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Date: Mon, 11 Sep 2000 08:53:50 -0700
From: "Craig R. McClanahan" <Craig.McClanahan@eng.sun.com>
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To: tomcat-dev@jakarta.apache.org
Subject: Re: Servlet-names are mappings !!
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Jim Rudnicki wrote:

> I noticed this, but thought it was just the way it should be.
> When you name a servlet to provide init parameters, but do not provide a
> mapping, the name is a mapping.
>
> > > The conclusion is: servlet-name values can, probably sometimes, be used
> as
> > > url-mappings !!
> > >
> > It has nothing to do with documentation, this shouldn't happen.
> >
>

More precisely, let's assume you have a servlet definition like this:

    <servlet>
        <servlet-name>MyServlet</servlet-name>
        <servlet-class>com.mycompany.mypackage.MyServlet</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>MyServlet</servlet-name>
        <url-pattern>/runmyservlet/*</url-pattern>
    </servlet-mapping>

Now, if you use this URL:

    http://localhost:8080/contextpath/runmyservlet

you will execute your servlet due to the servlet mapping entry.

In a standard Tomcat installation, you will find that the following two URLs
also work:

    http://localhost:8080/contextpath/servlet/com.mycompany.mypackage.MyServlet

    http://localhost:8080/contextpath/servlet/MyServlet

These work because of a Tomcat feature (not in the servlet spec) called the
"invoker" servlet.  This feature is very commonly provided by servlet
containers, because in simple situations you will not need to create <servlet>
definitions at all.  The invoker tries to match what is entered after
"/servlet" to either a <servlet-class> or <servlet-name>, and then executes the
corresponding servlet for you.

How does this work?  Simple:  the invoker servlet itself is mapped to
url-pattern "/servlet/*".  If you want to remove this facility, it's pretty
easy:

* Tomcat 3.1 or 4.0 :  remove the <servlet-mapping> for the invoker servlet
  from file $TOMCAT_HOME/conf/web.xml

* Tomcat 3.2: remove the <RequestInterceptor> for InvokerInterceptor
  from file $TOMCAT_HOME/conf/server.xml

Craig McClanahan

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