JDBC删除和更新方法

Question

I'm trying to make a doctor JDBC with SQLite, but when I call the Delete and the Update methods, I get these error messages:

Exception in thread "main" java.sql.SQLException: Doctor not deleted

[SQLITE_BUSY] The database file is locked (database is locked)

These are the main class and the two methods in the DoctorDAO class.

    public static void main(String[] args) throws SQLException, IOException {
        scanner = new Scanner(System.in);
        sc = new Scanner(System.in);
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        DoctorDAO a = new DoctorDAO() ;

        Doctor d1 = new Doctor(null,null,null,(char) 0,null,null,null,null,null,null);
                    boolean ins = a.insertEmployee(d1);
                    if(ins){System.out.println("has added");}
                    else{System.out.println("not added");}


       System.out.println("Give Doctor's Id");
                    String id1 = sc.nextLine();
                    a.updateDoctrorByIds(id1);
         }


   public boolean updateDoctrorByIds(String Id) throws SQLException, IOException
   {  
 boolean b = true; 



       try
       {
           getConnection();
           c.setAutoCommit(false);

         // create the java mysql update preparedstatement 
         Scanner sca = new Scanner(System.in);
         System.out.println("Give the new Name");
         String newName = sca.nextLine();
         String query = "update doctors set Name = ? where Id = ?";
         PreparedStatement preparedStmt = c.prepareStatement(query);
         preparedStmt.setString(1,Id);
         preparedStmt.setString (2,newName);

         // execute the java preparedstatement
         preparedStmt.executeUpdate();
         c.commit();


               closeConnection();

       } 
       catch (Exception e)
       { b =false ;
         System.err.println("Got an exception! ");
         System.err.println(e.getMessage());

       }
   return b;  
   }

public boolean deleteDoctrorById(String Id) throws SQLException` {

       boolean b = true;

       try {

            getConnection();
            c.setAutoCommit(false);
            System.out.println("Delete operation");

            String query = "DELETE FROM doctors WHERE ID ='"+Id+"';";
            s = c.createStatement();
            s.executeUpdate(query);
            //System.out.println(res);

            c.commit();
            s.close();
            c.close();


               //closeConnection();
               System.out.println("/");
               System.out.println("/");
               System.out.println("Successfully Deleted");
               System.out.println("/");
               System.out.println("/");

       }
       catch (SQLException s){
            b = false;
           throw new SQLException("Doctor not deleted"); }


    return b;

   }

Answer 1

One obvious error that I can see in your code - for Update, you are saying

String query = "update doctors set Name = ? where Id = ?";

then you are doing,

preparedStmt.setString(1,Id);
preparedStmt.setString (2,newName);

which is the reversed order. As per your query name is first parameter and id is second parameter but you are setting values in reverse.

Since code that you pasted isn't working code, can't suggest much for database is locked error but to avoid database is locked error, closing connection is recommended, even if you get an Exception so try to close connection inside a finally block.