javax.management
Class ImmutableDescriptor

java.lang.Object
  javax.management.ImmutableDescriptor

All Implemented Interfaces:

Serializable , Cloneable , Descriptor

public class ImmutableDescriptor
extends Object
implements Descriptor

An immutable descriptor.

Since:

1.6

See Also:

Serialized Form

Method Summary
Descriptor	clone ()           Returns a descriptor which is equal to this descriptor.
boolean	equals ( Object           Compares           Indicates whether some other object is "equal to" this descriptor to the given object. one.
String []	getFieldNames ()           Returns all the field names in the descriptor.
String []	getFields ()           Returns all of the fields contained in this descriptor as a string array.
Object	getFieldValue ( String  fieldName)           Returns the value for a specific field name, or null if no value is present for that name.
Object []	getFieldValues ( String ... fieldNames)           Returns all the field values in the descriptor as an array of Objects.
int	hashCode ()           Returns the a hash code value for this descriptor. the object.
boolean	isValid ()           Returns true if all of the fields have legal values given their names.
void	removeField ( String  fieldName)           Removes a field from the descriptor.
void	setField ( String  fieldName, Object  fieldValue)           This operation is unsupported since this class is immutable.
void	setFields ( String [] fieldNames, Object [] fieldValues)           This operation is unsupported since this class is immutable.
String	toString ()           Returns a string representation of the object.
static  ImmutableDescriptor	union ( Descriptor ... descriptors)           Return an ImmutableDescriptor whose contents are the union of the given descriptors.

EMPTY_DESCRIPTOR

public static final ImmutableDescriptor EMPTY_DESCRIPTOR

An empty descriptor.

ImmutableDescriptor

public ImmutableDescriptor(String[] fieldNames,
                           Object[] fieldValues)

Construct a descriptor containing the given fields and values.

Throws:

IllegalArgumentException - if either array is null, or if the arrays have different sizes, or if a field name is null or empty, or if the same field name appears more than once.

ImmutableDescriptor

public ImmutableDescriptor(String... fields)

Construct a descriptor containing the given fields. Each String must 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:

IllegalArgumentException - if the parameter is null, or if a field name is empty, or if the same field name appears more than once, or if one of the strings does not contain an = character.

ImmutableDescriptor

public ImmutableDescriptor(Map<String,?> fields)

Construct a descriptor where the names and values of the fields are the keys and values of the given Map.

Throws:

IllegalArgumentException - if the parameter is null, or if a field name is null or empty, or if the same field name appears more than once (which can happen because field names are not case sensitive).

union

public static ImmutableDescriptor union(Descriptor... descriptors)

Return an ImmutableDescriptor whose contents are the union of the given descriptors. Every field name that appears in any of the descriptors will appear in the result with the value that it has when the method is called. Subsequent changes to any of the descriptors do not affect the ImmutableDescriptor returned here.

In the simplest case, there is only one descriptor and the returned ImmutableDescriptor is a copy of its fields at the time this method is called:

 Descriptor d = something();
 ImmutableDescriptor copy = ImmutableDescriptor.union(d);
 

Parameters:

descriptors - the descriptors to be combined. Any of the descriptors can be null, in which case it is skipped.

Returns:

an ImmutableDescriptor that is the union of the given descriptors. The returned object may be identical to one of the input descriptors if it is an ImmutableDescriptor that contains all of the required fields.

Throws:

IllegalArgumentException - if two Descriptors contain the same field name with different associated values. Primitive array values are considered the same if they are of the same type with the same elements. Object array values are considered the same if Arrays.deepEquals(Object[],Object[]) returns true.

getFieldValue

public final Object getFieldValue(String fieldName)

Description copied from interface: Descriptor

Returns the value for a specific field name, or null if no value is present for that name.

Specified by:

getFieldValue in interface Descriptor

Parameters:

fieldName - the field name.

Returns:

the corresponding value, or null if the field is not present.

getFields

public final String[] getFields()

Description copied from interface: Descriptor

Returns all of the fields contained in this descriptor as a string array.

Specified by:

getFields in interface Descriptor

Returns:

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:

Descriptor.setFields(java.lang.String[], java.lang.Object[])

getFieldValues

public final Object[] getFieldValues(String... fieldNames)

Description copied from interface: Descriptor

Returns all the field values in the descriptor as an array of Objects. The returned values are in the same order as the fieldNames String array parameter.

