KeyExtractor Class |
(14.1.1.0)
E55634-01
The KeyExtractor is a special purpose IValueExtractor
implementation that serves as an indicator that a query should be run
against the key objects rather than the values.
Inheritance HierarchyNamespace: Tangosol.Util.Extractor
Assembly: Coherence (in Coherence.dll) Version: 14.1.1.1 (14.1.1.1)
SyntaxC#
public class KeyExtractor : AbstractExtractor, IPortableObject
The KeyExtractor type exposes the following members.
Constructors| Name | Description | |
|---|---|---|
 | KeyExtractor |
Default constructor.
|
| KeyExtractor(String) |
Construct a KeyExtractor for a specified member name.
|
| KeyExtractor(IValueExtractor) |
Construct a KeyExtractor based on a specified
IValueExtractor.
|
Properties| Name | Description | |
|---|---|---|
 | Extractor |
The underlying IValueExtractor.
|
| Target |
The target of the extractor.
(Inherited from AbstractExtractor.) |
Methods| Name | Description | |
|---|---|---|
| Compare |
Compares its two arguments for order.
(Inherited from AbstractExtractor.) |
| CompareEntries |
Compare two entries.
(Inherited from AbstractExtractor.) |
| Equals |
Compare the KeyExtractor with another object to determine
equality.
(Overrides ObjectEquals(Object).) |
| Extract |
Extract the value from the passed object.
(Overrides AbstractExtractorExtract(Object).) |
| ExtractFromEntry |
Extract the value from the passed Entry object. The returned
value should follow the conventions outlined in the
Extract(Object) method.
(Inherited from AbstractExtractor.) |
| ExtractOriginalFromEntry |
Extract the value from the "original value" of the passed
CacheEntry object or the key (if targeted). This method's conventions are exactly the same
as the ExtractFromEntry(ICacheEntry) method.
(Inherited from AbstractExtractor.) |
 | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
| GetHashCode |
Determine a hash value for the KeyExtractor object according
to the general Object.GetHashCode contract.
(Overrides ObjectGetHashCode.) |
| GetType | Gets the Type of the current instance. (Inherited from Object.) |
| MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
| ReadExternal |
Restore the contents of a user type instance by reading its state
using the specified IPofReader object.
|
| ToString |
Provide a human-readable description of this KeyExtractor
object.
(Overrides ObjectToString.) |
| WriteExternal |
Save the contents of a POF user type instance by writing its
state using the specified IPofWriter object.
|
Fields| Name | Description | |
|---|---|---|
 | m_extractor |
The underlying IValueExtractor.
|
| m_target |
Specifies which part of the entry should be used by the
ExtractFromEntry(ICacheEntry) operation. Legal values are
VALUE (default) or KEY.
(Inherited from AbstractExtractor.) |
RemarksThe major difference between the KeyExtractor and a standard ReflectionExtractor is that when used in various IFilter implementations it forces the evaluation of entry keys rather than entry values.
For example, consider a key object that consists of two properties: "FirstName" and "LastName". To retrieve all keys that have a value of the "LastName" property equal to "Smith", the following query could be used:
IValueExtractor extractor = new KeyExtractor("LastName");
ICollection keys = cache.GetKeys(new EqualsFilter(extractor, "Smith"));
As of Coherence 3.5, the same effect can be achieved for subclasses
of the AbstractExtractor, for example:
IValueExtractor extractor = new ReflectionExtractor("LastName",
null,AbstractExtractor.KEY);
ICollection keys = cache.GetKeys(new EqualsFilter(extractor, "Smith"));
See Also