Question
What are the methods for avoiding Java code in JSP files when using JSP 2?
Answer
In JSP 2, developers are encouraged to reduce or eliminate the use of Java code embedded in JSP files to enhance maintainability and separation of concerns. This is achievable through the use of Expression Language (EL) and JavaServer Pages Standard Tag Library (JSTL).
<c:if test='${not empty param.name}'>
Hello, ${param.name}!
</c:if>
<c:set var='counter' value='${counter + 1}'/>
Causes
- Overuse of scriptlets in JSP leads to code that is hard to read and maintain.
- Mixing presentation logic with business logic makes the application architecture convoluted.
Solutions
- Use Expression Language (EL) for simpler expressions instead of scriptlets: `Hello, ${param.name}`.
- Implement JSTL tags for control flow and looping instead of Java code: `<c:if test='${not empty param.name}'>...</c:if>`.
- Separate business logic into Java Beans or Servlets, thus keeping JSP files focused on presentation.
Common Mistakes
Mistake: Continuing to use scriptlets for business logic in JSP.
Solution: Refactor code to use JSTL and EL instead.
Mistake: Not initializing variables in a JavaBean or Servlet before using them in JSP.
Solution: Always ensure that beans are correctly instantiated in your servlets before referencing them in JSP.
Helpers
- avoid Java in JSP
- JSP 2
- Expression Language
- JSTL
- JavaServer Pages best practices
