <li><a href="#opening">Opening the Referenced HTML File</a></li>
  <li><a href="#registering">Registering the HyperlinkProvider Implementation Class</a></li>
       </ul>
         
<p><b>To follow this tutorial, you need the software and resources listed in the following 
table.</b></p>

      <table>
        <tbody>
            <tr>
                <th class="tblheader" scope="col">Software or Resource</th>
                <th class="tblheader" scope="col">Version Required</th>
            </tr> 
            <tr>
                <td class="tbltd1">NetBeans IDE</td>
                <td class="tbltd1">version 
                <a href="http://download.netbeans.org/netbeans/6.1/final/">version 6.1</a> or<br>
                version 6.0</td>
            </tr>
            <tr>
                <td class="tbltd1">Java Developer Kit (JDK)</td>
                <td class="tbltd1"><a href="http://java.sun.com/javase/downloads/index.jsp">version 6</a> or<br>
                version 5</td>
            </tr>
        </tbody>
    </table>
    
     <p class="tips">Optionally, for troubleshooting purposes, you can <a href="http://plugins.netbeans.org/PluginPortal/faces/PluginDetailPage.jsp?pluginid=3797">download the
   completed sample</a> and inspect the sources.
    

<h2 class="tutorial"><a name="intro"></a>Introduction to Hyperlinks</h2>

<p>Hyperlinks in the IDE are created
 when you implement the NetBeans API <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-modules-editor-lib/org/netbeans/lib/editor/hyperlink/spi/HyperlinkProvider.html">HyperlinkProvider</a> class.
 In this case, the hyperlink will let the user navigate from an HREF attribute in an HTML link to the referenced
  HTML file.


<p>The new hyperlink will appear when the user holds down the Ctrl
  key and moves the mouse over the value of the HREF attribute, as shown here:

<p><img border="1" src="../../images/tutorials/hyperlink/hyperlink.png"/>

<p>When the hyperlink is clicked, the referenced file opens and the cursor
 lands on the first BODY tag, if one exists.</p>

<p>This is what the completed project will look like in the Projects window:


<p><img border="1" src="../../images/tutorials/hyperlink/61-hyperlink2.png"/>

<p>Though the focus of this tutorial is on hyperlinking from one HTML file to another,
 the principles shown here could equally be applied to other types of files,
  such as to Java source files, XML files, and JSP files.


<!-- ===================================================================================== -->

<p><h2><a name="creating"></a>Creating the Module Project</h2>

<p>In this section, we use a wizard to create a module project.
  We declare dependencies on modules that provide the NetBeans API classes
 needed by our hyperlink module.

<ol>

<li>Choose File &gt; New Project. In the New Project wizard,
 choose NetBeans Modules under Categories and Module Project
 under Projects. Click Next. Type <tt>AHrefHyperlink</tt> in Project Name
  and set Project Location to an appropriate folder on your disk. If they
 are not selected, select
   Standalone Module and Set as Main Project. Click Next.
  
   <li>Type <tt>org.netbeans.modules.ahrefhyperlink</tt> in Code Name Base.
   Type <tt>org/netbeans/modules/ahrefhyperlink/layer.xml</tt>
   in XML Layer. Click Finish.

    
 <li>Right-click the project, choose Properties, click Libraries 
in the Project Properties dialog box and declare a dependency on the following APIs:
 
<p><ul>
<li>Datasystems API
<li>Editor
<li>Editor Library
<li>Editor Library 2
<li>File System API
<li>HTML Lexer
<li>Lexer
<li>Nodes API
<li>Text API
<li>Utilities API
</ul>
    

</ol>

      <br />

<!-- ===================================================================================== -->
<p><h2><a name="hyperlinkprovider"></a>Implementing the HyperlinkProvider Class</h2>

<p>The <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-modules-editor-lib/org/netbeans/lib/editor/hyperlink/spi/HyperlinkProvider.html">HyperlinkProvider</a> class
  implements three methods, each of which is discussed in detail below, accompanied by a
 practical example in the context of our module. First we set up the class and then
  we implement each of the three methods in turn.
    
