Errors running builder 'Google WebApp Project Validator'

Error:

Problems occurred building the selected resources.
Errors running builder 'Java Builder' on project 'curve_app'.
com/google/gdt/eclipse/suite/preferences/GdtPreferences
Errors running builder 'Google WebApp Project Validator' on project 'curve_app'.
java.lang.NullPointerException

Workaround solution:

Close all projects, close eclipse.

Start eclipse using, "eclipse -clean" option.

You can try repeating the process 2-3 times,  if it does not work first time.

Not sure of the exact reason why this appears.

GWT - Highchart export request - Read multipart/form-data parameters

Getting multipart-form-data request parameters in java servlet-

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
	throws IOException, ServletException {
	if (!ServletFileUpload.isMultipartContent(req)) {
	throw new ServletException("Not a file upload request");
	}
	ServletFileUpload upload = new ServletFileUpload();
	FileItemIterator iter;
	iter = upload.getItemIterator(req);
	while (iter.hasNext()) {
	FileItemStream item = iter.next();
	InputStream stream = item.openStream();
	if (item.isFormField()) {
	if (item.getFieldName().equalsIgnoreCase("svg")) {
	svg = Streams.asString(stream);
	}
	...
	...
	}
	}
	}

view raw MultipartRequestParam.java hosted with ❤ by GitHub

GWT Celltable - Add multiple anchors to a cell

I am trying to insert multiple anchors in a single celltable cell. This is how it would look like-

The cars column has multiple cars, each car link can be clicked to perform different actions.
I have extended a MultipleAnchorCell class from AbstractSafeHtmlCell like this-

	import java.util.List;
	import com.google.gwt.cell.client.AbstractSafeHtmlCell;
	import com.google.gwt.core.client.GWT;
	import com.google.gwt.dom.client.NativeEvent;
	import com.google.gwt.safehtml.client.SafeHtmlTemplates;
	import com.google.gwt.safehtml.shared.SafeHtml;
	import com.google.gwt.text.shared.SafeHtmlRenderer;
	import com.google.gwt.text.shared.SimpleSafeHtmlRenderer;
	import com.google.gwt.cell.client.ValueUpdater;
	import com.google.gwt.dom.client.Element;
	import com.google.gwt.dom.client.EventTarget;
	import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
	public class MultipleAnchorCell extends AbstractSafeHtmlCell {
	interface Templates extends SafeHtmlTemplates {
	@Template(" {0} ")
	SafeHtml alink(String text);
	}
	private final List items;
	public void clear() {
	this.items.clear();
	}
	public void addLink(String newOp) {
	String item = new String(newOp);
	items.add(item);
	}
	public MultipleAnchorCell(List items) {
	super(SimpleSafeHtmlRenderer.getInstance(), "click", "keydown");
	this.items = items;
	}
	public MultipleAnchorCell(SafeHtmlRenderer renderer,
	List items) {
	super(renderer, "click", "keydown");
	this.items = items;
	}
	private static Templates templates = GWT.create(Templates.class);
	@Override
	public void onBrowserEvent(Context context, Element parent, String value,
	NativeEvent event,
	com.google.gwt.cell.client.ValueUpdater valueUpdater) {
	super.onBrowserEvent(context, parent, value, event, valueUpdater);
	// Handle the click event.
	if ("click".equals(event.getType())) {
	EventTarget eventTarget = event.getEventTarget();
	if (parent.isOrHasChild(Element.as(eventTarget))) {
	Element el = Element.as(eventTarget);
	if (el.getNodeName().equalsIgnoreCase("a")) {
	doAction(el.getAttribute("aid"), valueUpdater);
	}
	}
	}
	};
	@Override
	protected void onEnterKeyDown(Context context, Element parent,
	String value, NativeEvent event, ValueUpdater valueUpdater) {
	doAction(value, valueUpdater);
	}
	private void doAction(String value, ValueUpdater valueUpdater) {
	if (valueUpdater != null)
	valueUpdater.update(value);
	}
	@Override
	protected void render(com.google.gwt.cell.client.Cell.Context context,
	SafeHtml data, SafeHtmlBuilder sb) {
	if (data == null) {
	return;
	}
	for (String item : items) {
	sb.append(templates.alink(item));
	}
	}
	}

view raw MultipleAnchorCell.java hosted with ❤ by GitHub

And then I use this cell in a celltable to create a column. My User class contains comma separated values of cars in a class variable.

	List linkNames = new ArrayList();
	final MultipleAnchorCell linksCell = new MultipleAnchorCell(linkNames);
	Column carColumn = new Column(
	linksCell) {
	@Override
	public String getValue(User object) {
	String currentVal = "";
	linksCell.clear();
	if (object.getLinksToShow() != null
	&& object.getLinksToShow().length() > 0) {
	for (String hg : object.getLinksToShow().split(",")) {
	if (hg.trim().length() > 0) {
	linksCell.addLink(hg);
	currentVal = hg;
	}
	}
	}
	return currentVal;
	}
	};
	carColumn.setFieldUpdater(new FieldUpdater() {
	@Override
	public void update(int index, User object, String value) {
	if (value != null && value.length() > 0) {
	Window.alert(value);
	}
	}
	});

view raw MultipleAnchorCell-User.java hosted with ❤ by GitHub

      

       

I am still learning GWT and it took me a while to figure this out.

