Additional metadata for a JMX element. A Descriptor
is associated with a MBeanInfo , MBeanAttributeInfo , etc.
It consists of a collection of fields. A field is a name and an
associated value.
Field names are not case-sensitive. The names descriptorType ,
descriptortype , and DESCRIPTORTYPE are all equivalent.
However, the case that was used when the field was first set is preserved
in the result of the getFields() and getFieldNames()
methods.
Not all field names and values are predefined.
New fields can be defined and added by any program.
A descriptor can be mutable or immutable.
An immutable descriptor, once created, never changes.
The Descriptor methods that could modify the contents
of the descriptor will throw an exception
for an immutable descriptor. Immutable descriptors are usually
instances of ImmutableDescriptor or a subclass. Mutable
descriptors are usually instances of
DescriptorSupport or a subclass.
Certain fields are used by the JMX implementation. This means
either that the presence of the field may change the behavior of
the JMX API or that the field may be set in descriptors returned by
the JMX API. These fields appear in italics in the table
below, and each one has a corresponding constant in the JMX
class. For example, the field defaultValue is represented
by the constant DEFAULT_VALUE_FIELD .
Certain other fields have conventional meanings described in the
table below but they are not required to be understood or set by
the JMX implementation.
Field names defined by the JMX specification in this and all
future versions will never contain a period (.). Users can safely
create their own fields by including a period in the name and be
sure that these names will not collide with any future version of
the JMX API. It is recommended to follow the Java package naming
convention to avoid collisions between field names from different
origins. For example, a field created by example.com might
have the name com.example.interestLevel .
Note that the values in the defaultValue , legalValues , maxValue , and minValue fields should
be consistent with the type returned by the getType()
method for the associated MBeanAttributeInfo or MBeanParameterInfo . For MXBeans, this means that they should be
of the mapped Java type, called opendata(J) in the MXBean type mapping rules.
An indication that this element of the information model is no
longer recommended for use. A set of MBeans defined by an
application is collectively called an information model.
The convention is for the value of this field to contain a string
that is the version of the model in which the element was first
deprecated, followed by a space, followed by an explanation of the
deprecation, for example "1.3 Replaced by the Capacity
attribute" .
descriptionResource BundleBaseName
String
Any
The base name for the ResourceBundle in which the key given in
the descriptionResourceKey field can be found, for example
"com.example.myapp.MBeanResources" . The meaning of this
field is defined by this specification but the field is not set or
used by the JMX API itself.
descriptionResourceKey
String
Any
A resource key for the description of this element. In
conjunction with the descriptionResourceBundleBaseName ,
this can be used to find a localized version of the description.
The meaning of this field is defined by this specification but the
field is not set or used by the JMX API itself.
The string "true" or "false" according as this
item is enabled. When an attribute or operation is not enabled, it
exists but cannot currently be accessed. A user interface might
present it as a greyed-out item. For example, an attribute might
only be meaningful after the start() method of an MBean has
been called, and is otherwise disabled. Likewise, a notification
might be disabled if it cannot currently be emitted but could be in
other circumstances.
The string "true" or "false" according as this
MBean's MBeanInfo is immutable. When this field is true,
the MBeanInfo for the given MBean is guaranteed not to change over
the lifetime of the MBean. Hence, a client can read it once and
cache the read value. When this field is false or absent, there is
no such guarantee, although that does not mean that the MBeanInfo
will necessarily change.
infoTimeout
String Long
MBeanInfo
The time in milli-seconds that the MBeanInfo can reasonably be
expected to be unchanged. The value can be a Long or a
decimal string. This provides a hint from a DynamicMBean or any
MBean that does not define immutableInfo as true
that the MBeanInfo is not likely to change within this period and
therefore can be cached. When this field is missing or has the
value zero, it is not recommended to cache the MBeanInfo unless it
has the immutableInfo set to true .
The Java interface name for a Standard MBean or MXBean, as
returned by getName() . A Standard MBean or MXBean
registered directly in the MBean Server or created using the StandardMBean class will have this field in its MBeanInfo
Descriptor.
The type of a metric, one of the strings "counter" or "gauge".
A metric is a measurement exported by an MBean, usually an
attribute but sometimes the result of an operation. A metric that
is a counter has a value that never decreases except by
being reset to a starting value. Counter metrics are almost always
non-negative integers. An example might be the number of requests
received. A metric that is a gauge has a numeric value
that can increase or decrease. Examples might be the number of
open connections or a cache hit rate or a temperature reading.
The string "true" or "false" according as this
MBean is an MXBean . A Standard MBean or MXBean registered
directly with the MBean Server or created using the StandardMBean class will have this field in its MBeanInfo
Descriptor.
