Class DescriptorSupport

All Implemented Interfaces:
Serializable, Cloneable, Descriptor 
public class DescriptorSupport
extends Object
implements Descriptor

This class represents the metadata set for a ModelMBean element. A descriptor is part of the ModelMBeanInfo, ModelMBeanNotificationInfo, ModelMBeanAttributeInfo, ModelMBeanConstructorInfo, and ModelMBeanParameterInfo.

A descriptor consists of a collection of fields. Each field is in fieldname=fieldvalue format. Field names are not case sensitive, case will be preserved on field values.

All field names and values are not predefined. New fields can be defined and added by any program. Some fields have been predefined for consistency of implementation and support by the ModelMBeanInfo, ModelMBeanAttributeInfo, ModelMBeanConstructorInfo, ModelMBeanNotificationInfo, ModelMBeanOperationInfo and ModelMBean classes.

The serialVersionUID of this class is -6292969195866300415L.

Since:
1.5
See Also:
Serialized Form

Constructors

Constructor Description
DescriptorSupport()

Descriptor default constructor.
DescriptorSupport​(int initNumFields)

Descriptor constructor.
DescriptorSupport​(String inStr)

Descriptor constructor taking an XML String.
DescriptorSupport​(String... fields)

Constructor taking fields in the fieldName=fieldValue format.
DescriptorSupport​(String[] fieldNames, Object[] fieldValues)

Constructor taking field names and field values.
DescriptorSupport​(DescriptorSupport inDescr)

Descriptor constructor taking a Descriptor as parameter.

Methods

Modifier and Type Method Description
Object clone()

Returns a new Descriptor which is a duplicate of the Descriptor.
boolean equals​(Object o)

Compares this descriptor to the given object.
int hashCode()

Returns the hash code value for this descriptor.
boolean isValid()

Returns true if all of the fields have legal values given their names.
String toString()

Returns a human readable string representing the descriptor.
String toXMLString()

Returns an XML String representing the descriptor.

Methods declared in class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Methods declared in interface javax.management.Descriptor

getFieldNames, getFields, getFieldValue, getFieldValues, removeField, setField, setFields

Constructors

DescriptorSupport

public DescriptorSupport()

Descriptor default constructor. Default initial descriptor size is 20. It will grow as needed.
Note that the created empty descriptor is not a valid descriptor (the method isValid returns false)

DescriptorSupport

public DescriptorSupport(int initNumFields)
                  throws MBeanException,
                         RuntimeOperationsException

Descriptor constructor. Takes as parameter the initial capacity of the Map that stores the descriptor fields. Capacity will grow as needed.
Note that the created empty descriptor is not a valid descriptor (the method isValid returns false).

Parameters:
initNumFields - The initial capacity of the Map that stores the descriptor fields.
Throws:
RuntimeOperationsException - for illegal value for initNumFields (<= 0)
MBeanException - Wraps a distributed communication Exception.

DescriptorSupport

public DescriptorSupport(DescriptorSupport inDescr)

Descriptor constructor taking a Descriptor as parameter. Creates a new descriptor initialized to the values of the descriptor passed in parameter.

Parameters:
inDescr - the descriptor to be used to initialize the constructed descriptor. If it is null or contains no descriptor fields, an empty Descriptor will be created.

DescriptorSupport

public DescriptorSupport(String inStr)
                  throws MBeanException,
                         RuntimeOperationsException,
                         XMLParseException

Descriptor constructor taking an XML String.

The format of the XML string is not defined, but an implementation must ensure that the string returned by toXMLString() on an existing descriptor can be used to instantiate an equivalent descriptor using this constructor.

In this implementation, all field values will be created as Strings. If the field values are not Strings, the programmer will have to reset or convert these fields correctly.

Parameters:
inStr - An XML-formatted string used to populate this Descriptor. The format is not defined, but any implementation must ensure that the string returned by method toXMLString on an existing descriptor can be used to instantiate an equivalent descriptor when instantiated using this constructor.
Throws:
RuntimeOperationsException - If the String inStr passed in parameter is null
XMLParseException - XML parsing problem while parsing the input String
MBeanException - Wraps a distributed communication Exception.

DescriptorSupport

public DescriptorSupport(String[] fieldNames,
                         Object[] fieldValues)
                  throws RuntimeOperationsException

Constructor taking field names and field values. Neither array can be null.

Parameters:
fieldNames - String array of field names. No elements of this array can be null.
fieldValues - Object array of the corresponding field values. Elements of the array can be null. The fieldValue must be valid for the fieldName (as defined in method isValid)

Note: array sizes of parameters should match. If both arrays are empty, then an empty descriptor is created.

Throws:
RuntimeOperationsException - for illegal value for field Names or field Values. The array lengths must be equal. If the descriptor construction fails for any reason, this exception will be thrown.

