Question

I have a question on how to update a particular record in a database using JSTL and java servlets.

Ok to call one record, I use a servlet to run a query to populate a jsp page using this type of format.

        ResultSet results = getRecords.executeQuery();  //run database query
        Result result = ResultSupport.toResult(results);  
        request.setAttribute("result", result);
        RequestDispatcher rd = request.getRequestDispatcher("/showReport.jsp");  //redirect to this page with query info
        rd.forward(request, response);

In the jsp page, I use this format to populate the page.
the row number is the corresponding to the index of the value on how the query is run.

    <c:forEach var="row" items="${result.rowsByIndex}"> 
<form action = "/runthis/servlet?id=${row[0]}" method = "get" >
    Employee Name<input type="text"  value="<c:out value="${row[2]}"/>" />
    Department<select>
    <option value="<c:out value="${row[4]}"/>"><c:out value="${row[4]}"/></option></select>
<input type="submit" value="Save">
</form>
    </c:forEach>

So for instance, if someone changes the Employee Name, but leaves the Department field alone, or vice versa, how would I go about this?

I think I should be able to kick this form action to a “update servlet”, but I would rather not “update” every element in the record if I do not need to.

Also I’m still learning web dev, so if you can think of a better way to prepopulate stuff, via javascript or whatever, I’m willing to try that as well, if it’s a possible solution.

Thanks for any help!

Answer 1

i think you need to do something like this:

<c:forEach var="row" items="${result.rowsByIndex}"> 
    <form action="/runthis/servlet" method="post">
        <input type="hidden" name="id" value="<c:out value="${row[1]}"/>" />
        <input type="hidden" name="EmployeeName_orig" value="<c:out value="${row[2]}"/>" />
        Employee Name<input type="text" name="EmployeeName" value="<c:out value="${row[2]}"/>" />
        <input type="hidden" name="Department_orig" value="<c:out value="${row[4]}"/>" />
        Department
        <select id="Department" name="Department">
            <option value="<c:out value="${row[4]}"/>"><c:out value="${row[4]}"/></option>
        </select>
        <input type="submit" value="Save" />
    </form>
</c:forEach>

and then, in your update servlet (here called /runthis/servlet) you do some form of update employee and set the name and department where the row is id. note that i send the id in a hidden field, but it could just as well be sent in the url as you mentioned in our discussion above!

about your remark on updating every element in a record:

this can be done in different ways. one way is to load the record from database first, and compare the fields to know what fields to update. but that would require an extra read from the database before the update.

another way (the one i have prepared for in my proposed solution) is to have hidden fields, one for each input in your form. this hidden field holds the original value for its input counterpart. this way you can compare the original value with the new value without having to do a read from the database. on the other hand, you’re now transferring the double amount of data over the line for each post request.