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Asked: 2026-05-12T16:57:04+00:00

I have two servlets ‘ExtensionServlet’ and ‘PatternServlet’ and a static html page. The HTML

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I have two servlets ‘ExtensionServlet’ and ‘PatternServlet’ and a static html page. The HTML code is given below.

<html>
    <head>
        <title>
            Resolve servlet ambiguity
        </title>
    </head>
    <body>
        <form action="servlets/form.col" method="POST">
            <input type="submit" value="Goto Servlet">
        </form>
    </body>
</html>

The Deployment descriptor is as follows.

<?xml version="1.0" encoding="ISO-8859-1" ?>   
<web-app version="2.4"
    xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" >
    <servlet>
        <servlet-name>Extension Servlet</servlet-name>
        <servlet-class>ExtensionServlet</servlet-class>     
        <servlet-name>Pattern Servlet</servlet-name>
        <servlet-class>PatternServlet</servlet-class>
    </servlet>
    <servlet-mapping>       
        <servlet-name>Extension Servlet</servlet-name>
        <url-pattern>*.col</url-pattern>
        <servlet-name>Pattern Servlet</servlet-name>
        <url-pattern>/servlets/*</url-pattern>
    </servlet-mapping>
</web-app>

When I click the button in the HTML page it leads to “PatternServlet”. If I rearrange the servlet order in the deployment descriptor as below, it goes to “ExtensionServlet”

<?xml version="1.0" encoding="ISO-8859-1" ?>   
<web-app version="2.4"
    xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" >
    <servlet>
        <servlet-name>Pattern Servlet</servlet-name>
        <servlet-class>PatternServlet</servlet-class>
        <servlet-name>Extension Servlet</servlet-name>
        <servlet-class>ExtensionServlet</servlet-class> 
    </servlet>
    <servlet-mapping>           
        <servlet-name>Pattern Servlet</servlet-name>
        <url-pattern>/servlets/*</url-pattern>
        <servlet-name>Extension Servlet</servlet-name>
        <url-pattern>*.col</url-pattern>
    </servlet-mapping>
</web-app>

Can anyone please explain this behavior?

Tomcat 6.0.20
JVM 1.6.0_15-b03

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1 Answer

  1. Editorial Team

    Is your schema a shortening of the following?

    <?xml version="1.0" encoding="ISO-8859-1" ?>   
<web-app version="2.4"
    xmlns="http://java.sun.com/xml/ns/j2ee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"   
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
    http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" >
    <servlet>
        <servlet-name>Pattern Servlet</servlet-name>
        <servlet-class>PatternServlet</servlet-class>
    </servlet>
    <servlet>
        <servlet-name>Extension Servlet</servlet-name>
        <servlet-class>ExtensionServlet</servlet-class> 
    </servlet>
    <servlet-mapping>                   
        <servlet-name>Pattern Servlet</servlet-name>
        <url-pattern>/servlets/*</url-pattern>
    </servlet-mapping>                   
    <servlet-mapping>                   
        <servlet-name>Extension Servlet</servlet-name>
        <url-pattern>*.col</url-pattern>
    </servlet-mapping>
</web-app>

    In your version I think you are defining only one servlet.

    When tomcat encounters several definitions that match a request (like in your case), it uses the first one.

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