/*
 * @author Elango 
 * @version 1.2
 *
 * Development Environment        :  Oracle9i JDeveloper 
 * Name of the Application        :  InheritanceSample.java
 * Creation/Modification History  :
 *
 *     Elango       21-Aug-2001      Created
 *     Venky        09-Oct-2001      Modified for SQLJ implementation
 *     Stephen      2-Apr-2003       Certified on Linux
 * 
 */ 


package oracle.otnsamples.sqlj.inheritance;

// import for JDBC classes
import java.sql.Connection;
import java.sql.SQLException;
import java.math.BigDecimal;

//import sqlj related classes
import oracle.sqlj.runtime.Oracle;


/**
 * Sample scenario 
 *         Consider a Residential University where the major players are 
 *  Students,Teachers and Parttime Students. This model has a Person object 
 *  which is the super type with attributes which are common to all persons such 
 *  as SSN, Name, Dateofbirth, sex and Address. It has two sub-types, a Teacher and 
 *  a Student. Teacher has addtional attributes like courses taught,salary and 
 *  date of joining. Student has courses taken, grade and year of completion.
 *  A Parttime student is a sub-type of student with some additional attributes 
 *  such as No of hours, Start time and Batch code. All the sub-types have 
 *  overriden methods for setting and retrieving the attributes.
 *
 * This sample illustrates 
 *
 *     1. Overloading Methods :- Here the method  getPersonDetails() is 
 *     overloaded. When invoked on Student Object, this method returns 
 *     the courses taken, grade etc information apart from Name, Address 
 *     information. When invoked on Teacher Object, this method returns the 
 *     information like courses taught, Salary, Dept apart from Name, Address. 
 *
 *     2. Dynamic Method Dispatch :- This is nothing but run-time polymorphism. 
 *     When you invoke a overriden method, the implementation of the methods is 
 *     searched , beginning from the current object , the method is searched
 *     upwards ( the type and then , all the super types of type).
 *     In other words, if setAddress() in invoked from a Student Object, then 
 *     method in Person Object is invoked ,since there is no implementation of
 *     setAddress() in Student Object but if the same method is called from 
 *     a Teacher object the implementation in the Teacher Object is called.
 *
 *     3. Substituting Types in a Type Hierarchy :-  A base object type can hold
 *     any of its sub-types objects (i.e) Person is the base type and it can 
 *     hold either a Student , Teacher or a parttimestudent object which are 
 *     sub-types of Person.
 *
 * In this sample the user can View/Edit person details. 
 *
 * For viewing person details, the overrided getPersonDetails() method is 
 * called which returns a String representation of the Object attributes.
 * 
 * For editing person details, the overrided setPersonDetails() method is
 * called, which sets the attributes and calls the setAddress() method for 
 * setting the address.
 *
 * The gui part of this sample is handled separately in PersonFrame.java
 */

public class InheritanceSample {
  private PersonFrame gui;              // Handle gui
  private Connection conn;                    

  /**
   * Constructor. Initializes the frame 
   */
  public InheritanceSample() {
    try {
      gui = new PersonFrame(this);
    } catch(Exception ex) {
      gui.putStatus(" Error : Couldn't  Initialize frame , "+ex.toString());
    }
  }

  /**
   * Main entry point for the class. Creates an object and calls the dbConnect()
   * method to establish connection to database. Sets the map between the java
   * classes and object types in the database.Invokes the displayPersonDetails()
   * to retrieve SSN,Name and Object type of the Objects inside the 
   * PersonDetails table.
   */
  public static void main(String args[])  {
    // Create an object of the Sample
    InheritanceSample inheritanceSample = new InheritanceSample();

    // Connect to the database
    inheritanceSample.dbConnect();

    // Display SSN, Name and Object type from PersonDetails table
    inheritanceSample.displayPersonDetails();
  }

  /**
   *  Connect to the database using the connection parameters specified in the 
   *  Connection.properties file.
   */
  void dbConnect() {
    try{
      gui.putStatus(" Connecting  to Database ....");      
      Oracle.connect(this.getClass(), "../../../../Connection.properties");
      gui.putStatus(" Connected to Database ...");
    }catch(Exception ex){   // Trap errors 
      System.out.println("Error while Connecting  to the database:  "+
          ex.toString());
      System.exit(0);
    }
  }

  /**
   * Dispatches the gui events to the appropriate method, which performs
   * the required SQLJ operations. This method is invoked when event occurs
   * in the gui (like table Selection, Button clicks etc.). This method
   * is invoked from the setupListeners section of PersonFrame.java
   */
  public void dispatchEvent (String eventName) {
    if (eventName.equals("GET PERSON DETAILS"))
      // Displays the person details in ViewPersonDetailsFrame
      selectPersonDetails(); 
      
    if (eventName.equals("SHOW PERSON DETAILS"))
      // Shows the person details in EditPersonDetailsFrame for editing   
      showPersonDetails();
       
    if (eventName.equals("SET PERSON DETAILS"))
      //  Updates the person details to the table
      setPersonDetails();

    if (eventName.equals("EXIT"))
      // performs clean up and closes the application
      exitApplication();
  }