DescriptorSupport

public DescriptorSupport(String... fields)

Constructor taking fields in the fieldName=fieldValue format.

Parameters:
fields - String array with each element containing a field name and value. If this array is null or empty, then the default constructor will be executed. Null strings or empty strings will be ignored.

All field values should be Strings. If the field values are not Strings, the programmer will have to reset or convert these fields correctly.

Note: Each string should be of the form fieldName=fieldValue. The field name ends at the first = character; for example if the String is a=b=c then the field name is a and its value is b=c.

Throws:
RuntimeOperationsException - for illegal value for field Names or field Values. The field must contain an "=". "=fieldValue", "fieldName", and "fieldValue" are illegal. FieldName cannot be null. "fieldName=" will cause the value to be null. If the descriptor construction fails for any reason, this exception will be thrown.

Methods

clone

public Object clone()
             throws RuntimeOperationsException

Returns a new Descriptor which is a duplicate of the Descriptor.

Specified by:
clone in interface Descriptor
Overrides:
clone in class Object
Returns:
a clone of this instance.
Throws:
RuntimeOperationsException - for illegal value for field Names or field Values. If the descriptor construction fails for any reason, this exception will be thrown.
See Also:
Cloneable

equals

public boolean equals(Object o)

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 must return true.
  • Otherwise Object.equals(Object) must return true.

Specified by:
equals in interface Descriptor
Overrides:
equals in class Object
Parameters:
o - the object to compare with.
Returns:
true if the objects are the same; false otherwise.
See Also:
Object.hashCode(), HashMap

hashCode

public int hashCode()

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 and value v is n.toLowerCase().hashCode() ^ h. Here h is the hash code of v, computed as follows:

  • If v is null then h is 0.
  • If v is a primitive array then h is computed using the appropriate overloading of java.util.Arrays.hashCode.
  • If v is an object array then h is computed using Arrays.deepHashCode.
  • Otherwise h is v.hashCode().
Specified by:
hashCode in interface Descriptor
Overrides:
hashCode in class Object
Returns:
A hash code value for this object.
See Also:
Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)

isValid

public boolean isValid()
                throws RuntimeOperationsException

Returns true if all of the fields have legal values given their names.

This implementation does not support interoperating with a directory or lookup service. Thus, conforming to the specification, no checking is done on the "export" field.

Otherwise this implementation returns false if:

  • name and descriptorType fieldNames are not defined, or null, or empty, or not String
  • class, role, getMethod, setMethod fieldNames, if defined, are null or not String
  • persistPeriod, currencyTimeLimit, lastUpdatedTimeStamp, lastReturnedTimeStamp if defined, are null, or not a Numeric String or not a Numeric Value >= -1
  • log fieldName, if defined, is null, or not a Boolean or not a String with value "t", "f", "true", "false". These String values must not be case sensitive.
  • visibility fieldName, if defined, is null, or not a Numeric String or a not Numeric Value >= 1 and <= 4
  • severity fieldName, if defined, is null, or not a Numeric String or not a Numeric Value >= 0 and <= 6
  • persistPolicy fieldName, if defined, is null, or not one of the following strings:
    "OnUpdate", "OnTimer", "NoMoreOftenThan", "OnUnregister", "Always", "Never". These String values must not be case sensitive.
Specified by:
isValid in interface Descriptor
Returns:
true if the values are legal.
Throws:
RuntimeOperationsException - If the validity checking fails for any reason, this exception will be thrown.

toXMLString

public String toXMLString()

Returns an XML String representing the descriptor.

The format is not defined, but an implementation must ensure that the string returned by this method can be used to build an equivalent descriptor when instantiated using the constructor DescriptorSupport(String inStr).

Fields which are not String objects will have toString() called on them to create the value. The value will be enclosed in parentheses. It is not guaranteed that you can reconstruct these objects unless they have been specifically set up to support toString() in a meaningful format and have a matching constructor that accepts a String in the same format.

If the descriptor is empty the following String is returned: <Descriptor></Descriptor>

Returns:
the XML string.
Throws:
RuntimeOperationsException - for illegal value for field Names or field Values. If the XML formatted string construction fails for any reason, this exception will be thrown.

toString

public String toString()

Returns a human readable string representing the descriptor. The string will be in the format of "fieldName=fieldValue,fieldName2=fieldValue2,..."
If there are no fields in the descriptor, then an empty String is returned.
If a fieldValue is an object then the toString() method is called on it and its returned value is used as the value for the field enclosed in parenthesis.

Overrides:
toString in class Object
Returns:
a string representation of the object.
Throws:
RuntimeOperationsException - for illegal value for field Names or field Values. If the descriptor string fails for any reason, this exception will be thrown.

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Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
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https://docs.oracle.com/en/java/javase/11/docs/api/java.management/javax/management/modelmbean/DescriptorSupport.html