[JSP] JSTL ( JSP Standard Tag Library )

JSTL 는 유용한 JSP 태그들을 모아놓은 라이브러리입니다. 커스텀 태그를 JSTL tags와 통합할 수 있는 프레임워크도 제공하므로 알아두시면 좋을거에요. 

JSTL태그는 기능별로 분류가 됩니다.  

• Core Tags

• Formatting tags

• SQL tags

• XML tags

• JSTL Functions

JSTL 설치하기

Apache Tomcat container 를 사용중이면 아래 두가지 스텝으로 설치가 완료됩니다.

• Apache Standard Taglib 이곳에서 라이브러리를 다운로드하고 압축을 풀어주세요.

• 압축이 풀린 디렉토리내의 lib디렉토리의 JAR 파일들을 여러분이 사용하려는 애플리케이션의 webapps\ROOT\WEB-INF\lib 디렉토리안에 넣어주세요. ( 이거는 이클립스에서 직접 하실 수 있는건 아시죠? )  

태그라이브러리를 사용하려면 <taglib> 디렉티브를 JSP 페이지 제일 위쪽에 선언해주셔야 합니다.  

Core Tags:

JSTL 태그 중에서 가장 많이 사용되는 태그입니다.  

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

 

Tag	Description
<c:out >	Like <%= ... >, but for expressions.
<c:set >	Sets the result of an expression evaluation in a 'scope'
<c:remove >	Removes a scoped variable (from a particular scope, if specified).
<c:catch>	Catches any Throwable that occurs in its body and optionally exposes it.
<c:if>	Simple conditional tag which evalutes its body if the supplied condition is true.
<c:choose>	Simple conditional tag that establishes a context for mutually exclusive conditional operations, marked by <when> and <otherwise>
<c:when>	Subtag of <choose> that includes its body if its condition evalutes to 'true'.
<c:otherwise >	Subtag of <choose> that follows <when> tags and runs only if all of the prior conditions evaluated to 'false'.
<c:import>	Retrieves an absolute or relative URL and exposes its contents to either the page, a String in 'var', or a Reader in 'varReader'.
<c:forEach >	The basic iteration tag, accepting many different collection types and supporting subsetting and other functionality .
<c:forTokens>	Iterates over tokens, separated by the supplied delimeters.
<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:

포매팅 관련 태그들입니다.다국적 Web 사이트를 만들때 유용하다고 하네요.

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

 

Tag	Description
<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>	To display an internationalized message.
<fmt:requestEncoding>	Sets the request character encoding

SQL tags:

JSTL SQL 태그는 관계형 데이타베이스 시스템을 핸들링할 수 있습니다. ( Oracle, MySQL, Microsoft SQL Server )

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

 

Tag	Description
<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.

XML tags:

JSTL XML 태그는 JSP에서 XML 문서를 생성 및 조작할 수 있도록 해줍니다. 하지만 XML을 파싱하거나 데이타를 변환하거나 XPath 표현식을 사용하려면 추가적인 커스텀 태그가 필요합니다.  

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

아래의 두 jar파일도 <Tomcat Installation Directory>\lib 에 추가해주셔야 합니다. 

• XercesImpl.jar: Download it from http://www.apache.org/dist/xerces/j/

• xalan.jar: Download it from http://xml.apache.org/xalan-j/index.html

 

Tag	Description
<x:out>	Like <%= ... >, but for XPath expressions.
<x:parse>	Use to parse 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 <when> and <otherwise>
<x:when >	Subtag of <choose> that includes its body if its expression evalutes to 'true'
<x:otherwise >	Subtag of <choose> that follows <when> tags and runs only if all of the prior conditions evaluated to 'false'
<x:transform >	Applies an XSL transformation on a XML document
<x:param >	Use along with the transform tag to set a parameter in the XSLT stylesheet

JSTL Functions:

JSTL 은 표준 함수들을 제공하고 있습니다. 대부분 스트링관련 함수들이죠.

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

 

Function	Description
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 could 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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Reference : http://www.tutorialspoint.com/jsp/jsp_standard_tag_library.htm