存储和检索布尔对象到MySql数据库

Question

This is my first question here, but before asking to you I have searched all around the Internet without solution.

I want to store Java Objects in a MySql database and to do so I'm using the data type BLOB for all the objects. The MySql table is:

CREATE TABLE settaggi_variabili_pc (`id` int(11) NOT NULL AUTO_INCREMENT, PC1 BLOB, PC2 BLOB, PC3 BLOB, PC4 BLOB, PC5 BLOB, PC6 BLOB, PC7 BLOB, PC8 BLOB, PC9 BLOB, PC10 BLOB, PRIMARY KEY (id)) ENGINE=InnoDB DEFAULT CHARSET=latin1;

In there I have to store Java objects like Color, Font and Boolean:

prpdStmnt = con.prepareStatement("UPDATE settaggi_variabili_pc SET PC1=?, PC2=?, PC3=?, PC4=?, PC5=?, PC6=?, PC7=?, PC8=?, PC9=?, PC10=? WHERE id=?");
for (int i = 0; i < vDati.size(); i++)
{   
    Variabile_variabili_pc vpc = (Variabile_variabili_pc) vDati.get(i);
    Object o = null;
    if (vpc.getOggetto() instanceof Color)
        o = (Color) vpc.getOggetto();
    else if (vpc.getOggetto() instanceof Font)
        o = (Font) vpc.getOggetto();
    else if (vpc.getOggetto() instanceof JSwitchButton)
        o = (Boolean)((JSwitchButton) vpc.getOggetto()).isSelected();

    prpdStmnt.setInt(11, i + 1);
    for (int x = 1; x <= 10; x++)
    {
        prpdStmnt.setObject(x, o);  
    }

    prpdStmnt.executeUpdate();

The JSwitchButton is a custom class that extends AbstractButton. All this code works right.

My problem is when I try to retrieve the Boolean Object, this is the code:

ritorno = db.eseguiQuery("SELECT PC1, descrizione FROM settaggi_variabili_pc");
try
{   
    while(ritorno.next())
    {
        InputStream is = ritorno.getBlob(1).getBinaryStream();
        ObjectInputStream ois = new ObjectInputStream(is);
        o = ois.readObject();

        if (o.getClass().equals(Color.class))
            System.out.println("Object type Color");
        else if (o.getClass().equals(Font.class))
            System.out.println("Object type Font");
        else if (o.getClass().equals(Boolean.class))
            System.out.println("Object type Boolean");
    }
}

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

When the ObjectInputStream read the Boolean object the code return a java.io.EOFException error. This error come becouse the Boolean Object, during the store action, was tranlated to TINYINT value in MySql database and it is not stored as a Boolean Object.

So the question is: how can I store a Boolean object to a BLOB MySql Type and how can I retrieve it to a Boolean object again like I done with Color or Font? Is there a way so I can store the Boolean like an Object and not like a primitive type?

Thank you to all.

Answer 1

First of all, as @Jorge Campos pointed out, what you have is not a good structure for storing things in a database. Even for your application, simple configuration data would better be stored in some sort of flat text format ( ie INI Files or similar. If you really must use a database, you should certainly think about using either an object oriented database or even an Object-Relational Mapping (ORM) tool (such as Hibernate ) sitting on-top of MySQL.

Getting down to an actual answer , Just change the line else if (o.getClass().equals( Boolean .class)) in your code above (note the bold), to use a more appropriate class, such as Integer or Byte - that way when the TINYINT is returned fro MySQL you will be able to represent it.

As an aside, I think you would benefit from The StackExchange code review site https://codereview.stackexchange.com/ . Your code is VERY sloppy, and would certainly benefit from a review. You can have your code reviewed without changing your database, if you really want.