source: other-projects/trunk/gs3-webservices-democlient/src/GS3DemoClient/org/greenstone/gs3client/BrowseDisplay.java@ 15661

/**
 *#########################################################################
 * BrowseDisplay.java - part of the demo-client for Greenstone 3, of the 
 * Greenstone digital library suite from the New Zealand Digital Library 
 * Project at the  * University of Waikato, New Zealand.
 * <BR><BR>
 * Copyright (C) 2008 New Zealand Digital Library Project
 * <BR><BR>
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * <BR><BR>
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *########################################################################
 */
package org.greenstone.gs3client;

import javax.swing.JPopupMenu;
import javax.swing.JList;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JEditorPane;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JSplitPane;
import javax.swing.JLabel;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

import java.awt.Component;
import java.awt.Container;
import java.awt.Cursor;
import java.awt.Dimension;
import java.awt.BorderLayout; 

import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

import java.net.MalformedURLException;
import java.net.URL;
import java.util.Vector;
import java.util.HashMap;

import javax.swing.JTree;
import javax.swing.text.html.HTMLDocument;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.TreeSelectionModel;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.event.TreeWillExpandListener;
import javax.swing.event.TreeExpansionEvent;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;

import org.apache.log4j.Logger;
import org.greenstone.gs3client.data.BrowseResponseData;
import org.greenstone.gs3client.data.DocumentNodeData;
import org.greenstone.gs3client.data.ClassifierNodeData;
import org.greenstone.gs3client.data.NodeData;
import org.greenstone.gs3client.data.ParseUtil;
import org.greenstone.gsdl3.util.GSXML;

/** 
 * The Browse panel inside the Java-client's tab pane that's labelled "Browse". 
 * This panel contains a tree view for expanding classifiers and their documents.
 * It also contains an area where the metadata is displayed, and a text area where
 * the textual or image content of a selected documentNode is displayed.
 * @author ak19
*/
public class BrowseDisplay extends JPanel 
    implements TreeSelectionListener, TreeWillExpandListener,
        ColourCombo.ColourChangeable 
{
    /** The Logger for this class */
    static Logger LOG = Logger.getLogger(SearchResultsDisplay.class);
    
    /** Access to the running instance of GS3JavaClient */
    protected GS3JavaClient client;
    /** A HashMap to store the displayData for the Browse operation. Usually  
     * just 2 elements long at most: displayName and displayDescription. */
    protected HashMap displayData;
    
    /* GUI items of this Browse Panel */
    protected JLabel browseLabel;
    protected JPanel browsePanel; 
    protected JSplitPane splitViewPane, structureMetaView;
    protected JPanel browseBar;
    protected ClassifierButton[] classifierList;
    protected JTree browsingTree;
    protected JEditorPane htmlPane;
    protected JList metanames, metavalues;
    /** Context menu that pops up when users right click in the browse tree area */
    protected JPopupMenu popup;
    
    /** Constructor that creates the Browse Panel and its internal GUI items.
     * @param client is the running instance of the client application through 
     * which its methods can be accessed. */
    public BrowseDisplay(GS3JavaClient client) {
        super(new BorderLayout());
        this.client = client;
        displayData = new HashMap(2); //usual maxsize
        
        browseBar = new JPanel(); // default FlowLayout L to R, centre aligned
        classifierList = null;
        this.add(browseBar, BorderLayout.NORTH);
        
        browsingTree = new JTree(new DefaultMutableTreeNode(null)); 
        browsingTree.getSelectionModel().setSelectionMode(
                TreeSelectionModel.SINGLE_TREE_SELECTION);
        browsingTree.addTreeSelectionListener(this);
        browsingTree.addTreeWillExpandListener(this);
    
        browsePanel = new JPanel(new BorderLayout());
            // new FlowLayout(FlowLayout.LEFT)); // don't use this, 
            // else view of tree is limited to the very minimum
        browsePanel.add(new JScrollPane(browsingTree), BorderLayout.CENTER);
        browseLabel = new JLabel("Browsing by...");
        browsePanel.add(browseLabel, BorderLayout.NORTH);
        
