JSP Custom Tags

JSP Custom Tags Svetlin Nakov National Academy for Software Development academy.devbg.org Creating and Using Custom Tags

Contents ,[object Object],[object Object],[object Object],[object Object],[object Object]

Tag Files ,[object Object],[object Object],[object Object],[object Object],[object Object],<books4u:shoppingCart currency="EUR" />

Types of Tag Files ,[object Object],[object Object],[object Object],[object Object],<abc:xyz /> <abc:yyz>This is some text</abc:yyz>

Stand-Alone Tags ,[object Object],[object Object],[object Object],[object Object],<fmt:formatNumber … /> <books4u:ShoppingCart … />

Containing Tags ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

A Simple Tag Example ,[object Object],[object Object],[object Object],<%@ tag body-content="empty" %> <h1>Hello, world!</h1> <%@ taglib prefix="my" tagdir="/WEB-INF/tags" %> <my:hello />

Attributes in Tags <%@ tag body-content="empty" %> <%@ attribute name="min" required="false" %> <%@ attribute name="max" required="false" %> <% double dMin = 0.0; if (min != null) { dMin = Double.parseDouble(min); } double dMax = 1.0; if (max != null) { dMax = Double.parseDouble(max); } double number = (Math.random()*(dMax-dMin)) + dMin; %> <%= number %>

JSTL in Tags <%@ tag body-content="empty" %> <%@ attribute name="firstName" required="false" %> <%@ taglib prefix="c“ uri="http://java.sun.com/jsp/jstl/core" %> <c:if test='${empty firstName}'> <h1>Hello, guest !</h1> </c:if> <c:if test='${not empty firstName}'> <h1>Hello, <c:out value='${firstName}' />!</h1> </c:if>

Body Content in Tags ,[object Object],[object Object],<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ attribute name="count" required="true" %> <c:forEach begin="1" end="${count}"> <jsp:doBody /> </c:forEach>

A Test JSP <%-- Include all tags from /WEB-INF/tags --%> <%@ taglib prefix="my" tagdir="/WEB-INF/tags" %> <html> <body> <%-- Use the tag "repeat.tag" --%> <my:repeat count="10"> <div>Hello!</div> </my:repeat> </body> </html>

Exporting Variables from Tags ,[object Object],<%@ tag body-content="scriptless" %> <%@ attribute name="numTimes" required="true" %> <%@ attribute name="var" rtexprvalue="false" required="true" %> <%@ variable name-from-attribute="var" alias="i" scope="NESTED" %> <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> <c:forEach begin='1' end='${numTimes}' var='i'> <jsp:doBody /> </c:forEach>

A Test JSP <%@ taglib prefix="tag_examples" tagdir="/WEB-INF/tags" %> <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> <html> <body> <tag_examples:repeat_var var='index' numTimes= '5' > <div>Hello #<c:out value='${index}' />!</div> </tag_examples:repeat_var> </body> </html>

Modifying Body Content in Tags ,[object Object],<%@ tag body-content="scriptless" %> <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> <jsp:doBody var='body' /> <c:forTokens var='token' items='${body}' delims=' '> <div><c:out value='${token}' /></div> </c:forTokens>

A Test JSP <%@ taglib prefix="tag_examples" tagdir="/WEB-INF/tags" %> <%@ taglib prefix="c" uri="http://java.sun.com/jstl/core" %> <html> <body> <p> The quick brown fox jumped over the lazy dog. </p> <p> <tag_examples:tokenize> The quick brown fox jumped over the lazy dog. </tag_examples:tokenize> </p> </body> </html>

JSP Custom Tags ,[object Object]

Problems ,[object Object],[object Object],[object Object],[object Object]

Problems (2) ,[object Object],[object Object],[object Object],[object Object],[object Object]

JSP Custom Tags

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