Sun people encapsulate the core functionality which is common to many web-applications in the form of JSTL. Programmer can use this predefined library without writing on his own. The main objective of EL is removing java code from jsp but it fails to replace java code which processes some functionality. We can recover this by using JSTL. Hence the main objective of JSTL is also for removing java code from the jsp.
JSTL library has been divided into the following 5 sub libraries

  1. Core library

    It defines some standard actions to perform programming general stuff like conditional and loops. It can also perform jsp fundamental task like setting and removing attributes,writing output, re-directing the request to other pages etc..

  2. Xml library

    Defines several standard actions useful for writing and parsing xml data.

  3. Fmt library
    Defines several standard actions which can be used for formatting numbers and dates as the part of internationalization.
  4. Sql library

    Defines several standard actions for data base operations.

  5. Functional library
    Defines several standard actions which can be used for manipulating collections and String objects.