        JPanel metadataPanel = new JPanel(new BorderLayout());
        this.metanames = new JList();
        this.metavalues = new JList();
        metadataPanel.add(metanames, BorderLayout.WEST);
        metadataPanel.add(metavalues, BorderLayout.CENTER);
        
        JPanel metaSuperPanel = new JPanel(new BorderLayout());
        metaSuperPanel.add(new JLabel("Metadata"), BorderLayout.NORTH);
        //metaSuperPanel.add(metadataPanel, BorderLayout.CENTER);
        metaSuperPanel.add(
            new JScrollPane(metadataPanel), BorderLayout.CENTER);
        
        structureMetaView = new JSplitPane(JSplitPane.VERTICAL_SPLIT);
        structureMetaView.setTopComponent(browsePanel);
        structureMetaView.setBottomComponent(new JScrollPane(metaSuperPanel));
        structureMetaView.setOneTouchExpandable(true);
                
        htmlPane = new JEditorPane();
        htmlPane.setEditable(false);
        htmlPane.setContentType("text/html");
        
        // Add the docStructure and metadata panels next to each 
        // other within a split pane
        splitViewPane = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT);
        splitViewPane.setLeftComponent(structureMetaView);
        splitViewPane.setRightComponent(new JScrollPane(htmlPane));
        splitViewPane.setOneTouchExpandable(true);
        
        this.add(splitViewPane, BorderLayout.CENTER);
        
        
        // add a (rightclick) popup menu to the browsing tree
        // (can only do this after tree and htmlPane have been instantiated):
        popup = new JPopupMenu();
        browsingTree.setComponentPopupMenu(popup);
        browsingTree.addMouseListener(new Displays.PopupListener(
                popup, browsingTree, client, this.htmlPane));
    }

    /** Clears the service-specific buttons in the browseBar and the 
     * service-specific display-data. The rest of the GUI (split panes, panels) 
     * remain as they are. */
    public void clear() {
        // empty the docStructureTree's popup menu too
        popup.removeAll();
        
        browseBar.removeAll();
        displayData.clear();
        
        htmlPane.setText("");
        // empty any classification/document metadata
        final String[] empty = {};
        BrowseDisplay.this.metanames.setListData(empty);
        BrowseDisplay.this.metavalues.setListData(empty);
            //metanames.removeAll(); // doesn't work
            //metavalues.removeAll(); // doesn't work
        
        // empty the tree:
        ((DefaultTreeModel)browsingTree.getModel()).setRoot(null);
        
        classifierList = null;
        System.gc();
        
        this.validate();
    }
    
    /** Changes the colour of the query form and its controls to the
     *  current colours set in class ColourCombo. Specified by
     *  the ColourCombo.ColourChangeable interface. */
    public void changeUIColour() {
        Component[] comps = { this, this.browseBar, this.browsePanel,
                browsingTree, metanames, metavalues, popup };
        ColourCombo.changeColor(comps);
        // ensures that the "metadata" JLabel (not an instance variable) 
        // is coloured appropriately as well
        ColourCombo.changeAncestorColor(metanames); 
        
    }
    
    /** For some reason, the overriden getPreferredSize() is not
     * called upon resize of this panel, so I am calling it manually 
     * whenever there's a call to paint this Panel. Painting will
     * be done when the parent container is resized (and this panel 
     * made visible) anyway, so it might as well work out what size
     * the interior panels will have on every resize.
     * @param g is the Graphics object
     * @see "JPanel's paint(Graphics g)"
    */
    public void paint(java.awt.Graphics g) {
        super.paint(g); // let the usual JPanel paint event happen 
        this.getPreferredSize();
    }
    