  
  /**
   * This method retrieves the objects from the PersonDetails table and displays
   * SSN, Name and Object type of objects in a JTable.
   */
  private void displayPersonDetails() {
    String    ssnNo    = null;
    String    fullName = null;
    String    objType  = null;

    Student st=new Student();
    ParttimeStudent ps=new ParttimeStudent();
    Teacher t=new Teacher();
   
    // To hold the retrieved object
    Person personObj=null;
    #sql iterator objectIter (Person);
    objectIter  tempIter=null;
  
    try {
      #sql  tempIter={SELECT P.PERSON FROM PERSONDETAILS P};
      while(true){
        #sql { FETCH :tempIter INTO :personObj};
        if(tempIter.endFetch())break;

        /* Retrieve the object and assign it to a person object, a person object
          can hold all its sub-types objects (substitutability) */

        /* An object of parttimestudent will also be an instance of student, 
          since parttimestudent is a sub-type of student. Hence the retrieved
          object is first compared with a partimestudent and then with a 
          student(a student object will not be an instance of parttimestudent)
        */

        // If the retrieved object is a parttimestudent
        if(personObj instanceof ParttimeStudent) 
          objType=" P ";

        // If the retrieved object is a student          
        else if(personObj instanceof Student) 
          objType=" S ";

        // If the retrieved object is a teacher        
        else if(personObj instanceof Teacher) 
          objType=" T ";

        // Some other sub-type of person  
        else
          objType=" O ";

        // Get the SSN
        ssnNo = personObj.getSsn();

        // Get the full name 
        fullName = personObj.getFirstname() + "  " + personObj.getLastname();          

        // Add a row in the person table
        gui.addToJTable(ssnNo,fullName,objType);
      }
      gui.putStatus(" Select a person ...");  
    } catch(Exception ex) {          // Trap errors
      gui.putStatus("Error while Displaying : "+ex.toString());
    } finally {
      try {
        tempIter.close();
      } catch(SQLException sqe){
        gui.putStatus("Error while Displaying : "+sqe.toString());
      }
    }
  }

  /**
   * This method retrieves the person details and displays it in the 
   * ViewPersonDetailsFrame.java
   */

  private void selectPersonDetails() {

    // Call the getSelectedPerson() method to retrieve the Person object
    // from the database 
    Person personObj = getSelectedPerson();
    if(personObj != null) {          
      try {  
        // If the retrieved object is a parttimestudent
        if(personObj instanceof ParttimeStudent) {
          // Get the parttimestudent object
          ParttimeStudent pstudent = (ParttimeStudent)personObj;
       
          // call the getpersondetails() member function of the parttimestudent
          // object ,it returns all the attributes of a parttime student object 
          gui.viewPerson.showParttime_studentDetails(
          pstudent.getpersondetails());
        }

        // If the retrieved object is a student
        else if(personObj instanceof Student) {
          // Get the Student object
          Student student = (Student)personObj;
        
          //* call the getpersondetails() member function of the student
          //object ,it returns all the attributes of a student object
          gui.viewPerson.showStudentDetails(student.getpersondetails());
        }

          // If the retrieved object is a teacher
          else if(personObj instanceof Teacher) {
            // Get the teacher object
            Teacher teacher = (Teacher)personObj;
        
            // call the getpersondetails() member function of the teacher object, 
            //it returns all the attributes of a teacher
            gui.viewPerson.showTeacherDetails(teacher.getpersondetails());
          }
          // hide the PersonFrame
          gui.setVisible(false);
      } catch(Exception ex) {       // Trap errors
        gui.putStatus("Error while Selecting:  "+ex.toString());
      } 
    }
  }

  /**
   * This method retrieves the person object and displays the attributes in the
   * EditPersonDetailsFrame for editing.
   */
  private void showPersonDetails() {
    // Call the getSelectedPerson() method to retrieve the Person object
    // from the database 
    Person personObj = getSelectedPerson();
    if(personObj != null)      
      // Display the person object
      gui.editPerson.showPersonDetails(personObj);
  }

  /**
   *  Update the person details to the database
   */
  private void setPersonDetails() {
    // Update the edited fields to the Object
    Person personObj = preparePerson();
    try {
      String ssn = personObj.getSsn();
      #sql  {UPDATE PERSONDETAILS P SET P.PERSON =:personObj WHERE
      P.PERSON.ssn= :ssn };
      #sql {COMMIT};
    } catch(Exception ex) {    // Trap errors
      gui.putStatus("Error while updating person:  "+ex.toString());
    }    
  }
  
