9 Spring Expression Language

WHAT YOU WILL LEARN IN THIS CHAPTER:

  • Configuring applications with SpEL
  • Creating a parser
  • Invoking methods
  • Working with variables and functions
  • Understanding SpEL operators
  • Using utilities in SpEL

An expression language (EL) is a special type of programming language that provides for the compilation and evaluation of expressions. With its simple syntax it offers an extensive set of features, including various operators, functions, and variables. The EL is also commonly used in web application frameworks, where these expressions help link the presentation layer with the application data. The first versions of EL derived from other languages like ECMAScript and XPath, but they didn't meet the requirements of enterprise development, so each framework brought its own implementation of EL into the field.

In the history of Java web development, EL was first introduced with JSTL version 1.0, which helped to bridge the application data with the view layer. Nowadays the Enterprise Java ecosystem offers a good deal of options when it comes to the EL. Presentation layer frameworks such as JSF and JSP adopted the Unified Expression Language (UEL); other frameworks such as Struts and Tapestry used Object Graph Navigation ...

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