    // FIX ME: The following problem was 'fixed' by overriding paint: 
    // Strangely, this method is called only once! Even though it should 
    // always be called on resize as indeed happens correctly in 
    // SearchResultsDisplay.java.
    // Reason might be because components are arranged differently in the 
    // JSplitPanes nested in this JPanel (they're arranged different from
    // SearchResultsDisplay.java)
    /** Overrode this method to resize the splitpanes within, upon resize. 
     * It calculates the size of this panel, as well as setting those of  
     * the splitpanes it contains based on the size of the parent container. 
     * @return the preferred dimensions of this JPanel. */
    public Dimension getPreferredSize() {
        Dimension size = this.getParent().getSize();
        int x = (int)size.getWidth() / 3; // WHY DOES THIS NOT WORK?????
        int y = (int)(size.getHeight() / 5 * 3); // WHY DOES THIS NOT WORK?????
        structureMetaView.setDividerLocation(y); // 400
            // structureMetaView.setDividerLocation(1.0); // as far down as 
                // possible to give more space to browse structure and less to meta
        splitViewPane.setDividerLocation(x); // 300
        splitViewPane.setPreferredSize(size);
        //System.err.println("SIZE: " + this.getSize() + "y: " + y);
        return size;
    }
    
    /** Will clear previous browse service's classification options and widgets, 
     * and redisplay browse options as specified by the describe Response Message 
     * XML returned from the browse Service. 
     * @param describeRespMsgTag - the (Classifier)Browse Service's describe  
     * response message element, used to reset the classifier buttons in the 
     * browseBar of this panel. */
    public void displayBrowseOptions(Element describeRespMsgTag){
        this.clear();
        // First set the displayItems
        Element service = ParseUtil.getFirstDescElementCalled(
                describeRespMsgTag, GSXML.SERVICE_ELEM);
        
        Vector displayItems = ParseUtil.getAllChildElementsCalled(
                service, GSXML.DISPLAY_TEXT_ELEM);
        if(displayItems != null) {
            for(int i = 0; i < displayItems.size(); i++) {
                Element e = (Element)displayItems.get(i);
                if(!e.hasAttribute(GSXML.NAME_ATT))
                    continue;
                // we are looking for <displayItem name="">value</displayItem>
                String name = e.getAttribute(GSXML.NAME_ATT);
                String value = ParseUtil.getBodyTextValue(e);
                this.displayData.put(name, value);
            }
            
            // get <displayItem name="description">descr</displayItem>
            String descr = (String)displayData.get(
                    GSXML.DISPLAY_TEXT_DESCRIPTION);
            if(descr != null)
                this.setBorder(BorderFactory.createTitledBorder(descr));
        }   
        
        // Now, process all <classifier> items inside <classifierList>
        NodeList nl = describeRespMsgTag.getElementsByTagName(
                GSXML.CLASSIFIER_ELEM+GSXML.LIST_MODIFIER);
        // There will be only one, as far as I can tell from the describe 
        // response returned from gs2mgppdemo's ClassifierBrowse service
        if(nl.getLength() <= 0)
            return; // nothing to do; but this should not happen
        Element classifierListTag = (Element)nl.item(0);
        
        // now get the <classifier>s children from <classifierList> 
        nl = classifierListTag.getElementsByTagName(GSXML.CLASSIFIER_ELEM);
        int size = nl.getLength();
        if(size > 0) 
            classifierList = new ClassifierButton[size];
        
        for(int i = 0; i < size; i++) {
            Element classifier = (Element)nl.item(i);
            classifierList[i] = new ClassifierButton(
                    new ClassifierData(classifier));
            this.browseBar.add(classifierList[i]);
        }
    }
    
    /** Called to populate the browsing tree with browse data. Only the
     * data for the top-level classifier and its direct descendants are
     * retrieved. 
     * @param browseResponseObj - stores the data of the response XML
     * message returned by the (Classifier)Browse service.
     * @param rootName - the title/name of the root classifier */
    public void displayBrowseResults(
            BrowseResponseData browseResponseObj, String rootName) 
    {
        browsingTree.removeAll();
        DefaultTreeModel model = (DefaultTreeModel)browsingTree.getModel();
        
        ClassifierNodeData rootClassNode 
            = browseResponseObj.getRootClassifier();
        rootClassNode.setTitle(rootName);
        DefaultMutableTreeNode newRoot 
            = new DefaultMutableTreeNode(rootClassNode);
        
