How do I store and retrieve a BLOB type from sqlite?

Question

I have a java class (Shell) that stores all the information I need to load for my application. Currently, it is saved into a .txt file and loaded from said file.

This class is responsible for saving and loading the Shell:

public void saveShell() throws IOException {
    ObjectOutputStream objectOutputStream = new ObjectOutputStream(
            new FileOutputStream(getPath()));

    objectOutputStream.writeObject(new Date());
    objectOutputStream.writeBoolean(true);
    objectOutputStream.writeFloat(1.0f);

    objectOutputStream.writeObject(shl);
    objectOutputStream.flush();
    objectOutputStream.close();
    System.out.println("Successfully saved");
}

public Shell loadShell() throws FileNotFoundException, IOException, ClassNotFoundException {
    ObjectInputStream objectInputStream = new ObjectInputStream(
            new FileInputStream(getPath()));

    Date date = (Date) objectInputStream.readObject();
    System.out.println(date);
    System.out.println(objectInputStream.readBoolean());
    System.out.println(objectInputStream.readFloat());

    Shell readShell = (Shell) objectInputStream.readObject();
    System.out.println("Shell Loaded");

    objectInputStream.close();
    System.out.println("Object output stream closed");

    return readShell;
}

However, now that I'm trying to distribute the application, using a file seems less viable than using a database so I have already set up SQLite.

Since Shell has everything I need, I'd like to store it as a BLOB and be able to retrieve the object later. I am new to databases so I don't quite know the specific java methods that I should use. I know that this question is very similar to How do i store and retrieve a blob from sqlite but its answer is in C#. Plus, most examples I've found are always storing pictures and images with a certain URL, there aren't many examples with objects.

Answer 1

I got it working. Basically I added two functions: saveShellDB and loadShellDB:

public void saveShellDB() throws ClassNotFoundException, IOException { 
        Class.forName(classForName); 
        Connection connection = null; 
        try 
        { 
          // create a database connection 
          connection = DriverManager.getConnection(connectionPath); 
          Statement statement = connection.createStatement(); 
          statement.setQueryTimeout(30);  // set timeout to 30 sec. 
          File file = new File("shell.txt"); 
          FileInputStream fis = new FileInputStream(file); 
          PreparedStatement ps = connection.prepareStatement("INSERT INTO shell (name, shl) VALUES (?, ?)"); 
          ps.setString(1, file.getName()); 
          ps.setBinaryStream(2, fis, (int)file.length()); 
          ps.executeUpdate(); 
          ps.close(); 
          fis.close(); 


          System.out.println("SQL save done"); 
        } 
        catch(SQLException e) 
        { 
          // if the error message is "out of memory", 
          // it probably means no database file is found 
          System.err.println(e.getMessage()); 
        } 
        finally 
        { 
          try 
          { 
            if(connection != null) 
              connection.close(); 
          } 

          catch(SQLException e) 
          { 
            // connection close failed. 
            System.err.println(e); 
          } 
        } 
      } 


    public void loadShellDB() throws ClassNotFoundException, SQLException, IOException { 
            Class.forName(classForName); 
        Connection conn = DriverManager.getConnection(connectionPath); 

        String sql = "SELECT name, shl FROM shell"; 
        PreparedStatement stmt = conn.prepareStatement(sql); 
        ResultSet resultSet = stmt.executeQuery(); 
        while (resultSet.next()) { 
          File shl = new File(fileOutputPath); 
          FileOutputStream fos = new FileOutputStream(shl); 

          byte[] buffer = new byte[1];         
          InputStream is = resultSet.getBinaryStream(2); 
          while (is.read(buffer) > 0) { 
            fos.write(buffer); 
          } 
          fos.close(); 
        } 
        conn.close(); 
        System.out.println("SQL Load Done"); 
      } 

Then, I just had to call them from my old save functions:

public void saveShell() throws IOException { 
        ObjectOutputStream objectOutputStream = new ObjectOutputStream( 
            new FileOutputStream(getPath())); 

        objectOutputStream.writeObject(new Date()); 
        objectOutputStream.writeBoolean(true); 
        objectOutputStream.writeFloat(1.0f); 

        objectOutputStream.writeObject(shl); 
        objectOutputStream.flush(); 
        objectOutputStream.close(); 
        System.out.println("Successfully saved"); 

    saveShellDB(); //here! 
} 

public Shell loadShell() throws FileNotFoundException, IOException, ClassNotFoundException { 
    loadShellDB(); //here! 
        ObjectInputStream objectInputStream = new ObjectInputStream( 
                new FileInputStream(getPath())); 

        Date date = (Date) objectInputStream.readObject(); 
        System.out.println(date); 
        System.out.println(objectInputStream.readBoolean()); 
        System.out.println(objectInputStream.readFloat()); 

        Shell readShell = (Shell) objectInputStream.readObject(); 
        System.out.println("Shell Loaded"); 

        objectInputStream.close(); 
        System.out.println("Object output stream closed"); 

        return readShell; 
}