transaction manager test JSP

<%@ page import="javax.transaction.TransactionManager" %>
<%@ page import="javax.transaction.TransactionSynchronizationRegistry" %>
<%@ page import="javax.naming.InitialContext" %>
<%@ page import="java.sql.Connection" %>
<%@ page import="javax.sql.DataSource" %>
<%@ page import="java.sql.Statement" %>
<%@ page import="java.sql.ResultSet" %>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title></title>
  </head>
  <body>


  <%!
      private static TransactionManager txManager;

      static {

          try {

              InitialContext ic = new InitialContext();

              txManager = (TransactionManager)
                      ic.lookup("java:appserver/TransactionManager");

          } catch (Throwable th) {
              throw new RuntimeException(th);
          }

      }

  %>

  <%

      TransactionManager tMgr = txManager;
      tMgr.begin();

      InitialContext ic = new InitialContext();
      DataSource ds = (DataSource) ic.lookup("mi_pe");
      Connection conn = ds.getConnection();

      Statement s = conn.createStatement();
      ResultSet rs = s.executeQuery("select nmr from inc_test");
      rs.next();
  %>

    Before : <%=rs.getLong("nmr")%><br>

  <%
      s.close();

      s = conn.createStatement();
      s.execute("update inc_test set nmr = nmr + 1");
      s.close();

      tMgr.rollback();
      conn.close();

      tMgr.begin();
      // re-create another connection in a new transaction

      ic = new InitialContext();
      ds = (DataSource) ic.lookup("mi_pe");
      conn = ds.getConnection();
      s = conn.createStatement();
      rs = s.executeQuery("select nmr from inc_test");
      rs.next();

  %>

  After : <%=rs.getLong("nmr")%><br>

  <%

      s.close();
      tMgr.rollback();
      conn.close();

  %>


  </body>
</html>