How is JSP configured in the deployment descriptor?

JSP configuration in the deployment descriptor (web.xml) allows managing their behavior and settings.

Main elements used for JSP configuration:

• <jsp-config>: Root element for JSP configuration.
  • <taglib>: Tag library configuration.
    • <taglib-uri>: URI used in the taglib directive in JSP.
    • <taglib-location>: Path to the TLD file (Tag Library Descriptor).
  • <jsp-property-group>: Group of properties applied to a set of JSP pages.
    • <url-pattern>: URL pattern to which properties are applied.
    • <el-ignored>: Specifies whether to ignore EL expressions (default false).
    • <page-encoding>: Page encoding.
    • <scripting-invalid>: Prohibits the use of scripting elements (<%, %!, %=).
    • <include-prelude>: Path to a file included at the beginning of each JSP.
    • <include-coda>: Path to a file included at the end of each JSP.
    • <default-content-type>: Default content type.
    • <buffer>: Output buffer size.
    • <error-on-undeclared-namespace>: Generate an error when using an undeclared tag prefix.

Configuration example:

<!-- web.xml -->
<web-app ...>

    <jsp-config>
        <taglib>
            <taglib-uri>/mytags</taglib-uri>
            <taglib-location>/WEB-INF/mytags.tld</taglib-location>
        </taglib>

        <jsp-property-group>
            <url-pattern>*.jsp</url-pattern>
            <el-ignored>false</el-ignored>
            <page-encoding>UTF-8</page-encoding>
            <scripting-invalid>true</scripting-invalid>
            <include-prelude>/WEB-INF/jspf/header.jspf</include-prelude>
            <include-coda>/WEB-INF/jspf/footer.jspf</include-coda>
        </jsp-property-group>

        <jsp-property-group>
             <url-pattern>/admin/*.jsp</url-pattern>
             <scripting-invalid>false</scripting-invalid>
        </jsp-property-group>
    </jsp-config>

</web-app>

This configuration:

• Associates the URI /mytags with the file /WEB-INF/mytags.tld for tag libraries.
• Applies the following properties to all JSPs (*.jsp):
  • EL is not ignored.
  • UTF-8 encoding.
  • Scripting is disabled.
  • /WEB-INF/jspf/header.jspf is included before the JSP content.
  • /WEB-INF/jspf/footer.jspf is included after the JSP content.
• For JSPs in the /admin/ directory, scripting is enabled, overriding the general setting.

Using <jsp-property-group> allows flexible configuration of JSP behavior depending on their location or filename pattern.