The Java Management Extensions (JMX) is perfect to build manageable applications without the need to create any administration frontend. Managed Beans (MBeans) are similar to regular Java Beans. Hibernate offers an MBean-wrapper around its Statistics API which is really interesting to optimize caching. Therefore, I was looking for a simple way to use JMX with Wicket. Fortunately, Wicket can also be managed with JMX. All it needs is to drop the wicket-jmx JAR on the classpath – no configuration needed! It is therefore sufficient to add wicket-jmx to the POM:
<dependency>
<groupid>org.apache.wicket</groupid>
<artifactid>wicket-jmx</artifactid>
<version>1.3.0-SNAPSHOT</version>
</dependency>
But Wicket (more precisely Wicketstuff) also contains a simple JMX client called wicketstuff-jmx-panel. Using this client is as simple as adding a single component to whatever Wicket-page:
POM:
<repository>
<id>wicket-stuff-repository</id>
<name>Wicket-Stuff Repository</name>
<url>http://www.wicketstuff.org/maven/repository</url>
</repository>
<!-- SNIP -->
<dependency>
<groupid>org.wicketstuff</groupid>
<artifactid>wicketstuff-jmx-panel</artifactid>
<version>1.3.0-SNAPSHOT</version>
</dependency>
Java:
add(new JmxPanel("jmx"));
However, documentation on this JMX panel is sparse. It took me some time to figure out the following: This panel filters all MBeans that do not have the Wicket-application’s name in their domain. This behaviour may be changed using an annonymous inner class:
add(new JmxPanel("jmx") {
protected IDomainFilter getDomainFilter() {
return DOMAIN_FILTER;
}
});
private static final IDomainFilter DOMAIN_FILTER = new IDomainFilter() {
private static final long serialVersionUID = 1L;
public boolean accept(String domain) {
// your filter code
return true;
}
};
It does make sense to filter out some MBeans as there are already some by default, e.g. for java.util.logging which you probably don’t use at all.
Now it’s time to add Hibernate’s statistics MBean. This MBean is can be used per SessionFactory. I therefore decided to do registration and unregistration together with SessionFactory creation. As I am also using Spring, I went for my own SessionFactoryBean:
public class MBeanRegisteringLocalSessionFactoryBean extends
org.springframework.orm.hibernate3.LocalSessionFactoryBean {
private String _sessionFactoryName;
private ObjectName _objectName;
private MBeanServer _mbeanServer;
@Override
protected void afterSessionFactoryCreation() throws Exception {
super.afterSessionFactoryCreation();
try {
// register JMX MBean
_objectName = new ObjectName("Hibernate:type=statistics,application="
+ getSessionFactoryName());
_mbeanServer = getMBeanServer();
final StatisticsService mBean = new StatisticsService();
mBean.setSessionFactory(getSessionFactory());
_mbeanServer.registerMBean(mBean, _objectName);
} catch (final Throwable t) {
log.warn("failed to register MBean for SessionFactory: " + _objectName, t);
_objectName = null;
_mbeanServer = null;
}
// if _objectName != null --> MBean was registered
}
@Override
protected void beforeSessionFactoryDestruction() {
if (_objectName != null) {
try {
_mbeanServer.unregisterMBean(_objectName);
} catch (final Throwable t) {
log.warn("failed to unregister MBean for SessionFactory: "
+ _objectName.getDomain());
}
}
}
/* SNIP: getMBeanServer(), getSessionFactoryName(), setSessionFactoryName(String) */
}
I copied (sorry, there is no nicer way yet) the code for getMBeanServer() from wicket-jmx’s Initializer class (sorry, can’t find an online version – you can get the source using Maven) in order to get the exact same behaviour. Now you only need to replace LocalSessionFactoryBean with MBeanRegisteringLocalSessionFactoryBean in your beans.xml and you are set. In order to enable statistics by default, add these two lines to your hibernate properties:
hibernate.generate_statistics=true
hibernate.cache.use_structured_entries=true
That’s it! Hibernate statistics directly from your webapp:
.