JSTL Tutorials

JSTL-Tutorials

• This is my JSTL Tutorial which is about JSTL (JSP Tag Libraries) that gives you a clear understanding about all the JSTL tags and their functionalities with practical code implementations for each tags.

Introduction

• The JavaServer Pages Standard Tag Library (JSTL) is a collection of useful JSP tags which encapsulates the core functionality common to many JSP applications.
• JSTL has support for common, structural tasks such as iteration and conditionals, tags for manipulating XML documents, internationalization tags, and SQL tags.
• It also provides a framework for integrating the existing custom tags with the JSTL tags.

Install JSTL Library

• To begin working with JSP tages you need to first install the JSTL library.
• If you are using the Apache Tomcat container, then follow these two steps −

Step 1 :

- Download the binary distribution from Apache Standard Taglib and unpack the compressed file.

Download JAR Files here : JSTL JAR 1.2

Step 2 :

− To use the Standard Taglib from its Jakarta Taglibs distribution, simply copy the JAR files in the distribution's 'lib' directory to your application's webappsROOTWEB-INFlib directory.

[Note: If you are creating a Maven Project, use the following dependency to add JSTL Jar files]

  <dependency>
      <groupId>jstl</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
  </dependency>
  <dependency>
      <groupId>taglibs</groupId>
      <artifactId>standard</artifactId>
      <version>1.1.2</version>
  </dependency>

To use any of the libraries, you must include a directive at the top of each JSP that uses the library.

Advantage of JSTL

• Fast Development - JSTL provides many tags that simplify the JSP
• Code Reusability - We can use the JSTL tags on various pages
• No need to use scriptlet tag - It avoids the use of scriptlet tag

JSTL Tags

JSTL Core Tags:

• JSTL Core tags provide support for iteration, conditional logic, catch exception, url, forward or redirect response etc.

• To use JSTL core tags, we should include it in the JSP page like below.

  <%@ taglib uri="https://java.sun.com/jsp/jstl/core" prefix="c" %>

JSTL Formatting and Localisation Tags:

• JSTL Formatting tags are provided for formatting of Numbers, Dates and i18n support through locales and resource bundles.

• We can include these jstl tags in JSP with below syntax:

  <%@ taglib uri="https://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>

JSTL SQL Tags:

• JSTL SQL Tags provide support for interaction with relational databases such as Oracle, MySql etc.

• Using JSTL SQL tags we can run database queries, we include these JSTL tags in JSP with below syntax:

  <%@ taglib uri="https://java.sun.com/jsp/jstl/sql" prefix="sql" %>

JSTL XML Tags:

• JSTL XML tags are used to work with XML documents such as parsing XML, transforming XML data and XPath expressions evaluation. -Syntax to include JSTL XML tags in JSP page is:

  <%@ taglib uri="https://java.sun.com/jsp/jstl/xml" prefix="x" %>

STL Functions Tags:

• JSTL tags provide a number of functions that we can use to perform common operation, most of them are for String manipulation such as String Concatenation, Split String etc.

• Syntax to include JSTL functions in JSP page is:

  <%@ taglib uri="https://java.sun.com/jsp/jstl/functions" prefix="fn" %>

JSTL Core Tags ⌚

<c:out>

• To write something in JSP page, we can use EL also with this tag

<c:import>

• Same as jsp:include or include directive

<c:redirect>

• redirect request to another resource

<c:set>

• To set the variable value in given scope.

<c:remove>

• To remove the variable from given scope

<c:catch>

• To catch the exception and wrap it into an object.

<c:if>

• Simple conditional logic, used with EL and we can use it to process the exception from <c:catch>

<c:choose>

• Simple conditional tag that establishes a context for mutually exclusive conditional operations, marked by <c:when> and <c:otherwise>

<c:when>

• Subtag of <c:choose> that includes its body if its condition evalutes to ‘true’.

<c:otherwise>

• Subtag of <c:choose> that includes its body if its condition evalutes to ‘false’.

<c:forEach>

• for iteration over a collection

<c:forTokens>

• for iteration over tokens separated by a delimiter.

<c:param>

• used with <c:import> to pass parameters

<c:url>

• To create a URL with optional query string parameters

JSTL Formatting Tags ⌛

<fmt:formatNumber>

• To render numerical value with specific precision or format.

<fmt:parseNumber>

• Parses the string representation of a number, currency, or percentage.

<fmt:formatDate>

• Formats a date and/or time using the supplied styles and pattern.

<fmt:parseDate>

• Parses the string representation of a date and/or 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 scoped variable or the bundle configuration variable.

<fmt:timeZone>

• Specifies the time zone for any time formatting or parsing actions nested in its body.

<fmt:setTimeZone>

• Stores the given time zone in the time zone configuration variable

<fmt:message>

• Displays an internationalized message.

<fmt:requestEncoding>

• Sets the request character encoding

JSTL SQL Tags ⏩

<sql:setDataSource>

• Creates a simple DataSource suitable only for prototyping

<sql:query>

• Executes the SQL query defined in its body or through the sql attribute.

<sql:update>

• Executes the SQL update defined in its body or through the sql attribute.

<sql:param>

• Sets a parameter in an SQL statement to the specified value.

<sql:dateParam>

• Sets a parameter in an SQL statement to the specified java.util.Date value.

<sql:transaction>

• Provides nested database action elements with a shared Connection, set up to execute all statements as one transaction.

JSTL XML tags

<x:out>

• Like <%= ... >, but for XPath expressions.

<x:parse>

• Used to parse the XML data specified either via an attribute or in the tag body.

<x:set >

• Sets a variable to the value of an XPath expression.

<x:if >

• Evaluates a test XPath expression and if it is true, it processes its body. If the test condition is false, the body is ignored.

<x:forEach>

• To loop over nodes in an XML document.

<x:choose>

• Simple conditional tag that establishes a context for mutually exclusive conditional operations, marked by and tags.

<x:when >

• Subtag of that includes its body if its expression evalutes to 'true'.

<x:otherwise >

• Subtag of that follows the tags and runs only if all of the prior conditions evaluates to 'false'.

<x:transform >

• Applies an XSL transformation on a XML document

<x:param >

• Used along with the transform tag to set a parameter in the XSLT stylesheet

JSTL Function Tags

<fn:contains()>

• Tests if an input string contains the specified substring.

<fn:containsIgnoreCase()>

• Tests if an input string contains the specified substring in a case insensitive way.

<fn:endsWith()>

• Tests if an input string ends with the specified suffix.

<fn:escapeXml()>

• Escapes characters that can be interpreted as XML markup.

<fn:indexOf()>

• Returns the index withing a string of the first occurrence of a specified substring.

<fn:join()>

• Joins all elements of an array into a string.

<fn:length()>

• Returns the number of items in a collection, or the number of characters in a string.

<fn:replace()>

• Returns a string resulting from replacing in an input string all occurrences with a given string.

<fn:split()>

• Splits a string into an array of substrings.

<fn:startsWith()>

• Tests if an input string starts with the specified prefix.

<fn:substring()>

• Returns a subset of a string.

<fn:substringAfter()>

• Returns a subset of a string following a specific substring.

<fn:substringBefore()>

• Returns a subset of a string before a specific substring.

<fn:toLowerCase()>

• Converts all of the characters of a string to lower case.

<fn:toUpperCase()>

• Converts all of the characters of a string to upper case.

<fn:trim()>

• Removes white spaces from both ends of a string.

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Code and documentation Copyright 2021 : Gowthamraj K