Java MySQL preparedStatement Batch

Question

I am trying to use the preparedStatement Batch but I am having a problem.

The following code does not give me errors, but it inserts in the table only last key of the map and I do not know why.

It will be surely a very stupid error, but this is the first time I use the addBatch() method..

        Class.forName("com.mysql.jdbc.Driver");
        this.connect = DriverManager.getConnection("jdbc:mysql://localhost/" + this.database + "?user=" + this.user + "&password=" + this.password);
        String s;
        for (String key : this.map.keySet())
        {
            s = ("insert into " + this.database + ".user (nickname) values (?)");
            this.preparedStatement = this.connect.prepareStatement(s);
            this.preparedStatement.setString(1, key);
            this.preparedStatement.addBatch();
        }

        this.preparedStatement.executeBatch();

Thanks in advance!

Answer 1

Prepare your Statement and query outside of the loop:

      s = ("insert into " + this.database + ".user (nickname) values (?)");
      this.preparedStatement = this.connect.prepareStatement(s);
      for (String key : this.map.keySet())
        {
            this.preparedStatement.setString(1, key);
            this.preparedStatement.addBatch();
        }
        this.preparedStatement.executeBatch();

Answer 2

You are using the addBatch() method wrong. In your code you are doing the prepareStatement in each iteration of for loop, and this replaces the prepared query each time.

You should only be calling prepareStatement once per batch. You should place the prepared statement before the loop (only one call)