com.dpslink.base.jdbc

Class JDBCConnectionPool

java.lang.Object

com.dpslink.base.jdbc.JDBCConnectionPool

All Implemented Interfaces:

java.io.Serializable

public class JDBCConnectionPool
extends java.lang.Object
implements java.io.Serializable

A pool of JDBC connections to a configured database. Provides methods to retrieve connections from the pool and to return connections to the pool.

Direct references to this class and its methods should only be made by the JDBCPoolManager class.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
private java.util.ArrayList<JDBCConnectionInfo>	ivAllConnections The list of all JDBC connections ever created by the pool.
private int	ivCheckedOut The number of checked out connections from the pool.
private java.lang.String	ivDriverName The name of the JDBC driver class for the driver used to access this connection pool's database.
private java.util.ArrayList<JDBCConnectionInfo>	ivFreeConnections The pool of free JDBC connections available for use.
private int	ivMaxConns The maximum number of open connections.
private java.lang.String	ivName The connection pool name.
private java.lang.String	ivPassword The password for a connection.
private java.lang.String	ivSQLName The SQL collection name for a connection.
private java.util.ArrayList<java.lang.String>	ivTableNames A collection of the database table and view names, derived from the database associated with the connection pool.
private long	ivTimeOut The number of milliseconds to wait for a connection if none is available and the maximum limit is reached.
private java.lang.String	ivURL The URL for the database.
private java.util.Hashtable<JDBCConnectionInfo,java.lang.String>	ivUsedConnections A list of the in-use JDBC connections.
private java.lang.String	ivUserId The user id for a connection.
private static long	serialVersionUID The class' serialization version id.

Constructor Summary

Constructors

Constructor and Description
JDBCConnectionPool(java.lang.String name, java.lang.String url, java.lang.String sqlname, java.lang.String userid, java.lang.String password, int maxconns, int initconns, int waittimeout) Constructs a new JDBCConnectionPool object.

Method Summary

Modifier and Type	Method and Description
private void	addToUsedList(JDBCConnectionInfo cninf, java.lang.String consumer) Adds the given JDBC connection info object to the list of used connection info objects.
void	freeConnection(JDBCConnectionInfo cninf) Frees a used JDBC connection info object.
JDBCConnectionInfo	getConnection() Retrieves a JDBC connection info object from the pool.
private JDBCConnectionInfo	getConnection(java.lang.String consumer, long timeout) Retrieves a JDBC connection info object from the pool using the given maximum wait time.
private java.lang.String	getConnectionConsumer() Returns the consumer of a connection (the reference point within the code where a connection is being requested or returned).
protected java.lang.String	getConnectionConsumers() Returns a sorted list of the connection consumers associated with the connections currently in-use, suitable for display in a listbox (list is delimited by newline character).
protected java.lang.String	getConnectionStats() Returns string containing information on total number of connections, number of checked out connections, and number of available ones.
private JDBCConnectionInfo	getPooledConnection() Retrieves a JDBC connection info object if one is available from the pool.
java.lang.String	getPoolName() Returns the connection pool's name.
java.lang.String	getRevisedSQL(java.lang.String sqlstmt) Returns the given sql statement with revisions based on the current rules for revising sql statements (sql collection name, etc.).
java.lang.String	getRevisedSQLForTestOnly(java.lang.String sqlname, java.lang.String sqlstmt) Returns the given sql statement with revisions based on the given sql collection name.
java.lang.String	getSQLName() Returns the connection pool's SQL collection name.
private void	initializePool(int initconns) Opens the initial JDBC connections for the pool.
private void	initializeTableNames() Initializes the collection of database table and view names.
private boolean	isConnectionOK(JDBCConnectionInfo cninf) Checks if the given JDBC connection info object is functioning properly.
boolean	isDB2e() Answers if this connection pool uses an IBM DB2 Everyplace database.
boolean	isDB2i() Answers if this connection pool uses an IBM DB2 System i (AS/400) database.
boolean	isDB2iNative() Answers if this connection pool uses an IBM DB2 System i (AS/400) database in native mode (i.e.
boolean	isDB2w() Answers if this connection pool uses an IBM DB2 Windows database.
boolean	isDerby() Answers if this connection pool uses an Apache Derby (IBM Cloudscape) database.
private JDBCConnectionInfo	newConnection() Retrieves a newly created JDBC connection info object.
void	release() Releases all JDBC connection info objects in the pool.
private java.lang.String	removeFromUsedList(JDBCConnectionInfo cninf) Removes the given JDBC connection info object from the list of used connection info objects.
private java.lang.String	reviseForSQLName(java.lang.String sqlname, java.lang.String sqlstmt) Returns the given sql statement with the database sql collection name inserted into the statement prior to all occurrences of table or view names.
private boolean	searchTableNames(java.lang.String name) Answers if ivTableNames contains a given name, regardless of case.

