Trying to migrate away from Scriptlets.. need some advice...

Question

I have both created and inherited some seriously horrible JSP's that have a lot of business logic and scriptlets in them. What I am looking to do is:
1 - Clean up the JSP's
2 - Move away from scriptlets
3 - Move all business logic to the back end
4 - Create custom tag's where I can to simplify the JSP's and clean up code logic.
Here is just a small example of what the other coders on my team did before they were "axed". They put ResultSet logic into the actual served JSP itself.
What would the best (meaning the correct way) of doing away with this logic in the JSP be? I thought of writing a set of tags that would convert a ResultSet to an ArrayList then iterate over the arraylists to populate the DDL's, but that is not my strong point. There is no time like the present to learn taglibs though :). This way I can hit the DB, get the data that is read only and release the connection back into the ConnectionPool. Am I going at this the wrong way? Can someone possibly post an example of how a JSP should ideally look?
<table border="0">
<%for (int i = 1; i <= tableContentsMD.getColumnCount(); i++){
   String colName = tableContentsMD.getColumnName(i);
   String colVal = singleTableRowRS.getString(i);
   if (colName.equals(tablename + "_id") || colName.equals("status")){%>
          <input type="hidden" name="<%=colName%>" value="<%=colVal%>">
          <% continue;
   }%>
  <tr>
     <td class="textblack_td" style="text-align:left;">
          <%String m = GeneralFunctions.stringMasker(tableContentsMD.getColumnName(i));
          out.print(m);%>:
     </td>
     <td style="text-align:left;">
          <%if(colName.equals("parent_"+tablename+"_id")){%>
               <select name="<%=colName%>" style="width:180px;">
               <%
                    String selected = "selected=\"selected\"";
                    PKName = null;
                    PKID = null;
                    ResultSet primaryKeyTableRS = GeneralFunctions.getTableContentsABC(tablename);
                    if(tablename.equals("department")){%>
                        <option value="0" <%= colVal.equals("0") ? selected : "" %>>-No Parent Department-</option>
                    <%}
                    while (primaryKeyTableRS.next()) {
                         PKName = primaryKeyTableRS.getString(tablename + "_name");
                         PKID = primaryKeyTableRS.getString(tablename + "_id");
                         if(!(id.equals(PKID) || PKName.equals("default"))){%>
                              <option value="<%=PKID %>" <%= colVal.equals(PKID) ? selected : "" %>><%=PKName %></option>
                         <%}
                    GeneralFunctions.closeResources(primaryKeyTableRS);%>
          </select>
          <%}
          else
          {%>
          <div class="alert_text">
               <input type="text" name="<%=colName%>" value="<%=colVal %>" style="width:175px;">
               <%if (tablename.equalsIgnoreCase("occupation") || tablename.equalsIgnoreCase("department")){%>
               <%}%>
          </div>
          <%}%>
     </td>
<%}%>
     </tr>
</table>Thanks in advance for any insight you can provide.
- Josh

Answer 1

TheWhiteKnight wrote:
I need to start very small in what I do. Removing the SQL calls is optimal yes, but if I cam even start with removing all the ResultSet's from the JSP's (it's kind of a similar goal). I mean there is a list a mile long. I want to create objects instead of dealing with SQL calls to constantly get data. For Ex. - With the program, you log in, get a RS for your data. At that point (ideally to me) it should load ALL of your user info into an object (user name, session authentication, role, department, occupation, etc.) As of right now it doesn't. Every time you need the information(except your user name & role), you have to re-query the DB. So you see, there is a LOT of overhead to the server.
On this I would suggest caution. Before you consider loading ALL of the info into an object, you should analyse
1. How many screens/request flow require the entire dataset?
2. How often does a user navigate to such screens/flows?
If it's not a frequently used screen/scenario, you can maintain a minimal (absolutely essential and frequently referred to) data in the object and then progressively build up the data in the object as the user navigates to the screens/flows where such dataset is required.
For example you can have two dao methods -
1. getBasicUserInfo() for the minimalistic dataset and
2. fillUpUserInfo(User u) which takes a User object and fills it up with all data from the db.
You can even model objects accordingly
1. BasicUserInfo (which contains minimalistic fields - say id, name and dept)
2. UserInfo extends BasicUserInfo (which has all the other fields)
And then your second dao() method would be
public UserInfo fillUpUserInfo(BasicUserInfo u).........
This is especially important if the User object is held in session because when you use large and heavy objects in session, memory becomes a constraint sometimes as the number of concurrent users on your system increases. Also it provides clean seperation when you have different kinds of Users.
ram.
Edit
1. Metadata, should always of course be cached.
2. All result sets should be closed before returning from the dao layer. Just to be clear, when I said have 2 methods, I didnt mean keep the result set open :)