        NodeData[] childNodes = rootClassNode.getChildren();
        // First set their titles:
        client.retrieveTitledStructureFor(rootClassNode);
        
        if(childNodes != null) { 
            for(int i = 0; i < childNodes.length; i++) {
                DefaultMutableTreeNode child 
                    = new DefaultMutableTreeNode(childNodes[i]);
                newRoot.add(child);
                if(childNodes[i].hasChildren)
                    child.add(new DefaultMutableTreeNode(null));
                //browsingTree.setRootVisible(false); //No, because it 
                    // has a root: the root classifierNode
            }
            model.setRoot(newRoot);
        }
    }
    
    /** This method of the TreeWillExpandListener interface is called when
     * the user clicked on an expandable node in the browsingTree. 
     * Since we are loading substructures in the tree lazily (i.e. loading
     * childnodes lazily) we have dummy/null childTreeNodes that make 
     * expandable parentNodes look like folders (make the parents look 
     * expandable). 
     * Therefore, when the user clicks on an expandable node, we first check
     * whether we already have loaded the datastructure/subtree or whether
     * its child is a dummy (null). If a dummy (null child), then we work
     * out whether it's a classifierNodeData or a documentNodeData that the
     * expanding treeNode represents. Based on that, we retrieve the sub-
     * structure for the treeNode that's expanding. 
    */
    public void treeWillExpand(TreeExpansionEvent e) 
    {
        DefaultMutableTreeNode node = null;
        
        // Don't use browsingTree.getLastSelectedPathComponent(). That 
        // method doesn't deal with the case when someone clicked on the 
        // expand/collapse knob next to folders.
        // Use e.getPath().getLastPathComponent() instead:
        node = (DefaultMutableTreeNode)e.getPath().getLastPathComponent();
        if(node == null || node.isLeaf())
            return; // leafnode, shouldn't happen: we're in Expansion method!
        
        Object nodeInfo = node.getUserObject();
        
        // First check whether this expanding/folder node's child contains 
        // a dummy object (null) or is already set:
        DefaultMutableTreeNode child 
            = (DefaultMutableTreeNode)node.getFirstChild();
        Object childNodeInfo = child.getUserObject();
        // if the child is null (therefore not a NodeData object), it was a 
        // dummy we added for delayed lazy-loading - so remove child
        if(childNodeInfo != null) {
            return; // we've already retrieved the structure for
                    // this node, don't need to process it any further
        }
        
        // Child is null: not a NodeData object, so we change the dummy child. 
        // This is done by populating the node's children with the actual 
        // document node/classifier node structure:
        node.removeAllChildren(); // first remove the dummy child
        
        // now, construct the structure of the treenode that's expanding
        // based on whether it represents a classifierNodeData or
        // documentNodeData object:
        NodeData nodeData = (NodeData)nodeInfo;
        if(nodeData instanceof ClassifierNodeData) {
            ClassifierNodeData classNode = (ClassifierNodeData)nodeData;
            this.client.retrieveTitledStructureFor((classNode));
            
            // The above will have set the expanding classNode's children.
            // Now, we add a treeNode for each child of classNode -
            // and for each childclassNode that's expandable, add a dummy
            // child for them to make them expandable:  
            NodeData[] children = classNode.getChildren();
            for(int i = 0; i < children.length; i++) {
                DefaultMutableTreeNode childTreeNode
                    = new DefaultMutableTreeNode(children[i]);
                node.add(childTreeNode);
                // If the classifier node has children (expands further), make 
                // it a folder by adding in a null child to allow lazy tree- 
                // expansion as when required
                if(children[i].hasChildren) 
                    childTreeNode.add(new DefaultMutableTreeNode(null));
            }
        } else { // if instanceof DocumentNodeData
            DocumentNodeData docNode = (DocumentNodeData)nodeData;
            if(docNode.nodeType.equals(GSXML.NODE_TYPE_ROOT)) {
                this.client.retrieveTitledStructureFor(docNode);
                    
                Displays.createNodesForChildren(docNode, node);
            } //else { document can't be a leaf node *and* expand at the
                // same time. So shouldn't ever be here!
                // After all, this is the method that's called when a node
                // is expanding, and leaf nodes should not expand.
            //}
        }   
    }
    