Specified by:

getFieldValues in interface Descriptor

Parameters:

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 Descriptor.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.

Returns:

Object array of field values. If the list of fieldNames is empty, you will get an empty array.

getFieldNames

public final String[] getFieldNames()

Description copied from interface: Descriptor

Returns all the field names in the descriptor.

Specified by:

getFieldNames in interface Descriptor

Returns:

String array of field names. If the descriptor is empty, you will get an empty array.

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:

Description copied from class: Object

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

• 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[])
• Otherwise Object.equals(Object)
• It is reflexive : for any non-null reference value x, x.equals(x) should return true.
• It is symmetric : for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
• It is transitive : for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
• It is consistent : for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
• For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Specified by:

equals in interface Descriptor

Overrides:

equals in class Object

Parameters:

o - the reference object with which to compare with. compare.

Returns:

true if this object is the objects are same as the same; obj argument; false otherwise.

See Also:

Object.hashCode() , Hashtable

hashCode

public int hashCode()

Description copied from class: Object

Returns a hash code value for the object. This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable.

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:

The general contract of hashCode is:

• 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(Object[])
• Otherwise h is v.hashCode().
• Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
• If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
• It is not required that if two objects are unequal according to the Object.equals(java.lang.Object) hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hashtables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java ^TM programming language.)

Specified by:

hashCode in interface Descriptor

Overrides:

hashCode in class Object

Returns:

A a hash code value for this object.

See Also:

Object.equals(java.lang.Object) , Hashtable

toString

public String toString()

Description copied from class: Object

Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Overrides:

toString in class Object

Returns:

a string representation of the object.

isValid

public boolean isValid()

Returns true if all of the fields have legal values given their names. This method always returns true, but a subclass can override it to return false when appropriate.

Specified by:

isValid in interface Descriptor

Returns:

true if the values are legal.

Throws:

RuntimeOperationsException - if the validity checking fails. The method returns false if the descriptor is not valid, but throws this exception if the attempt to determine validity fails.

clone

public Descriptor clone()

Returns a descriptor which is equal to this descriptor. Changes to the returned descriptor will have no effect on this descriptor, and vice versa.

This method returns the object on which it is called. A subclass can override it to return another object provided the contract is respected.

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

setFields

public final void setFields(String[] fieldNames,
                            Object[] fieldValues)
 throws RuntimeOperationsException[] fieldValues) 

This operation is unsupported since this class is immutable. If this call would change a mutable descriptor with the same contents, then a RuntimeOperationsException wrapping an UnsupportedOperationException is thrown. Otherwise, the behavior is the same as it would be for a mutable descriptor: either an exception is thrown because of illegal parameters, or there is no effect.

Specified by:

setFields in interface Descriptor

Parameters:

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.

Throws:

RuntimeOperationsException - if the change fails for any reason. Wrapped exception is IllegalArgumentException - for illegal value for field Names or field Values. Neither can be null. The array lengths must be equal. If the call would succeed on a mutable descriptor and change its contents, then this exception will be thrown and the wrapped exception will be UnsupportedOperationException if fieldNames or fieldValues is null, or if the arrays are of different lengths, or if there is an illegal value in one of them. Wrapped exception is UnsupportedOperationException if the descriptor is immutable, and the call would change its contents. .

See Also:

Descriptor.getFields() getFields()

setField

public final void setField(String fieldName,
                           Object fieldValue)
 throws RuntimeOperationsException fieldValue) 

This operation is unsupported since this class is immutable. If this call would change a mutable descriptor with the same contents, then a RuntimeOperationsException wrapping an UnsupportedOperationException is thrown. Otherwise, the behavior is the same as it would be for a mutable descriptor: either an exception is thrown because of illegal parameters, or there is no effect.

Specified by:

setField in interface Descriptor

Parameters:

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.

Throws:

RuntimeOperationsException - if the field name or field value is illegal (wrapped exception is IllegalArgumentException ); or if the descriptor is immutable (wrapped exception is UnsupportedOperationException ). If the call would succeed on a mutable descriptor and change its contents, then this exception will be thrown and the wrapped exception will be UnsupportedOperationException ). .

removeField

public final void removeField(String fieldName)

Removes a field from the descriptor.

Specified by:

removeField in interface Descriptor

Parameters:

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.

Throws:

RuntimeOperationsException - if a field of the given name exists and the descriptor is immutable. The wrapped exception will be an UnsupportedOperationException .