Saving ArrayList in SQLite database in Android

Question

I\'ve been working with SQLite on android and I would like to add an arraylist to a column in a table, and then fetch the data back as an arraylist. The arraylist is a list

Answer 1

Please forgive me for savagely plagiarizing my previous answer to BLOB vs. VARCHAR for storing arrays in a MySQL table. The other answers over there are also very pertinent.

I think Con's approach is probably better than using java serialization since java's builtin serialization will need additional bytes, and non-java applications will have a harder time dealing with the data.

public static void storeInDB(ArrayList longs) throws IOException, SQLException {

    ByteArrayOutputStream bout = new ByteArrayOutputStream();
    DataOutputStream dout = new DataOutputStream(bout);
    for (long l : longs) {
        dout.writeLong(l);
    }
    dout.close();
    byte[] asBytes = bout.toByteArray();

    PreparedStatement stmt = null;  // however you get this...
    stmt.setBytes(1, asBytes);
    stmt.executeUpdate();
    stmt.close();
}

public static ArrayList readFromDB() throws IOException, SQLException {

    ArrayList longs = new ArrayList();
    ResultSet rs = null;  // however you get this...
    while (rs.next()) {
        byte[] asBytes = rs.getBytes("myLongs");
        ByteArrayInputStream bin = new ByteArrayInputStream(asBytes);
        DataInputStream din = new DataInputStream(bin);
        for (int i = 0; i < asBytes.length/8; i++) {
            longs.add(din.readLong());
        }
        return longs;
    }

}

Note: If your lists will sometimes contain more than 31 longs (248 bytes), then you'll need to use BLOB. You cannot use BINARY() or VARBINARY() in MySQL. I realize you're asking about SQLite, but in the spirit of completely plagiarizing my previous answer, I will pretend you're asking about MySQL:

mysql> CREATE TABLE t (a VARBINARY(2400)) ;
ERROR 1074 (42000): Column length too big for column 'a' (max = 255);
use BLOB or TEXT instead