com.joanju.cg.db
Class DB

java.lang.Object
  com.joanju.cg.db.DB

public class DB
extends java.lang.Object

Core database access.

Most of this class's methods are synchronized for thread-safety.

General access to the database is done through thread-local LocalConnection objects, which are acquired through localConnection().

For the embedded database, we use JDBC directly. If the user has a Hibernate config file, then we use Hibernate and their connection settings.

Field Summary

protected static java.sql.Connection	connection
protected java.sql.SQLException	connectionException
protected static DB	instance
protected java.lang.ThreadLocal<com.joanju.cg.db.LocalConnection>	localConnections

Constructor Summary

protected

DB()

Method Summary

protected static void	clear() Drop and reload the tables.
protected void	dropTables()
protected static java.lang.String	generateDBName()
static java.sql.Connection	getThreadLocalConnection() Get this thread's Connection TO BE USED FOR READ-ONLY QUERIES ONLY.
protected static DB	instance() We use a Singleton, because the existance of the instance of this object gives us a promise that the database has been loaded sucessfully, and that it has the schema and startup data loaded.
protected void	loadDatabase()
protected static void	loadWrapper()
static java.sql.Connection	newConnection() Create a new connection, for reports and such that have to create temp tables.
java.lang.String	schemaString() This is only used in my unit tests.
static void	shutdown()
static void	touch() Touch the database, just to keep the db connection alive.
protected void	update(java.lang.String expression) Executes the given SQL statement, which may be an INSERT, UPDATE, or DELETE statement or an SQL statement that returns nothing, such as an SQL DDL statement.
protected void	writeMeta()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

connectionException

protected java.sql.SQLException connectionException

connection

protected static java.sql.Connection connection

instance

protected static DB instance

localConnections

protected java.lang.ThreadLocal<com.joanju.cg.db.LocalConnection> localConnections

Constructor Detail

DB

protected DB()

Method Detail

instance

protected static DB instance()
                      throws java.sql.SQLException

We use a Singleton, because the existance of the instance of this object gives us a promise that the database has been loaded sucessfully, and that it has the schema and startup data loaded. If the load fails, then the instance will be null, and an exception will have been thrown.

Returns:

null if the database fails to load.

Throws:

java.io.IOException

java.sql.SQLException

clear

protected static void clear()
                     throws java.sql.SQLException,
                            java.io.IOException

Drop and reload the tables. See Admin.clear(). This should never be public.

Throws:

java.sql.SQLException

java.io.IOException

dropTables

protected void dropTables()
                   throws java.sql.SQLException

Throws:

java.sql.SQLException

generateDBName

protected static java.lang.String generateDBName()

getThreadLocalConnection

public static java.sql.Connection getThreadLocalConnection()
                                                    throws java.sql.SQLException

Get this thread's Connection TO BE USED FOR READ-ONLY QUERIES ONLY. Each thread on the server is given one db connection. This returns it. This is the same connection as is used by table accessors like StringTable. Normally the table accessors should be used instead, but this connection might be used for heavy SQL queries. DO NOT USE THIS WHEN CREATING TEMP TABLES. See newConnection() instead.

Throws:

java.sql.SQLException

loadDatabase

protected void loadDatabase()
                     throws java.sql.SQLException

Throws:

java.sql.SQLException

loadWrapper

protected static void loadWrapper()
                           throws java.sql.SQLException

Throws:

java.sql.SQLException

newConnection

public static java.sql.Connection newConnection()
                                         throws java.sql.SQLException

Create a new connection, for reports and such that have to create temp tables. Usually, the regular table accessors should be used. For read-only SQL access, use getThreadLocalConnection(). Using this for new connections should only be necessary when temp tables need to be created.

Throws:

java.sql.SQLException

schemaString

public java.lang.String schemaString()
                              throws java.sql.SQLException

This is only used in my unit tests.

Throws:

java.sql.SQLException

shutdown

public static void shutdown()
                     throws java.sql.SQLException

Throws:

java.sql.SQLException

touch

public static void touch()
                  throws java.sql.SQLException

Touch the database, just to keep the db connection alive.

Throws:

java.sql.SQLException

update

protected void update(java.lang.String expression)
               throws java.sql.SQLException

Executes the given SQL statement, which may be an INSERT, UPDATE, or DELETE statement or an SQL statement that returns nothing, such as an SQL DDL statement.

Throws:

java.sql.SQLException

writeMeta

protected void writeMeta()
                  throws java.sql.SQLException

Throws:

java.sql.SQLException