Problem understanding JMX

Hi,

To register an MBean in an application is really simple: you only need to do something like:

<pre>

final MyMBean mbean = new My(....);

final ObjectName myName = new ObjectName("mydomain:type=My,name=myname");

final MBeanServer server = ManagementFactory.getPlatformMBeanServer();

server.registerMBean(mbean, myName);

</pre>

However, if your application is a Web application and is deployed in a WebServer

things are not so easy:

Indeed, in that case, if you don't take care, registering your own MBean in the

Platform MBeanServer may prevent your application to be correctly undeployed

or redeployed - or even could prevent the Web Server from optimizing memory

space by offloading your application classes when they are dormant.

If you want to expose your own MBeans in the platform MBeanServer when your

application is deployed in a web server you will need also to write the code

that will unregister these MBeans when it is needed (e.g. when your application

needs to be undeployed).

This is why deploying MBeans in a WebServer is usually a process which is

WebServer/AppServer dependant.

I suggest you ask your question to the JMX-FORUM mailing list (see instructions

here)

http://blogs.sun.com/roller/page/jmxetc?entry=where_can_i_get_my

precising where some members of the JMX community may have some

experience in this area.

Hope this helps,

-- daniel

JMX, SNMP, Java, etc...

http://blogs.sun.com/roller/page/jmxetc

dfuchsa at 2007-7-14 1:21:36 >

Hi,

An Entity Bean with BMP would be a business object.

An MBean is a management interface. This doesn't mean that an MBean

couldn't tap into an Entity Bean to expose part of the management inormation.

JMX does not define any standard persistence mechanism - and it's up to the

application code to manage persistence if needed.

Usually, in a Java SE application, there would be some part of code that would

be responsible for creating and registering the application MBeans at start-up.

One possibility is that the application logic allows for the MBeans to be created

from introspection of the application state (the application stores its states

and recreates its management infrastructure=MBeans from it).

Another possibility is that the application is designed in such a way that the

state of the application is recreated from its management infrastructure (the

management infrastructure stores the state of the application, and at startup

recreate the MBeans from that state, and the MBean in turn will push that

state into the application).

There is no absolute rule for this, and it is generally a design choice which

may depend on the nature of the application.

Eamonn McMannus talked about different technics to link MBeans to

application objects in his talk at Java One. The slides should be available

there - it's in Java SE - session TS-3523:

<a href="http://java.sun.com/javaone/sf/sessions/main_session_pdfs.jsp"

>http://java.sun.com/javaone/sf/sessions/main_session_pdfs.jsp</a>

[see also Eamonn's blog:

<a href="http://weblogs.java.net/blog/emcmanus/archive/2006/05/javaone_is_next.html"

> http://weblogs.java.net/blog/emcmanus/archive/2006/05/javaone_is_next.html</a>]

Once again, since your question is at the frontier between JMX and Java EE,

you could very well ask this question to your appserver dedicated forum.

If you're using glasfish, then The Aquarium

<a href="http://blogs.sun.com/theaquarium"

>http://blogs.sun.com/theaquarium</a>

may be a place to search - and

<a href="http://java.sun.com/javaee/glassfish/"

>http://java.sun.com/javaee/glassfish/</a>

may be a place to ask...

BTW: if you're using glassfish - or Sun AppServer 9, you may be interested

by the training offers here:

<a href="http://blogs.sun.com/roller/page/theaquarium?entry=free_web_class_on_sjs"

>http://blogs.sun.com/roller/page/theaquarium?entry=free_web_class_on_sjs</a>

Hope this helps,

-- daniel

JMX, SNMP, Java, etc...

<a href="http://blogs.sun.com/roller/page/jmxetc">http://blogs.sun.com/roller/page/jmxetc</a>

dfuchsa at 2007-7-14 1:21:36 >