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This subproject is an extension of the Struts tag library. Each JSP custom tag in this library is a subclass of an associated tag in the Struts tag library. One difference is that this tag library does not use "rtexprvalues", it uses the expression evaluation engine in the Jakarta Taglibs implementation of the JSP Standard Tag Library (version 1.0) to evaluate attribute values. In addition, some of the Struts tags were not ported to this library, as it was determined that their functionality was entirely supplied by the JSTL. These particular Struts tags, and the reason for their non-porting will be described in the documentation for this library. In order to fully understand the correct utilization of this library, you must understand the use and operation of the Struts tag library, and the use and operation of the JavaServer Pages Standard Tag Library (hereafter called the "JSTL"), along with the expression language (sometimes called the "EL") used for evaluating attribute values.

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  Package Documentation for org.apache.strutsel Package
 
 
  
   The "Struts-EL" library
   contains a set of tag libraries, all of whose classes are derived from
   classes in the Struts tag libraries.  The Struts-EL tags all implement the
   same attributes as their counterparts in the base Struts tag libraries.  The
   difference provided by Struts-EL is that the tag attribute values are not
   evaluated as run-time scriptlets (sometimes called "rtexprvalue"s), but are
   instead evaluated by the expression language engine in the JavaServer Pages
   Standard Tag Library (often called the JSTL).
  
      
   
    [Introduction]
    [HTML-EL Tag Library]
    [Logic-EL Tag Library]
    [Bean-EL Tag Library]
  
  
  Introduction
  
   The Struts-EL library is intended to be used alongside the Struts library,
   and with the JSTL.  In the development of the Struts-EL library, each tag in
   the Struts tag libraries was examined to see if all of its functionality is
   covered in an existing tag in the JSTL.  If this was the case, then it was
   decided to not include a version of this tag in the
   Struts-EL library.  The tags that were "ported" to Struts-EL were deemed to
   have functionality which the JSTL could not directly cover.
  
  
   The rest of this package description will briefly review the Struts tags
   which were not ported to the Struts-EL library (or which
   were "on the bubble", and why.  The detailed package descriptions for each
   section of the library (html-el, logic-el, and bean-el) will demonstrate in
   detail the usage of the Struts-EL tags, focusing on attribute value
   evaluation issues.  Details of the operation of these tags in the Struts
   framework can be learned from the package descriptions and documentation for
   the base Struts library.
  
  
  HTML-EL tag library
  This is a short section.  The JSTL does not include any functionality for
generating HTML elements, thus every tag in the "struts-html" tag library was
ported to the "struts-html-el" tag library.
  
  Logic-EL tag library
  
   The following table lists the "struts-logic" tags which were not ported to
   the "struts-logic-el" tag library, including which JSTL elements or features
   will provide that functionality.  Examples after the table will demonstrate
   these.
  
  
   
    Struts-Logic tag
    JSTL tags or feature
   
   
    empty
    c:if, c:when, EL
   
   
    equal
    c:if, c:when, EL
   
   
    greaterEqual
    c:if, c:when, EL
   
   
    greaterThan
    c:if, c:when, EL
   
   
    lessEqual
    c:if, c:when, EL
   
   
    lessThan
    c:if, c:when, EL
   
   
    notEmpty
    c:if, c:when, EL
   
   
    notEqual
    c:if, c:when, EL
   
  
  
   The following are some examples of "Before" and "After", where the first
   example is pure Struts usage, and the second example will be pure JSTL
   usage, not involving Struts-EL at all.
  
