Deploying an Application

    For a detailed tutorial on how web applications are packaged, please refer to any Java book that discusses Java Servlets.

    In the Java Servlet parlance, a “web application” means a collection of Java servlets or portlets, JSP and static HTML pages, and various other resources that form an application. Such a Java web application is typically packaged as a WAR package for deployment. Server-side Vaadin UIs run as servlets within such a Java web application. There exists also other kinds of web applications. To avoid confusion with the general meaning of “web application”, we often refer to Java web applications with the slight misnomer “WAR” in this book.

    To deploy an application to a web server, you need to create a WAR package. Here we give the instructions for Eclipse.

    1. Select File › Export and then Web › WAR File. Or, right-click the project in the Project Explorer and select Web › WAR File.

    2. Select the Web project to export. Enter Destination file name (.war).

    3. Make any other settings in the dialog, and click Finish.

    Web Application Contents

    The following files are required in a web application in order to run it.

    WEB-INF/web.xml (optional with Servlet 3.0)

    his is the web application descriptor that defines how the application is rganized, that is, what servlets and such it has. You can refer to any Java book about the contents of this file. It is not needed if you define the Vaadin servlet with the @WebServlet annotation in Servlet API 3.0.

    WEB-INF/lib/*.jar

    These are the Vaadin libraries and their dependencies. They can be found in the installation package or as loaded by a dependency management system such as Maven or Ivy.

    Your UI classes

    You must include your UI classes either in a JAR file in WEB-INF/lib or as classes in WEB-INF/classes

    Your own theme files (OPTIONAL)

    If your application uses a special theme (look and feel), you must include it in VAADIN/themes/themename directory.

    Widget sets (OPTIONAL)

    If your application uses add-ons or custom widgets, they must be compiled to the VAADIN/widgetset/ directory. When using add-ons, this is done automatically in Maven projects. See for more information.

    When using the Servlet 3.0 API, you normally declare the Vaadin servlet classes with the @WebServlet annotation. The Vaadin UI associated with the servlet and other Vaadin-specific parameters are declared with a separate @VaadinServletConfiguration annotation.

    The Vaadin Plugin for Eclipse creates the servlet class as a static inner class of the UI class. Normally, you may want to have it as a separate regular class.

    The value parameter is the URL pattern for mapping request URLs to the servlet, as described in Servlet Mapping with URL Patterns. The ui parameter is the UI class. Production mode is disabled by default, which enabled on-the-fly theme compilation, debug window, and other such development features. See the subsequent sections for details on the different servlet and Vaadin configuration parameters.

    You can also use a web.xml deployment descriptor in Servlet 3.0 projects.

    Using a web.xml Deployment Descriptor

    A deployment descriptor is an XML file with the name web.xml in the WEB-INF sub-directory of a web application. It is a standard component in Java EE describing how a web application should be deployed. The descriptor is not required with Servlet API 3.0, where you can also define servlets with the @WebServlet annotation as decribed earlier, as web fragments, or programmatically. You can use both a web.xml and WebServlet in the same application. Settings in the web.xml override the ones given in annotations.

    2. <web-app
    3.   id="WebApp_ID" version="2.4"
    4.   xmlns="http://java.sun.com/xml/ns/j2ee"
    5.   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    6.   xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
    7.      http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
    9.   <servlet>
    10.     <servlet-name>myservlet</servlet-name>
    11.     <servlet-class>
    12.         com.vaadin.server.VaadinServlet
    13.     </servlet-class>
    15.     <init-param>
    16.       <param-name>UI</param-name>
    17.       <param-value>com.ex.myprj.MyUI</param-value>
    18.     </init-param>
    19.     <!-- If not using the default widget set-->
    20.     <init-param>
    21.       <param-name>widgetset</param-name>
    22.       <param-value>com.ex.myprj.AppWidgetSet</param-value>
    23.     </init-param>
    24.   </servlet>
    26.   <servlet-mapping>
    27.     <servlet-name>myservlet</servlet-name>
    28.     <url-pattern>/*</url-pattern>
    29.   </servlet-mapping>
    30. </web-app>

    The descriptor defines a servlet with the name myservlet. The servlet class, com.vaadin.server.VaadinServlet, is provided by Vaadin framework and is normally the same for all Vaadin projects. For some purposes, you may need to use a custom servlet class that extends the VaadinServlet. The class name must include the full package path.

