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variable from servlet editing inside JSP

In have this transfer from a servlet to the jsp. Since the AllPost is a list and I go through it with for, I do not know whether it's a short way close to what I give here.
Meanwhile I solved the issue inside the class, i.e. before the value coming to the servlet & jsp, as below.
So, at this point I do not know whether it makes sense to try further.
Thank you in advance!
<c:forEach items="${AllPost}" var ="p">
<tr>
<%! int len = Integer.valueOf(${p.detail.length()}); %>
<%
if(len<25){
${p.detail}.concat("....");
}
%>
<td>${p.detail.substring(0,25)}...</td>
The 2nd option code from routine class:
ResultSet rs = DB.getPreparedStatement(SQL).executeQuery();
while(rs.next()){
News n = new News(rs.getInt(1),...);
if(Integer.valueOf(rs.getString(1.length())<25){
String sz = n.getDetail().concat(".........................");
n.setDetail(sz);
}

<%! int len = Integer.valueOf(${p.detail.length()}); %>
Here you're mixing EL and scriptlets, it's not possible to use both. Not only that, you're using JSTL in your code as well, but still resorting to scriptlets? In almost all cases, if you're using JSTL & EL, you don't need to use any scriptlets. Scriptlets is an oldschool way of using JSPs.
Your code for the first option should look something like this (without scriptlets):
<c:forEach items="${AllPost}" var ="p">
<tr>
<c:if test="${fn:length(p.detail) lt 25}">
<td>${p.detail}...</td>
</c:if>
<c:if test="${fn:length(p.detail) gt 25}">
<td>${fn:substring(p.detail, 0, 25)}...</td>
</c:if>
</tr>
</c:forEach>
make sure to include this at the top of the page for jstl functions (if you haven't already)
<%# taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>

Is there a better way to write this JSP custom tag?

I'm creating a JSP .tag file that will handle this use case:
<my:safeParam paramName="param1" defaultValue="testvalue"/>
Where the behavior will be to take a request parameter, escape its value for "safe" usage, and place that escaped value back on some scope (e.g. request) under the same name as the parameter (although it could be another name).
I have an implementation that works, but I've got scriptlet in there because I couldn't find a way to use variable variable names in just JSTL. But I'm no JSTL wizard, so I thought I'd see if there's a syntax/approach I'm missing. Here's the working safeParam.tag file:
<%# taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%# taglib uri="http://java.sun.com/jsp/jstl/functions" prefix="fn" %>
<%# attribute name="paramName" required="true" %>
<%# attribute name="defaultValue" %>
<%
String name = (String) pageContext.getAttribute("paramName");
%>
<c:if test="${not empty defaultValue}">
<%
request.setAttribute(name, pageContext.getAttribute("defaultValue"));
%>
</c:if>
<c:if test="${not empty param[paramName]}">
<c:set var="escaped" value="${fn:escapeXml(param[paramName])}"/>
<%
request.setAttribute(name, pageContext.getAttribute("escaped"));
%>
</c:if>
(I sure wish EL was escaped automatically.)

<c:if test="${empty paramName}">
${defaultValue}
</c:if>
<c:if test="${not empty paramName}">
<c:out value="${paramName}" escapeXml="true"/>
</c:if>

I probably won't use this approach because it reduces the conciseness I was seeking with this custom tag, but just to document it as an option... (I'm not sure if this is what Frank Yeung is getting at.)
I could make the tag simply output the default-or-escaped parameter value, then make the user of the tag wrap that in a <c:set>.
Tag:
<c:choose>
<c:when test="${empty param[paramName]}">
${defaultValue}
</c:when>
<c:otherwise>
<c:out value="${param[paramName]}"/>
</c:otherwise>
</c:choose>
JSP:
<c:set var="myVariable">
<my:safeParam paramName="folder" defaultValue="homeFolder"/>
</c:set>
But really my goal has been to do everything inside the tag.

Using together JSTL forEach tag and custom JSP-based tag

I am implementing paging support using custom tag. I decided to use JSP-based tag because there is more formatting than any heavy logic. But this is not the main story. The trouble is that JSTL forEach simply doesn't work at my .tag file and throws java.lang.NoSuchFieldError: deferredExpression .Even this code is throwing exception when I'm using my tag at JSP:
<%#tag description="paging support for employee" pageEncoding="UTF-8"%>
<%#taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<div>
<div>
<c:forEach var="i" begin="1" end="20" step="1" varStatus ="status">
<c:out value="${i}" />
</c:forEach>
</div>
</div>
Also in my previous project i met this exception while was mixing together struts tags and forEach tag in a single JSP. I couldn't find out what was it, but handled it through replacing forEach by similar struts tag iterate. But this time I need exactly forEach because of it's attribute "step". Any ideas ?

Why my included JSP file won't get processed correctly?

I am trying (and learning) to build a java web framework, and in the process of developing its' code generator based on the content of the database. In the view making process, I stumble in a difficulty, which I don't know how to solve it.
Firstly, I want all the pages to be created using the following index.jsp :
<body>
<%# include file="header.jsp" %>
<hr/>
<%# include file="body.jsp" %>
<hr/>
<%# include file="footer.jsp" %>
</body>
And, in the body.jsp, I want it to be like this :
<jsp:include page="${application_modul}" %>
Where application_modul is an attribute defined in its' controller this way :
request.setAttribute("application_modul","user_account\\view_user_account.jsp");
It can find the file correctly, but the processed jsp is not what I expected. Here :
<c:forEach items="[application.models.UserAccountModel#18a49e0, application.models.UserAccountModel#1f82982]" var="item" varStatus="status" >
<tr>
....
You can see the items attribute of jstl forEach, got its variable name (toString())...
Any Idea what the problem is????
I hope I describe my problem correctly
Many thanks!
PS :
I already create a quick fix for this, but not what I want it though. In the generated view_user_account.jsp, I do it like this :
<body>
<%# include file="header.jsp" %>
<hr/>
<c:forEach items="${row}" var="item" varStatus="status" >
<tr>
....
<hr/>
<%# include file="footer.jsp" %>
</body>
You can see that I create the whole file here...
EDITED:
PS : ${row} is an ArrayList populated with data from certain table

So, to summarize your problem in a single sentence, JSTL tags are not been parsed and they end up plain in generated HTML output?
You need to declare JSTL taglib in top of the JSP page where you're using JSTL tags to get them to run. For the JSTL core taglib, that'll be
<%#taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

I am not sure but, Try this...
index.jsp
<jsp:param name="parameterName" value="{parameterValue | <%= expression %>}" />

JSTL 2d Array Iteration

I have a 2d array stored in a java bean and I'm trying to iterate through its contents to print a corresponding table on a JSP page. The array is a bean data member which I'm accessing through the EL code ${board.cells}. I tried to do this with a c:forEach tag, but it's only printing a single cell. I know the array contents are valid, as I can see them when I index them directly by ${board.cells[0][0]}
Here's my loop code, embedded in the JSP.
<c:forEach items="${board.cells}" var="row">
<tr>
<c:forEach items="${row}" var="cell">
<td><img src=${cell} align="" alt="cell"></td>
</c:forEach>
</tr>
</c:forEach>
Any help is much appreciated!

As per the comments, JSTL core tags are simply not been interpreted/parsed. They are been sent plain to the HTML response. You need to declare the JSTL core taglib in top of your JSP to get them to run.
<%# taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
See also:
Our JSTL wiki page