JSTL Overview: Simplifying JSP Development with Expression Language and Core Tags

1. JSP Standard Tag Library Jay Sissom

2. Agenda • JSTL Overview • Expression Language • Core tags • Format tags • Struts-EL

3. JSTL Overview • JSP Standard Tag Library • Will be included in all Servlet containers at some point in the future • Jakarta provides 2 implementations • Version 1.1.1 for Tomcat 5+ (Servlet spec 2.4/JSP 2.0) • Version 1.0.6 for Tomcat 4 (Servlet spec 2.3/JSP 1.2) • Jakarta implementation written by Shawn Bayern who designed and wrote CAS

4. JSTL Overview (con’t) • Comprised of 4 tag libraries • Core - Iteration, Conditions, etc • Format - Formatting, i18n • XML - XML processing • SQL - Database access • All tags support expression language

5. Expression Language • Very simple language • Allows easy access to Javabeans, properties and perform simple operations • Expressions must start with ${ and end with } • Example: • <c:out value=“1 + 2 = ${1+2}”/> Prints 1 + 2 = 3 • <c:out value=“${username}”/> Looks for a javabean named username and prints it’s value

6. Expression Language (con’t) • Access Javabean properties using . • ${user.name} translates to user.getName() • EL searches each scope area if a scope isn’t specified • Specific scope areas can be used: • ${pageScope.username} • ${requestScope.username} • ${sessionScope.username} • ${applicationScope.username}

7. Expression Language (con’t) • Comparisons • == or eq for Equals • != or ne for Not Equals • < or lt for Less Than • > or gt for Greater Than • <= or le for Less than or Equal • >= or ge for Greater than or Equal • Example • ${campus eq “BL”}

8. Core tags • Print data to the browser • Conditional output • Iterations

9. Core tags <c:out> • Prints an expression to browser • Attributes: • value - Expression to print • default - Value to print if expression is null or invalid • escapeXml - Escape tags in expression true/false

10. Core tags <c:if> • Conditionally include part of page • Specify logical expression • empty keyword tests for null or missing parameters

11. Core tags <c:choose> • Choose output based on tests

12. Format tags • Format numbers and dates • Print i18n messages from ApplicationResources

13. Format tags <fmt:message> • Print a message from ApplicationMessages file

14. Format tags <fmt:formatNumber> • Format a number for printing • Decimal places, and comma grouping can be specified • Print a percentage • Print currency (watch out)

15. Format tags <fmt:formatDate> • Format a date • Print time, date or both • Print in just about any style • Handles i18n

16. Format tags <fmt:message> • Print messages from message bundle • Automatically handle locale based on browser (just like Struts) • <fmt:bundle> can specify the bundle once on the page instead of for each message tag

17. Resources • Book: JSTL in Action by Shawn Bayern • Safari: Core JSTL: Mastering the JSP Standard Tag Library by David M. Geary • Safari: JSTL: JSP Standard Tag Library Kick Start by Jeff Heaton

18. Struts-EL • Add-on to Struts 1.1 • Included in Struts 1.1 download • Allows use of Expression Language in Struts tags • http://struts.apache.org/faqs/struts-el.html • Some Struts tags aren’t implemented in Struts-EL