| Sun ONE Application Server 7, Enterprise Edition Application Design Guidelines for Storing Session State |
Appendix A
Code SamplesThis appendix provides code examples for the following:
WebServiceLocatorpackage com.sun.j2ee.blueprints.web;
import java.util.*;
import java.net.*;
import javax.ejb.*;
import javax.jms.*;
import javax.naming.*;
import javax.rmi.*;
import javax.sql.*;
import javax.transaction.*;
/**
* This class is an implementation of the Service Locator pattern. It is
* used to looukup resources such as EJBHomes, JMS Destinations, etc.
* This implementation uses the "singleton" strategy and also the "caching"
* strategy.
* This implementation is intended to be used on the web tier and
* not on the ejb tier.
* This class should never be serialized or saved in HttpSession.
*/
public class WebServiceLocator {
private InitialContext ic;
//used to hold references to EJBHomes/JMS Resources for re-use
private Map cache = Collections.synchronizedMap(new HashMap());
private static WebServiceLocator instance = new WebServiceLocator();
public static WebServiceLocator getInstance() {
return instance;
}
private WebServiceLocator() throws ServiceLocatorException {
try {
ic = new InitialContext();
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
/**
* will get the ejb Local home factory. If this ejb home factory has already
* been clients need to cast to the type of EJBHome they desire
*
* @return the EJB Home corresponding to the homeName
*/
public EJBLocalHome getLocalHome(String jndiHomeName) throws
ServiceLocatorException {EJBLocalHome home = (EJBLocalHome) cache.get(jndiHomeName);
if (home == null) {
try {
home = (EJBLocalHome) ic.lookup(jndiHomeName);
cache.put(jndiHomeName, home);
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
return home;
}
/**
* will get the ejb Remote home factory. If this ejb home factory has already
* been clients need to cast to the type of EJBHome they desire
*
* @return the EJB Home corresponding to the homeName
*/
public EJBHome getRemoteHome(String jndiHomeName, Class className) throws
ServiceLocatorException {EJBHome home = (EJBHome) cache.get(jndiHomeName);
if (home == null) {
try {
Object objref = ic.lookup(jndiHomeName);
Object obj = PortableRemoteObject.narrow(objref, className);
home = (EJBHome)obj;
cache.put(jndiHomeName, home);
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
return home;
}
/**
* @return the factory for the factory to get queue connections from
*/
public QueueConnectionFactory getQueueConnectionFactory(String
qConnFactoryName)throws ServiceLocatorException {
QueueConnectionFactory factory = (QueueConnectionFactory)
cache.get(qConnFactoryName);if (factory == null) {
try {
factory = (QueueConnectionFactory) ic.lookup(qConnFactoryName);
cache.put(qConnFactoryName, factory);
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
return factory;
}
/**
* @return the Queue Destination to send messages to
*/
public Queue getQueue(String queueName) throws ServiceLocatorException {
Queue queue = (Queue) cache.get(queueName);
if (queue == null) {
try {
queue =(Queue)ic.lookup(queueName);
cache.put(queueName, queue);
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
return queue;
}
/**
* This method helps in obtaining the topic factory
* @return the factory for the factory to get topic connections from
*/
public TopicConnectionFactory getTopicConnectionFactory(String
topicConnFactoryName) throws ServiceLocatorException {TopicConnectionFactory factory = (TopicConnectionFactory)
cache.get(topicConnFactoryName);if (factory == null) {
try {
factory = (TopicConnectionFactory)
ic.lookup(topicConnFactoryName);cache.put(topicConnFactoryName, factory);
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
return factory;
}
/**
* This method obtains the topc itself for a caller
* @return the Topic Destination to send messages to
*/
public Topic getTopic(String topicName) throws ServiceLocatorException {
Topic topic = (Topic) cache.get(topicName);
if (topic == null) {
try {
topic = (Topic)ic.lookup(topicName);
cache.put(topicName, topic);
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
return topic;
}
/**
* This method obtains the datasource itself for a caller
* @return the DataSource corresponding to the name parameter
*/
public DataSource getDataSource(String dataSourceName) throws
ServiceLocatorException {DataSource dataSource = (DataSource) cache.get(dataSourceName);
if (dataSource == null) {
try {
dataSource = (DataSource)ic.lookup(dataSourceName);
cache.put(dataSourceName, dataSource );
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
return dataSource;
}
/**
* This method obtains the UserTransaction itself for a caller
* @return the UserTransaction corresponding to the name parameter
*/
public UserTransaction getUserTransaction(String utName) throws
ServiceLocatorException {try {
return (UserTransaction) ic.lookup(utName);
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
/**
* @return the URL value corresponding
* to the env entry name.
*/
public URL getUrl(String envName) throws ServiceLocatorException {
try {
return (URL)ic.lookup(envName);
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
/**
* @return the boolean value corresponding
* to the env entry such as SEND_CONFIRMATION_MAIL property.
*/
public boolean getBoolean(String envName) throws ServiceLocatorException {
try {
return ((Boolean)ic.lookup(envName)).booleanValue();
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
/**
* @return the String value corresponding
* to the env entry name.
*/
public String getString(String envName) throws ServiceLocatorException {
try {
return (String)ic.lookup(envName);
} catch (Exception e) {
throw new ServiceLocatorException(e);
}
}
}
ServiceLocatorExceptionpackage com.sun.j2ee.blueprints.web;
/**
* This class implements an exception which can wrapped a lower-level exception.
*/
public class ServiceLocatorException extends RuntimeException {
public ServiceLocatorException() {}
public ServiceLocatorException(String msg) { super(msg); }
public ServiceLocatorException(String msg, Throwable cause) {
super(msg, cause); // will not work with JDK 1.3
}
public ServiceLocatorException(Throwable cause) {
super(cause); // will not work with JDK 1.3
}
}
