JSP Insert footer based on condition in for loop

问题:

I want to loop a table of records for printing, based on the following condition:

If the number of records is more than 35, I will need to pause the loop, insert a footer, and a new header for the next page and continue its count till the last record.

The condition here is to use only jsp classic scriplet.

Here is what I have and I am stuck: (in pseudo code format)

<% int j=0;
   for(int i=0; i < list.size(); i++){
    col1 = list.get(i).getItem1();
    col2 = list.get(i).getItem2();
    col3 = list.get(i).getItem3();
    j++;

    if (j==35) {%> // stops to render footer and next page's header 
    </table>
    <table>
       <!-- footer contents -->
    </table>
    <table>
       <!-- header for next page -->
    </table>
    <%}%>
<tr><td><%=col1%></td><td><%=col1%></td><td><%=col1%></td></tr>

<%}%>

the problem with this model is that if I use a break inside this if, I'd stop the loop and I can't loop from record #36 to end of record. How do I go about doing this?

回答1:

Use an if (i % 35 == 0) to write the footer and then validate if there are more elements in the list so you would have to add a new table and its header. The code would look like this:

<!-- table header -->
<%
int size = list.size();
int i = 0;
for(Iterator<YourObject> it = list.iterator(); it.hasNext(); ) {
    i++;
    YourObject someObject = it.next();
    col1 = someObject.getItem1();
    col2 = someObject.getItem2();
    col3 = someObject.getItem3();
    if (i % 35 == 0) {
%>
    <!-- table footer -->
<%
        if (i < size) {
%>
    <!-- breakline and new table header -->
<%
        }
    }
}
%>
<!-- table footer -->

Note that in this code sample I'm using Iterator instead of List#get(int index) since if your List is a LinkedList internally it would need to traverse all the elements until reach the element on the desired index (in this case, i). With this implementation, your code is even cleaner.

回答2:

If you don't want to use proper pagination then use JSTL as below. Easier to read than scrip-lets as well, apart from the obvious benefits.

//The counter variable initialization
<c:set var="counter" value="0" scope="page"/>
<c:forEach items="${itemList}" var="item">

  //Counter increment
  <c:set var="counter" value="${counter + 1}" scope="page"/>
  <tr>
    <td>${item.propertyOne}</td>
    <td>${item.propertyOne}</td>
  </tr>
  <c:if test="${counter % 35 == 0}">
    //Include your footer here.
  </c:if>
</c:forEach>