public interface Descriptor extends Serializable, Cloneable
Field names are not case-sensitive. The names
DESCRIPTORTYPEare all equivalent. However, the case that was used when the field was first set is preserved in the result of the
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
ImmutableDescriptoror a subclass. Mutable descriptors are usually instances of
DescriptorSupportor 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
JMXclass. For example, the field
defaultValueis represented by the constant
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.commight have the name
Note that the values in the
minValuefields should be consistent with the type returned by the
getType()method for the associated
MBeanParameterInfo. For MXBeans, this means that they should be of the mapped Java type, called opendata(J) in the MXBean type mapping rules.
Name Type Used in Meaning defaultValue Object MBeanAttributeInfo
Default value for an attribute or parameter. See
deprecated String Any 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".
String Any The base name for the
ResourceBundlein which the key given in the
descriptionResourceKeyfield 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.
enabled String MBeanAttributeInfo
"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.
exceptions String MBeanAttributeInfo, MBeanConstructorInfo, MBeanOperationInfo The class names of the exceptions that can be thrown when invoking a constructor or operation, or getting an attribute. The meaning of this field is defined by this specification but the field is not set or used by the JMX API itself. Exceptions thrown when setting an attribute are specified by the field
immutableInfo String MBeanInfo The string
"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. See also the
MBeanInfo The time in milli-seconds that the MBeanInfo can reasonably be expected to be unchanged. The value can be a
Longor a decimal string. This provides a hint from a DynamicMBean or any MBean that does not define
truethat 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
trueor it has
interfaceClassName String MBeanInfo The Java interface name for a Standard MBean or MXBean, as returned by
Class.getName(). A Standard MBean or MXBean registered directly in the MBean Server or created using the
StandardMBeanclass will have this field in its MBeanInfo Descriptor.
legalValues Set<?> MBeanAttributeInfo
Legal values for an attribute or parameter. See
locale String Any The locale of the description in this
MBeanAttributeInfo, etc, as returned by
maxValue Object MBeanAttributeInfo
Maximum legal value for an attribute or parameter. See
metricType String MBeanAttributeInfo
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. minValue Object MBeanAttributeInfo
Minimum legal value for an attribute or parameter. See
mxbean String MBeanInfo The string
"false"according as this MBean is an
MXBean. A Standard MBean or MXBean registered directly with the MBean Server or created using the
StandardMBeanclass will have this field in its MBeanInfo Descriptor.
The Open Type of this element. In the case of
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
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 datawill have.
originalType String MBeanAttributeInfo
The original Java type of this element as it appeared in the
MXBeaninterface method that produced this
MBeanAttributeInfo(etc). For example, a method
in an MXBean interface defines an attribute called
originalTypefield in the Descriptor for this attribute will have the value
The format of this string is described in the section Type Names of the MXBean specification.
setExceptions String MBeanAttributeInfo The class names of the exceptions that can be thrown when setting an attribute. The meaning of this field is defined by this specification but the field is not set or used by the JMX API itself. Exceptions thrown when getting an attribute are specified by the field
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
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.
units String MBeanAttributeInfo
The units in which an attribute, parameter, or operation return value is measured, for example
Some additional fields are defined by Model MBeans. See the information for
ModelMBeanOperationInfo, as well as the chapter "Model MBeans" of the JMX Specification. The following table summarizes these fields. Note that when the Type in this table is Number, a String that is the decimal representation of a Long can also be used.
Nothing prevents the use of these fields in MBeans that are not Model MBeans. The displayName, severity, and visibility fields are of interest outside Model MBeans, for example. But only Model MBeans have a predefined behavior for these fields.
Name Type Used in Meaning class String ModelMBeanOperationInfo Class where method is defined (fully qualified). currencyTimeLimit Number ModelMBeanInfo
How long cached value is valid: <0 never, =0 always, >0 seconds. default Object ModelMBeanAttributeInfo Default value for attribute. descriptorType String Any Type of descriptor, "mbean", "attribute", "constructor", "operation", or "notification". displayName String Any Human readable name of this item. export String ModelMBeanInfo Name to be used to export/expose this MBean so that it is findable by other JMX Agents. getMethod String ModelMBeanAttributeInfo Name of operation descriptor for get method. lastUpdatedTimeStamp Number ModelMBeanAttributeInfo
When value was set. log String ModelMBeanInfo
t or T: log all notifications, f or F: log no notifications. logFile String ModelMBeanInfo
Fully qualified filename to log events to. messageID String ModelMBeanNotificationInfo Unique key for message text (to allow translation, analysis). messageText String ModelMBeanNotificationInfo Text of notification. name String Any Name of this item. persistFile String ModelMBeanInfo File name into which the MBean should be persisted. persistLocation String ModelMBeanInfo The fully qualified directory name where the MBean should be persisted (if appropriate). persistPeriod Number ModelMBeanInfo
Frequency of persist cycle in seconds. Used when persistPolicy is "OnTimer" or "NoMoreOftenThan". persistPolicy String ModelMBeanInfo
One of: OnUpdate|OnTimer|NoMoreOftenThan|OnUnregister|Always|Never. See the section "MBean Descriptor Fields" in the JMX specification document. presentationString String Any XML formatted string to allow presentation of data. protocolMap Descriptor ModelMBeanAttributeInfo See the section "Protocol Map Support" in the JMX specification document. Mappings must be appropriate for the attribute and entries can be updated or augmented at runtime. role String ModelMBeanConstructorInfo
One of "constructor", "operation", "getter", or "setter". setMethod String ModelMBeanAttributeInfo Name of operation descriptor for set method. severity Number ModelMBeanNotificationInfo 0-6 where 0: unknown; 1: non-recoverable; 2: critical, failure; 3: major, severe; 4: minor, marginal, error; 5: warning; 6: normal, cleared, informative targetObject Object ModelMBeanOperationInfo Object on which to execute this method. targetType String ModelMBeanOperationInfo type of object reference for targetObject. Can be: ObjectReference | Handle | EJBHandle | IOR | RMIReference. value Object ModelMBeanAttributeInfo
Current (cached) value for attribute or operation. visibility Number Any 1-4 where 1: always visible, 4: rarely visible.