    The descriptor example given above was for Servlet 2.4. For a later version, such as Servlet 3.0, you should use:

    2.   id="WebApp_ID" version="3.0"
    3.   xmlns="http://java.sun.com/xml/ns/j2ee"
    4.   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    5.   xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">

    Servlet 3.0 support is useful for at least server push.

    Widget Set

    The widget set is normally defined and compiled automatically in Maven projects. It may be necessary to define it manually in some cases, such as when developing custom widgets or if you need to include special rules in the widget set definition file (.gwt.xml module descriptor).

    The widget set of a UI can be defined with the @WidgetSet annotation for the UI class.

    Java

    1. @WidgetSet("com.example.myproject.MyWidgetSet")
    2. class MyUI extends UI {
    3.     …​

    You can also define it in the web.xml descriptor for the servlet:

    XML

    1. <init-param>
    2.   <param-name>widgetset</param-name>
    3.   <param-value>com.example.myproject.MyWidgetSet</param-value>
    4. </init-param>

    The name of a widget set is technically a Java class name with the same path as the widget set definition file, but without the .gwt.xml extension.

    If a widget set is not specified, the default is used. In a project that does not use add-ons or custom widgets, the com.vaadin.DefaultWidgetSet is used. It contains all the widgets for the built-in Vaadin components. When using add-ons, the Vaadin Maven Plugin automatically defines an AppWidgetSet that includes all the add-on widget sets.

    The widget set must be compiled, as described in (for add-ons) or “Compiling a Client-Side Module” (for custom widgets and client-side modules), and properly deployed with the application.

    The servlet needs to be mapped to an URL path, which requests it is to handle.

    With @WebServlet annotation for the servlet class:

    1. @WebServlet(value = "/*", asyncSupported = true)

    In a web.xml:

    The URL pattern is defined in the above examples as /*. This matches any URL under the project context. We defined above the project context as myproject so the URL for the page of the UI will be .

    Mapping Sub-Paths

    If an application has multiple UIs or servlets, they have to be given different paths in the URL, matched by a different URL pattern. Also, you may need to have statically served content under some path. Having an URL pattern /myui/* would match a URL such as . Notice that the slash and the asterisk must be included at the end of the pattern. In such case, you also need to map URLs with /VAADIN/* to a servlet (unless you are serving it statically as noted below).

    With a @WebServlet annotation for a servlet class, you can define multiple mappings as a list enclosed in curly braces as follows:

    1. @WebServlet(value = {"/myui/*", "/VAADIN/*"},
    2.             asyncSupported = true)

    In a web.xml:

    1.     …​
    2.     <servlet-mapping>
    3.         <servlet-name>myservlet</servlet-name>
    4.         <url-pattern>/myui/*</url-pattern>
    5.     </servlet-mapping>
    7.     <servlet-mapping>
    8.         <servlet-name>myservlet</servlet-name>
    9.         <url-pattern>/VAADIN/*</url-pattern>
    10.     </servlet-mapping>

    If you have multiple servlets, you should specify only one /VAADIN/* mapping.It does not matter which servlet you map the pattern to, as long as it is a Vaadin servlet.

    You do not have to provide the above /VAADIN/* mapping if you serve both the widget sets and (custom and default) themes statically in the /VAADIN directory in the web application. The mapping simply allows serving them dynamically from the Vaadin JAR. Serving them statically is recommended for production environments as it is faster. If you serve the content from within the same web application, you may not have the root pattern /* for the Vaadin servlet, as then all the requests would be mapped to the servlet.

    Other Servlet Configuration Parameters

    The servlet class or deployment descriptor can have many parameters and options that control the execution of a servlet. You can find complete documentation of the basic servlet parameters in the appropriate .

    @VaadinServletConfiguration accepts a number of special parameters, as described below.

    By default, Vaadin applications run in debug mode (or development mode), which should be used during development. This enables various debugging features. For production use, you should have the productionMode=true setting in the @VaadinServletConfiguration, or in web.xml:

    1.   <param-name>productionMode</param-name>
    2.   <param-value>true</param-value>
    3.   <description>Vaadin production mode</description>
    4. </context-param>

    The parameter and the debug and production modes are described in more detail in “Debug Mode and Window”.

