[weld-issues] [JBoss JIRA] Created: (WELD-718) register Weld Servlet listener in web fragment

[Dan Allen (JIRA)]

register Weld Servlet listener in web fragment
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                 Key: WELD-718
                 URL: https://jira.jboss.org/browse/WELD-718
             Project: Weld
          Issue Type: Feature Request
          Components: Servlet Container Support
    Affects Versions: 1.1.0.Beta1
            Reporter: Dan Allen
            Priority: Minor


Instead of making the developer add the Weld Servle listener in their web.xml when using weld-servlet, might we consider registering it for them automatically but including it in a web.xml fragment or TLD that's bundled in weld-servlet.jar? The benefit of using the TLD is that it would work in pre-Servlet 3.0 environments.

META-INF/web-fragment.xml
<web-fragment xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-fragment_3_0.xsd"
    version="3.0">
   <listener>
      <listener-class>org.jboss.weld.environment.servlet.Listener</listener-class>
   </listener>
</web-fragment>

META-INF/weld.tld
<taglib xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
       http://java.sun.com/xml/ns/javaee
       http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_0.xsd"
    version="2.0">
    <description>
       An empty tag library that registers a listener to bootstrap Weld in a Servlet container.
    </description>
    <tlib-version>1.0</tlib-version>
    <short-name>w</short-name>
    <uri>http://jboss.org/weld</uri>

    <!--
       This ServletContextListener initializes the runtime environment of the CDI
       Reference Implementation (Weld) when a web application including it is
       initialized by the container.
    -->
    <listener>
       <listener-class>org.jboss.weld.environment.servlet.Listener</listener-class>
    </listener>
</taglib>

Btw, we are already including other automatic configurations, such as a JSF phase listener and view handler (META-INF/faces-config.xml).

If we require ordering, that leans more to web-fragment.xml as a solution, since it's possible to have ordering control. There is no guarantee as to when a listener will load that's defined in a TLD (the advantage is only for non-Servlet 3.0 containers). Given that Weld is a new programming model and likely to be used with newer containers, then I'd say we should go with web-fragment.xml.

(Worse case scenario is we introduce a classifier for weld-servlet that will be for pre-Servlet 3.0 environments. Something like org.jboss.weld.servlet:weld-servlet:1.1:pre-servlet-3)

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