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Cumulus4j API (1.1.0) |
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java.lang.Objectorg.cumulus4j.store.query.eval.AbstractExpressionEvaluator<X>
X
- the Expression
to be evaluated.public abstract class AbstractExpressionEvaluator<X extends Expression>
Abstract base class for all Expression
evaluators.
DataNucleus gives the query implementation a tree composed of Expression
s. This tree is nothing more
than an object-oriented representation of the query to be executed. In order to actually query data, there
needs to be evaluation logic applying the Expression
to the Cumulus4j data structure. This logic is
implemented in subclasses of AbstractExpressionEvaluator
.
Constructor Summary | |
---|---|
AbstractExpressionEvaluator(QueryEvaluator queryEvaluator,
AbstractExpressionEvaluator<?> parent,
X expression)
Create an AbstractExpressionEvaluator instance. |
Method Summary | |
---|---|
protected Set<Symbol> |
_getResultSymbols()
Get the Symbol s for which queryResultDataEntryIDs(ResultDescriptor) (and thus
queryResultObjects(ResultDescriptor) ) can return a result. |
protected abstract Set<Long> |
_queryResultDataEntryIDs(ResultDescriptor resultDescriptor)
Execute a query for the given resultDescriptor . |
protected List<Object> |
_queryResultObjects(ResultDescriptor resultDescriptor)
Get those objects that match the query criteria for the specified resultDescriptor
or null , if the given symbol is not queryable by the
evaluator implementation. |
X |
getExpression()
Get the expression that is to be evaluated by this AbstractExpressionEvaluator . |
protected Class<?> |
getFieldType(PrimaryExpression primaryExpression)
Get the field type of the PrimaryExpression . |
AbstractExpressionEvaluator<? extends Expression> |
getLeft()
Get the left branch in the tree structure. |
AbstractExpressionEvaluator<?> |
getParent()
Get the parent-node in the tree. |
QueryEvaluator |
getQueryEvaluator()
Get the evaluator responsible for evaluating the entire query. |
Set<Symbol> |
getResultSymbols()
Get the Symbol s for which queryResultDataEntryIDs(ResultDescriptor) (and thus
queryResultObjects(ResultDescriptor) ) can return a result. |
AbstractExpressionEvaluator<? extends Expression> |
getRight()
Get the right branch in the tree structure. |
Set<Long> |
queryResultDataEntryIDs(ResultDescriptor resultDescriptor)
Get those dataEntryID s that match the query
criteria for the specified resultDescriptor or null ,
if the given symbol is not queryable by the
evaluator implementation. |
List<Object> |
queryResultObjects(ResultDescriptor resultDescriptor)
Get those objects that match the query criteria for the specified resultDescriptor
or null , if the given symbol is not queryable by the
evaluator implementation. |
void |
setLeft(AbstractExpressionEvaluator<? extends Expression> left)
Set the left branch in the tree structure. |
void |
setRight(AbstractExpressionEvaluator<? extends Expression> right)
Set the right branch in the tree structure. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public AbstractExpressionEvaluator(QueryEvaluator queryEvaluator, AbstractExpressionEvaluator<?> parent, X expression)
AbstractExpressionEvaluator
instance.
queryEvaluator
- the evaluator responsible for evaluating the entire query. Must not be null
.parent
- the parent-node in the tree. The AbstractExpressionEvaluator
s form a tree analogue to the
tree provided by DataNucleus. This parent
is null
, if it is the root of the tree.expression
- the expression that is to be evaluated by this AbstractExpressionEvaluator
instance.Method Detail |
---|
public QueryEvaluator getQueryEvaluator()
public AbstractExpressionEvaluator<?> getParent()
AbstractExpressionEvaluator
s form a tree analogue to the
tree provided by DataNucleus. This parent
is null
, if it is the root of the tree.
null
, if this is the root.public X getExpression()
AbstractExpressionEvaluator
.
AbstractExpressionEvaluator
.public AbstractExpressionEvaluator<? extends Expression> getLeft()
null
if there is none.setLeft(AbstractExpressionEvaluator)
,
getRight()
public void setLeft(AbstractExpressionEvaluator<? extends Expression> left)
left
- the left branch in the tree structure or null
if there is none.getLeft()
public AbstractExpressionEvaluator<? extends Expression> getRight()
null
if there is none.setRight(AbstractExpressionEvaluator)
,
getLeft()
public void setRight(AbstractExpressionEvaluator<? extends Expression> right)
right
- the right branch in the tree structure or null
if there is none.getRight()
public final Set<Symbol> getResultSymbols()
Get the Symbol
s for which queryResultDataEntryIDs(ResultDescriptor)
(and thus
queryResultObjects(ResultDescriptor)
) can return a result. For all other Symbol
s,
said methods return null
.
The implementation in AbstractExpressionEvaluator
delegates to
_getResultSymbols()
and caches the result.
Do not override this method, if you're not absolutely sure you want to
deactivate/override the caching! In most cases, you should override
_getResultSymbols()
instead.
