Question

I’m working with MySQL and their last available JDBC driver, on a User table with NOT NULL constraints on all its fields, which are id, name, password and email.

In my Java EE application, I first called a simple Statement this way :

statement = connection.createStatement();
statement.executeUpdate( "INSERT INTO User (name, password, email) "
         + "VALUES ('" + paramName + "', '" + paramPassword + "', '" + paramEmail + "');" );

Where paramName, paramPassword and paramEmail are strings. I passed empty strings to this request, and a new line with empty values got successfully inserted in the table, since MySQL considers empty strings different than null entries.

Then, I used a PreparedStatement instead :

preparedStatement = connection.prepareStatement( "INSERT INTO User (name, password, email) VALUES(?, ?, ?);" );
preparedStatement.setString( 1, paramName );
preparedStatement.setString( 2, paramPassword );
preparedStatement.setString( 3, paramEmail );
preparedStatement.executeUpdate();

But this time, when I passed empty strings to the request, I got the following error :

com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column ‘name’ cannot be null

So here’s my question : does the PreparedStatement, or maybe its setString() method, convert empty strings to null values? I looked it up and didn’t find any information about this behavior in the javadoc.

Answer 1

The documentation of java.sql.PreparedStatatement didn’t say anything about this in the method setString. I take a look at the sources of the MySQL ConnectorJ and I didn’t find anything too. Are you sure that your String is not null?