Methods Modifier and Type Method and Description
clone()Returns a descriptor which is equal to this descriptor.
equals(Object obj)Compares this descriptor to the given object.
getFieldNames()Returns all the field names in the descriptor.
getFields()Returns all of the fields contained in this descriptor as a string array.
getFieldValue(String fieldName)Returns the value for a specific field name, or null if no value is present for that name.
getFieldValues(String... fieldNames)Returns all the field values in the descriptor as an array of Objects.
hashCode()Returns the hash code value for this descriptor.
isValid()Returns true if all of the fields have legal values given their names.
removeField(String fieldName)Removes a field from the descriptor.
setField(String fieldName, Object fieldValue)Sets the value for a specific field name.
setFields(String fieldNames, Object fieldValues)Sets all fields in the field names array to the new value with the same index in the field values array.
Object getFieldValue(String fieldName) throws RuntimeOperationsExceptionReturns the value for a specific field name, or null if no value is present for that name.
fieldName- the field name.
- the corresponding value, or null if the field is not present.
RuntimeOperationsException- if the field name is illegal.
void setField(String fieldName, Object fieldValue) throws RuntimeOperationsException
Sets the value for a specific field name. This will modify an existing field or add a new field.
The field value will be validated before it is set. If it is not valid, then an exception will be thrown. The meaning of validity is dependent on the descriptor implementation.
fieldName- The field name to be set. Cannot be null or empty.
fieldValue- The field value to be set for the field name. Can be null if that is a valid value for the field.
RuntimeOperationsException- if the field name or field value is illegal (wrapped exception is
IllegalArgumentException); or if the descriptor is immutable (wrapped exception is
String getFields()Returns all of the fields contained in this descriptor as a string array.
- String array of fields in the format fieldName=fieldValue
If the value of a field is not a String, then the toString() method will be called on it and the returned value, enclosed in parentheses, used as the value for the field in the returned array. If the value of a field is null, then the value of the field in the returned array will be empty. If the descriptor is empty, you will get an empty array.
- See Also:
String getFieldNames()Returns all the field names in the descriptor.
- String array of field names. If the descriptor is empty, you will get an empty array.
getFieldValuesReturns all the field values in the descriptor as an array of Objects. The returned values are in the same order as the
fieldNamesString array parameter.
fieldNames- String array of the names of the fields that the values should be returned for. If the array is empty then an empty array will be returned. If the array is null then all values will be returned, as if the parameter were the array returned by
getFieldNames(). If a field name in the array does not exist, including the case where it is null or the empty string, then null is returned for the matching array element being returned.
- Object array of field values. If the list of
fieldNamesis empty, you will get an empty array.
void removeField(String fieldName)Removes a field from the descriptor.
fieldName- String name of the field to be removed. If the field name is illegal or the field is not found, no exception is thrown.
RuntimeOperationsException- if a field of the given name exists and the descriptor is immutable. The wrapped exception will be an
void setFields(String fieldNames, Object fieldValues) throws RuntimeOperationsException
Sets all fields in the field names array to the new value with the same index in the field values array. Array sizes must match.
The field value will be validated before it is set. If it is not valid, then an exception will be thrown. If the arrays are empty, then no change will take effect.
fieldNames- String array of field names. The array and array elements cannot be null.
fieldValues- Object array of the corresponding field values. The array cannot be null. Elements of the array can be null.
RuntimeOperationsException- if the change fails for any reason. Wrapped exception is
fieldValuesis null, or if the arrays are of different lengths, or if there is an illegal value in one of them. Wrapped exception is
UnsupportedOperationExceptionif the descriptor is immutable, and the call would change its contents.
- See Also:
Object clone() throws RuntimeOperationsException
Returns a descriptor which is equal to this descriptor. Changes to the returned descriptor will have no effect on this descriptor, and vice versa. If this descriptor is immutable, it may fulfill this condition by returning itself.
- A descriptor which is equal to this descriptor.
RuntimeOperationsException- for illegal value for field names or field values. If the descriptor construction fails for any reason, this exception will be thrown.
boolean isValid() throws RuntimeOperationsExceptionReturns true if all of the fields have legal values given their names.
- true if the values are legal.
RuntimeOperationsException- If the validity checking fails for any reason, this exception will be thrown. The method returns false if the descriptor is not valid, but throws this exception if the attempt to determine validity fails.
boolean equals(Object obj)
Compares this descriptor to the given object. The objects are equal if the given object is also a Descriptor, and if the two Descriptors have the same field names (possibly differing in case) and the same associated values. The respective values for a field in the two Descriptors are equal if the following conditions hold:
- If one value is null then the other must be too.
- If one value is a primitive array then the other must be a primitive array of the same type with the same elements.
- If one value is an object array then the other must be too and
Arrays.deepEquals(Object,Object)must return true.
Object.equals(Object)must return true.
Returns the hash code value for this descriptor. The hash code is computed as the sum of the hash codes for each field in the descriptor. The hash code of a field with name
n.toLowerCase().hashCode() ^ h. Here
his the hash code of
v, computed as follows:
vis null then
vis a primitive array then
his computed using the appropriate overloading of
vis an object array then
his computed using
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Document créé le 30/08/2006, dernière modification le 04/03/2020
Source du document imprimé : https://www.gaudry.be/java-api-rf-javax/management/Descriptor.html
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