Link two classes

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Link two classes

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Hello, everybody!

I am developing a work of college that is a mini banking system with Java SE and I am using Swing for interface. I have a little difficulty with the OO paradigm and wanted to know how I relate a client class to an account class. In the bank, I used foreign key to relate my table cliente with the table conta. But in the Java classes? how do I associate a new account with an existing client? I’ve tested my client crud and it’s working. This is my client class:

package modelo;

public class Cliente {
Conta conta;
private int id;
private String nome;
private String sobrenome;
private String cpf;
private String rg;
private String endereco;



public Cliente(String nome, String sobrenome, String cpf,
        String rg, String endereco) {
    this.nome = nome;
    this.sobrenome = sobrenome;
    this.cpf = cpf;
    this.rg = rg;
    this.endereco = endereco;
}



public int getId() {
    return id;
}



public void setId(int id) {
    this.id = id;
}



public Cliente(){
}

public String getNome() {
    return nome;
}
public void setNome(String nome) {
    this.nome = nome;
}
public String getSobrenome() {
    return sobrenome;
}
public void setSobrenome(String sobrenome) {
    this.sobrenome = sobrenome;
}
public String getCpf() {
    return cpf;
}
public void setCpf(String cpf) {
    this.cpf = cpf;
}
public String getRg() {
    return rg;
}
public void setRg(String rg) {
    this.rg = rg;
}
public String getEndereco() {
    return endereco;
}
public void setEndereco(String endereco) {
    this.endereco = endereco;
}




}

And this is my clienteDAO:

package dao;

import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;
import java.sql.PreparedStatement;
import java.sql.Connection;
import java.sql.SQLException;

import conexao.ConnectionFactory;
import modelo.Cliente;
import dao.ClienteDAO;

public class ClienteDAO {
Connection con;
PreparedStatement ps = null;
ResultSet rs;

public void cadastraCliente(Cliente cliente) {
    con = ConnectionFactory.getConnection();
    try {
        ps = con.prepareStatement("INSERT INTO cliente (nome, sobrenome, rg, cpf, endereco)" +
        "VALUES (?, ?, ?, ?, ?)");
        ps.setString(1, cliente.getNome());
        ps.setString(2, cliente.getSobrenome());
        ps.setString(3, cliente.getRg());
        ps.setString(4, cliente.getCpf());
        ps.setString(5, cliente.getEndereco());

        PreparedStatement ps2 = con.prepareStatement("SELECT idCliente FROM cliente WHERE nome LIKE '?' AND sobrenome "
            +   "LIKE '?' AND rg LIKE '?' AND cpf LIKE '?' AND  endereco LIKE '?'");
        ps2.setString(1, cliente.getNome());
        ps2.setString(2, cliente.getSobrenome());
        ps2.setString(3, cliente.getRg());
        ps2.setString(4, cliente.getCpf());
        ps2.setString(5, cliente.getEndereco());
        rs = ps2.executeQuery();
        cliente.setId(rs.getInt("idCliente"));

        ps.executeUpdate();
        ps.close();
        con.close();

    } catch (SQLException e) {
        e.printStackTrace();
    }
}



public Cliente buscaCliente(String busca){
    con = ConnectionFactory.getConnection();
    try {
        PreparedStatement ps = con.prepareStatement("SELECT * FROM cliente WHERE nome LIKE '%?%' OR sobrenome "
            +   "LIKE '%?%' OR rg LIKE '%?%' OR cpf LIKE '%?%' OR  endereco LIKE '%?%'");
        ps.setString(1, busca);
        ps.setString(2, busca);
        ps.setString(3, busca);
        ps.setString(4, busca);
        ps.setString(5, busca);
        rs = ps.executeQuery();
        Cliente cliente = new Cliente();
            cliente.setNome(rs.getString("nome"));
            cliente.setSobrenome(rs.getString("sobrenome"));
            cliente.setRg(rs.getString("rg"));
            cliente.setCpf(rs.getString("cpf"));
            cliente.setEndereco(rs.getString("endereco"));
        ps.close();
        rs.close();
        con.close();
        return cliente;
    } catch (SQLException e) {
        e.printStackTrace();
        return null;
    }
}

public List<Cliente> listaClientes() {
    List<Cliente> clientes = new ArrayList<Cliente>();
    con = ConnectionFactory.getConnection();
    try {
        PreparedStatement ps = con.prepareStatement("SELECT * FROM cliente");
        rs = ps.executeQuery();
        Cliente cliente = new Cliente();
        while(rs.next()){
            cliente.setNome(rs.getString("nome"));
            cliente.setSobrenome(rs.getString("sobrenome"));
            cliente.setRg(rs.getString("rg"));
            cliente.setCpf(rs.getString("cpf"));
            cliente.setEndereco(rs.getString("endereco"));
            clientes.add(cliente);
        }
        ps.close();
        rs.close();
        con.close();

