Problem reading property file

Question

I created a propertie file for the database to read this file from there but the console presents me the following error:

Erronull\properties\conexao.propertie (O sistema não pode encontrar o caminho especificado)
Erronull\properties\conexao.propertie (O sistema não pode encontrar o caminho especificado)
Erronull\properties\conexao.propertie (O sistema não pode encontrar o caminho especificado)
ConexaoMySQL: The url cannot be null
java.sql.SQLException: The url cannot be null
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at modelo.ConexaoMySQL.conectar(ConexaoMySQL.java:18)
    at helper.BancoDadosHelper.getNomeColunas(BancoDadosHelper.java:18)
    at principal.Main.testaConexDB(Main.java:38)
    at principal.Main.menu(Main.java:30)
    at principal.Main.main(Main.java:17)
Exception in thread "main" java.lang.NullPointerException
    at helper.BancoDadosHelper.getNomeColunas(BancoDadosHelper.java:21)
    at principal.Main.testaConexDB(Main.java:38)
    at principal.Main.menu(Main.java:30)
    at principal.Main.main(Main.java:17)

Related Classmysql:

package modelo;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;

public class ConexaoMySQL {

    private static Connection conexao;

    public static boolean conectar() {
        Propriedade.setPath(System.getProperty("jdbc.url")+"\\properties\\conexao.propertie");
        String url = Propriedade.getValor("url");
        String usr = Propriedade.getValor("user");
        String pwd = Propriedade.getValor("password");
        try {
            Class.forName("com.mysql.jdbc.Driver");
            conexao = DriverManager.getConnection(url,usr,pwd);
            System.out.println("ConexaoMySQL.conectar");
            return true;
        } catch (Exception e) {
            System.out.println("ConexaoMySQL: " + e.getMessage());
            e.printStackTrace();
            return false;
        }
    }

    public static void fecharConexao() {
        if (conexao != null) {
            try {
                conexao.close();
                conexao = null;
                System.out.println("ConexaoMySQL.fecharConexao");
            } catch (SQLException e) {
                System.out.println("ConexaoMySQL: " + e.getMessage());
                e.printStackTrace();
            }
        }
    }

    public static Connection getConexao(){
        return conexao;
    }

}

Property class :

package modelo;

import java.io.FileInputStream;
import java.util.Properties;

public class Propriedade {

    private static String path;

    public static void setPath(String caminhoDoArquivo) {
        path = caminhoDoArquivo;
    }

    public static String getValor(String key) {
        String returning = null;
        FileInputStream fis = null;
        Properties prop = new Properties();
        try {
            fis = new FileInputStream(path);
            prop.load(fis);
            returning = prop.getProperty(key);
            if (fis != null) {
                fis.close();
            }
        } catch (Exception e) {
            System.out.println("Erro" + e.getMessage());
        }
        return returning;
    }

}

File connected.propertie.:

url = jdbc:mysql://localhost:3306/sistema;
user = root;
password = ;

Answer 1

Both your property file and the code that retrieves it are wrong, being the root of the error due to the fact that the file is not found.

The error presented is:

System cannot find specified path

See that you’re recovering (System.getProperty("jdbc.url")) a system property that is currently non-existent, to form the path and is returning null being the final generated path equal to null\properties\conexao.propertie

For this, consider recovering the file from properties as a Resource stream, case he’s in the classpath of its application, something like this:

InputStream fis = Propriedade.class.getResourceAsStream("/properties/conexao.propertie")

This makes it unnecessary setPath class Propriedade. Another observation is that you can load the properties file only once, in a static block even.

So in the end, the class Propriedade would look like this:

public final class Propriedade {

    private Propriedade() {}

    private static final Properties prop = new Properties();

    static {
        try (final InputStream fis = Propriedade.class.getResourceAsStream("/properties/conexao.propertie")) {
            prop.load(fis);
        } catch (final IOException e) {
            throw new ExceptionInInitializerError(e.getMessage());
        }
    }

    public static String getValor(final String key) {
        final String returning = prop.getProperty(key);
        return returning != null ? returning : key;
    }

}

Finally, considering the contents of your property file:

url = jdbc:mysql://localhost:3306/sistema;
user = root;
password = ;

This will always return the ; which, in the case of user and password, will probably generate error.

If possible, prefer this content:

url = jdbc:mysql://localhost:3306/sistema
user = root
password = 

To use it is the same way you were doing before, Propriedade.getValor("propriedade"), but in conectar of ConexaoMySQL you should remove the first line of the method.

One example recovering is this:

System.out.println("Propriedade 'user' (valor=root;): " + Propriedade.getValor("user"));
System.out.println("Propriedade 'key' (inexistente): " + Propriedade.getValor("key"));

That generates this result:

Propriedade 'user' (valor=root;): root;
Propriedade 'key' (inexistente): key