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angelo1793
Asked: 2020-07-25 07:10:23 +0800 CST 2020-07-25 07:10:23 +0800 CST

Can't get 1 object from my database, problem with SQLite and PreparedStatement

  • 772

I'm making a system with a complete CRUD, the only problem I have is that I can't retrieve 1 object from my database, I can list all the objects but not get only 1, I'm using MVC and java web.

Here I leave the servlet that executes the search

@Override
    public Usuario_DTO_bean mostrarUsuario(String usu) {
        Usuario_DTO_bean usuarioMostrar= new Usuario_DTO_bean(1, "falla", "falla", "falla", 1, "falla", "falla", "falla");
        try {
            String sql="select * from usuario where usuario =?";
            con=Conector.connect();
            PreparedStatement statement;
            statement=con.prepareStatement(sql);
            statement.setString(1,usu);
            ResultSet resultSet = statement.executeQuery(sql);
            if (resultSet.next()) {
                int id = resultSet.getInt("id");
                String usuario = resultSet.getString("usuario");
                String clave = resultSet.getString("clave");
                String permisos=resultSet.getString("permisos");
                int estado=resultSet.getInt("estado");
                String nombre=resultSet.getString("nombre");
                String apellido_p=resultSet.getString("apellido_p");
                String apellido_m=resultSet.getString("apellido_m");
                usuarioMostrar=new Usuario_DTO_bean(id, usuario, clave, permisos, estado, nombre, apellido_p,apellido_m);
            }
            resultSet.close();
            statement.close();
            con.close();

        } catch (Exception e) {
            // TODO: handle exception
        }
        return usuarioMostrar;



    }

After testing, I think the problem is in this line of code

ResultSet resultSet = statement.executeQuery(sql);

Since after this line no code is executed, not even a simple println in the console and it jumps straight to the return, as if the try detected an error and exited the block.

With this code in a main I execute the function

String registro="SI-84";
    Usuario_DTO_bean usuario;
    Usuario_DTO_bo bo=new Usuario_DTO_bo();
    usuario=bo.mostrarUsuario(registro);
    System.out.println(usuario.getId());
    System.out.println(usuario.getUsuario());

They must know that the user with record SI-84 exists, but instead of returning their values, it returns the following

They are not user values ​​SI-84

java

2 Answers

  1. Best Answer

    In addition to the error of not putting an exception in the catch as they told me, the problem was that perhaps because I was using SQLite it did not let me use PrepareStatement, since the console error indicated an SQL error saying that it did not support the PrapareStatement with which I wanted to use the typical "?" to replace the data.

    Now instead of using PrepareStatement , just use Statement and I made a small change in the sql statement, with this it works great :D

    //Metodo para mostrar 1 solo usuario
    @Override
    public Usuario_DTO_bean mostrarUsuario(String usu) {
        Usuario_DTO_bean usuarioMostrar= new Usuario_DTO_bean(1, "falla", "falla", "falla", 1, "falla", "falla", "falla");
        try {
            String sql="select * from usuario where usuario ='"+usu+"'";
            con=Conector.connect();
            Statement statement;
            statement=con.createStatement();
            //statement.setString(1,usu);
            ResultSet resultSet = statement.executeQuery(sql);
            if (resultSet.next()) {
                int id = resultSet.getInt("id");
                String usuario = resultSet.getString("usuario");
                String clave = resultSet.getString("clave");
                String permisos=resultSet.getString("permisos");
                int estado=resultSet.getInt("estado");
                String nombre=resultSet.getString("nombre");
                String apellido_p=resultSet.getString("apellido_p");
                String apellido_m=resultSet.getString("apellido_m");
                usuarioMostrar=new Usuario_DTO_bean(id, usuario, clave, permisos, estado, nombre, apellido_p,apellido_m);
            }
            resultSet.close();
            statement.close();
            con.close();

        } catch (Exception e) {
            System.err.println(e.getMessage());
        }
        return usuarioMostrar;
    • 1

  2. In the first place, those values ​​are returned to you because you are instantiating it at the beginning

    Usuario_DTO_bean usuarioMostrar= new Usuario_DTO_bean(1, "falla", "falla", "falla", 1, "falla", "falla", "falla");

    From what I see, so far the method seems fine to me. As they tell you, you have to print the exception something like this:

    try{
//La lógica
}catch(SQLException ex){
      System.out.println("No se pudo encontrar el usuario " + ex.getMessage());
}

    If there is an error, know exactly what the error is that you get in order to help you. Cheers

    • 0