org.dspace.storage.rdbms
Class DatabaseManager

java.lang.Object
  org.dspace.storage.rdbms.DatabaseManager

public class DatabaseManager
extends Object

Executes SQL queries.

Version:

$Revision: 3038 $

Author:

Peter Breton, Jim Downing

Constructor Summary

protected

DatabaseManager() Protected Constructor to prevent instantiation except by derived classes.

Method Summary

static TableRow	create(Context context, String table) Create a new row in the given table, and assigns a unique id.
static int	delete(Context context, String table, int id) Delete a table row via its primary key.
static int	delete(Context context, TableRow row) Delete row from the RDBMS.
static int	deleteByValue(Context context, String table, String column, Object value) Delete all table rows with the given value.
static TableRow	find(Context context, String table, int id) Find a table row by its primary key.
static TableRow	findByUnique(Context context, String table, String column, Object value) Find a table row by a unique value.
static void	freeConnection(Connection c) Release resources associated with this connection.
protected static List	getColumnNames(ResultSetMetaData meta) Return the names of all the columns of the ResultSet.
protected static List	getColumnNames(String table) Return the names of all the columns of the given table.
static Connection	getConnection() Obtain an RDBMS connection.
protected static String	getPrimaryKeyColumn(String table) Return the name of the primary key column in the given table.
static String	getPrimaryKeyColumn(TableRow row) Return the name of the primary key column.
static void	insert(Context context, TableRow row) Insert a table row into the RDBMS.
protected static void	loadParameters(PreparedStatement statement, Object[] parameters) Iterate over the given parameters and add them to the given prepared statement.
static void	loadSql(Reader r) Load SQL from a reader into the RDBMS.
static void	loadSql(String sql) Load SQL into the RDBMS.
static TableRowIterator	query(Context context, String query, Object... parameters) Return an iterator with the results of the query.
static TableRowIterator	queryPrepared(PreparedStatement statement) Return an iterator with the results of executing statement.
static TableRowIterator	queryPreparedTable(String table, PreparedStatement statement) Return an iterator with the results of executing statement.
static TableRow	querySingle(Context context, String query, Object... parameters) Return the single row result to this query, or null if no result.
static TableRow	querySingleTable(Context context, String table, String query, Object... parameters) Return the single row result to this query, or null if no result.
static TableRowIterator	queryTable(Context context, String table, String query, Object... parameters) Return an iterator with the results of the query.
static TableRow	row(String table) Create a table row object that can be passed into the insert method, not commonly used unless the table has a referential integrity constraint.
static void	shutdown() Provide a means for a (web) application to cleanly terminate the connection pool.
static int	update(Context context, TableRow row) Update changes to the RDBMS.
static int	updateQuery(Context context, String query, Object... parameters) Execute an update, insert or delete query.

Methods inherited from class java.lang.Object

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

Constructor Detail

DatabaseManager

protected DatabaseManager()

Protected Constructor to prevent instantiation except by derived classes.

Method Detail

queryTable

public static TableRowIterator queryTable(Context context,
                                          String table,
                                          String query,
                                          Object... parameters)
                                   throws SQLException

Return an iterator with the results of the query. The table parameter indicates the type of result. If table is null, the column names are read from the ResultSetMetaData.

Parameters:

context - The context object

table - The name of the table which results

query - The SQL query

parameters - A set of SQL parameters to be included in query. The order of the parameters must correspond to the order of their reference within the query.

Returns:

A TableRowIterator with the results of the query

Throws:

SQLException - If a database error occurs

query

public static TableRowIterator query(Context context,
                                     String query,
                                     Object... parameters)
                              throws SQLException

Return an iterator with the results of the query.

Parameters:

context - The context object

query - The SQL query

parameters - A set of SQL parameters to be included in query. The order of the parameters must correspond to the order of their reference within the query.

