How to Debug No Output for ATG ForEach


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.

    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/

    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="" />

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" />

ATG ForEach Output with Separators Between Items

Pez Collection

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 name="output">
  <dspel:valueof param="dvd.title" valueishtml="true"/>
  <dspel:getvalueof var="count" param="count" />
  <c:if test="${size != count}"> , </c:if>

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?