The Open Type of this element. In the case of MBeanAttributeInfo and MBeanParameterInfo , this is the
Open Type of the attribute or parameter. In the case of MBeanOperationInfo , it is the Open Type of the return value. This
field is set in the Descriptor for all instances of OpenMBeanAttributeInfoSupport , OpenMBeanOperationInfoSupport , and OpenMBeanParameterInfoSupport . It is also set for attributes,
operations, and parameters of MXBeans.
This field can be set for an MBeanNotificationInfo , in
which case it indicates the Open Type that the user data will have.
The original Java type of this element as it appeared in the
MXBean interface method that produced this MBeanAttributeInfo (etc). For example, a method public
MemoryUsage getHeapMemoryUsage();
in an MXBean interface defines an attribute called HeapMemoryUsage of type CompositeData . The originalType field in the Descriptor for this attribute will have
the value "java.lang.management.MemoryUsage" .
The format of this string is described in the section Type Names of the MXBean
specification.
severity
String Integer
MBeanNotificationInfo
The severity of this notification. It can be 0 to mean
unknown severity or a value from 1 to 6 representing decreasing
levels of severity. It can be represented as a decimal string or
an Integer .
since
String
Any
The version of the information model in which this element
was introduced. A set of MBeans defined by an application is
collectively called an information model. The
application may also define versions of this model, and use the
"since" field to record the version in which an element
first appeared.
Additional metadata for a JMX element. A Descriptor is associated with a MBeanInfo , MBeanAttributeInfo , etc. It consists of a collection of fields. A field is a name and an associated value.
Field names are not case-sensitive. The names descriptorType , descriptortype , and DESCRIPTORTYPE are all equivalent. However, the case that was used when the field was first set is preserved in the result of the getFields() and getFieldNames() methods.
Not all field names and values are predefined. New fields can be defined and added by any program.
A descriptor can be mutable or immutable. An immutable descriptor, once created, never changes. The
Descriptormethods that could modify the contents of the descriptor will throw an exception for an immutable descriptor. Immutable descriptors are usually instances of ImmutableDescriptor or a subclass. Mutable descriptors are usually instances of DescriptorSupport or a subclass.Certain fields are used by the JMX implementation. This means either that the presence of the field may change the behavior of the JMX API or that the field may be set in descriptors returned by the JMX API. These fields appear in italics in the table below, and each one has a corresponding constant in the JMX class. For example, the field defaultValue is represented by the constant DEFAULT_VALUE_FIELD .
Certain other fields have conventional meanings described in the table below but they are not required to be understood or set by the JMX implementation.
Field names defined by the JMX specification in this and all future versions will never contain a period (.). Users can safely create their own fields by including a period in the name and be sure that these names will not collide with any future version of the JMX API. It is recommended to follow the Java package naming convention to avoid collisions between field names from different origins. For example, a field created by example.com might have the name com.example.interestLevel .
Note that the values in the defaultValue , legalValues , maxValue , and minValue fields should be consistent with the type returned by the getType() method for the associated MBeanAttributeInfo or MBeanParameterInfo . For MXBeans, this means that they should be of the mapped Java type, called opendata(J) in the MXBean type mapping rules.
MBeanParameterInfo
BundleBaseName
MBeanNotificationInfo
MBeanOperationInfo
Long
MBeanParameterInfo
MBeanParameterInfo
MBeanOperationInfo
MBeanParameterInfo
MBeanOperationInfo
MBeanParameterInfo
The Open Type of this element. In the case of MBeanAttributeInfo and MBeanParameterInfo , this is the Open Type of the attribute or parameter. In the case of MBeanOperationInfo , it is the Open Type of the return value. This field is set in the Descriptor for all instances of OpenMBeanAttributeInfoSupport , OpenMBeanOperationInfoSupport , and OpenMBeanParameterInfoSupport . It is also set for attributes, operations, and parameters of MXBeans.
This field can be set for an MBeanNotificationInfo , in which case it indicates the Open Type that the user data will have.
MBeanOperationInfo
MBeanParameterInfo
The original Java type of this element as it appeared in the MXBean interface method that produced this MBeanAttributeInfo (etc). For example, a method
publicMemoryUsagegetHeapMemoryUsage();in an MXBean interface defines an attribute called HeapMemoryUsage of type CompositeData . The originalType field in the Descriptor for this attribute will have the value "java.lang.management.MemoryUsage" .
The format of this string is described in the section Type Names of the MXBean specification.
Integer
MBeanParameterInfo
MBeanOperationInfo
Some additional fields are defined by Model MBeans. See ModelMBeanInfo and related classes and the chapter "Model MBeans" of the JMX Specification.