<br />
<div class="indent">
  <p><h3 class="tutorial"><a name="method1"></a>Setting Up the HyperlinkProvider Class</h3>

<p>Setting up our class means implementing <a href="https://netbeans.org/download/dev/javadoc/org-netbeans-modules-editor-lib/org/netbeans/lib/editor/hyperlink/spi/HyperlinkProvider.html">HyperlinkProvider</a>
 and initializing some values that we will need in our implementation.

 <ol>
     
     <li>Create a Java class in <tt>org.netbeans.modules.ahrefhyperlink</tt>,
 and call it AHrefHyperlinkProvider.
     
     <li>Change the signature so that HyperlinkProvider is implemented.
     
     <li>Note that the following import statements will be needed:
     
<p><pre class="examplecode">import org.openide.util.RequestProcessor;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import javax.swing.text.Document;
import javax.swing.text.JTextComponent;
import javax.swing.text.StyledDocument;
import org.netbeans.api.editor.EditorRegistry;
import org.netbeans.api.html.lexer.HTMLTokenId;
import org.netbeans.api.lexer.Token;
import org.netbeans.api.lexer.TokenHierarchy;
import org.netbeans.api.lexer.TokenSequence;
import org.netbeans.lib.editor.hyperlink.spi.HyperlinkProvider;</pre>
     
     <li>Add the following initial values at the top of the class:
 
<p><pre class="examplecode">private static String AHREF_IDENTIFIER = "href";
private Reference&lt;Document&gt; lastDocument;
private int startOffset;
private int endOffset;
private String identifier;</pre>

<li>Define the Constructor as follows:

<p><pre class="examplecode">public AHrefHyperlinkProvider() {
        
  lastDocument = null;
        
}</pre>

<li>Add accessors for the document:

<p><pre>private Document getLastDocument() {
    return lastDocument == null ? null : lastDocument.get();
}

private void setLastDocument(Document doc) {
    lastDocument = new WeakReference&lt;Document&gt;(doc);
}</pre>

 </ol>


</div>
      <br />
      
      <br />
<div class="indent">
  <p><h3 class="tutorial"><a name="method1"></a>isHyperlinkPoint(Document doc, int offset)</h3>

<p><a href="https://netbeans.org/download/dev/javadoc/org-netbeans-modules-editor-lib/org/netbeans/lib/editor/hyperlink/spi/HyperlinkProvider.html#isHyperlinkPoint(javax.swing.text.Document,%20int)">isHyperlinkPoint(Document doc, int offset)</a>
 determines whether there should be a hyperlink at the given offset within the given document. The inline
  comments in the method below, as well as in the code in the remainder of this tutorial,
   serve to explain the purpose of the code.

<p><pre class="examplecode">public boolean isHyperlinkPoint(Document doc, int offset) {

        JTextComponent target = EditorRegistry.lastFocusedComponent();
        final StyledDocument styledDoc = (StyledDocument) target.getDocument();
        if (styledDoc == null) {
            return false;
        }

        <b>// Work only with the open editor 
        //and the editor has to be the active component:</b>
        if ((target == null) || (target.getDocument() != doc)) {
            return false;
        }

        TokenHierarchy hi = TokenHierarchy.get(doc);
        TokenSequence&lt;HTMLTokenId&gt; ts = hi.tokenSequence(HTMLTokenId.language());
        ts.move(offset);
        ts.moveNext();
        Token&lt;HTMLTokenId&gt; tok = ts.token();
        if (tok != null) {
            int tokOffset = ts.offset();
            switch (tok.id()) {
                case VALUE:
                    while (ts.movePrevious()) {
                        Token&lt;HTMLTokenId&gt; prev = ts.token();
                        switch (prev.id()) {
                            case ARGUMENT:
                                if (AHREF_IDENTIFIER.equals(prev.text().toString())) {
                                    identifier = tok.text().toString();
                                    setLastDocument(doc);
                                    startOffset = tokOffset;
                                    endOffset = startOffset + tok.text().length();
                                    return true;
                                }
                            case OPERATOR:
                                continue;
                            case EOL:
                            case ERROR:
                            case WS:
                                continue;
                            default:
                                return false;
                        }
                    }
                    return false;
            }
            return false;
        }
        return false;
}</pre>


</div>
      <br />

<div class="indent">
  <p><h3 class="tutorial"><a name="method2"></a>getHyperlinkSpan(Document doc, int offset)</h3>

<p><tt><a href="https://netbeans.org/download/dev/javadoc/org-netbeans-modules-editor-lib/org/netbeans/lib/editor/hyperlink/spi/HyperlinkProvider.html#getHyperlinkSpan(javax.swing.text.Document,%20int)">getHyperlinkSpan(Document doc, int offset)</a></tt> determines the length of the hyperlink.


