betweenGo

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The ATG Date Tag Converter is buggy because Java’s DateFormat is inherently unsafe for multithreaded use.  This is documented in ATG PR #123210 DateTagConverter.convertObjectToString() method is not thread safe.

You run into this problem whenever you do something like this.

<dsp:valueof param=”creationDate” converter=”date” date=”M/dd/yyyy”/>

Unfortunately there is no work around.  If using the Date Tag Converter is not causing problems for you, i.e you don’t see a stack trace like below, then you can ignore this bug.

2009-04-17 00:19:08,220 ERROR [nucleusNamespace.atg.dynamo.servlet.dafpipeline.DynamoServlet] java.lang.ArrayIndexOutOfBoundsException: 502
  at sun.util.calendar.BaseCalendar.getCalendarDateFromFixedDate(BaseCalendar.java:436)
  at java.util.GregorianCalendar.computeFields(GregorianCalendar.java:2081)
  at java.util.GregorianCalendar.computeFields(GregorianCalendar.java:1996)
  at java.util.Calendar.setTimeInMillis(Calendar.java:1071)
  at java.util.Calendar.setTime(Calendar.java:1037)
  at java.text.SimpleDateFormat.format(SimpleDateFormat.java:785)
  at java.text.SimpleDateFormat.format(SimpleDateFormat.java:778)
  at java.text.DateFormat.format(DateFormat.java:314)
  at atg.droplet.DateTagConverter.convertObjectToString(DateTagConverter.java:176)

But if you do see a bug like this then you might need to create a custom droplet to format the date.  The droplet should only use DateFormat instances that are not static.  I usually make my DateFormat instances local.

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This was bedeviling me for awhile.  I could not figure out why my RQLQueryRange droplet was not sorting by dates correctly.  It turns out this is a known ATG bug which only happens when you are using Oracle, which is 99% of the time.

Considering that this bug has been open since 2003 one can assume ATG is not interested in fixing it.  This is probably because there is a simple work around.

Instead of using the sortProperties parameter, put the the sort directive directly in the RQL statement in the queryRQL parameter.

<dsp:param name="queryRQL" value="ALL ORDER BY creationDate DESC"/>

 
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When I create a DSP textarea tag like this it outputs the value of the bean property in the text area box.

<dsp:textarea bean="MyFormHandler.foo" rows="5" cols="20"/>

Similarly if I create a DSP textarea tag like this I get the same output.

<dsp:textarea bean="MyFormHandler.foo" rows="5" cols="20"></dsp:textarea>

However when I leave some space between the textarea opening and closing tag I get a blank instead of the value of the bean property in the text area box.

<dsp:textarea bean="MyFormHandler.foo" rows="5" cols="20">
</dsp:textarea>

Anyone know why there is a difference?

Anyway after reading the documentation it turns out if I want to control what is output in the text box I can use the default attribute.

<dsp:textarea bean="MyFormHandler.foo" rows="5" cols="20" default="bar"/>

Maybe I should have read the documentation before writing this post.

Update 2009-09-03: I also found this strange pattern of behavior with the DSP droplet tag.  When I invoked a droplet that took no parameters and had no open parameters like this:

<dsp:droplet name="MyDroplet"/>

or like this:

<dsp:droplet name="MyDroplet"></dsp:droplet>

the droplet would not be invoked.

However when I did this the droplet was invoked.  Strange …

<dsp:droplet name="MyDroplet">
</dsp:droplet>

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In the Setting Property Values in Forms section of the ATG Page Developer’s Guide there are two examples for setting values of array properties in forms.

1. Grouped Checkboxes
2. Multiple-Selection List Box

Both examples are for a simple form.  But what if you are generating a form using a ForEach droplet and want to set an array property in each iteration of the loop.  Fortunately it turns out to be relatively easy.

Hidden or Text Inputs

<dsp:droplet name="/atg/dynamo/droplet/ForEach">
  <dsp:oparam name="output">
    <dsp:input type="hidden" paramvalue="element.id" bean="MyFormHandler.ids"/>
  </dsp:oparam>
</dsp:droplet>

Select Inputs

<dsp:droplet name="/atg/dynamo/droplet/ForEach">
  <dsp:oparam name="output">
    <dsp:select bean="MyFormHandler.answers">
     <dsp:option value="foo">foo</dsp:option>
     <dsp:option value="bar">bar</dsp:option>
    </dsp:select>
  </dsp:oparam>
</dsp:droplet>

By the way if you try to set the array element directly using the param:index notation as in the following example it will not work.

<dsp:droplet name="/atg/dynamo/droplet/ForEach">
  <dsp:oparam name="output">
    <dsp:select bean="MyFormHandler.answers[param:index]">
     <dsp:option value="foo">foo</dsp:option>
     <dsp:option value="bar">bar</dsp:option>
    </dsp:select>
  </dsp:oparam>
</dsp:droplet>

When submitting the above form you will get this exception.

atg.droplet.DropletException:
  Can't set an element of the array property without a set <name> (int index, Object value) method.

