Java Reference
In-Depth Information
After creating the template, the constructor starts a lookup service-finding
process by creating a
LookupDiscoveryManager
instance. This object actively
searches for Jini lookup services across the network. The constructor adds the
client class as a
DiscoveryListener
and will be notified via the
discovered()
callback when a lookup service is found. When a lookup service is found, the cli-
ent is notified and can search that lookup service for an instance of the
JINICon-
nector
service.
As mentioned in the previous paragraph, the
discovered()
method is invoked by
the
LookupDiscoveryManager
when a lookup service is found. Now that the client
has a reference to a lookup service, it uses the
ServiceTemplate
object created in
the constructor to search for the
JINIConnector
service. Service matches are
returned from the lookup service in a
ServiceMatches
object that contains an
array of
ServiceItem
objects. A
ServiceItem
object contains the actual Jini ser-
vice that matched the search (in this case, an instance of
JINIConnector
). At this
point, your client acquires a reference to the Jini service for use. It stores the ref-
erence in a class member called
server
.
The
getMBeanCount()
method is the first of two methods implemented on the cli-
ent side to correspond to remote MBean server methods. It simply invokes the
identically named method on the
JINIConnector
service and returns the result.
The final method implemented in the
JINIConnectorClient
class is
create-
MBean()
(which corresponds to the remote MBean server
createMBean()
method
that is identically declared). This method is singled out here as an example of
using the
JINIConnectorException
class.
When this method is invoked, like
getMBeanCount()
, it simply invokes the same
method on the
JINIConnector
service. However, unlike the
getMBeanCount()
method, it must be prepared to throw a variety of exceptions back to the user. To
accomplish this, you use the
JINIConnectorClient
exception class. When the
method catches a
JINIConnectorException
exception, it acquires the wrapped
server-side exception, casts it to the appropriate type (the
getWrappedException()
method returns the type
Exception
), and throws it.
Recall that we stubbed out the remaining methods declared in the
MBeanServer
interface. They are included below the comment block in order to successfully
compile the connector client class.
We include a
main()
method to use in a quick test later. The
main()
method cre-
ates a
JINIConnectorClient
instance and uses it to connect to a remote MBean
server, get the MBean count, and create an instance of the
HelloWorld
MBean.
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