    } catch (SQLException e) {
        e.printStackTrace();
    }

    return clientes;
}

public void atualizaDados(Cliente cliente, int id) {
    con = ConnectionFactory.getConnection();
    try {
        ps = con.prepareStatement("UPDATE banco.cliente SET nome = ?, sobrenome = ?, rg = ?, cpf =?, endereco = ? where idCliente = ?");
        ps.setString(1, cliente.getNome());
        ps.setString(2, cliente.getSobrenome());
        ps.setString(3, cliente.getRg());
        ps.setString(4, cliente.getCpf());
        ps.setString(5, cliente.getEndereco());
        ps.setInt(6, id);

        ps.executeUpdate();
        ps.close();
        con.close();

    } catch (SQLException e) {
        e.printStackTrace();
    }

}

public void excluiCliente(String nome) {
    con = ConnectionFactory.getConnection();
    try {
        ps = con.prepareStatement("DELETE FROM cliente WHERE nome = ?");
        ps.setString(1, nome);

        ps.executeUpdate();
        ps.close();
        con.close();

    } catch (SQLException e) {
        e.printStackTrace();
    }

}


public List<Cliente> ordenaLista(String coluna) {
    List<Cliente> clientes = new ArrayList<Cliente>();
    con = ConnectionFactory.getConnection();
    try {
        PreparedStatement ps = con.prepareStatement("SELECT * FROM cliente ORDER BY ?");
        ps.setString(1, coluna);
        rs = ps.executeQuery();
        Cliente cliente = new Cliente();
        while(rs.next()){
            cliente.setNome(rs.getString("nome"));
            cliente.setSobrenome(rs.getString("sobrenome"));
            cliente.setRg(rs.getString("rg"));
            cliente.setCpf(rs.getString("cpf"));
            cliente.setEndereco(rs.getString("endereco"));
            clientes.add(cliente);
        }
        ps.close();
        rs.close();
        con.close();

    } catch (SQLException e) {
        e.printStackTrace();
    }

    return clientes;
}

public List<String> populaCombo(){
    List<String> nomes = new ArrayList<String>();
    try {
        con = ConnectionFactory.getConnection();
        PreparedStatement ps = con.prepareStatement("SELECT nome FROM cliente");
        rs = ps.executeQuery();
        while(rs.next()){
            nomes.add(rs.getString("nome"));
        }
        ps.close();
        rs.close();
        con.close();
        return nomes;           
    } catch (SQLException e) {
        e.printStackTrace();
        return null;
    }

}


}

I created a classe ContaCorrente and a ContaInvestimento that inherit from Account and implement a interface ContaI. That’s the ContaCorrente:

package modelo;

public class ContaCorrente extends Conta {
double limite;

public ContaCorrente(){

}



public ContaCorrente(double saldo, double limite) {
    this.saldo = saldo;
    this.limite = limite;
}



public double getLimite() {
    return limite;
}

public void setLimite(double limite) {
    this.limite = limite;
}

@Override
public boolean deposita(double valor) {
    return super.deposita(valor);
}

@Override
public boolean saca(double valor) {
    if(valor > this.saldo + limite){
        System.out.println("Você não tem saldo suficiente para realizar esse saque");
    }
    System.out.println("Saque realizado com sucesso");
    return true;
}

@Override
public Cliente getDono() {
    return null;
}

@Override
public int getNumero() {
    return this.numero;
}

@Override
public double getSaldo() {
    return this.saldo;
}

@Override
public void remunera() {
    this.saldo *= 0.01;
}

}

And this is the ContaInvestimento:

package modelo;

public class ContaInvestimento extends Conta{
double montanteMinimo;
double depositoMinimo;

public ContaInvestimento(){

}



public ContaInvestimento(double saldo, double montanteMinimo, double depositoMinimo) {
    this.saldo = saldo;
    this.montanteMinimo = montanteMinimo;
    this.depositoMinimo = depositoMinimo;
}



@Override
public boolean deposita(double valor) {
    if(valor >= depositoMinimo){
        super.deposita(valor);
    }
    return false;
}
@Override
public boolean saca(double valor) {
    return super.deposita(valor);
}
@Override
public Cliente getDono() {
    return null;
}
@Override
public int getNumero() {
    return this.numero;
}
@Override
public double getSaldo() {
    return this.saldo;
}
@Override
public void remunera() {
    this.saldo *= 0.01;
}
}

