Low Level Database Access: Difference between revisions

The level code database access code is encapsulated in DAO classes. Only these classes use JDBC to send SQL queries to the database.

You start a transaction by obtaining a DBTransaction object from the [http://stendhal.game-host.org/hudson/job/marauroa_HEAD/javadoc/marauroa/server/db/TransactionPool.html TransactionPool]. The you use the methods of the [http://stendhal.game-host.org/hudson/job/marauroa_HEAD/javadoc/marauroa/server/db/DBTransaction.html DBTransaction] object to talk to the database. Note that many methods expect a parameter map as second parameter. This allows you to use <nowiki>[variables]</nowiki> in your SQL statement without having to worry about escaping input parameters to prevent SQL injection attacks.

DBTransaction, however, does not execute the SQL statements itself. It internally forwards them to a subclass of DatabaseAdapter. This is a very tiny abstraction layer of to hide SQL dialects used by different database systems.

[[Image:Classdiagram_database_access.png]]