JSTL tutorials.txt

JSTL (JSP Standard Tag Libraries)

- It is a collection of JSP custom tags developed by java community process, www.jcp.org. 
- Full JSTL contains many common and useful JSP custom tags, particulary used for MVC projects, 
  based on struts looping and logic tags, not part of the jsp 1.2,2.0 & 2.1
- It allows to use JSP custom tags rather using scriplet code that most JSP programmers are not preferred.
- It encapsulates core functionalities common to many jsp applications.
- It supports for common, structural tasks such as iteration, conditionals, tags for manipulating xml docs,
  internationalization tags, sql tags. 

1) Core Tags => looping, expression evaluation, basic input and output, etc...
2) Formatting Tags => used to parse data such as dates, etc...
3) SQL tags => enables tags for database access
4) XML tags => can be used to access XML elements
5) JSTL functions => standard functions used mostly for string manipulation


CORE TAGS : 

<%@ tagib prefic = "c" uri = "http://java.sun.com/jsp.jstl.core" %>

<c:out>  =>  used for displaying things
<c:set>  =>  set the result of an expression 
<c:remove>  =>  removes a scope variable
<c:catch>  =>  catch any exceptions that occur in its body
<c:if>  =>  conditional tag
<c:choose>  =>  conditional tag for mutually exclusive conditional operations using <c:when> and <c:otherwise>
<c:when>  =>  sub tag of <c:choose> which evaluates condition to true
<c:otherwise>  =>  sub tag of <c:choose> that follows <c:when> which runs only when previos condition are false
<c:import>  =>  retreives an absolute or relative url 
<c:forEach>  =>  used for Iteration 
<c:forTokens>  =>  Itearates over tokens
<c:param>  =>  adds a parameter to a containing import tag's url
<c:redirect>  =>  redirects to a new url
<c:url>  =>  creates a url with optional query parameters


FORMATTING TAGS : 

<%@ tagib prefic = "fmt" uri = "http://java.sun.com/jsp.jstl.fmt" %>

<fmt:formatNumber>  =>  to render numeric value with specific precision or format
<fmt:parseNumber>  =>  parse string to number
<fmt:formatDate>  =>  formats date/time using given pattern or style
<fmt:parseDate>  =>  parses string representation of date/time
<fmt:bundle>  =>  loads a resource bundle to be used by its tag body
<fmt:setLocale>  =>  stores the given locale in the locale configuration variable
<fmt:setBundle>  =>  loads a resource bundle and stores it in the named scope variable
<fmt:timeZone>  =>  specifies the timezone for any time formatting 
<fmt:setTimeZone>  =>  stores the given time zone 
<fmt:message>  =>  to display an internationalized message
<fmt:requestEncoding>  =>  sets the request character encoding


SQL TAGS : 

<%@ tagib prefic = "sql" uri = "http://java.sun.com/jsp.jstl.sql" %>

<sql:setDataSource>  =>  creates a simple data source suitable only for prototyping
<sql:query>  =>  executes the sql query defined in its body or the sql attribute
<sql:update>  =>  executes the sql update query defined in its body or the sql attribute
<sql:param>  =>  sets a parameter in an sql statement to the specific value
<sql:dateParam>  =>  sets a parameter in an sql statement to the specific java.util.Date value
<sql:transaction>  =>  provides nested database action elements with a shared connection


XML TAGS : 

<%@ tagib prefic = "x" uri = "http://java.sun.com/jsp.jstl.xml" %>

<x:out>  =>  like <%= ... %>, but for Xpath expressions
<x:parse>  =>  use to parse xml data specified
<x:set>  =>  sets a variable to the value of a Xpath expression
<x:if>  =>  evaluates a test Xpath expression and if it is true, it processits body. else it's ignored
<x:forEach>  =>  to loop over nodes in an XML document
<x:choose>  =>  simple conditional tag
<x:when>  =>  sub tag of <choose> which evaluates condition to true
<x:otherwise>  =>  sub tag of <choose> that follows <when> which runs only when previos condition are false 
<x:transform>  =>  applies an XSL transformation on a XML document
<x:param>  =>  use along with the transaform tag to set a parameter in the XSLT stylesheet


JSTL FUNCTIONS : 

<%@ tagib prefic = "fn" uri = "http://java.sun.com/jsp.jstl.functions" %>

fn:contains()  =>  Tests if input string contains specified substring or not
fn:containsIgnoreCase()  =>  Tests if input string contains specified substring or not ignoring cases
fn:endsWith()  =>  Tests if input string endswith the specified suffix
fn:escapeXml()  =>  escapes character that could be interpreted as XML
fn:indexOf()  =>  returns the index within a string of the first occurance 
fn:join()  =>  joins all elements of an array into a string
fn:length()  =>  returns the number of items in a collection or characters in a string
fn:replace  =>  returns string resulting from replacing in an input string all occurances with a given string
fn:split()  =>  splits a string into an array of substrings


EL Expression Language : 

- mentioned by using ${..}

eg: ${SessionScope.attribute_name}



Examples using JSTL : 

1) counting 1-10 : (using scriplet)

<html>
<body>
  <% for(int i=1;i<=10;i++) { %>
     <%= i %>
     <br>
  <% } %>
</body>
</html>

2) counting 1-10 : (using JSTL)

<html>
<body>
  <c:forEach var="i" begin="1" end="10" step="1">
    <c:out value="${i}"/>
    <br>
  </c:forEach>
</body>
</html>