Jetty's DispatcherType (and 1000 other undocumented things)

Question

Can someone tell me, what DispatcherType is doing?

Seems to be an important configuration.

Class usage didn't helped me as well by pointing to things such as ServletContextHandler#addFilter, which is "documented" with the wise words: convenience method to add a filter.

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In general, any chance to "understand" the undocumented Jetty API without code-example-search-fun or try-and-fail-and-wonder?

Answer 1

This is also a setting in web.xml; and probably has been in existence for quite some time.

http://download.oracle.com/docs/cd/B32110_01/web.1013/b28959/filters.htm#BCFIEDGB

Configuring Filters for Forward or Include Targets

This section provides a few sample configurations to have a filter act on forward or include targets. We start with the filter declaration, followed by alternative filter mapping configurations:

<filter>
    <filter-name>myfilter</filter-name>
    <filter-class>mypackage.MyFilter</filter-class>
</filter>

To execute MyFilter to filter an include target named includedservlet:

<filter-mapping>
   <filter-name>myfilter</filter-name>
   <servlet-name>includedservlet</servlet-name>
   <dispatcher>INCLUDE</dispatcher>
</filter-mapping>

Note that the include() call can come from any servlet (or other resource) in the application. Also note that MyFilter would not execute for a direct request of includedservlet, unless you have another element with the value REQUEST.

To execute MyFilter to filter any servlet directly requested through a URL pattern "/mypath/", or to execute it to filter any forward target that is invoked through a URL pattern starting with "/mypath/":

<filter-mapping>
   <filter-name>myfilter</filter-name>
   <url-pattern>/mypath/*</url-pattern>
   <dispatcher>FORWARD</dispatcher>
   <dispatcher>REQUEST</dispatcher>
</filter-mapping>

~~~~~~~~~~~~~~~~~~~~~~

Also, the default is Request; read appliesTo(...) method on following page:

http://grepcode.com/file/repo1.maven.org/maven2/org.eclipse.jetty/jetty-servlet/8.0.0.M0/org/eclipse/jetty/servlet/FilterMapping.java#FilterMapping.0_dispatches