How can I get the content from a session variable?

Question

My situation:

On my jsp site I show a table. When somebody click a row, this row must be marked with an other backround color for example. Also more then one row can be marked. Two things are important. First: I bear in mind which rows are marked. Secend: In which order.

My idea is:

I have a ArrayList and put all row IDs in this. So I solve both problems. Now I put this ArrayList in the session for the next click and the row ID ( req.getSession().setAttribute(req.getParameter("rowID") , ""+arrayList.size()); ) for the jsp file.

My problem in jsp file:

I don't now what's called session variable name.

if this rowId alrady clicked? ..

I have got only the bean name. How can I get the content from the session, if exact this line must be marked?

Normally I set a session variable so: req.getSession.setAttribut("printView", Boolean.TRUE) and get a session variable so:

I work with struts, formbeans and jsp.

Sorry, I haven't good English and this problem is so difficult for me. So I can't declare it better at this time.

Answer 1

Let's first analyze what you are storing in session:

req.getSession().setAttribute(req.getParameter("rowID") , ""+arrayList.size());

req.getParameter("rowID") returns String value of the request parameter. If your page link is yourPage.jsp?rowID=3 its value will be "3". This value will be used as a key in the invocation of the method HttpSession#setAttribute(String, Object).

""+arrayList.size() is just a String representation of the size of your arrayList in which you are trying to store IDs of clicked rows

Answer to your question "I don't now what's called session variable name." cannot be given since it depends on the value of rowID request parameter.

If you want to check what is in the session just iterate through its attributes:

for (Enumeration elem : req.getSession().getAttributeNames()) {
    String name = elem.nextElement();
    System.out.println(name + " : " + req.getSession().getAttribute(name));
}

If you don't store your arrayList in the session previous code will probably return something like this:

1 : 0
5 : 0
1 : 0

As Vinegar suggested I would do next:

String clickedRowId = req.getParameter("rowID");
List<String> arrayList = (List)req.getSession().getAttribute("clickedRows");
if (!arrayList.contains(clickedRowId)) {
    arrayList.add(clickedRowId);
}
req.getSession().setAttribute("clickedRows", arrayList);

Your arrayList will be holding a list of clicked row IDs and their indices will be telling you about their chronological order.

Note: There are certainly better and more scalable ways to achieve this. Anyway, it's a good idea to implement your solution and then look for a better one.

Answer 2

Thank you very much. How evaluate the arryList in jsp file, which is in session?

<datagrid:tableEx ...>
<c:if test="${ arrayList.contains(bean.rowID)}">
 <div id="tableheader">
                 <datagrid:column property="bean.rowID" ... bgcolor="#BDC6DD"/>
                 <datagrid:column ... bgcolor="#BDC6DD" />
                 <datagrid:column ... bgcolor="#BDC6DD" />
                  ...
 </div>
</c:if>
<c:if test="${!arrayList.contains(bean.rowID)}">
 <div id="tableheader">
                 <datagrid:column property="bean.rowID"/>
                 <datagrid:column ... />
                 <datagrid:column ... /> 
            </div>
</c:if>