Dangling Connections

Question

Hi all,
The connectivity program that i used for my application is as follows:
public Vector selectQueryReports(String serverid, String dbName,String query){
     Connection conn = null;
     Statement  stmt = null;
     ResultSet  rs   = null;
     Vector vReportRecords = new Vector();
      try{
               conn = getConnection(serverid,dbName);
               stmt = conn.createStatement();
               rs = stmt.executeQuery(query);
               while(rs.next())
                    vReportRecords.add(rs.getString("userid"));
                    vReportRecords.add(rs.getString("chapterid"));
                    vReportRecords.add(rs.getString("chauthor"));
                    vReportRecords.add(rs.getString("ebookisbn"));
                    vReportRecords.add(rs.getString("pagecount"));
                    vReportRecords.add(rs.getString("chtitle"));
                    vReportRecords.add(rs.getString("source"));
               } // while(rs.next())
               System.out.println("! Query : "+query);
          }catch(Exception e){
               //System.out.println("!! Exception in DatabaseConnect.selectQuery() : "+e);
               System.out.println("Exception in dbgeneric.DatabaseConnect.selectQuery() ="+e);
               System.out.println("!! Query : "+query);
               return null;
          finally
               try
                    if(rs != null) rs.close();
                    if(stmt != null) stmt.close();
                    if(conn != null) conn.close();
               }catch(Exception e)
      return vReportRecords;
}// end of selectQueryReports */
//getConnection function:
   public Connection getConnection(String serverid, String dbName){
         Connection conn = null;
     try{
          //debug(".......serverid   : "+serverid);
          //debug(".......dbName     : "+dbName);
        utility.ConfigProperties obCP = new utility.ConfigProperties();
         String user     = obCP.getValue(serverid+"_user");
         String password = obCP.getValue(serverid+"_password");
         String driver   = obCP.getValue(serverid+"_driver");
         Context env = (Context) new InitialContext().lookup("java:comp/env");
          DataSource ds=null;
          if(dbName.equals("DXMGHReaderCache"))
               ds = (DataSource) env.lookup("jdbc/dxreadercache");
          else if(dbName.equals("DXMGHReaderDB"))
               ds = (DataSource) env.lookup("jdbc/dxreaderuser");
           String url = "jdbc:mysql://localhost:3306/"+dbName+"?user="+user+"&password="+password;
           //debug("......getConnection() url : "+url);
           conn = ds.getConnection();
        }catch(Exception e){
            System.out.println("Exception in dbgeneric.DatabaseConnect.getConnection() ="+e);
           return null;
      return conn;
   }The vector is returned fine.........
but followring stack trace appears........
[00:38:12.536] Closing dangling connections.  All connections must have a close() in a finally block.
[00:38:12.536] java.lang.IllegalStateException: Connection com.caucho.sql.ManagedConnectionImpl@130453 was not closed. Connections must have a close() in a finally block.
[00:38:12.536]  at com.caucho.jca.UserTransactionImpl.abortTransaction(UserTransactionImpl.java:253)
[00:38:12.536]  at com.caucho.jca.UserTransactionProxy.abortTransaction(UserTransactionProxy.java:175)
[00:38:12.536]  at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:193)
[00:38:12.536]  at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:221)
[00:38:12.536]  at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:262)
[00:38:12.536]  at com.caucho.server.port.TcpConnection.run(TcpConnection.java:315)
[00:38:12.536]  at com.caucho.util.ThreadPool.runTasks(ThreadPool.java:353)
[00:38:12.536]  at com.caucho.util.ThreadPool.run(ThreadPool.java:302)
[00:38:12.536]  at java.lang.Thread.run(Thread.java:534)i didn't understand where is the problem actually evenif the connection is closed successfully in the finally block........
Plz help me.....
Thanx,
Reema.

Answer 1

HI,
As the stack trace reveals, somewhere in your code you have used try...catch... finally, and the connection that you have opened in the try block, you haven't closed in the finally block.
To be more clear, the finally block must close any connection that are opened in the try block. This is to ensure that the connection should definitely close whether or not the exception occurs.
This will free your application from dangling connections.
I think my views will help you.