Communication Problem Vaading + GAE

Dears, 

I have a problem with Vaadin application deployed to GAE.
After deployement end after some activities error occur:

Communication problem Take note of any unsaved data, and click here or press ESC to continue

Below please find my main Vaading class:

package com.pl.look4soft.codeanalyzer.ui;

import com.googlecode.objectify.ObjectifyService;
import com.pl.look4soft.codeanalyzer.enums.ConnectionTypesEnum;
import com.pl.look4soft.codeanalyzer.model.ConnectionData;
import com.vaadin.annotations.Theme;
import com.vaadin.annotations.Title;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.data.util.BeanItemContainer;
import com.vaadin.event.SelectionEvent;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.ui.*;

import javax.servlet.annotation.WebServlet;
import java.util.List;

@Title("Code Analyzer")
@Theme("valo")
public class MyVaadinApplication extends UI {

    Button newContact = new Button("Add new connection hh");
    TextField filter = new TextField();
    ConnectionForm connectionForm = new ConnectionForm();
    Grid connectionList = new Grid();

    @Override
    public void init(VaadinRequest request) {
        initComponents();
        buildLayout();
    }

    private void initComponents(){
        //ConnectionData data = new ConnectionData(1l, "sssss", "sadasd", "adsa", "dasd");
        //ObjectifyService.ofy().save().entity(data).now();
        newContact.addClickListener(new Button.ClickListener() {
            @Override
            public void buttonClick(Button.ClickEvent clickEvent) {
                connectionForm.edit(new ConnectionData());
            }
        });
        List<ConnectionData> list = ObjectifyService.ofy().load().type(ConnectionData.class).list();

        connectionList.setContainerDataSource(new BeanItemContainer<>(ConnectionData.class, list));
        connectionList.setColumnOrder("connectionName");
        connectionList.removeColumn("id");
        connectionList.setSelectionMode(Grid.SelectionMode.SINGLE);
         connectionList.addSelectionListener(new SelectionEvent.SelectionListener() {
            @Override
            public void select(SelectionEvent selectionEvent) {
                connectionForm.edit((ConnectionData) connectionList.getSelectedRow());
                            }
        });
        connectionForm.setVisible(false);
    }

    private void buildLayout(){
        HorizontalLayout actions = new HorizontalLayout(filter, newContact);
        actions.setWidth("100%");
        filter.setWidth("100%");
        actions.setExpandRatio(filter, 1);

        VerticalLayout left = new VerticalLayout(actions, connectionList);
        left.setSizeFull();
        connectionList.setSizeFull();
        left.setExpandRatio(connectionList, 1);

        HorizontalLayout mainLayout = new HorizontalLayout(left, connectionForm);
        mainLayout.setSizeFull();
        mainLayout.setExpandRatio(left, 1);

        // Split and allow resizing
        setContent(mainLayout);
    }

    @WebServlet(urlPatterns = "/*", asyncSupported = true)
    @VaadinServletConfiguration(ui = MyVaadinApplication.class, productionMode = false)
    public static class MyUIServlet extends VaadinServlet {
    }

}

And my web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">
    <servlet>
        <servlet-name>VaadinApplicationServlet</servlet-name>
        <servlet-class>com.vaadin.server.VaadinServlet</servlet-class>
        <init-param>
            <param-name>UI</param-name>
            <param-value>com.pl.look4soft.codeanalyzer.ui.MyVaadinApplication</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>VaadinApplicationServlet</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>
    <filter>
        <filter-name>ObjectifyFilter</filter-name>
        <filter-class>com.googlecode.objectify.ObjectifyFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>ObjectifyFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
    <listener>
        <listener-class>com.pl.look4soft.codeanalyzer.dataStore.OfyHelper</listener-class>
    </listener>
    <session-config>
        <session-timeout>60</session-timeout>
    </session-config>
</web-app>

Thanks in advance.

You need to extend GAEVaadinServlet instead of VaadinServlet

Hi Artur,

Thank you very much fot your quick response.
I changed in java class and in web.xml and it works.

Is there any other issues which i should keep in mind during working with GEA and Vaadin?

Łukasz

See http://vaadin.com/download/release/7.5/7.5.6/release-notes.html