<p><pre class="examplecode">public int[] getHyperlinkSpan(Document doc, int offset) {

    JTextComponent target = EditorRegistry.lastFocusedComponent();
    final StyledDocument styledDoc = (StyledDocument) target.getDocument();
    if (styledDoc == null) {
        return null;
    }
    
    <b>// Return the position, which was set in the isHyperlink method:</b>
    return new int[]{startOffset, endOffset};
}</pre>


</div>
      <br />
      
      
      <div class="indent">
  <h3 class="tutorial"><a name="method3"></a>performClickAction(Document doc, int offset)</h3>


<p><a href="https://netbeans.org/download/dev/javadoc/org-netbeans-modules-editor-lib/org/netbeans/lib/editor/hyperlink/spi/HyperlinkProvider.html#performClickAction(javax.swing.text.Document,%20int)">performClickAction(Document doc, int offset)</a>
 determines what happens when the hyperlink is clicked. In general, a document
 should open, the cursor should move to a certain place in a document, or both.

<p><pre class="examplecode">public void performClickAction(Document doc, int offset) {

    JTextComponent target = EditorRegistry.lastFocusedComponent();
    final StyledDocument styledDocdoc = (StyledDocument) target.getDocument();
    if (styledDocdoc == null) {
        return;
    }

    <b>//Start a new thread for opening the HTML document:</b>
    OpenHTMLThread run = new OpenHTMLThread(styledDocdoc, identifier);
    RequestProcessor.getDefault().post(run);

}</pre>


</div>
      <br />

     
 <!-- ===================================================================================== -->
<p><h2><a name="opening"></a>Opening the Referenced HTML File</h2>

<p>Next, you need to create a class that opens an HTML file in a separate thread.
 Here, the class is called <tt>OpenHTMLThread</tt>. 

<p>The token identified in the <tt>isHyperlinkPoint</tt> method is
 received by this class. Then the token is analyzed to see whether
  it contains a slash, which indicates that it is a relative link. In
   that case, the file object is extrapolated from the URL to the file.
   Otherwise, the file object is created from the token itself. Next, the
    document with the name of the file object is opened and the cursor
     is positioned at the BODY tag, if found.

<pre class="examplecode">public class OpenHTMLThread implements Runnable {

    private StyledDocument doc;
    private String identifier;

    public OpenHTMLThread(StyledDocument doc, String identifier) {

        super();
        this.doc = doc;
        this.identifier = identifier;
    }

    public void run() {
        try {

            String cleanedIdentifier = identifier.replaceAll("\"", "");

            FileObject fo = NbEditorUtilities.getFileObject(doc);
            FileObject foHtml = null;

            <b>// Here we're working out whether we're dealing with a relative link or not:</b>
            if (cleanedIdentifier.contains("/")) {
                String fullPath = fo.getPath();
                try {
                    URL f = new File(fullPath).toURI().resolve(cleanedIdentifier).toURL();
                    foHtml = URLMapper.findFileObject(f);
                } catch (MalformedURLException ex) {
                    ex.printStackTrace();
                }
            } else {
                foHtml = fo.getParent().getFileObject(cleanedIdentifier);
            }

            <b>// Here we're finding our HTML file:</b>
            DataObject dObject;
            dObject = DataObject.find(foHtml);
            final EditorCookie.Observable ec = (EditorCookie.Observable) dObject.getCookie(EditorCookie.Observable.class);
            if (ec != null) {
                org.netbeans.editor.Utilities.runInEventDispatchThread(new Runnable() {

                    public void run() {
                        final JEditorPane[] panes = ec.getOpenedPanes();

                        <b>//Here we're positioning the cursor,
                        //if the document isn't open, we need to open it first:</b>
                        
                        if ((panes != null) && (panes.length > 0)) {
                            setPosition(panes[0], identifier);
                        } else {
                            ec.addPropertyChangeListener(new PropertyChangeListener() {

