JEditorPane, HTMLEditorKit - custom action inserting custom tag

Question

I'm faithing with JEditorPane. I need simple editor. I've solved the problem with loading and modified HTML containing custom (two) tags (see my older post). It displays the document properly and I can even edit it now. I can write text, delete either characters or my custom elements. I won a battle, but haven't won the war. The next step is regrettably very problematical too. I'm unable to insert my custom tags.

I have a custom action:

import my.own.HTMLEditorKit; //extends standard HTMLEditorKit
import my.own.HTMLDocument; //extends standard HTMLDocument

class InsertElementAction extends StyledTextAction {
    private static final long serialVersionUID = 1L;

    public InsertElementAction(String actionName) {
        super(actionName);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        JEditorPane editor = getEditor(e);

        if (editor == null)
            return;

        HTMLDocument doc = (HTMLDocument) editor.getDocument();
        HTMLEditorKit ekit = (HTMLEditorKit) editor.getEditorKit();
        int offset = editor.getSelectionStart();

        try {
            ekit.insertHTML(doc, offset, "<span>ahoj</span>", 0, 0, HTML.Tag.SPAN);
            Element ele = doc.getRootElements()[0];
            ele = ele.getElement(1).getElement(0);
            doc.setInnerHTML(ele, "<bar medium=\"#DEFAULT\" type=\"packaged\" source=\"identifier\" />");
        }
        catch (BadLocationException ble) {
            throw new Error(ble);
        }
        catch (IOException ioe) {
            throw new Error(ioe);
        }
    }
}

It workts properly. I can insert the span element. But I cannot insert non-standard tag in this way. I can insert just code, span and so on, but not my tag. For my tag I'm forced to use this:

ekit.insertHTML(doc, offset, "x<bar medium=\"#DEFAULT\" type=\"packaged\" source=\"identifier\" />x", 0, 0, null);

There are two critical problems

1. The custom tag must be bounded with non-whispace characters (here x)
2. The current element's body is split

When I insert span element into <p>paragraph</p>, I get <p>par<span>ahoj</span>agraph</p> as expected. Howerever unknown tag is allways inserted as child of body element and the result (e.g. for unknown tag x) is <p>par</p><x>ahoj</x><p>agraph</p>.

The work is dead exhausting. I'm faithing with this relatively simple task since weeks. I'm already wasted. If the insertion won't to work, I can scrap it all...

Answer 1

I've found a workaround. The tag is inserted this way:

ModifiedHTMLDocument doc = (ModifiedHTMLDocument) editor.getDocument();
int offset = editor.getSelectionStart();
//insert our special tag (if the tag is not bounded with non-whitespace character, nothing happens)
doc.insertHTML(offset, "-<specialTag />-");
//remove leading and trailing minuses
doc.remove(offset, 1); //at the current position is the minus before tag inserted
doc.remove(offset + 1, 1); //the next sign is minus after new tag (the tag is nowhere)
//Note: no, you really cannot do that: doc.remove(offset, 2), because then the tag is deleted

My ModifiedHTMLDocument contains a method insertHTML(), which calls the medhod hidden by reflection:

public void insertHTML(int offset, String htmlText) throws BadLocationException, IOException {
    if (getParser() == null)
        throw new IllegalStateException("No HTMLEditorKit.Parser");

    Element elem = getCurrentElement(offset);

    //the method insertHTML is not visible
    try {
        Method insertHTML = javax.swing.text.html.HTMLDocument.class.getDeclaredMethod("insertHTML",
                new Class[] {Element.class, int.class, String.class, boolean.class});
        insertHTML.setAccessible(true);
        insertHTML.invoke(this, new Object[] {elem, offset, htmlText, false});
    }
    catch (Exception e) {
        throw new IOException("The method insertHTML() could not be invoked", e);
    }
}

The last piece of our brick-box is a method looking for the current element:

public Element getCurrentElement(int offset) {
    ElementIterator ei = new ElementIterator(this);
    Element elem, currentElem = null;
    int elemLength = Integer.MAX_VALUE;

    while ((elem = ei.next()) != null) { //looking for closest element
        int start = elem.getStartOffset(), end = elem.getEndOffset(), len = end - start;
        if (elem.isLeaf() || elem.getName().equals("html"))
            continue;
        if (start <= offset && offset < end && len <= elemLength) {
            currentElem = elem;
            elemLength = len;
        }
    }

    return currentElem;
}

This method is also a member of the ModifiedHTMLDocument class.

The solution is not pure, but it solves provisionally the problem. I hope I'll find a better kit. I'm thinking about JWebEngine. That should be replacement for current poor HTMLEditorKit, but I don't know, whether it allows me to add my custom tags.

Answer 2

Hope this helps http://java-sl.com/custom_tag_html_kit.html