Symbol
s; never null
._getResultSymbols()
protected Set<Symbol> _getResultSymbols()
Get the Symbol
s for which queryResultDataEntryIDs(ResultDescriptor)
(and thus
queryResultObjects(ResultDescriptor)
) can return a result. For all other Symbol
s,
said methods return null
.
The default implementation in AbstractExpressionEvaluator
collects the result-symbols
from its left
and its right
side and returns this combined
Set
.
This is the actual implementation of getResultSymbols()
and should be overridden
instead of the non-"_"-prefixed version, in most cases.
Symbol
s or null
(null
is equivalent to an
empty Set
).getResultSymbols()
public final Set<Long> queryResultDataEntryIDs(ResultDescriptor resultDescriptor) throws UnsupportedOperationException
Get those dataEntryID
s that match the query
criteria for the specified resultDescriptor
or null
,
if the given symbol
is not queryable by the
evaluator implementation.
This method delegates to _queryResultDataEntryIDs(ResultDescriptor)
and caches the
result. Thus a second call to this method with the same symbol does not trigger a
second query but instead immediately returns the cached result.
If the subclass of AbstractExpressionEvaluator
does not support querying on its
own (e.g. querying a literal
makes no sense at all), this method
throws an UnsupportedOperationException
. The same exception is thrown, if the requested
query functionality is not yet implemented.
resultDescriptor
- the descriptor specifying what candidates (usually "this" or a variable) the
caller is interested in as well as modifiers (e.g. negation
)
affecting the query.
dataEntryID
s that match the query
criteria for the specified resultSymbol
or null
, if the symbol is not
supported (this should be consistent with the implementation of _getResultSymbols()
).
UnsupportedOperationException
- if the implementation does not support querying at all
(e.g. because it makes no sense without more context) or if the concrete query situation is not
yet supported._queryResultDataEntryIDs(ResultDescriptor)
protected abstract Set<Long> _queryResultDataEntryIDs(ResultDescriptor resultDescriptor) throws UnsupportedOperationException
resultDescriptor
. This method should contain
the concrete logic for queryResultDataEntryIDs(ResultDescriptor)
and must be implemented
by subclasses.
resultDescriptor
- the descriptor specifying what candidates (usually "this" or a variable) the
caller is interested in as well as modifiers (e.g. negation
)
affecting the query.
dataEntryID
s that match the query
criteria for the specified resultSymbol
or null
, if the symbol is not
supported (this should be consistent with the implementation of _getResultSymbols()
).
UnsupportedOperationException
- if the implementation does not support querying at all
(e.g. because it makes no sense without more context) or if the concrete query situation is not
yet supported.queryResultDataEntryIDs(ResultDescriptor)
public final List<Object> queryResultObjects(ResultDescriptor resultDescriptor) throws UnsupportedOperationException
Get those objects that match the query criteria for the specified resultDescriptor
or null
, if the given symbol
is not queryable by the
evaluator implementation.
This method delegates to _queryResultObjects(ResultDescriptor)
and caches the
result. Thus a second call to this method with the same symbol does not trigger a
second query but instead immediately returns the cached result.
If the subclass of AbstractExpressionEvaluator
does not support querying on its
own (e.g. querying a literal
makes no sense at all), this method
throws an UnsupportedOperationException
. The same exception is thrown, if the requested
query functionality is not yet implemented.
resultDescriptor
- the descriptor specifying what candidates (usually "this" or a variable) the
caller is interested in as well as modifiers (e.g. negation
)
affecting the query.
null
, if the given resultSymbol
is not supported (this should be consistent with the implementation of _getResultSymbols()
).
UnsupportedOperationException
- if the implementation does not support querying at all
(e.g. because it makes no sense without more context) or if the concrete query situation is not
yet supported._queryResultObjects(ResultDescriptor)
protected List<Object> _queryResultObjects(ResultDescriptor resultDescriptor) throws UnsupportedOperationException
Get those objects that match the query criteria for the specified resultDescriptor
or null
, if the given symbol
is not queryable by the
evaluator implementation.
The default implementation of this method in AbstractExpressionEvaluator
calls
queryResultDataEntryIDs(ResultDescriptor)
and then resolves the corresponding objects
(including decrypting their data).
resultDescriptor
- the descriptor specifying what candidates (usually "this" or a variable) the
caller is interested in as well as modifiers (e.g. negation
)
affecting the query.
null
, if the given resultDescriptor
is not supported (ResultDescriptor.getSymbol()
should be consistent with the implementation of
_getResultSymbols()
).
UnsupportedOperationException
queryResultObjects(ResultDescriptor)
protected Class<?> getFieldType(PrimaryExpression primaryExpression)
Get the field type of the PrimaryExpression
. This is always the type of the last element in the list of tuples.
For example, if the given PrimaryExpression
references
this.rating.name
and the field name
of the class Rating
is a String
,
this method returns java.lang.String
.
primaryExpression
- the PrimaryExpression
of which to find out the field's type.
primaryExpression
.
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