Required Components
In the /lib directory you'll find the turbine-pool.jar
jar package that contains the Turbine Connection Pool binary files
(a new addition to Cocoon in version 1.8).
While this package may not be the most up-to-date version, it is
guaranteed and tested to work properly with Cocoon so, we suggest that you
use it.
Installing Turbine Connection Pool
Installing on Apache JServ
On JServ, it is necessary to make sure that the new turbine-pool.jar is visible to Java.
This implies adding
the following to the servlet engine classpath by adding a line
to your jserv.properties file for the connection pool jar package.
 | | | | wrapper.classpath=[path-to-jar]/[jar-name].jar | | | | |
Here is an example:
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wrapper.classpath=/usr/local/java/cocoon/lib/turbine-pool.jar
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Please also read the next section.
Generic Installation for All Servlet Engines
To use the pool, you need to have the appropriate properties defined
in your cocoon.properties file. The important ones are listed below.
This is an example of creating a default pool for use with Oracle. Currently
Turbine supports a wide number of different databases. If your database
is not already supported, please subscribe to the mailing list and ask
for help or try on your own. It is quite easy to add support for your favorite
database.
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# These are your database settings, look in the
# org.apache.turbine.util.db.pool.* package for more information.
processor.xsp.pool.database.default.driver=oracle.jdbc.driver.OracleDriver
processor.xsp.pool.database.default.url=jdbc:oracle:thin:@localhost:1521:ORCL
processor.xsp.pool.database.default.username=dbUser
processor.xsp.pool.database.default.password=dbPass
processor.xsp.pool.database.default.maxConnections=3
processor.xsp.pool.database.default.expiryTime=3600000
# These are the supported jdbc-drivers and their adaptors.
# These properties are used by the DBFactory.
processor.xsp.pool.database.adaptor=DBWeblogic,DBOracle,DBInstantDB,DBPostgres,DBSybase,DBInformix
processor.xsp.pool.database.adaptor.DBWeblogic=weblogic.jdbc.pool.Driver
processor.xsp.pool.database.adaptor.DBOracle=oracle.jdbc.driver.OracleDriver
processor.xsp.pool.database.adaptor.DBInstantDB=org.enhydra.instantdb.jdbc.idbDriver
processor.xsp.pool.database.adaptor.DBPostgres=postgresql.Driver
processor.xsp.pool.database.adaptor.DBInformix=com.informix.jdbc.IfxDriver
processor.xsp.pool.database.adaptor.DBSybase=com.sybase.jdbc.SybDriver
# The full path name to a pool log file
# if not given, commands to log events using org.apache.turbine.util.Log will be ignored.
# This file must already exist and be writable.
# Default: none
#
processor.xsp.pool.logfile=/opt/apache/var/log/dbPool.log
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The default is by convention the default connection used
by the Turbine Connection Pool. To define a Named connection, add new entries
with the word "default" replaced with the name you want. Here is an example
for defining a connection to an Oracle database called "helpdesk":
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processor.xsp.pool.database.helpdesk.driver=oracle.jdbc.driver.OracleDriver
processor.xsp.pool.database.helpdesk.url=jdbc:oracle:thin:@localhost:1521:ORCL
processor.xsp.pool.database.helpdesk.username=dbUser
processor.xsp.pool.database.helpdesk.password=dbPass
processor.xsp.pool.database.helpdesk.maxConnections=3
processor.xsp.pool.database.helpdesk.expiryTime=3600000
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The maxConnections setting is the maximum number
of connections to cache. The expiryTime setting is for automaticially timing
out cached connections to the database. This is to prevent connections
from becoming stale. The username and password settings should be obvious.
If your database does not support users, then simply leave these items
blank. The rest of the settings are database specific and you should read
the various connection interfaces javadoc and drivers to find out the appropriate
strings to use.
Known Limitations
The version of Turbine connection pool used in Cocoon has a bug in which you cannot define
separate connection pools within the same Classloader Context - in plain English, that means
if you want separate pools, you'll probably have to run separate Java virtual machines!
Using Turbine Connection Pool
This section is to describe how you can use the Turbine connection pool
in your own code. However, the esql taglib
will do it for you, so
most people will want to just use the esql taglib, which is much easier!
(At the time of writing, in Cocoon only the SQL/ESQL taglibs
use connection pooling - another good reason to use the SQL/ESQL taglibs!)
To demonstrate this, I'll show an example of how I modified
Ricardo Rocha's excellent example XSQL. This is some of the code that he
had before:
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import java.sql.*;
import java.util.*;
import org.w3c.dom.*;
import DBConnectionManager;
public class XSQL {
static DBConnectionManager manager = DBConnectionManager.getInstance();
public static Element executeQuery(
String connectionName,
String statementId,
String statementText,
Document factory
)
throws SQLException
{
Connection connection = null;
try {
connection = manager.getConnection(connectionName);
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery(statementText);
ResultSetMetaData metaData = resultSet.getMetaData();
int columnCount = metaData.getColumnCount();
Element rowSet = factory.createElement("xsql:rowset");
rowSet.setAttribute("id", statementId);
for (int i = 0; resultSet.next(); i++) {
Element row = factory.createElement("xsql:row");
row.setAttribute("sequence", String.valueOf(i + 1));
rowSet.appendChild(row);
for (int j = 0; j < columnCount; j++) {
String value = resultSet.getString(j + 1);
Element element = factory.createElement(
metaData.getColumnLabel(j + 1).toLowerCase()
);
row.appendChild(element);
if (value != null) {
element.appendChild(
factory.createTextNode(value)
);
}
}
}
resultSet.close();
statement.close();
return rowSet;
} catch (SQLException e) {
throw(new SQLException(statementText));
} finally {
if (connection != null) {
manager.freeConnection(connectionName, connection);
}
}
}
}
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Now this is the code modified to use the Turbine connection pool:
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import java.sql.*;
import java.util.*;
import org.w3c.dom.*;
import DBConnectionManager;
public class XSQL {
static DBBroker pool = DBBroker.getInstance(); // <---- Pool code!
public static Element executeQuery(
String connectionName,
String statementId,
String statementText,
Document factory
)
throws SQLException
{
Connection connection = null;
DBConnection db = null; // <---- Pool code!
try {
db = pool.getConnection(connectionName); // <---- Pool code!
connection = db.getConnection(); // <---- Pool code!
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery(statementText);
ResultSetMetaData metaData = resultSet.getMetaData();
int columnCount = metaData.getColumnCount();
Element rowSet = factory.createElement("xsql:rowset");
rowSet.setAttribute("id", statementId);
for (int i = 0; resultSet.next(); i++) {
Element row = factory.createElement("xsql:row");
row.setAttribute("sequence", String.valueOf(i + 1));
rowSet.appendChild(row);
for (int j = 0; j < columnCount; j++) {
String value = resultSet.getString(j + 1);
Element element = factory.createElement(
metaData.getColumnLabel(j + 1).toLowerCase()
);
row.appendChild(element);
if (value != null) {
element.appendChild(
factory.createTextNode(value)
);
}
}
}
resultSet.close();
statement.close();
return rowSet;
} catch (SQLException e) {
throw(new SQLException(statementText));
} finally {
if (connection != null) {
pool.releaseConnection(db); // <---- Pool code!
}
}
}
}
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Please see the getting
started documentation at the Turbine
homepage for more information about Turbine (a server-side framework which is
the home of the connection pool code).
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