Returns:

A TableRowIterator with the results of the query

Throws:

SQLException - If a database error occurs

queryPreparedTable

public static TableRowIterator queryPreparedTable(String table,
                                                  PreparedStatement statement)
                                           throws SQLException

Return an iterator with the results of executing statement. The table parameter indicates the type of result. If table is null, the column names are read from the ResultSetMetaData. The context is that of the connection which was used to create the statement.

Parameters:

statement - The prepared statement to execute.

table - The name of the table which results

Returns:

A TableRowIterator with the results of the query

Throws:

SQLException - If a database error occurs

queryPrepared

public static TableRowIterator queryPrepared(PreparedStatement statement)
                                      throws SQLException

Return an iterator with the results of executing statement. The context is that of the connection which was used to create the statement.

Parameters:

statement - The prepared statement to execute.

Returns:

A TableRowIterator with the results of the query

Throws:

SQLException - If a database error occurs

querySingle

public static TableRow querySingle(Context context,
                                   String query,
                                   Object... parameters)
                            throws SQLException

Return the single row result to this query, or null if no result. If more than one row results, only the first is returned.

Parameters:

context - Current DSpace context

query - The SQL query

parameters - A set of SQL parameters to be included in query. The order of the parameters must correspond to the order of their reference within the query.

Returns:

A TableRow object, or null if no result

Throws:

SQLException - If a database error occurs

querySingleTable

public static TableRow querySingleTable(Context context,
                                        String table,
                                        String query,
                                        Object... parameters)
                                 throws SQLException

Return the single row result to this query, or null if no result. If more than one row results, only the first is returned.

Parameters:

context - Current DSpace context

table - The name of the table which results

query - The SQL query

parameters - A set of SQL parameters to be included in query. The order of the parameters must correspond to the order of their reference within the query.

Returns:

A TableRow object, or null if no result

Throws:

SQLException - If a database error occurs

updateQuery

public static int updateQuery(Context context,
                              String query,
                              Object... parameters)
                       throws SQLException

Execute an update, insert or delete query. Returns the number of rows affected by the query.

Parameters:

context - Current DSpace context

query - The SQL query to execute

parameters - A set of SQL parameters to be included in query. The order of the parameters must correspond to the order of their reference within the query.

Returns:

The number of rows affected by the query.

Throws:

SQLException - If a database error occurs

create

public static TableRow create(Context context,
                              String table)
                       throws SQLException

Create a new row in the given table, and assigns a unique id.

Parameters:

context - Current DSpace context

table - The RDBMS table in which to create the new row

Returns:

The newly created row

Throws:

SQLException

find

public static TableRow find(Context context,
                            String table,
                            int id)
                     throws SQLException

Find a table row by its primary key. Returns the row, or null if no row with that primary key value exists.

Parameters:

context - Current DSpace context

table - The table in which to find the row

id - The primary key value

Returns:

The row resulting from the query, or null if no row with that primary key value exists.

Throws:

SQLException - If a database error occurs

findByUnique

public static TableRow findByUnique(Context context,
                                    String table,
                                    String column,
                                    Object value)
                             throws SQLException

Find a table row by a unique value. Returns the row, or null if no row with that primary key value exists. If multiple rows with the value exist, one is returned.

Parameters:

context - Current DSpace context

table - The table to use to find the object

column - The name of the unique column

value - The value of the unique column

Returns:

The row resulting from the query, or null if no row with that value exists.

Throws:

SQLException - If a database error occurs

delete

public static int delete(Context context,
                         String table,
                         int id)
                  throws SQLException

Delete a table row via its primary key. Returns the number of rows deleted.

Parameters:

context - Current DSpace context

table - The table to delete from

id - The primary key value

Returns:

The number of rows deleted

Throws:

SQLException - If a database error occurs

deleteByValue

public static int deleteByValue(Context context,
                                String table,
                                String column,
                                Object value)
                         throws SQLException

Delete all table rows with the given value. Returns the number of rows deleted.

