Jstl Tag Library

1, Jstl dependent El, use Jstl need to import Jstl jar package. Jstl has four main libraries, respectively:

Core: Kernel library, FMT format (date, number), Sql,xml

2, Import jstl Tag library: First need to import the jar package, and then <%taglib prefix= "prefix" uri= "path"%> in the JSP page (eg:1.2 version: <%@ taglib prefix= "C" uri=http:// Java.sun.com/jsp/jstl/core%>)

3. Core Tag library core-> is called C tag (prefix is usually C)

(1) Out and set

<c:out/>: Output

<c:out value= "abc"/> output abc;<c:out value=${num}/> and ${num}

<c:out value=${num} default= "abc"/> Output ABC when ${num} does not exist

<c:out value=${num} default= "abc" escapexml= "false"/> "<", ">" is not converted when EscapeXML is false. Eccapexml default to True

　　

<c:set/>: setting

<c:set var= "num" value= "abc"/> Add a key to PageContext as "ABC" Data in Num,value

<c:set var= "num" VALUE=${ABC} scope= "Session"/> Add the data of key Num,value to ${ABC in session, scope selectable values: Session, page, Request, Application

(2) Remove

<c:remove var= "A" scope= "session"/> Delete domain variable, remove from all domains if no scope is specified

(3) URL

Value: Specifies a path that automatically adds the project name in front of the path

<c:url value= "/index.jsp"/> Actual output is/project name/index.jsp

　　

Sub-label:<c:param> used to add parameters behind the URL

<c:url value= "/index.jsp" >

<c:param name= "username" value= "test"/>

</c:url >

Actual output is/project name/index.jsp?username=%7f7fwwd%9f

　　

var: Specifies the variable name, and once the property is specified, the URL is not output to the page but is saved to the domain variable

Scope: Use with Var

(4) if

If the test property of the If label must be a Boolean value, if the value of test is true, then the contents of the If label are executed, otherwise the

<c:if test= "${not Empty num}" >

<c:out value= "${num}"/>

</c:if>

(Note: no else)

(5) Choose
corresponding switch

<c:choose>

<c:when test= "${num < ten}" > Less than 10</c:when>

<c:when test= "${num > && num <" > greater than 10 less than 20</c:when>

<c:otherwise> Greater than 20</c:otherwise>

</c:choose>

(6) ForEach

Used to loop through arrays, collections, and counting.

Counting method:

I variables from 1 to 100 each plus 2

<c:foreach var= "I" begin= "1" end= "step=" 2 "> (contains 100, equivalent to <=100)

<c:out value= "${i}" >

</c:forEach>

Assigns each element in an array or collection to a variable specified by var

<c:foreach items= "${products}" var= "Product" >

<c:out value= "${product}" >

</c:forEach>

Loop Status:

You can use Varstatus to create a loop state variable

<c:foreach items= "${arr}" var= "E" varstaus= "vs" >

${vs.count} (number of looping elements)

${vs.index} (subscript for the current element)

${vs.first} (whether it is the first element)

${vs.last} (whether it is the last element)

${vs.current} (current Element)

<c:out value= "${e}" >

</c:forEach>

4. FMT Library, Format library

Formatted Date:

<% Date date = new Date (); Pagecontext.setattribute ("date", date); %>

<fmt:formatdate value= "${d}" pattern= "Yyyy-mm-dd HH:mm:ss"/>

Format numbers:

<% request.setattribute ("num", 3.141592653)%>

<fmt:formatnumber value= "${requestscope.num}" pattern= "0.00" > Output Decimal Two bits (4 5 in), 0 (if value=3.1 actually outputs 3.10)

<fmt:formatnumber value= "${requestscope.num}" pattern= "#.##" > Non-complement

　　

Jstl Tag Library