JSTL

JSTL, or JavaServer Pages Standard Tag Library, is a collection of reusable tags for building JSP pages. It provides a higher-level, tag-based approach to common tasks such as iteration, conditional logic, formatting, and data access, reducing the need to embed Java code directly in HTML. JSTL is designed to work with the JSP 2.0 specification and relies on the Expression Language (EL) to access data from JavaBeans, maps, and other objects.

The JSTL specification defines several tag libraries. The core library (prefix c) covers control flow and iteration (forEach, if, choose). The formatting library (fmt) handles internationalization and formatting of dates, numbers, and messages. The SQL library (sql) enables basic database operations. The XML library (xml) provides simple XML processing capabilities, and the functions library (fn) offers string and utility functions that can be used within EL expressions.

Usage and requirements: To use JSTL, a web application must include the JSTL library jars in WEB-INF/lib and declare the tag libraries in JSPs with directives such as prefix="c" and URI "http://java.sun.com/jsp/jstl/core" (and corresponding URIs for fmt, sql, xml, and fn). The hosting servlet container must support JSP 2.0 or newer, and EL must be enabled. JSTL is designed to work with standard data sources and Java objects exposed to the page via request, session, or application scopes.

History and status: JSTL was developed as a standard tag library for JSP under the Java Community Process and gained widespread use in the early 2000s. The current, widely deployed version is JSTL 1.2, aligned with newer JSP specifications. While still supported for legacy JSP projects, many modern applications favor alternative frameworks or front-end approaches, though JSTL remains a stable option for existing codebases.