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

private static final long serialVersionUID

The class' serialization version id.

See Also:

Constant Field Values

ivName

private java.lang.String ivName

The connection pool name.

ivURL

private java.lang.String ivURL

The URL for the database.

ivSQLName

private java.lang.String ivSQLName

The SQL collection name for a connection.

ivUserId

private java.lang.String ivUserId

The user id for a connection.

ivPassword

private java.lang.String ivPassword

The password for a connection.

ivMaxConns

private int ivMaxConns

The maximum number of open connections.

ivTimeOut

private long ivTimeOut

The number of milliseconds to wait for a connection if none is available and the maximum limit is reached.

ivDriverName

private java.lang.String ivDriverName

The name of the JDBC driver class for the driver used to access this connection pool's database.

ivTableNames

private java.util.ArrayList<java.lang.String> ivTableNames

A collection of the database table and view names, derived from the database associated with the connection pool.

ivCheckedOut

private int ivCheckedOut

The number of checked out connections from the pool.

ivFreeConnections

private java.util.ArrayList<JDBCConnectionInfo> ivFreeConnections

The pool of free JDBC connections available for use.

ivAllConnections

private java.util.ArrayList<JDBCConnectionInfo> ivAllConnections

The list of all JDBC connections ever created by the pool.

ivUsedConnections

private java.util.Hashtable<JDBCConnectionInfo,java.lang.String> ivUsedConnections

A list of the in-use JDBC connections.

Constructor Detail

JDBCConnectionPool

public JDBCConnectionPool(java.lang.String name,
                          java.lang.String url,
                          java.lang.String sqlname,
                          java.lang.String userid,
                          java.lang.String password,
                          int maxconns,
                          int initconns,
                          int waittimeout)

Constructs a new JDBCConnectionPool object. Any Exceptions possibly caused by the system unavailability are ignored here (only logged) because, by the time the application asks for a connection from the pool, the connection might then be successfully created. If the problem still persists, it is handled at that time.

Parameters:

name - (String) The connection pool name.

url - (String) The JDBC URL for the database.

sqlname - (String) The SQL collection name for a connection.

userid - (String) The user id for a connection.

password - (String) The password for a connection.

maxconns - (int) The maximum number of connections in the pool. 0 means no limit.

initconns - (int) The number of initial connections to open for the pool.

waittimeout - (int) The number of seconds to wait for a connection if none is available and the maximum limit is reached.

Method Detail

freeConnection

public void freeConnection(JDBCConnectionInfo cninf)

Frees a used JDBC connection info object. Returns the connection info object back to the pool.

Parameters:

cninf - (JDBCConnectionInfo) The connection info object to free.

getConnection

public JDBCConnectionInfo getConnection()
                                 throws java.sql.SQLException

Retrieves a JDBC connection info object from the pool. If an object cannot be retrieved, an Exception is logged and then thrown back to the invoker.

Returns:

JDBCConnectionInfo - A connection info object from the pool.

Throws:

java.sql.SQLException - - if a connection info object cannot be retrieved.

getConnection

private JDBCConnectionInfo getConnection(java.lang.String consumer,
                                         long timeout)
                                  throws java.sql.SQLException

Retrieves a JDBC connection info object from the pool using the given maximum wait time. The object is returned immediately if one is available or, if the maximum number of connections has not been reached yet, a new one is created.

Parameters:

consumer - (String) The connection consumer (the reference point within the code where the connection is being requested).

timeout - (long) The maximum wait time for a connection.

Returns:

JDBCConnectionInfo - A connection info object from the pool.

Throws:

java.sql.SQLException - - if a connection info object cannot be retrieved.

getConnectionConsumer

private java.lang.String getConnectionConsumer()

Returns the consumer of a connection (the reference point within the code where a connection is being requested or returned).

Returns:

String - The connection consumer, generally formatted as "at package.class.method(class.java:statement)".

getConnectionConsumers

protected java.lang.String getConnectionConsumers()

Returns a sorted list of the connection consumers associated with the connections currently in-use, suitable for display in a listbox (list is delimited by newline character).

Returns:

String - The connection consumers for the connections currently being used.

getConnectionStats

protected java.lang.String getConnectionStats()

Returns string containing information on total number of connections, number of checked out connections, and number of available ones.

Returns:

String - The current connection statistics.

getPooledConnection

private JDBCConnectionInfo getPooledConnection()
                                        throws java.sql.SQLException

Retrieves a JDBC connection info object if one is available from the pool. If one is not available, invokes the newConnection method.

