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simple jmx-managed resource


Resources can be JMX managed by exposing a management interface and registering as an MBean.

Demo

Files in this tutorial

FILEDESCRIPTION
WEB-INF/web.xmlConfigures the JMX-managed bean
WEB-INF/classes/example/Basic.javaThe resource bean implementation.
WEB-INF/classes/example/BasicMBean.javaThe management interface for the bean.
index.jspUsing the managed bean.

JMX Resource

Any resource in Resin can be managed by JMX by implementing an MBean interface and by specifying an MBean name. The interface exposes the resource's methods to be managed.

The Basic resource

TheBasicbean is the example resource implementation. It exposes its managed interface by implementing aBasicMBeaninterface. ThexxxMBeannaming convention lets JMX determine which interface to use for management. The MBean interface will expose the Data attribute to JMX.

Basic.java
package example;

public class Basic implements BasicMBean {
  private String _data = "default";

  public void setData(String data)
  {
    _data = data;
  }

  public String getData()
  {
    return _data;
  }
}

BasicMBeanis the bean's management interface. It exposes a single attribute, Data, as a getter/setter pair. The name of the interface is important. Since the resource is namedBasic, the MBean interface will be namedBasicMBean.

BasicMBean.java
package example;

public interface BasicMBean {
  public void setData(String data);

  public String getData();
}

MBean names

MBeans are stored in the MBean server using anObjectNameas its key. Essentially, the MBean server stores the managed beans in a map using the mbean name as a key.

The mbean name consists of a set of <name,value> properties and a "domain" used like a namespace. The properties allow for querying related mbeans. For example, you could request for all mbeans with "J2EEType=Servlet", which would return all the managed servlets.

The example uses the name "example:name=basic". "example" is the domain and the bean's single property is "name" with a value of "basic". By convention, an mbean would normally also have a "type" property, but this example is using a name as simple as possible.

web.xml configuration

The web.xml (or resin.conf) configures the resource with the <resource> tag just as withother resources. The resources is registered as an MBean by specifying anmbean-name.

web.xml
<web-app xmlns="http://caucho.com/ns/resin">
  <resource mbean-name="example:name=basic" type="example.Basic">
    <init>
      <data>An Example Resource</data>
    </init>
  </resource>
</web-app>
TAGDESCRIPTION
resourcedefines the resource
mbean-namethe MBean name of the resource
typethe class name of the resource bean
initAny bean-style configuration goes here
dataThe example bean's setData parameter.

Using the resource proxy

Resin's JMX implementation provides a proxy to managed object using the interface for an API. You can, of course, use the standard JMX interface, the proxy interface is much easier to use.

index.jsp
<%@ page import='com.caucho.jmx.Jmx, example.BasicMBean' %>
<%
BasicMBean basic = (BasicMBean) Jmx.find("example:name=basic");

out.println("data: " + basic.getData());
%>
data: An example resource

Compatibility

The resource's code is completely compatible with other JMX implementations. The proxy interface, however, is unique to Resin. If you choose, you can use the JMX API to access the resource. The configuration, of course, is Resin-dependent.

Demo


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