    /** Part of the TreeWillExpandListener interface. Nothing to do here. */
    public void treeWillCollapse(TreeExpansionEvent e) {}
    
    /* THE FOLLOWING DOES NOT APPLY ANYMORE:
     * In this method, we are not dealing with expandable nodes 
     * (we check for whether the clicked node is a leaf), but with document-
     * NodeData objects that are leaves: for these, we display the document. */
    /** 
     * Whenever an item is clicked in the browsingTree, this method is called. 
     * We display the document associated with a documentNode that is clicked,
     * or "" for classifierNodes.
    */
    public void valueChanged(TreeSelectionEvent e) {
        // remove any menuItems in the popup from the previously 
        // selected docNode
        popup.removeAll();

        DefaultMutableTreeNode node = null;
        node = (DefaultMutableTreeNode)
            browsingTree.getLastSelectedPathComponent();
        
        if(node == null) return;
        Object nodeInfo = node.getUserObject();
        // after construction there's nothing in the trees, so check for that:
        if(nodeInfo == null) return; 
       
        // We need to change to a Wait cursor while we load the documentNode
        Container c = client.getContentPane();
        c.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
        
        
        if(nodeInfo instanceof DocumentNodeData) { 
            //whether leaf or folder, the document element may contain text
            DocumentNodeData docNode = (DocumentNodeData)nodeInfo;
            client.retrieveContentFor(docNode);
            // for docNodes, there's more than title metadata, so ensure 
            // all metadata has been retrieved
            client.retrieveAllMetadataFor(docNode);
            
            if(docNode.hasNoText()) { //NoText field is 1, meaning it's an img
                // now display the image
                this.htmlPane.setText(
                        Displays.getImgUrlEnclosedInHtml(docNode.getImgURL()));
            } else { // it has text 
                // Java's htmlpane does not recognise justified alignment.
                // It displays them all centred.
                // So here we replace all ALIGN="JUSTIFY" with ALIGN="LEFT" 
                // (we don't do this in the DocumentNodeData class itself,
                // because our nodeContent should not be transformed: it will
                // display properly in browsers and other html displays).
                    //System.err.println("docNode can not be an image");
                String docContent = docNode.getContent().replaceAll(
                        "ALIGN=\"JUSTIFY\"", "ALIGN=\"LEFT\"");
                String baseURL = client.getBaseURL();
                // TODO: make the docNode itself work out its URL by passing
                // baseURL to the docNode?
                if(!baseURL.equals("") && docNode.getRoot() != null) { 
                        // "" is the case where dlAPIA = gs3 
                        // where the _httpdocimg_ macro will deal with
                        // resolving the relative urls into their full ones
                        // We don't want to set the base and meddle with macro
                        // for those cases.
                    // For Fedora's case:
                    HTMLDocument doc 
                        = (HTMLDocument)this.htmlPane.getDocument();
                    try{
                        URL url = new URL(baseURL+docNode.getRoot().nodeID+"/");
                        //System.err.println("url: " + url.toString());
                        doc.setBase(url);
                        //docContent = docContent.replaceAll("_httpdocimg_/", "");
                        LOG.debug(docContent);
                    }catch(MalformedURLException mex) {
                        ; //nothing to be done, leave the base as it is
                    }
                }
                this.htmlPane.setText(docContent);
            }
            this.htmlPane.setCaretPosition(0);
        } else // treenode is a ClassifierNodeData, clear the html Pane
            this.htmlPane.setText("");
         
        // In any case -- whatever kind of nodedata it may be -- we display 
        // the metadata for this NodeData:
        Displays.showMeta((NodeData)nodeInfo, metanames, metavalues);

        c.setCursor(Cursor.getDefaultCursor()); // set the cursor back to normal
    }
    
    /** Inner class (not static, as it needs access to outerclass' this object.
     * This class represents a button that encapsulates a ClassifierData 
     * object and sets its own name and tooltip text based on the displayName 
     * and displayDescription of that ClassifierData object. */
    public class ClassifierButton 
        extends JButton implements ActionListener 
    {
        /** Encapsulated classifierData obj */
        public ClassifierData classifier; 
        
