To be able to specify which mappers will be applied to a request, create the file [web-app]/WEB-INF/sitemesh.xml that contains the following:

<sitemesh>
    <property name="decorators-file" value="/WEB-INF/decorators.xml" />
    <excludes file="${decorators-file}" />

    <page-parsers>
        <parser content-type="text/html"
            class="com.opensymphony.module.sitemesh.parser.FastPageParser" />
        <parser content-type="text/html;charset=ISO-8859-1"
            class="com.opensymphony.module.sitemesh.parser.FastPageParser" />
    </page-parsers>

    <decorator-mappers>
        <mapper class="com.opensymphony.module.sitemesh.mapper.ConfigDecoratorMapper">
            <param name="config" value="${decorators-file}" />
        </mapper>
    </decorator-mappers>
</sitemesh>

in this example, the only mapper that will be applied is the ConfigDecoratorMapper, and that will only be applied to responses of type text/html or text/html;charset=ISO-8859-1. Responses of any other content type (eg image/gif) will be ignored by Sitemesh. Additionally, any files that match a pattern specified in the excludes file (in this case '/WEB-INF/decorators.xml') will not be touched by Sitemesh.

The excludes file points to an XML file that contains an <excludes /> block similar to the following: add the following code in your decorators.xml

<decorators defaultdir="/decorators">
?<excludes>
??<pattern>/plainPage.jsp</pattern>
??<pattern>/ewebeditor/*.*</pattern>
?</excludes>
?<decorator name="main" page="main.jsp">
??<pattern>/*</pattern>
?</decorator>
</decorators>