But I made a single contaDAO for both of us classes:

package dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import conexao.ConnectionFactory;
import modelo.Cliente;
import modelo.ContaCorrente;
import modelo.ContaInvestimento;

public class ContaDAO {
Connection con;
PreparedStatement ps = null;
ResultSet rs;

public void criaContaCorrente(ContaCorrente conta){
    con = ConnectionFactory.getConnection();
    try {
        ps = con.prepareStatement("INSERT INTO conta (saldo) VALUES (?)");
        ps.setDouble(1, conta.getSaldo() + conta.getLimite());

        PreparedStatement ps2 = con.prepareStatement("SELECT idConta FROM conta WHERE idCliente = ?");
            ps.setInt(1,conta.getDono().getId());
            rs = ps2.executeQuery();
            conta.setNumero(rs.getInt("idConta"));

        ps.executeUpdate();
        ps.close();
        con.close();

    } catch (SQLException e) {
        e.printStackTrace();
    }
}

public void criaContaInvestimento(ContaInvestimento conta){
    con = ConnectionFactory.getConnection();
    try {
        ps = con.prepareStatement("INSERT INTO banco.conta (saldo) VALUES (?)");
        ps.setDouble(1, conta.getSaldo());

        ps.executeUpdate();
        ps.close();
        con.close();

    } catch (SQLException e) {
        e.printStackTrace();
    }
}

public boolean atualizaSaldo(double valor, int numero) {
    synchronized (this) {
        try {
            con = ConnectionFactory.getConnection();
            ps = con.prepareStatement("UPDATE conta SET saldo = ? WHERE idConta = ?");
            ps.setDouble(1, valor);
            ps.setInt(2, numero);
            return true;
        } catch (SQLException e) {
            return false;
        }
    }
}

public Cliente getDono() {
    return null;
}

public double getSaldo(int numero) {
    synchronized (this) {
        try {
            con = ConnectionFactory.getConnection();
            ps = con.prepareStatement("SELECT saldo WHERE idConta = ?");
            ps.setInt(1, numero);
            rs = ps.executeQuery();
            double saldo = rs.getDouble("saldo");
            return saldo;
        } catch (SQLException e) {
            System.out.println(e);
            return 0;
        }
    }
}

}

In my class VincularConta I have the following actionPerformed:

public void actionPerformed(ActionEvent e) {
    if(tipoConta.getSelectedItem().equals("Conta Corrente")){
        ContaDAO cd = new ContaDAO();
        ContaCorrente conta = new ContaCorrente(Double.parseDouble(depositoInicial.getText()),
                Double.parseDouble(limite.getText()));
        cd.criaContaCorrente(conta);
    }
    if(tipoConta.getSelectedItem().equals("Conta Investimento")){
        ContaDAO cd = new ContaDAO();
        ContaInvestimento conta = new ContaInvestimento(Double.parseDouble(depositoInicial2.getText()),
                Double.parseDouble(depositoMinimo.getText()), Double.parseDouble(montanteMinimoInput.getText()) );
        cd.criaContaInvestimento(conta);
    }
}

In my ClienteDAO i try to get the customer id generated by the bd and in my ContaDAO I try to use the id I got from the client to get the account id. But I can’t even create the account, let alone get the id. Can you help me understand what’s wrong with my CRUD? Thanks in advance!

1 answer

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by Andrew Ribeiro • **1,718** points · Answer 1 · 2016-06-29T23:04:18+00:00

To be able to create any account whatsoever, as you have a foreign-key account within account, it is necessary to first create the client, have the Id customer, to finally register the account.

It is very interesting what you are doing, I can advise some things but it will depend a lot on the business rules of your software for you to achieve a good requirement implemented.

First, in the class Conta, that is super-class of all other accounts, you must create a client object as class attribute. That way, from an account, you can know which customer is.

Any insertion in the account bank you perform will follow that order:

Have a client object, whether it exists (in the bank) or not.
If existing, it is not necessary to call the DAO customer, since this customer already has one Id setate
If it is not existing, it is first necessary to include this account in the bank and generate the Id his.
Finally, always having a customer with Id setate, is enough of you set that customer in the object of Account, (conta.setCliente(cliente); be it current, or whatever. Remember that when creating a client attribute in super-class Account, all other accounts will inherit this attribute.
Run the account DAO in the field Id customer, you will already have referenced the Id of the existing customer.

It would look something like:

public abstract Conta {
//...
private Cliente cliente; //atributo de cliente em conta
//getters and setters
}

The most interesting part of this approach, which is the only association you need to keep your application running.

Let’s say for example that you wanted to search which accounts a particular customer has.

You must select in the account table searching for the accounts you have in the Id_client field, the Id of the client you are looking for.

You will always return zero, one or several accounts that has that customer as Id_client. So it is not necessary, for example, to create any other account association with client (such as creating an Account List attribute within the customer class)

I hope you have understood the concept. For any doubt, I am available.