
  The Blender/Python API can’t (yet)...
  ...
  - Define callbacks or listeners to be notified when data is changed.


Source: API docs

App handlers can't be created with Python, they need to the coded in C. The fact that registering arbitrary event callback isn't supported suggests that such an event driven design is not intended in Blender.

Possible to create new Application Handler?
I wrote this code in order to display the name of employee who has the maximum salary 
but when the output wasn't correct it appeared null not "mmm kkk" !! although I filled the table and this is the contents :

HERE

this is my code, can any one help me ?? :(

 public static void displayMaxSalary() throws ClassNotFoundException, SQLException

{   
    int size=0;
    int count=0;
    String maxSalary=null;
    Class.forName("com.mysql.jdbc.Driver");
    Connection con = DriverManager.getConnection("jdbc:mysql://localhost/task4DB?"
              + "user=root&amp;password=123");
    PreparedStatement st = con.prepareStatement("select * from task4Table ");
    ResultSet r1=st.executeQuery();

      while (r1.next()) {

          size++;
      }


      int salaries[]=new int[size];
      String Names[]=new String[size];

       while (r1.next()) {


          salaries[count]= r1.getInt("salary");
          Names[count]=  r1.getString("fName")+""+r1.getString("lName");
          count++;
      }

       for(int i=1;i&lt; salaries.length;i++)

       {
           if(salaries[i]&gt;salaries[i-1])
           {
               maxSalary= Names[i];
           }

       }


     System.out.println("The name of employee who has the higher salary is :");
     System.out.println( maxSalary);



} //end-displayMaxSalary.