  Struts Example:
     <logic:empty name="foo" property="stuff">
    Some stuff
   </logic:empty>
  JSTL Version: 
     <c:if test="${empty foo.stuff}">
    Some stuff
   </c:if>
  Struts Example:
     <logic:notEmpty name="foo" property="stuff">
    Some stuff
   </logic:notEmpty>
  JSTL Version:
     <c:if test="${!empty foo.stuff}">
    Some stuff
   </c:if>
  Struts Example:
     <logic:equal name="foo" property="stuff" value="<%=thing.getStuff()%>">
    Some stuff
   </logic:equal>
  JSTL Version:
     <%-- Assumes "thing" is a scoped variable --%>
   <c:if test="${foo.stuff eq thing.stuff}">
    Some stuff
   </c:if>
  Struts Example:
     <logic:greaterThan name="foo" property="stuff" value="<%=thing.getStuff()%>">
    Some stuff
   </logic:empty>
  JSTL Version:
     <%-- Assumes "thing" is a scoped variable --%>
   <c:if test="${foo.stuff ge thing.stuff}">
    Some stuff
   </c:if>
  Struts Example:
     <logic:present cookie="shoppingCart">
    Some stuff
   </logic:present>
  JSTL Version:
     <c:if test='${!empty cookie["shoppingCart"]}">
    Some stuff
   </c:if>
  Struts Example:
     <logic:present header="User-Agent">
    Some stuff
   </logic:present>
  JSTL Version:
     <c:if test='${!empty header["User-Agent"]}">
    Some stuff
   </c:if>
 
  Bean-EL tag library
  
   The following table lists the "struts-bean" tags which were not ported to
   the "struts-bean-el" tag library, including which JSTL elements or features
   will provide that functionality.  Examples after the table will demonstrate
   these.
  
  
   
    Struts-Bean tag
    JSTL tags or feature
   
   
    cookie
    c:set, EL
   
   
    define
    c:set, EL
   
   
    header
    c:set, EL
   
   
    include
    c:import
   
   
    parameter
    c:set, EL
   
   
    write
    c:out
   
  
  
   Note that the "bean:resource" Struts tag is similar, at least superficially,
   to the functionality of the "c:import" tag, but "bean:resource"
   was ported to the Struts-EL library.  This is because
   resources requested through the "c:import" tag may be processed through a
   mapped servlet, preventing direct access to the resource.  The
   "bean:resource" tag allows direct access to the resource, without an
   intervening servlet.  For instance, if it is desired to obtain the raw text
   of a JSP page, using "c:import" will not work, because the JSP page will be
   processed by the JSP servlet.  However, using "bean:resource" will retrieve
   just the text of the JSP page, if that is desired.
  
  
   Also note that some functionality of the "bean:include" tag, which was not
   ported to the Struts-EL library, is not available in the JSTL.  This
   includes the ability to specify the name of a Struts forward, and the
   ability to include the current transaction control token.  These features
   will be addressed in a future minor release of Struts-EL.
  
  
   The following are some examples of "Before" and "After", where the first
   example is pure Struts usage, and the second example will be pure JSTL
   usage, not involving Struts-EL at all.
  
  Struts Example:
     <bean:cookie id="cookieVal" name="stuff"/>
  JSTL Version:
     <c:set var="cookieVal" value='${cookie["stuff"]}'/>
  Struts Example:
     <bean:define id="thing" name="foo" property="stuff"/>
  JSTL Version:
     <c:set var="thing" value="${foo.stuff}"/>
  Struts Example:
     <bean:header id="headerVal" name="stuff"/>
  JSTL Version:
     <c:set var="headerVal" value='${header["stuff"]}'/>
  Struts Example:
     <bean:include id="stuffOut" href="http://somewhere.com/stuff.jsp"/>
  JSTL Version:
     <c:import var="stuffOut" value="http://somewhere.com/stuff.jsp"/>
  Struts Example:
     <bean:parameter id="parameterVal" name="stuff"/>
  JSTL Version:
     <c:set var="parameterVal" value='${param["stuff"]}'/>

Struts-Logic tag	JSTL tags or feature
empty	c:if, c:when, EL
equal	c:if, c:when, EL
greaterEqual	c:if, c:when, EL
greaterThan	c:if, c:when, EL
lessEqual	c:if, c:when, EL
lessThan	c:if, c:when, EL
notEmpty	c:if, c:when, EL
notEqual	c:if, c:when, EL

Struts-Bean tag	JSTL tags or feature
cookie	c:set, EL
define	c:set, EL
header	c:set, EL
include	c:import
parameter	c:set, EL
write	c:out