Re: Need help with JDBC code walk

Lew <>
Wed, 26 Mar 2008 23:44:57 -0400
<> wrote:

This is the crux: when I take away the JDBC calls everything works
fine except for the session persistence between server reboots. I

There are some problems in the code, including in the JDBC, but I don't know
if they cause your trouble.

Imports not shown... no compile time errors like
objects returned null; Typically the select component of JSF gets a
null enumeration.


 * This class provides methods to interact with the session. Its
exposes methods to put and get objects into
 * Session and also exposes methods to do cleanup.
 * @author rajasekhark
public class SessionManager {

   * Sets an attribute in the session. These attributes would be
independent of the module,
   * and would be removed when the session expires. Or
<code>flush(HttpSession session)</code>
   * is called in the session.
   * @param key
   * @param value
   * @param session
   * @throws InvalidParameterException
  public static void setAttribute(String key, Object value,
HttpSession session)
                                    throws InvalidParameterException{

Crazy indentation and the lack of braces on 'if' blocks make for difficult
code to read.

Use logging instead of System.out.println(). (Even if you use println() for
debugging, it should be to System.err, but logging is much, much better.)

I'm just going to delete the superfluous System.out.println() lines. They
really don't belong in a Usenet listing anyway.

if (value == null) {

You said you're using JBoss? Don't use System.exit() in an application
container like JBoss or Tomcat or whatever.


    String sessid = (String)session.getId();

You don't need to cast a String to a String.

     UserContext ucon = (UserContext)
    String uid="";
    if (ucon != null)
        String uname="";

Indentation and braces - confusing when they aren't right.

     if (ucon != null) uname=ucon.getStrUserName();
if (uname == null) uname="";

if (!sessid.equals("notset") && uid !=null && !uid.equals("")) {
Connection conn = null;
ResultSet rs=null;
PreparedStatement ps=null;

               String userName = "jboss";
               String password = "*********";
               String url = "jdbc:mysql://localhost:3306/jsfsession";
               Class.forName ("com.mysql.jdbc.Driver").newInstance ();

You only need to load the JDBC driver once per application run, not repeatedly
on every single freaking connection, and never need to instantiate it explicitly.

               conn = DriverManager.getConnection (url, userName,

 ps = conn.prepareStatement("update session_tbl set val=?,
datestamp=NOW() where keyid=? and sessid=?");
        ps.setString(3, sessid);
        ps.setString(2, key);

ByteArrayOutputStream baos1 = new ByteArrayOutputStream();

ObjectOutputStream oout1 = new ObjectOutputStream(baos1);

Luckily for you, ByteArrayOutputStreams don't close.

ps.setBytes(1, baos1.toByteArray());

        int r=ps.executeUpdate();


        if (r==0) {
          ps = conn.prepareStatement("insert into session_tbl (sessid, uid,
keyid, val, uname, datestamp) values (?, ?, ?, ?, ?, NOW())");
        ps.setString(1, sessid);
        ps.setString(2, uid);
        ps.setString(3, key);

        ByteArrayOutputStream baos2 = new ByteArrayOutputStream();
ObjectOutputStream oout2 = new ObjectOutputStream(baos2);
ps.setBytes(4, baos2.toByteArray());

        ps.setString(5, uname);

How come you don't check for the return value of this execution?

           catch (Exception e)
               System.err.println ("Cannot connect to database server"
+ e.getMessage());

You ignore this error after logging it. does you r log show any errors?

BTW, errors other than inability to connect will trigger this catch block.
Also, your error message is extremely weak; it would never help anyone in
operations track down an error.

As you might have seen for yourself by now.

        if (ps != null) {
            try {
            } catch (Exception e2) {};
               if (conn != null)
                       conn.close ();
                       System.out.println ("Setattribute Database
connection terminated");
                   catch (Exception e) { /* ignore close errors */ }
} //if

Now suddenly you switch to a whole different functionality inside the same
method. Consider refactoring - it'll make bugs like yours easier to solve.


          //checks if the key is null or empty. Throws an exception if
it is.
          if(null == key || "" == key){

Don't compare Strings with ==, use equals(). This test might be letting an
empty String through to the following logic. Would that cause your error?

              Object [] values = new Object[1];
              values[0] = "key";
              throw new

This exception is from the package - probably not the right
package. What's wrong with java.lang.IllegalArgumentException?

That would be the normal choice.


Huh? "//end-if"? The block is only three lines long - did you think people
would forget?

          if(null == session){
              Object [] values = new Object[1];
              values[0] = "session";
              throw new

          //set the session attribute
          session.setAttribute(key, value);
      }catch(RuntimeException ex){
          throw new InvalidParameterException(ex);

Since is already a RuntimeException,
and the only one that will be thrown by the try block, you are rethrowing the
original exception wrapped in another instance of the same type of exception.
  Why catch-and-rethrow at all? You could just let the exception through.

The java.lang.IllegalArgumentException. Of which InvalidParameterException is
a subtype. From the package, when this isn't a security error.

    System.out.println("leaving set attribute");
  }//end setAttribute

You aren't doing a very good job of checking for or handling the various
SQLExceptions that could occur in your JDBC code. One of them might be
triggering the behavior you see.


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