Zen Water by darkpatator

Sometimes you want to check in your JSP page fragment which page loaded it.  Fortunately this is simple with JSTL.

<c:if test="${fn:indexOf(pageContext.request.requestURI,'foo.jsp') != -1}">
  The request URI ${pageContext.request.requestURI} contains foo.jsp.
</c:if>

Simple but something I always forget how to do.

Related posts:

1. Get JSTL Vars from PageContext
2. JSTL for current URI
3. JSP redirect to another page

pageContext.setAttribute("foo", bar);

Therefore to get a JSTL variable use the pageContext within a tag or a JSP page.  For example:

// get item from pageContext and put in request
atg.servlet.DynamoHttpServletRequest drequest = atg.servlet.ServletUtil.getDynamoRequest(request);
drequest.setParameter("foo", pageContext.getAttribute("foo"));

Note that getAttribute assumes the variable is in the page scope.  If you want to get a variable from for example the request scope you would do this.

pageContext.getAttribute("foo", javax.servlet.PageContext.REQUEST_SCOPE);

For further reading please see PageContext.

Related posts:

1. JSTL for current URI
2. Accessing RepositoryItems with JSTL
3. JSP Dynamo Request Retrieval

In JSP:

<%=request.getParameter("foo")%>
<img src="<%=request.getParameter("foo")%>">

In JSTL:

<c:out value="${param.foo}"/>

In DSP:

<dspel:valueof param="foo"/>

Related posts:

1. Comparison of DSP and DSPEL
2. Accessing RepositoryItems with JSTL
3. Display formatted HTML text

org.apache.jasper.JasperException: Unable to compile class for JSP
        at org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:375)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)

org.apache.jasper.JasperException: Unable to compile class for JSP
        at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:572)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:303)

java.lang.NumberFormatException: For input string: "${status.index}"
        at java.lang.NumberFormatException.forInputString(NumberFormatException.java:48)
        at java.lang.Integer.parseInt(Integer.java:447)
        at java.lang.Integer.valueOf(Integer.java:553)
        at org.apache.jasper.compiler.JspUtil.coerceToInt(JspUtil.java:752)
        at org.apache.jasper.compiler.Generator$GenerateVisitor.convertString(Generator.java:2949)

The major problem was this was happening on the server but not locally.  The compilation problem was occurring for this line.

<uportal:module definition="${module}" moduleIndex="${status.index}"/>

The moduleIndex value is “${status.index}”. Locally when the JSP compiler encounters this it knows to call my setter for moduleIndex that takes a String parameter. But on the server the JSP compiler seemed to insist on using the setter for moduleIndex that takes an integer parameter, hence the compilation problem.

I finally posted on the Sun Forums and with the help of evnafets I came up with two solutions.

1. The correct solution is to upgrade my application to use JSTL 1.1.  Then the JSTL expressions such as “${status.index}” will be evaluated by the container.  Then I don’t have to have a setter that takes a String parameter, the JSTL expression, and evaluate it myself.  I can just use a setter that takes an integer parameter.
2. The quick, hack solution which is to get rid of the setter that takes an integer parameter.  Wherever the application passes in an integer parameter, I change it to pass in a String representation of that integer.

Related posts:

1. Size of collection in a JSP/DSP page
2. Accessing JavaBean’s Getters and Setters
3. Upgrading to JSTL 1.1

1. Update URI in JSP pages to use JSTL 1.1.

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

2. Install in WEB-INF/lib the two JSTL 1.1 jars, standard.jar and jstl.jar.  You can get these from The Jakarta Site – Standard 1.1 Taglib Downloads.
3. Update the start of web.xml to look like this.

   <?xml version="1.0" encoding="ISO-8859-1"?>
   <web-app xmlns="http://java.sun.com/xml/ns/j2ee"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
       version="2.4">

Related posts:

1. JSTL for current URI
2. Trim White Space from JSP
3. Accessing RepositoryItems with JSTL

One efficient way to get rid of white space is to add this configuration to your web.xml on Tomcat/JBoss as described in this article, Trim Spaces in your JSP’s HTML.

/jboss/jboss-eap-4.2/jboss-as/server/atg/deploy/jboss-web.deployer/conf/web.xml
OR
/jboss/jboss-eap-5.1/jboss-as/server/atg/deployers/jbossweb.deployer/web.xml

<servlet>
    <servlet-name>jsp</servlet-name>
    ...

