Class KeyManager
- All Implemented Interfaces:
Serializable
The memory management in this class is subtle, with extensive use of weak references. The idea is that an index should continue to exist in memory so long as both the compiled stylesheet and the source document exist in memory: if either is removed, the index should go too. The document itself holds no reference to the index. The compiled stylesheet (which owns the KeyManager) holds a weak reference to the index. The index, of course, holds strong references to the nodes in the document. The Controller holds a strong reference to the list of indexes used for each document, so that indexes remain in memory for the duration of a transformation even if the documents themselves are garbage collected.
Potentially there is a need for more than one index for a given key name, depending on the primitive type of the value provided to the key() function. An index is built corresponding to the type of the requested value; if subsequently the key() function is called with the same name and a different type of value, then a new index is built.
- Author:
- Michael H. Kay
- See Also:
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Constructor Summary
ConstructorsConstructorDescriptionKeyManager
(Configuration config) create a KeyManager and initialise variables -
Method Summary
Modifier and TypeMethodDescriptionvoid
addKeyDefinition
(int fingerprint, KeyDefinition keydef, Configuration config) Register a key definition.void
explainKeys
(Configuration config) Diagnostic output explaining the keysgetKeyDefinitions
(int fingerprint) Get all the key definitions that match a particular fingerprintselectByKey
(int fingerprint, DocumentInfo doc, AtomicValue value, XPathContext context) Get the nodes with a given key value
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Constructor Details
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KeyManager
create a KeyManager and initialise variables
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Method Details
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addKeyDefinition
public void addKeyDefinition(int fingerprint, KeyDefinition keydef, Configuration config) throws XPathException Register a key definition. Note that multiple key definitions with the same name are allowed- Parameters:
fingerprint
- Integer representing the name of the keykeydef
- The details of the key's definitionconfig
- The configuration- Throws:
XPathException
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getKeyDefinitions
Get all the key definitions that match a particular fingerprint- Parameters:
fingerprint
- The fingerprint of the name of the required key- Returns:
- The key definition of the named key if there is one, or null otherwise.
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selectByKey
public SequenceIterator selectByKey(int fingerprint, DocumentInfo doc, AtomicValue value, XPathContext context) throws XPathException Get the nodes with a given key value- Parameters:
fingerprint
- The fingerprint of the name of the required keydoc
- The source document in questionvalue
- The required key valuecontext
- The dynamic context, needed only the first time when the key is being built- Returns:
- an enumeration of nodes, always in document order
- Throws:
XPathException
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explainKeys
Diagnostic output explaining the keys
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