  /**
   *  Update the attributes of the person object with the edited values
   */
  private Person preparePerson() {
    // Object of the EditPersonDetailsFrame
    EditPersonDetailsFrame EditFrame = gui.editPerson;

    // The person object that was edited
    Person personObj = gui.personObj;

    // if the person is a Parttimestudent
    if(personObj instanceof ParttimeStudent) {
      // Get the parttime student object
      ParttimeStudent pstudent   =  (ParttimeStudent)personObj;        

      // Get the edited values
      String Grade                       =   EditFrame.txtGrade.getText();
      String Yearofcompletion    =   EditFrame.txtYearofCompletion.getText();
      String Coursestaken           =   EditFrame.txtCoursesTaken.getText();
      BigDecimal Hours              =   new BigDecimal(EditFrame.txtHours.getText());
      String Batchcode              =   EditFrame.txtBatchCode.getText();
      String Starttime              =   EditFrame.txtStartTime.getText();


      try { 
        /* Call the overrided setpersondetails() member procedure to set the 
        updated values to the object*/
        personObj = pstudent.setpersondetails(Grade,Yearofcompletion,
        Coursestaken,Hours,Batchcode,Starttime);
      } catch(Exception e){             // Trap errors
        gui.putStatus("Error while setting parttime student:  "+e.toString());
      }
    } else if(personObj instanceof Student) {
      // Get the student object
      Student student           =    (Student)personObj;
      // Get the edited values
      String Grade                      =    EditFrame.txtGrade.getText();
      String Yearofcompletion   =    EditFrame.txtYearofCompletion.getText();
      String Coursestaken               =    EditFrame.txtCoursesTaken.getText();
      try { 
        /* Call the overrided setpersondetails() member procedure to set the 
        updated values to the object*/
        personObj = student.setpersondetails(Grade,Yearofcompletion,Coursestaken);
      } catch(Exception e){           // Trap errors
        gui.putStatus("Error while setting student details :  "+e.toString());
      }
    } else if(personObj instanceof Teacher) {
      // Get the student object
      Teacher teacher           =    (Teacher)personObj;
      // Get the edited values           
      BigDecimal Experience     =    new BigDecimal(EditFrame.txtExperience.getText());
      BigDecimal Salary             =    new BigDecimal(EditFrame.txtSalary.getText());
      String Courseshandled         =    EditFrame.txtCoursesHandled.getText();
      try { 
        /* Call the overrided setpersondetails() member procedure to set the 
        updated values to the object*/      
        personObj = teacher.setpersondetails(Experience,Salary,Courseshandled);
      } catch(Exception e){          // Trap errors
        gui.putStatus("Error while setting teacher details:  "+e.toString());
      }
    }
    // return the updated person object
    return((Person)personObj);   
  }
  
  /**
   * This method gets the ssn of the person who has been selected in the JTable
   * and retrieves the person's object from the database.
   */  
  private Person getSelectedPerson() {
    Person personObj = null;
    // Get the selected SSN in the JTable(personTable)
    String ssn = getSSNo();
    #sql iterator objectIter (Person);
    objectIter tempIter=null;

    // If not selected , return
    if(!ssn.equals("NS")){
      try {
        //select person object from PERSONDETAILS table type
        #sql  tempIter={SELECT P.PERSON FROM PERSONDETAILS P WHERE P.PERSON.ssn=:ssn};
        #sql { FETCH :tempIter INTO :personObj};
      } catch(Exception ex) {       // Trap errors
        gui.putStatus("Error while Selecting person :  "+ex.toString());
      } finally {
        try {
          tempIter.close();
        } catch(SQLException sqe){
          gui.putStatus("Error while Displaying : "+sqe.toString());
        }
      }
    }
    // Return the person object
    return(personObj);   
  }

  /**
   * This method returns the selected person's SSN from the JTable 
   */  
  private String getSSNo() {
    // Get the selected row number
    int selectedRow =  gui.personTable.getSelectedRow();
    // If no rows are selected , return "NS" - Not Selected
    if(selectedRow==-1) {
      gui.putStatus("  Select a Person from the Table ...");
      return("NS");
    }
    // Check if the object type is not other sub-types of person , since 
    // only student,teacher and parttimeStudent objects are handled
    String objType=(String)gui.tableModel.getValueAt(selectedRow,2);
    if(objType.equals(" O ")) {
      gui.putStatus("The selected person is some other sub type of person .");
      return("NS");    
    }

    // Get the SSN from table
    String ssnNo = (String)gui.tableModel.getValueAt(selectedRow,0);

    // return the SSN
    return(ssnNo); 
  }
 
  /**
   * This method performs the clean up action and closes the application
   */
  private void exitApplication(){
    // if connected to database
      try {
        Oracle.close();
      } catch (SQLException ex){      // Trap errors
        gui.putStatus(" Error while Closing the connection: "+ex.toString()); 
      }
    // Close the application
    System.exit(0);
  }
}//End of class