http://nexus.sonatype.org/oss-repository-hosting.html/ST4: StringTemplate is a java template engine for generating source code, web pages, emails, or any other formatted text output. StringTemplate is particularly good at multi-targeted code generators, multiple site skins, and internationalization/localization. It evolved over years of effort developing jGuru.com. StringTemplate also powers the ANTLR 3 and 4 code generator. Its distinguishing characteristic is that unlike other engines, it strictly enforces model-view separation. Strict separation makes websites and code generators more flexible and maintainable; it also provides an excellent defense against malicious template authors. 
/*
 * [The "BSD license"]
 *  Copyright (c) 2011 Terence Parr
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *  1. Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *  2. Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *  3. The name of the author may not be used to endorse or promote products
 *     derived from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 *  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 *  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 *  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 *  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 *  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 *  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 *  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.stringtemplate.v4.gui;

import org.stringtemplate.v4.Interpreter;
import org.stringtemplate.v4.ST;
import org.stringtemplate.v4.StringRenderer;
import org.stringtemplate.v4.debug.EvalTemplateEvent;

import javax.swing.event.TreeModelListener;
import javax.swing.tree.TreeModel;
import javax.swing.tree.TreePath;

public class JTreeSTModel implements TreeModel {
    public Interpreter interp;
    public Wrapper root;

    public static class Wrapper {
        EvalTemplateEvent event;
        public Wrapper(EvalTemplateEvent event) { this.event = event; }

        @Override
        public int hashCode() {
            return event.hashCode();
        }

        @Override
        public boolean equals(Object o) {
            if ( o == null ) return false;
            //System.out.println(event+"=="+((Wrapper)o).event+" is "+(this.event == ((Wrapper)o).event));
            return this.event == ((Wrapper)o).event;
        }

        @Override
        public String toString() {
            ST st = event.scope.st;
            if ( st.isAnonSubtemplate() ) return "{...}";
            if ( st.debugState!=null && st.debugState.newSTEvent!=null ) {
                String label = st.toString()+" @ "+st.debugState.newSTEvent.getFileName()+":"+
                       st.debugState.newSTEvent.getLine();
                return "<html><b>" + StringRenderer.escapeHTML(label) + "</b></html>";
            }
            else {
                return st.toString();
            }
        }
    }

    public JTreeSTModel(Interpreter interp, EvalTemplateEvent root) {
        this.interp = interp;
        this.root = new Wrapper(root);
    }

    @Override
    public Object getChild(Object parent, int index) {
        EvalTemplateEvent e = ((Wrapper)parent).event;
        return new Wrapper(e.scope.childEvalTemplateEvents.get(index));
    }

    @Override
    public int getChildCount(Object parent) {
        EvalTemplateEvent e = ((Wrapper)parent).event;
        return e.scope.childEvalTemplateEvents.size();
    }

    @Override
    public int getIndexOfChild(Object parent, Object child) {
        EvalTemplateEvent p = ((Wrapper)parent).event;
        EvalTemplateEvent c = ((Wrapper)parent).event;
        int i = 0;
        for (EvalTemplateEvent e : p.scope.childEvalTemplateEvents) {
            if ( e.scope.st == c.scope.st ) {
//              System.out.println(i);
//              System.out.println("found "+e.self+" as child of "+parentST);
                return i;
            }
            i++;
        }
        return -1;
    }

    @Override
    public boolean isLeaf(Object node) {
        return getChildCount(node) == 0;
    }

    @Override
    public Object getRoot() { return root; }

    @Override
    public void valueForPathChanged(TreePath treePath, Object o) {
    }

    @Override
    public void addTreeModelListener(TreeModelListener treeModelListener) {
    }

    @Override
    public void removeTreeModelListener(TreeModelListener treeModelListener) {
    }
}