    <init-param>
        <param-name>trimSpaces</param-name>
        <param-value>true</param-value>
    </init-param>

    ...
</servlet>

However this sometimes has undesired side-effects. For example this DSP:

<div class="foo">
  <dspel:valueof param="displayName" />
</div>

causes this undesired result:

<div class="foo"/>
  Frank Kim

The work around is to do this.

<dspel:getvalueof  var="displayName" param="displayName" />
<div  class="foo"><c:out  value="${displayName}"/></div>

Update 06-09-2010: The above problem might have been happening because we were running with a version of ATG that is for Servlet 2.3. When we run with a version of JBoss that runs with Servlet 2.4, e.g.  ATG 9.1 with JBoss EAP 4.2, we no longer see this problem.

There is another tip on removing white space in this JSP FAQ: Why I am getting extra whitespace in the output of my JSP?  In our code we had one file which included a bunch of tag libraries.  It originally looked like this.

<%/** Taglibs.jsp: include to pull in all taglibs */%>

<%@ taglib uri="/dspELTaglib" prefix="dspel" %>
<%@ taglib uri="/jstlCoreTaglib" prefix="c" %>
<%@ taglib uri="/struts-bean" prefix="bean" %>
<%@ taglib uri="/struts-tiles" prefix="tiles" %

When we changed it to this we saved about 5% in terms of page size in bytes.

<%@ taglib uri="/dspELTaglib" prefix="dspel"
%><%@ taglib uri="/jstlCoreTaglib" prefix="c"
%><%@ taglib uri="/struts-bean" prefix="bean"
%><%@ taglib uri="/struts-tiles" prefix="tiles" %>

You can use this tip with a DSP page and maintain indentation.

<dspel:page    ><dspel:droplet name="/betweengo/droplet/Foo"      ><dspel:oparam name="output"        >Name: <dspel:valueof param="name"      /></dspel:oparam    ></dspel:droplet
></dspel:page>

Related posts:

1. Size of collection in a JSP/DSP page
2. Accessing RepositoryItems with JSTL
3. JSTL for current URI

<dspel:valueof param="displayName" valueishtml="true"/>

For example “foo &amp; bar” becomes “foo & bar”.

In JSTL to do this you tell JSTL not to escape the XML.  For example:

<c:out value="${displayName}" escapeXml="false" />

Related posts:

1. Upgrading to JSTL 1.1
2. Get JSTL Vars from PageContext
3. Trim White Space from JSP

(Photo: Singur suflet pustiu by dani81_const)

This article, Expression Language Overview” href=”http://www.informit.com/articles/article.aspx?p=30946″>InformIT: The JSTL Expression Language > Expression Language Overview, informed me on how to test if something is empty or not.

Empty?

<c:if test="${empty foo}">...</c:if>

Not empty?

<c:if test="${not empty foo}">...</c:if>

Related posts:

1. Upgrading to JSTL 1.1
2. Get JSTL Vars from PageContext
3. JSTL for current URI

Well you have two options. Either you’ll do a server side forward or a client side redirect.
Server side forward has no interaction with the browser and therefore the URL on the location bar won’t change.
But if you do the HTTP redirect, the browser is instructed to load the other page and the contents of the location will change.
It’s your call which one to choose.

forward:

<% if (s1.equals(s2) ) { %>

     <jsp:forward page="s2.jsp"/>

<% } %>

redirect:

<% if (s1.equals(s2) ) {

    response.sendRedirect("s2.jsp");

} %>

Related posts:

1. Testing Which Page Loaded your JSP Page Fragment
2. Size of collection in a JSP/DSP page
3. Trim White Space from JSP

If you want the actual URI of the JSP that is being rendered:

<c:out value="${pageContext.request.requestURI}"/>

If you want the original URI, which is probably the case, then:

<c:out value="${requestScope['javax.servlet.forward.request_uri']}"/>

In DSP if you want the original URI you can use the OriginatingRequest bean which implements the HttpServletRequest.

<dsp:valueof bean="/OriginatingRequest.requestURI" />

Related posts:

1. Get JSTL Vars from PageContext
2. Upgrading to JSTL 1.1
3. Accessing RepositoryItems with JSTL