Thursday, June 28, 2007

JSTL and Expression Language

JavaServer Pages Standard Tag Library (JSTL) is a custom tags collection that executes common functionalities in web applications, including iteration and selection, data formatting, XML manipulation and database access. JSTL allows JSP developers to focus on development specific necessities, instead of reinventing the wheel.

JSTL is composed of:

  • An expression language.
  • Standard actions libraries.
  • Validators (2 validators).

What is Expression Language (EL)?

Expression Language is a simple language based on ECMAScript (also known as JavaScript) and XPath. It provides expressions and identifiers and type conversion.

Expression Language makes easier the access to implicit objects, such as request / response servlet, scope variables and stored objects on JSP scope (page, request, session and application). EL reduces drastically the need of using JSP expressions and scriptlets, increasing web applications maintainability and extensibility.


EL expressions are invoked with this syntax: ${expression}. Expressions consist of:

  • Identifiers.
  • Operators.

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