ex7_6.txt

j2ee core design patterns

Example 7.6 	ServiceLocator.java: Implementing JMS Topic Service Locator
Strategy
package com.corej2eepatterns.servicelocator;

// imports
public class ServiceLocator {
    . . . 

    // lookup and return a TopicConnectionFactory
    public TopicConnectionFactory getTopicConnectionFactory(
        String topicConnectionFactoryName) 
    throws ServiceLocatorException {
        TopicConnectionFactory topicFactory = null;
        try {
          if (cache.containsKey(topicConnectionFactoryName)) {
              topicFactory = (TopicConnectionFactory) 
                  cache.get(topicConnectionFactoryName);
          } else {
              topicFactory = (TopicConnectionFactory) 
                 initialContext.
                     lookup(topicConnectionFactoryName);
              cache.put(topicConnectionFactoryName,
                  topicFactory);
          }
        } catch (NamingException nex) {
            throw new ServiceLocatorException(nex);
        } catch (Exception ex) {
            throw new ServiceLocatorException(ex);
        }
        return topicFactory;
    }

    // lookup and return a TopicConnectionFactory
    public  Topic getTopic(String topicName)
    throws ServiceLocatorException {
        Topic topic = null;
        try {
            if (cache.containsKey(topicName)) {
                topic = (Topic) cache.get(topicName);
            } else {
                topic =
                    (Topic)initialContext.lookup(topicName);
                cache.put(topicName, topic);
            }
        } catch (NamingException nex) {
            throw new ServiceLocatorException(nex);
        } catch (Exception ex) {
            throw new ServiceLocatorException(ex);
        }
        return topic;
    }

    . . .
}