Question

I have created a database using SQLite. I want to update the value of a “features” column( type Blob)…but i do not know how to write the “update” statement .
This is what i tried:

    try {
        stat = conn.createStatement();
    } catch (SQLException e) {
    }
    try {
        byte[] b = getFunction();
        stat.executeUpdate("update table set features="+b);
    } catch (SQLException e) {
    }

i get the follwing error :

java.sql.SQLException: unrecognized token: "[B@13a317a"

so i guess that “b” is the problem ?

Answer 1

Try this one with PreparedStatement:

Connection con = null;
PreparedStatement stmt = null;

try {
    byte[] b = getFunction();
    con = ...;
    stmt = con.prepareStatement("update table set features=?");
    stmt.setBytes(1, b);
    stmt.executeUpdate();

    con.commit();
}
catch (SQLException e) {
    //handle exception (consider con.rollback()) and con maybe null here)
}
finally {
    //close stmt and at least con here (all maybe null here)
}

Personally I am always using PreparedStatements. When you have to write a lot of this code then consider writing some Utility-Classes to reduce Boilerplate-Code.

In particular you should consider writing Utilty-Classes for null-safe calling methods on Connection, Statement and ResultSet methods when you are dealing with plain JDBC.

EDIT
What Thomas Jung wrote about preventing SQL Injections is another big pro for always using PreparedStatements. +1 for him 🙂