Parameters:

context - Current DSpace context

table - The table to delete from

column - The name of the column

value - The value of the column

Returns:

The number of rows deleted

Throws:

SQLException - If a database error occurs

getConnection

public static Connection getConnection()
                                throws SQLException

Obtain an RDBMS connection.

Returns:

A new database connection.

Throws:

SQLException - If a database error occurs, or a connection cannot be obtained.

freeConnection

public static void freeConnection(Connection c)

Release resources associated with this connection.

Parameters:

c - The connection to release

row

public static TableRow row(String table)
                    throws SQLException

Create a table row object that can be passed into the insert method, not commonly used unless the table has a referential integrity constraint.

Parameters:

table - The RDBMS table in which to create the new row

Returns:

The newly created row

Throws:

SQLException

insert

public static void insert(Context context,
                          TableRow row)
                   throws SQLException

Insert a table row into the RDBMS.

Parameters:

context - Current DSpace context

row - The row to insert

Throws:

SQLException - If a database error occurs

update

public static int update(Context context,
                         TableRow row)
                  throws SQLException

Update changes to the RDBMS. Note that if the update fails, the values in the row will NOT be reverted.

Parameters:

context - Current DSpace context

row - The row to update

Returns:

The number of rows affected (1 or 0)

Throws:

SQLException - If a database error occurs

delete

public static int delete(Context context,
                         TableRow row)
                  throws SQLException

Delete row from the RDBMS.

Parameters:

context - Current DSpace context

row - The row to delete

Returns:

The number of rows affected (1 or 0)

Throws:

SQLException - If a database error occurs

getColumnNames

protected static List getColumnNames(String table)
                              throws SQLException

Return the names of all the columns of the given table.

Parameters:

table - The name of the table

Returns:

The names of all the columns of the given table, as a List. Each element of the list is a String.

Throws:

SQLException - If a database error occurs

getColumnNames

protected static List getColumnNames(ResultSetMetaData meta)
                              throws SQLException

Return the names of all the columns of the ResultSet.

Parameters:

meta - The ResultSetMetaData

Returns:

The names of all the columns of the given table, as a List. Each element of the list is a String.

Throws:

SQLException - If a database error occurs

loadSql

public static void loadSql(String sql)
                    throws SQLException

Load SQL into the RDBMS.

Parameters:

sql - The SQL to load. throws SQLException If a database error occurs

Throws:

SQLException

loadSql

public static void loadSql(Reader r)
                    throws SQLException,
                           IOException

Load SQL from a reader into the RDBMS.

Parameters:

r - The Reader from which to read the SQL.

Throws:

SQLException - If a database error occurs

IOException - If an error occurs obtaining data from the reader

getPrimaryKeyColumn

public static String getPrimaryKeyColumn(TableRow row)
                                  throws SQLException

Return the name of the primary key column. We assume there's only one primary key per table; if there are more, only the first one will be returned.

Parameters:

row - The TableRow to return the primary key for.

Returns:

The name of the primary key column, or null if the row has no primary key.

Throws:

SQLException - If a database error occurs

getPrimaryKeyColumn

protected static String getPrimaryKeyColumn(String table)
                                     throws SQLException

Return the name of the primary key column in the given table. We assume there's only one primary key per table; if there are more, only the first one will be returned.

Parameters:

table - The name of the RDBMS table

Returns:

The name of the primary key column, or null if the table has no primary key.

Throws:

SQLException - If a database error occurs

shutdown

public static void shutdown()
                     throws SQLException

Provide a means for a (web) application to cleanly terminate the connection pool.

Throws:

SQLException

loadParameters

protected static void loadParameters(PreparedStatement statement,
                                     Object[] parameters)
                              throws SQLException

Iterate over the given parameters and add them to the given prepared statement. Only a select number of datatypes are supported by the JDBC driver.

Parameters:

statement - The unparameterized statement.

parameters - The parameters to be set on the statement.

Throws:

SQLException