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Andreas Kohlbecker, 02/10/2017 08:33 AM


Vaadin Development Resources

See also the VaadinEditorDevelopersGuide

Vaadin is an open source Web application framework for rich Internet applications. In contrast to JavaScript libraries and browser-plugin based solutions, it features a server-side architecture, which means that the majority of the logic runs on the servers. Ajax technology is used at the browser-side to ensure a rich and interactive user experience. On the client-side Vaadin is built on top of and can be extended with Google Web Toolkit.

This page holds information and resources for developing with the GWT-based Vaadin-Framework. For general information to this framework see: https://vaadin.com/faq

(quoted from Wikipedia:https://en.wikipedia.org/wiki/Vaadin, the free encyclopedia)


General Structure of Vaadin

The Vaadin architecture can be split very roughly into client and server side.

The server side holds all the business logic and services as well as the standard java vaadin components, which will be translated into JavaScript later on.

The client side incorporates the GWT-part as well as client side specific JavaScript code, to do some more dynamic manipulation on the browser side.

All Vaadin Components are written in plain Java. There is no need to program in JavaScript or even HTML. This all will be compiled by the framework. See the next section for supported browsers.

Browser compatibility

Vaadin 7 supports the following browsers:

  • Android 2.3 or newer
  • Google Chrome 23 or newer
  • Internet Explorer 8 or newer
  • iOS 5,6,7 or newer
  • Mozilla Firefox 17 or newer
  • Opera 12 or newer
  • Safari 6 or newer

NOTE: From release 7.2+ all permutations have been merged into a single one - refer #13274

Development Environment Setup

please refer to VaadinEditorDevelopersGuide

cdm-vaadin project

The cdm-vaadin project is a stand-alone war Eclipse / Maven project, which includes cdmlib dependencies allowing it to function as a full-fledged web application. This allows for testing the vaadin framework with the cdmlib. This project itself is not a target for deployment as a webapp, but is integrated into the cdmlib-remote-webapp project as described below.

For more details on the Vaadin integration in Maven please see https://vaadin.com/wiki/-/wiki/Main/Creating+a+Maven+project

Vaadin specific maven goals include,

vaadin:clean
vaadin:resources
vaadin:update-theme
vaadin:update-widgetset
vaadin:compile-theme
vaadin:compile

cdm-vaadin project integration with the cdmlib-remote-webapp

To Be Done

Servlet Deployment Configuration

With Servlet 3.0+ all configuration other wise declared in web.xml can now be declared using annotations in specfic Java classes. The servlet deployment configuration for the project consists of,

  • Web Application Initializer : consists currently of two main parts, both of which are declared in the 'eu.etaxonomy.cdm.vaadin.CdmAppInitializer' class.
    • ContextLoaderListener, a servlet context listener that associates a Spring application context with your servlet context and makes it accessible to other Spring classes. Typically this is defined via an applicationContext.xml file that sits in WEB-INF.
    • DispatcherServlet, a regular Java servlet that Spring provides. Each such servlet has its own Spring application context - distinct from, though a "child" of, the one mentioned above associated with the ContextLoaderListener. If your servlet is named foobar then the default XML file name is foobar-servlet.xml.
  • Servlet Mapping : primarily connects a Vaadin UI class to a VaadinServlet class, with 'init-param' style annotations. Any of the UI classes in the project can be looked up for examples of this configuration.

NOTE: The 'Web Application Initializer' part of the configuration does not yet work for the moment (refer #4527) and is set for now in the web.xml.

Vaadin run modes

Production Mode

Configured in /src/main/webapp/WEB-INF/web.xml and also via the @VaadinServletConfiguration(productionMode = true, ...) annotation for the classes in the eu.etaxonomy.cdm.vaadin.ui package. The annotation based configuration does not seem to have an effect though.

SuperDev Mode

see VaadinEditorDevelopersGuide for details

Vaadin Components

Vaadin AddOn's

The official Vaadin website hosts a directory of all available AddOn's http://vaadin.com/directory.

In order to add an extension to your project add the maven dependencies to your pom file and run

mvn eclipse:eclipse

the needed libraries will be downloaded. Check if the libraries are added in you IDE specific dependency tree. Sometimes it can be necessary to clean the whole project and build it again with

mvn clean install

Design patterns

For a general overview on how to develop with Vaadin, you can refer to the online version of the Book Of Vaadin Some of the important aspects are listed here.

Creating a server-side UI

Normally, you need to:

  • extend the UI class
  • build an initial UI from components
  • define event listeners to implement the UI logic

Optionally, you can also:

  • set a custom theme for the UI, for a harmonized look and feel it is however recommended to use the same theme for all UIs in cdm-vaadin
  • bind components to data
  • bind components to resources

Model-View-Presenter (MVP) Pattern

The pattern is described in section 11.10.2 #advanced.architecture.mvp of the Book of Vaadin. An example of the pattern in the project is the 'eu.etaxonomy.cdm.vaadin.view.AuthenticationView' class.

The example given in the book of vaadin however is quite simple and misses covering important aspects of complex applications. This shortcoming has been discussed in the vaadin blog post model-view-presenter-pattern-with-vaadin. In the according discussion thread rajeeshk comes up with a more elaborated appoach of a MVP framework example implementation which is available at github rajeeshk/mvpcalculator. http://www.syngenio.com/de/blog/posts/VaadinSpring-und-das-Model-View-Presenter-Pattern.php

CDM Library Specific Development

This section lists the important CDM specific development issues to integrating Vaadin.

Managing Sessions

The strategies to solve the lazy loading problem and in more general to manage sessions properly include,

  • Conversational Sessions : which essentially involves linking any UI which requires long running sessions to a 'eu.etaxonomy.cdm.vaadin.servlet.CdmVaadinConversationalServlet'. The servlet creates an instance of the ConversationHolder when a VaadinSession is initialized and binds it on every service call, ensuring that a single hibernate session is attached to a corresponding vaadin session.NOTE: One major issue with this strategy is the bug (#4528) which flushes the entire session even if a save / saveOrUpdate call is made on a single CDM entity. This implies that this strategy is safe to use only in 'session-save' UIs and not 'auto-save' UIs.

Exposing CDM Application Context

This issue relates to the problem that in the Vaadin framework it is not possible to autowire beans from the underlying application context as Vaadin prevents this possibility. To overcome this problem, a singleton helper class eu.etaxonomy.cdm.vaadin.util.CdmSpringContextHelper has been written to retrieve the beans given the bean name.

Miscellaneous Notes

  • Currently the Server Push functionality of Vaadin has been disabled (by commenting out the relevant section in the pom file)

Conventions & Policies

Vaadin Security

https://www.youtube.com/watch?v=PNAo3ApWA-A

Updated by Andreas Kohlbecker about 7 years ago · 52 revisions