Comments/feedback is welcome.
===============================================================

GWT dygraph example using visualization datatable

Here is a quick example of how to create a dygraph using GWT and visualization api to get the datatable.

1. Add dygraph-gwt.jar to your build path and these inherits tags in your mysamplegwtproj.gwt.xml file

<inherits name="com.google.gwt.visualization.Visualization"/>
<inherits name="org.danvk.dygraphs"/>

2. Add the following script tag in mysamplegwtproject.html file

<script type="text/javascript" src="dygraph-combined.js">
<script type="text/javascript" src="http://www.google.com/jsapi">
3. Add the following code in your onModuleLoad() function-

        final VerticalPanel vp = new VerticalPanel();
        vp.setWidth("700px");
        vp.setHeight("700px");
        VisualizationUtils.loadVisualizationApi(new Runnable() {
            @Override
            public void run() {
                Query q = Query
                        .create("mysampleproj/getMyDatatable?params=2&id=1");

                q.send(new Callback() {
                    @Override
                    public void onResponse(QueryResponse response) {
                        JavaScriptObject jdygraph = createDygraph(
                                vp.getElement(), response.getDataTable(), 0,
                                100);
                    }
                });
            }
        }, LineChart.PACKAGE);

        RootPanel.get().add(vp);

4. Here is the JSNI function which actually creates the dygraph.




public static native JavaScriptObject createDygraph(Element element,
            DataTable dataTable, double minY, double maxY) /*-{
        var chart = new $wnd.Dygraph.GVizChart(element);
        chart.draw(dataTable, {
            valueRange : [ minY, maxY ],
            displayAnnotations : true,
            showRangeSelector : true,
            legend : 'always',
            labelsDivStyles : {
                'textAlign' : 'right'
            },
            title : 'TITLE',
            titleHeight : 25,            
            axes : {
                x : {
                    pixelsPerLabel : 50
                }
            }            
        });
        return chart;
    }-*/;




Hope this helps. Suggestions/improvements are welcome.

===============================================================
 

NoClassDefFoundError: com.google.common.collect.Sets

Error-
NoClassDefFoundError: "com.google.common.collect.Sets"

Solution-
Add guava-11.0.2.jar to WEB-INF/lib and add it to the build path.

GWT wrapper for visualization treemap with mouse events

A treemap is a helpful visualization of a data tree. It would be nice if the treemap had features like weighted box sizes for intermediate levels and explicitly setting up colors for non-leaf nodes. I wrote a  quick Google Web Toolkit(GWT) wrapper for Google visualization treemap-

 public class TreeMap extends Visualization<TreeMap.Options>
{
   public static class Options extends AbstractDrawOptions {
       public static Options create() {
           return JavaScriptObject.createObject().cast();
       }

       protected Options() { }
   }

   public static final String PACKAGE = "treemap";

   public TreeMap() {
       super();
   }

   public TreeMap(AbstractDataTable data, Options options) {
       super(data, options);
   }

   @Override
   protected native JavaScriptObject createJso(Element parent) /*-{
       return new $wnd.google.visualization.TreeMap(parent);                
   }-*/;
   
   public final void addOnMouseOverHandler(OnMouseOverHandler handler) {
       Handler.addHandler(this, "onmouseover", handler);
   }
   
   public final void addOnMouseOutHandler(OnMouseOutHandler handler) {
       Handler.addHandler(this, "onmouseout", handler);
   }
}

Problem - GWT logging not working

When you inherit certain modules in .gwt.xml file, it disables GWT logging. This happened to me when I tried inheriting Requestfactory. Some modules inherit com.google.gwt.logging.LoggingDisabled  internally and thus affect your logging.

To fix this you should explicitly enable logging after you have inherited all your modules. At the end of your list of inherits add the following to your .gwt.xml file-

<set-property name="gwt.logging.enabled" value="TRUE"/>

Executing Postgres crosstab query as a prepared statement

I was executing a crosstab query as a prepared statement in Java(in a GWT app) and getting the following error -

PSQLException - Can't use query methods that take a query string on a PreparedStatement.

With some helpful folks from stackflow, I was able to resolve the error with the following code -

String query = "SELECT * FROM crosstab(
                      'SELECT rowid, a_name, value
                       FROM test WHERE a_name = ''att2''
                                    OR a_name = ''att3''
                      ORDER BY 1,2'

) AS ct(row_name text, cat_1 text, cat_2 text, cat_3 text);";

PreparedStatement stat = conn.prepareStatement(query);
ResultSet rs = stat.getResultSet();
//Note that, it is executeQuery() and not executeQuery(query)
stat.executeQuery();
rs = stat.getResultSet();
while (rs.next()) {
    //TODO
}




Thanks!