        /** Constructor that creates a button to visually represent
         * the classifier.
         * @param classifier - the ClassifierData object for which to 
         * create a button, using its display data. */
        public ClassifierButton(ClassifierData classifier) {
            super(classifier.displayName);
            this.classifier = classifier;
            this.setToolTipText(classifier.displayDescription);
            this.addActionListener(this);
        }
        
        /** Called when someone presses the ClassifierButton: when pressed,
         * perform the browse request associated with the classifier. */
        public void actionPerformed(ActionEvent e) {
            Container c = client.getContentPane();
            c.setCursor(Cursor.getPredefinedCursor(Cursor.WAIT_CURSOR));
            // empty the previous classification's/document's metadata
            // and any text in the html pane
            final String[] empty = {};
            BrowseDisplay.this.metanames.setListData(empty);
            BrowseDisplay.this.metavalues.setListData(empty);
            BrowseDisplay.this.htmlPane.setText("");
            
            // Now use the outerclass' MessagerClient object to perform the 
            // browse request:
            BrowseDisplay.this.client.doBrowse(this.classifier);
            BrowseDisplay.this.browseLabel.setText("Browsing by " 
                    + classifier.displayName);
            c.setCursor(Cursor.getDefaultCursor());
        }
    }
    
    /** Static inner class that represents the data in a &lt;classifier&gt;
     * element - itself nested inside a list (&lt;classifierList&gt;) of them.
     * These elements are to be found in the response returned for a describe 
     * request sent to a collection's BrowseService. */
    public static class ClassifierData {
        /** The content attribute of the &lt;classifier&gt; */
        public final String content;
        /** The name attribute of the &lt;classifier&gt; */
        public final String name;
        /** The display name attribute of the &lt;classifier&gt; */
        public final String displayName;
        /** The description attribute of the &lt;classifier&gt; */
        public final String displayDescription;
        
        /** Constructor. 
         * @param classifierTag - creates a ClassifierData object from the 
         * data stored in a &lt;classifier&gt; element */
        public ClassifierData(Element classifierTag) {
            content = classifierTag.hasAttribute(GSXML.CLASSIFIER_CONTENT_ATT) ?
                classifierTag.getAttribute(GSXML.CLASSIFIER_CONTENT_ATT) : "";
            name = classifierTag.hasAttribute(GSXML.NAME_ATT) ?
                classifierTag.getAttribute(GSXML.NAME_ATT) : "";
            
            // now get <displayItem name="name">value</displayItem>
            // and <displayItem name="description">descr</displayItem>  
            HashMap displayData = new HashMap(2); //size = 2, because 
                // generally expecting only display Name and Description
            NodeList nl = classifierTag.getElementsByTagName(
                    GSXML.DISPLAY_TEXT_ELEM);
            for(int i = 0; i < nl.getLength(); i++) {
                Element displayItem = (Element)nl.item(0);
                if(displayItem.hasAttribute(GSXML.NAME_ATT)) {
                    String nameAtt = displayItem.getAttribute(GSXML.NAME_ATT);
                    String value = ParseUtil.getBodyTextValue(displayItem);
                    displayData.put(nameAtt, value);
                }
            }
            String dName = (String)displayData.get(GSXML.DISPLAY_TEXT_NAME);
            String dDescr = (String)displayData.get(
                    GSXML.DISPLAY_TEXT_DESCRIPTION);
            this.displayName = (dName == null) ? "" : dName;
            this.displayDescription = (dDescr == null) ? "" : dDescr;
            
            // Can get rid of HashMap now:
            displayData.clear();
            displayData = null;
        }
    
        /** The displayName can be used as a label in any widget. 
         * @return the displayName of this ClassifierData object */
        public String toString() { return this.displayName; } 
        
        /** @return a display String with the data stored in this ClassifierData
         * object. Useful for debugging purposes. */
        public String show() {
            StringBuffer buf = new StringBuffer(this.name);
            buf.append(" ");
            buf.append(this.content);
            buf.append(" ");
            buf.append(this.displayName);
            buf.append(" ");
            buf.append(this.displayDescription);
            
            return buf.toString();
        }
    }   
}