Returns:

JDBCConnectionInfo - A connection info object from the pool.

Throws:

java.sql.SQLException - - if a connection info object cannot be retrieved.

getPoolName

public java.lang.String getPoolName()

Returns the connection pool's name.

Returns:

String - The pool's name.

getRevisedSQL

public java.lang.String getRevisedSQL(java.lang.String sqlstmt)

Returns the given sql statement with revisions based on the current rules for revising sql statements (sql collection name, etc.).

Parameters:

sqlstmt - (String) The sql statement that is to be revised.

Returns:

String - The revised sql statement string.

getRevisedSQLForTestOnly

public java.lang.String getRevisedSQLForTestOnly(java.lang.String sqlname,
                                                 java.lang.String sqlstmt)

Returns the given sql statement with revisions based on the given sql collection name.

FOR TESTING ONLY. NOT INTENDED FOR PRODUCTION.

Parameters:

sqlname - (String) The sql collection name that is to be used for testing the revisions.

sqlstmt - (String) The sql statement that is to be revised.

Returns:

String - The revised sql statement string.

getSQLName

public java.lang.String getSQLName()

Returns the connection pool's SQL collection name.

Returns:

String - The pool's SQL collection name.

initializePool

private void initializePool(int initconns)
                     throws java.lang.Exception

Opens the initial JDBC connections for the pool.

Parameters:

initconns - (int) The number of initial connections.

Throws:

java.lang.Exception - - if an error occurs while opening the connections.

initializeTableNames

private void initializeTableNames()
                           throws java.lang.Exception

Initializes the collection of database table and view names. Fills the ivTableNames array list with the table names and view names that exist in the database associated with this connection pool.

Throws:

java.lang.Exception - - if an error occurs while creating the collection.

isConnectionOK

private boolean isConnectionOK(JDBCConnectionInfo cninf)

Checks if the given JDBC connection info object is functioning properly.

Parameters:

cninf - (JDBCConnectionInfo) The connection info object to check.

Returns:

boolean - true if the connection info object is okay, otherwise false.

isDB2e

public boolean isDB2e()

Answers if this connection pool uses an IBM DB2 Everyplace database.

Returns:

boolean - true if this is a DB2 Everyplace database, otherwise false.

isDB2i

public boolean isDB2i()

Answers if this connection pool uses an IBM DB2 System i (AS/400) database.

Returns:

boolean - true if this is a DB2 System i database, otherwise false.

isDB2iNative

public boolean isDB2iNative()

Answers if this connection pool uses an IBM DB2 System i (AS/400) database in native mode (i.e. uses the native JDBC driver).

Returns:

boolean - true if this is a DB2 System i native database, otherwise false.

isDB2w

public boolean isDB2w()

Answers if this connection pool uses an IBM DB2 Windows database.

Returns:

boolean - true if this is a DB2 Windows database, otherwise false.

isDerby

public boolean isDerby()

Answers if this connection pool uses an Apache Derby (IBM Cloudscape) database.

Returns:

boolean - true if this is an Apache Derby database, otherwise false.

newConnection

private JDBCConnectionInfo newConnection()
                                  throws java.sql.SQLException

Retrieves a newly created JDBC connection info object.

Returns:

JDBCConnectionInfo - A new connection info object.

Throws:

java.sql.SQLException - - if a connection info object cannot be created.

release

public void release()

Releases all JDBC connection info objects in the pool.

reviseForSQLName

private java.lang.String reviseForSQLName(java.lang.String sqlname,
                                          java.lang.String sqlstmt)

Returns the given sql statement with the database sql collection name inserted into the statement prior to all occurrences of table or view names.

Parameters:

sqlname - (String) The sql collection name that is to be used for the insertions.

sqlstmt - (String) The sql statement that is to revised.

Returns:

String - The revised sql statement string.

searchTableNames

private boolean searchTableNames(java.lang.String name)

Answers if ivTableNames contains a given name, regardless of case.

Parameters:

name - (String) The table or view name to be searched for.

Returns:

boolean - true if the name was found, otherwise false.

addToUsedList

private void addToUsedList(JDBCConnectionInfo cninf,
                           java.lang.String consumer)

Adds the given JDBC connection info object to the list of used connection info objects.

Parameters:

cninf - (JDBCConnectionInfo) The connection info object to add to the list.

consumer - (String) The connection's consumer.

removeFromUsedList

private java.lang.String removeFromUsedList(JDBCConnectionInfo cninf)

Removes the given JDBC connection info object from the list of used connection info objects.

Parameters:

cninf - (JDBCConnectionInfo) The connection info object to remove from the list.

Returns:

String - The consumer associated with the connection.