Complex Table and JSTL

[Gregg Bolinger]

I have a Model that contains a Collection of Characteristic Groups. Each Characteristic Group contains a Collection of Characteristics. I need to construct a table that looks something like this:

ID            Char Group          Char
----------------------------------------
id 1            chargroup 1       char 1
                                  char 2
                                  char 3
                chargroup 2       char 1
                                  char 2
id 2            chargroup 1       char 1
                                  char 2
id 3            chargroup 1       char 1
                chargroup 2       char 1
                chargroup 3       char 1
                                  char 2
                                  char 3
                                  char 4
id 4            chargroup 1       char 1

and so on and so on. I'm having a hard time coming up with the jstl logic to handle this. My first attempt went something like this:

<c:forEach var="part" items="${ actionBean.partList }">
  <tr>
    <td>${ part.ident }</td>
    <c:forEach var="charGroup" items="${ part.modelCharGrps }">
      <td rowspan="${ fn:length(charGroup.modelChars) }">${ charGroup.ident }</td>
      <c:forEach var="modelChar" items="${ charGroup.modelChars }">
        <td>${ modelChar.ident }</td>                            
      </c:forEach>
    </c:forEach>                           
    </td>
  </tr>
</c:forEach>

Obviously, that didn't work out well. I didn't have the row breaks where I needed them and several characteristic group were on the same row instead of seperate rows. Any tips as to a good solution for this would be much appreciated. Should I not be using a table?

Thanks.

[Ben Souther]

Have you considered nested List <UL><LI>... objects?

[Gregg Bolinger]

Adding some opening and closing TR elements seems to fix some of the issues. My code now looks like:

<c:forEach var="part" items="${ actionBean.partList }">
  <tr>
    <td>${ part.ident }</td>
    <c:forEach var="charGroup" items="${ part.modelCharGrps }">
      <td rowspan="${ fn:length(charGroup.modelChars) }">${ charGroup.ident }</td>
      <c:forEach var="modelChar" items="${ charGroup.modelChars }">
        <td>${ modelChar.ident }</td>
        </tr>
        <tr>                            
      </c:forEach>
      </tr>
      <tr>
    </c:forEach>                           
  </td>
  </tr>
</c:forEach>

I'll keep plugging away.
[ January 10, 2007: Message edited by: Gregg Bolinger ]

[Gregg Bolinger]

Originally posted by Ben Souther:
Have you considered nested List <UL><LI>... objects?

Yea, I thought about that. What would be the best way to get the indenting I need for the columns on the nested elements?

[Ben Souther]

Hmm
I wasn't thinking about lining up the columns.
Maybe tables would make more sense.

Is is always the same number of columns?

[Gregg Bolinger]

Originally posted by Ben Souther:
Hmm
I wasn't thinking about lining up the columns.
Maybe tables would make more sense.

Is is always the same number of columns?

Yes, it's always the same number of columns. I kind of like the UL LI idea. Been playing around with it. Problem is getting the LI widths to work right. If I text-alright: right, then the bullets don't line up.

[Ben Souther]

This one is a little uglier but it will allow you to create a simple HTML table:

                                                                                           
     19 <table border="1">
     20   <c:forEach var="parent" items="${parentList}">
     21       <c:set var="pname" value="${parent.name}" />
     22       <c:forEach var="child" items="${parent.children}">
     23         <tr>
     24           <td>
     25             <c:if test="${pname != ''}">
     26               ${pname}
     27               <c:set var="pname" value="" />
     28             </c:if>
     29           </td>
     30           <td>${child.name}</td>
     31         </tr>
     32       </c:forEach>
     33   </c:forEach>
     34 </table>
 

 

 
    

[Ben Souther]

I think, if it were my issue, I'd flatten the table out in the Java code and just pass a list of row beans to the JSP page.

[Gregg Bolinger]

Originally posted by Ben Souther:
I think, if it were my issue, I'd flatten the table out in the Java code and just pass a list of row beans to the JSP page.

Darn good suggestion. Thanks Ben.

[Stefan Evans]

You could do it in JSTL by storing the "last" entry printed for each of the repeating fields, and only print it out if it changes..

Just for fun...

<c:set var="lastPartIdent" value="dummyValue"/>
<c:set var="lastChargroupIdent" value="dummyValue"/>
<c:forEach var="part" items="${ actionBean.partList }">
  <c:forEach var="charGroup" items="${ part.modelCharGrps }">
    <c:forEach var="modelChar" items="${ charGroup.modelChars }">
      <tr>
        <td><c:if test="${part.ident != lastPartIdent}">${ part.ident }</c:if> </td>
        <td><c:if test="${charGroup.ident != lastChargroupIdent}">${ charGroup.ident }</c:if> </td>
        <td>${ modelChar.ident }</td>
      </tr>
      <c:set var="lastPartIdent" value="${ part.ident }"/>
      <c:set var="lastChargroupIdent" value="${ charGroup.ident }"/>
    </c:forEach>
  </c:forEach>                           
</c:forEach>

[Joel Jorgensen]

The c:forEach tag also allows you to track the status of the loop if you use the "varStatus" attribute (e.g. varStatus="charGroupStatus"). You can then use c:if tags to check whether the index is 0 (i.e. whether it is the first time through the loop) and print out the cells accordingly.

Like so:

<c:forEach var="part" items="${ actionBean.partList }">
  <c:forEach var="charGroup" items="${ part.modelCharGrps }" varStatus="charGroupStatus">
    <c:forEach var="modelChar" items="${ charGroup.modelChars }" varStatus="modelCharStatus">
      <tr>
        <td>
          <c:if test="${charGroupStatus.index == 0}">
            ${ part.ident }
          </c:if>
        </td>
        <td>
          <c:if test="${modelCharStatus.index == 0}">
            ${ charGroup.ident }
          </c:if>
        </td>
        <td>
          ${ modelChar.ident }
        </td>
      </tr>
    </c:forEach>
  </c:forEach>                           
</c:forEach>

This might not be the most efficient way to do it (because it does the two if checks for every single modelChar), but it seems readable and doesn't involve slightly unsual </tr> <tr> pairs (which the other solution that I thought of would require ;) ) and as long as you don't have thousands upon thousands of modelChars you can probably get away with it