How can I avoid Java code in JSP files, using JSP 2?

java

form-processing

mvc-architecture

xss-attacks

byAlex Kataev·Nov 3, 2024

To evict Java code from JSPs, enlist JSTL for a suite of robust functionalities and EL for seamless data access. Scriptlets (<% %>) are passé; embrace tags like (<c:forEach>), ensuring your JSPs are more elegant and maintainable.

To illustrate:

Replace this:

<%
// Here lie some discarded java codes. May they rest in peace ☠️.
    for(String item : (List<String>)request.getAttribute("items")) {
        out.println(item);
    }
%>

With this:

<c:forEach items="${items}" var="item">
// Forgive me father, for I have 'sout'ed. I promise to repent (or use EL from now on)!
    ${item}
</c:forEach>

Golden rule to remember: Business logic belongs with your Java classes. Servlets are your workhorses for processing, while JSPs are your canvas for rendering, painting a rich UI with JSTL/EL for maximum effect.

Get right to the point

Leveraging Servlets & EL

Moving from cinematic scriptlets to sturdy servlets unlocks clear form processing and data parsing. Like an over-caffeinated barista, the servlet churns through the requests, presenting the results elegantly with EL—a '${param.name}' here, a '${x + 1}' there.

Perfecting the MVC pattern

Embrace MVC architecture for your applications. Render scriptlets toothless in web.xml with a <scripting-invalid>true</scripting-invalid> configuration. Enforce a clean, structured approach paving the way for consistent JSP development.

Keep it modern

Use <jsp-config> in web.xml to light the modern practices beacon across all JSP pages. With tag libraries defining the formatting logic, JSPs can focus on rendering beautiful pages without cramming Java code.

Ensuring security and maintainability

Hold the fort against XSS attacks

"Don't be a sitting duck for XSS attacks. Use fn:escapeXml to escape output. Safety first, because the best offence is a good defence.

Exploiting filters and tag libraries

Servlet filters are trusty sidekicks for shared functionalities like authentication. Preload the heavy data-lifting in servlets, forwarding to JSP using request attributes. Tag libraries are your ticket for maintaining a clean separation of presentation and logic.

Deputize the frameworks

Frameworks like Spring MVC breathe life into a comprehensive MVC approach while Wicket offers sophisticated HTML generation straight-up, no chaser. Facelets, the strict disciplinarian in JSF, will ensure scriptlets are no way near your codebase.

Hitting the best practices

Tag libraries and EL power-up

Modularize your views for optimal reuse and maintainability with customized tag libraries and dynamic properties assignment via EL expressions. Your JSP horizons are limitless.

Commune with the JSTL documentation

Plug into the JSTL collective at jstl.java.net for a deep understanding of JSP 2 features, preventative measures against common pitfalls, and the latest best practices.

explain-codes / Java / How can I avoid Java code in JSP files, using JSP 2?

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