                                public void propertyChange(PropertyChangeEvent evt) {
                                    if (EditorCookie.Observable.PROP_OPENED_PANES.equals(evt.getPropertyName())) {
                                        final JEditorPane[] panes = ec.getOpenedPanes();
                                        if ((panes != null) && (panes.length > 0)) {
                                            setPosition(panes[0], identifier);
                                        }
                                        ec.removePropertyChangeListener(this);
                                    }
                                }
                            });
                            ec.open();
                        }
                    }

                    <b>//Here we specify where the cursor will land:</b>
                    private void setPosition(JEditorPane pane, String identifier) {

                        try {
                            <b>//The whole text:</b>
                            String text = pane.getDocument().getText(0, pane.getDocument().getLength() - 1);
                            <b>//The place where we want the cursor to be:</b>
                            int index = text.indexOf("&lt;body&gt;");
                            /<b>/If we can find it, we place the cursor there:</b>
                            if (index > 0) {
                                pane.setCaretPosition(index);
                            }
                        } catch (BadLocationException ex) {
                            ex.printStackTrace();
                        }
                    }
                });
            }
        } catch (DataObjectNotFoundException ex) {
            Exceptions.printStackTrace(ex);
        }
    }
}</pre>

<p>Make very sure that the following import statements
 are declared:
 
<pre>import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import javax.swing.JEditorPane;
import javax.swing.text.BadLocationException;
import javax.swing.text.StyledDocument;
import org.netbeans.modules.editor.NbEditorUtilities;
import org.openide.cookies.EditorCookie;
import org.openide.filesystems.FileObject;
import org.openide.filesystems.URLMapper;
import org.openide.loaders.DataObject;
import org.openide.loaders.DataObjectNotFoundException;
import org.openide.util.Exceptions;</pre>
     

 <!-- ===================================================================================== -->
<p><h2><a name="registering"></a>Registering the HyperlinkProvider Implementation Class</h2>

<p>Finally, you need to register the hyperlink provider implementation class
  in the module's <tt>layer.xml</tt> file. Do this as follows, while making sure
   that the line in bold below is the fully qualified class name of the class that
   implements HyperlinkProvider:

<pre class="examplecode">&lt;folder name="Editors"&gt;
    &lt;folder name="text"&gt;
        &lt;folder name="html"&gt;
            &lt;folder name="HyperlinkProviders"&gt;
            
                &lt;file name="AHrefHyperlinkProvider.instance"&gt;
                    &lt;attr name="instanceClass" 
                          stringvalue="<b>org.netbeans.modules.ahrefhyperlink.AHrefHyperlinkProvider</b>"/&gt;
                    &lt;attr name="instanceOf" 
                          stringvalue="org.netbeans.lib.editor.hyperlink.spi.HyperlinkProvider"/&gt;
                &lt;/file&gt;
                
            &lt;/folder&gt;
        &lt;/folder&gt;
    &lt;/folder&gt;
&lt;/folder&gt;</pre>

<p>If you create a hyperlink for a different MIME type, you need to change the
 <tt>text/html</tt> folders above to the appropriate MIME type.</p>

 <p>Now that the HyperlinkProvider is registered, you can install the module and
  try out your new hyperlinks. Hold down the Ctrl key, move the mouse over an HREF
   attribute as shown at the start of this tutorial:
 
<p><img border="1" src="../../images/tutorials/hyperlink/hyperlink.png"/>

   
<p>When the hyperlink appears,
    you can click it and let the IDE navigate to the referenced HTML file.
 
  <br />

  <br>
<div class="feedback-box"><a href="https://netbeans.org/about/contact_form.html?to=3&amp;subject=Feedback:%20Hyperlink%20Module%20Tutorial">Send Us Your Feedback</a></div>
<br style="clear:both;" />
  
 <!-- ===================================================================================== -->
<p><h2><a name="gettingtoknowthesample"></a>Next Steps</h2>

<ul>
    
    <li>Utility method for finding and opening Java source files.
    <li>Working with JSP and XML documents. (Same principle as above.)
    <li>Need to provide for the situation where the referenced HTML file doesn't exist.
    <li>Show hyperlink within same document.
    <li>Implement external links, i.e., http links should go to external browser.
    <li>Provide links to NetBeans sources, such as StrutsHyperlinkProvider, etc.
</ul>

<hr><p>
 
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