@Documented
@Inherited
@Target(value={CONSTRUCTOR,METHOD,FIELD,PARAMETER,TYPE})
@Retention(value=RUNTIME)
public @interface DescriptorFields
Annotation that adds fields to a Descriptor. This can be the Descriptor for an MBean, or for an attribute, operation, or constructor in an MBean, or for a parameter of an operation or constructor.
Consider this Standard MBean interface, for example:
public interface CacheControlMBean { @DescriptorFields("units=bytes") public long getCacheSize(); }
When a Standard MBean is made using this interface, the usual rules
mean that it will have an attribute called CacheSize
of type
long
. The DescriptorFields
annotation will ensure
that the MBeanAttributeInfo for this attribute will have a
Descriptor
that has a field called units
with
corresponding value bytes
.
Similarly, if the interface looks like this:
public interface CacheControlMBean { @DescriptorFields({"units=bytes", "since=1.5"}) public long getCacheSize(); }
then the resulting Descriptor
will contain the following
fields:
Name | Value |
---|---|
units | "bytes" |
since | "1.5" |
The @DescriptorFields
annotation can be applied to:
Other uses of the annotation will either fail to compile or be ignored.
Interface annotations are checked only on the exact interface
that defines the management interface of a Standard MBean or an
MXBean, not on its parent interfaces. Method annotations are
checked only in the most specific interface in which the method
appears; in other words, if a child interface overrides a method
from a parent interface, only @DescriptorFields
annotations in
the method in the child interface are considered.
The Descriptor fields contributed in this way must be consistent with each other and with any fields contributed by DescriptorKey annotations. That is, two different annotations, or two members of the same annotation, must not define a different value for the same Descriptor field. Fields from annotations on a getter method must also be consistent with fields from annotations on the corresponding setter method.
The Descriptor resulting from these annotations will be merged
with any Descriptor fields provided by the implementation, such as
the immutableInfo
field for an MBean. The fields from the annotations
must be consistent with these fields provided by the implementation.
The DescriptorKey annotation provides
another way to use annotations to define Descriptor fields.
@DescriptorKey
requires more work but is also more
robust, because there is less risk of mistakes such as misspelling
the name of the field or giving an invalid value.
@DescriptorFields
is more convenient but includes
those risks. @DescriptorFields
is more
appropriate for occasional use, but for a Descriptor field that you
add in many places, you should consider a purpose-built annotation
using @DescriptorKey
.
Modifier and Type | Required Element and Description |
---|---|
java.lang.String[] |
value
The descriptor fields.
|