How to Configure JSTL in Struts Applications

To configure JSTL in a Struts project, follow these steps:

1. Add the necessary libraries: Copy jstl.jar and standard.jar to the WEB-INF/lib folder (if only using EL expressions, these jars are not needed).

2. Include taglib in JSP: At the beginning of your JSP file, include the JSTL tag library.

3. JSTL key concepts:

* EL expressions: Used to access data and variables easily.

* c:out: Outputs the value of expressions.

* Control flow tags:

* c:if: Conditional tags for checking boolean values.

* c:choose/c:when/c:otherwise: Used for more complex conditional logic.

* Iteration tags:

* c:forEach: For looping over collections like lists or maps.

* Formatting tags:

* fmt:formatDate and fmt:formatNumber: Format dates and numbers for display.

4. Custom functions:

* You can define custom functions in a class with public static methods.

* To use these in JSP, create a TLD file and place it in the WEB-INF folder.

* Import the custom function library into your JSP using taglib.

* Example for JSTL core tags testing:

* Example for c:out tag:

- a(default)=, a(el)=${a}

- b(default)=, bj(default)=, bj(escapeXml=true)=, bj(escapeXml=false)=.

* c:if tag for conditional logic:

- boolean value=${v} for comparing values of v1 and v2.

* c:choose, c:when, and c:otherwise for multiple conditions and choices.

* c:forEach for iterating over collections like name, age, and group.

* c:forTokens and c:forEach with maps for key-value iteration.