MBeans on-the-fly - JMX in Action - page 148

Table 7.2 The MBean-level descriptor attributes (continued)

Descriptor attribute Possible values Default value Description

OnUpate , OnTimer ,
NoMoreOftenThan ,
Always , Never

never How often to persist this MBean

persistPolicy

Seconds Time value for a persist-

Policy value of NoMore-
OftenThan or OnTimer

persistPeriod

Directory value Directory of the persistent file

persistLocation

Filename The filename of the

persistent state

persistName

t , f t logs all notifications;

f logs none

log F

Filename Fully qualified file path

for a log file

logfile

User-defined Lookup name of the MBean,

if it is to be exposed to an
external registry

export F

1 , 2 , 3 , 4 1 means always visible;

4 means rarely visible

visibility 1

XML format Creates a rendering of the

MBean for display purposes

presentationString

You should be able to understand most of these attributes without much explana-
tion. For instance, the attribute displayName is used only by applications that dis-
play information about a Model MBean; the JMX agent would not use this field
to manage the MBean. The same is true for presentationString and visibil-
ity —the visibility attribute is intended for use by management applications to
provide some level of viewing access for different users.
Examining the remaining attributes, we are left with those that describe the
MBean's persistence policy and notification logging, and one called export . In
this JMX RI , the export attribute is not used by the agent. However, it is intended
to be used when exposing an MBean to the outside world via some lookup regis-
try; the export value is the lookup name for this MBean.
JMX agents use the persistPolicy and persistPeriod attributes to determine
how often to persist their state, and they use the persistLocation and persist-
Name attributes to determine where to store it. Agents use these values to deter-
mine when to persist a Model MBean. Finally, you can use the log and logfile