    Custom UI Provider

    Vaadin normally uses the DefaultUIProvider for creating UI class instances. If you need to use a custom UI provider, you can define its class with the UIProvider parameter. The provider is registered in the VaadinSession.

    In a web.xml:

    1.   <servlet>
    3.     <init-param>
    4.       <param-name>UIProvider</param-name>
    5.       <param-value>com.ex.my.MyUIProvider</param-value>
    6.     </init-param>

    The parameter is logically associated with a particular servlet, but can be defined in the context as well.

    UI Heartbeat

    Vaadin monitors UIs by using a heartbeat, as explained in . If the user closes the browser window of a Vaadin application or navigates to another page, the Client-Side Engine running in the page stops sending heartbeat to the server, and the server eventually cleans up the UI instance.

    The interval of the heartbeat requests can be specified in seconds with the heartbeatInterval parameter either as a context parameter for the entire web application or an init parameter for the individual servlet. The default value is 300 seconds (5 minutes).

    In a web.xml:

    1. <context-param>
    2.   <param-name>heartbeatInterval</param-name>
    3.   <param-value>300</param-value>
    4. </context-param>

    In normal servlet operation, the session timeout defines the allowed time of inactivity after which the server should clean up the session. The inactivity is measured from the last server request. Different servlet containers use varying defaults for timeouts, such as 30 minutes for Apache Tomcat. You can set the timeout under <web-app> with:

    In a web.xml:

    The session timeout should be longer than the heartbeat interval or otherwise sessions are closed before the heartbeat can keep them alive. As the session expiration leaves the UIs in a state where they assume that the session still exists, this would cause an Out Of Sync error notification in the browser.

    However, having a shorter heartbeat interval than the session timeout, which is the normal case, prevents the sessions from expiring. If the closeIdleSessions parameter for the servlet is enabled (disabled by default), Vaadin closes the UIs and the session after the time specified in the session-timeout parameter expires after the last non-heartbeat request.

    In a web.xml:

    1.   <servlet>
    2.     ...
    3.     <init-param>
    4.       <param-name>closeIdleSessions</param-name>
    5.       <param-value>true</param-value>
    6.     </init-param>

    Push Mode

    You can enable server push, as described in , for a UI either with a @Push annotation for the UI or in the descriptor. The push mode is defined with a pushmode parameter. The automatic mode pushes changes to the browser automatically after access() finishes. With manual mode, you need to do the push explicitly with push(). If you use a Servlet 3.0 compatible server, you also want to enable asynchronous processing with the async-supported parameter.

    In a web.xml:

    1. <servlet>
    2.   …​
    3.   <init-param>
    4.     <param-name>pushmode</param-name>
    5.     <param-value>automatic</param-value>
    6.   </init-param>
    7.   <async-supported>true</async-supported>

    Cross-Site Request Forgery Prevention

    Vaadin uses a protection mechanism to prevent malicious cross-site request forgery (XSRF or CSRF), also called one-click attacks or session riding, which is a security exploit for executing unauthorized commands in a web server. This protection is normally enabled. However, it prevents some forms of testing of Vaadin applications, such as with JMeter. In such cases, you can disable the protection by setting the disable-xsrf-protection parameter to true.

    In a web.xml:

    1. <context-param>
    2.   <param-name>disable-xsrf-protection</param-name>
    3.   <param-value>true</param-value>
    4. </context-param>

    The Vaadin-specific parameters defined in the deployment configuration are available from the DeploymentConfiguration object managed by the VaadinSession.

    Java

    1. DeploymentConfiguration conf =
    2.         getSession().getConfiguration();
    4. // Heartbeat interval in seconds
    5. int heartbeatInterval = conf.getHeartbeatInterval();

    Parameters defined in the Java Servlet definition, such as the session timeout, are available from the low-level HttpSession or PortletSession object, which are wrapped in a WrappedSession in Vaadin. You can access the low-level session wrapper with getSession() of the VaadinSession.

    Java

    You can also access other HttpSession and PortletSession session properties through the interface, such as set and read session attributes that are shared by all servlets belonging to a particular servlet or portlet session.