The exception message is a red herring, there is no way you can set the element of an array property no matter what kind of set method you create.  Trust me, I spent many hours delving into the ATG code to verify this.

This JSP code was not outputting the properly formatted amount.

<dspel:valueof value="${dollars}" converter="currency" />

I tried forcing it by specifying the conversion parameters.

<dspel:valueof value="${dollars}" converter="currency" locale="en-CA" format="#.00" currency="$" />

I then debugged atg.droplet.CurrencyTagConverter using Eclipse and found this code being executed.

public String convertObjectToString(DynamoHttpServletRequest pRequest,
                                 Object pValue, Properties pAttributes)
  throws TagConversionException
{
  if ((pValue == null) || (pValue instanceof String))
    return (String)pValue;

It turns out pValue was a String which is why it was never being formatted.  But why is it a String?

Well the code that sets dollars looks like this.

<dspel:tomap var="paymentGroup" param="commerceItem.paymentGroups[1]" />
<c:set var="dollars" value="0" />
<c:if test="${not empty paymentGroup}">
  <c:set var="dollars" value="${paymentGroup.amount}" />
</c:if>

Apparently c:set converts the Double to a String.

To work around this problem I did this.

$<dspel:valueof number="0.00" value="${dollars}" />

For further reading please see Tag Converters in the ATG Page Developer’s Guide.

Today I added a feature in my shopping cart JSP page but nothing was showing up.  This was because the output of ATG ForEach droplet was blanks.

To debug this I did the following steps.

1. I added an empty oparam to see if the ForEach droplet thought the collection was empty.

   <dsp:oparam="empty">Empty?</dsp:oparam>

   It did not.

2. I outputted the count in the output oparam to see if it was looping through the collection.

   <dsp:oparam="output"><dsp:valueof param="count"/> <dsp:valueof param="element"/></dsp:oparam>

   It was looping through the collection.

3. Finally I debugged using Eclipse the ForEach code.  The ForEach code can be found in <ATG>/DAS/src/Java/atg/droplet/ForEach.java. 

   Using the debugger I realized that the element name of the loop was being set to something else which is why <dsp:valueof param=”element”/> was blank.

It turned out that the ForEach droplet was inside another ForEach droplet and in that droplet they set the element name like this.

<dsp:param name="elementName" value="CommerceItem" />

By setting the elementName parameter to something else in my ForEach droplet and then referencing it properly I was finally able to get the expected output.

<dsp:droplet name="/atg/dynamo/droplet/ForEach">
 <dsp:param name="array" param="CommerceItem.auxiliaryData.productRef.dvds"/>
 <dsp:param name="elementName" value="dvd" />
 <dsp:oparam name="output">
  <dsp:valueof param="dvd.name" />
 </dsp:oparam>
</dsp:droplet>

By the way ATG documentation suggests not using elementName.

elementName and indexName allow you to provide a parameter name other than element and index, respectively. A better way to provide a different parameter name is to use the dsp:setvalue tag.

In our example we would do this instead of setting the elementName param.

 <dsp:setvalue param="dvd" paramvalue="element" />

Sometimes you want to list each item in the collection with a separator in between like a comma or slash.  However the trick is to have the separator only in between items.

In ATG DSP you can use the ForEach droplet to iterate through each item in a collection.  However to put a separator between each item is not straight-forward with this droplet.  To do this I used JSTL to test if we are at the end of the collection.  If we are then I don’t add the separator, otherwise I do.

Here is an example.

<dspel:droplet name="/atg/dynamo/droplet/ForEach">
 <dspel:param name="array" param="dvds"/>
 <dspel:setvalue param="dvd" paramvalue="element" />
 <dspel:oparam name="outputStart">
  <dspel:getvalueof var="size" param="size" />
 </dspel:oparam>
 <dspel:oparam name="output">
  <dspel:valueof param="dvd.title" valueishtml="true"/>
  <dspel:getvalueof var="count" param="count" />
  <c:if test="${size != count}"> , </c:if>
 </dspel:oparam>
</dspel:droplet>

And here is the output for this example.

The Incredibles, Ratatouille, Cars

Do you have a better or more elegant solution?  Please feel free to let me know in the comments?

I always forget how to do this so I thought I should write it down.

In JSP:

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

In JSTL:

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

In DSP:

<dspel:valueof param="foo"/>

Sometimes the resultant HTML from JSP files has too much white space.  This is because a lot of JSP logic will end up in only a few lines of actual HTML code and the rest is white space.

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.

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

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>

The above problem might have been happening because we are running with a version of ATG that is for Servlet 2.3 but we are running with a version of JBoss that runs with Servlet 2.4.

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>

In DSP to display formatted HTML text you use the valueishtml converter attribute.  For example:

<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" />