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public interface Query
handle to a node in a S.O.D.A. query graph.
A node in the query graph can represent multiple
classes, one class or an attribute of a class.
The graph
is automatically extended with attributes of added constraints
(see constrain(java.lang.Object)
) and upon calls to descend(java.lang.String)
that request nodes that do not yet exist.
References to joined nodes in the query graph can be obtained
by "walking" along the nodes of the graph with the method
descend(java.lang.String)
.
execute()
evaluates the entire graph against all persistent objects.
execute()
can be called from any Query
node
of the graph. It will return an ObjectSet
filled with
objects of the class/classes that the node, it was called from,
represents.
Note:
Native queries
are the recommended main query
interface of db4o.
Method Summary | |
---|---|
Constraint |
constrain(java.lang.Object constraint)
adds a constraint to this node. |
Constraints |
constraints()
returns a Constraints
object that holds an array of all constraints on this node. |
Query |
descend(java.lang.String fieldName)
returns a reference to a descendant node in the query graph. |
ObjectSet |
execute()
executes the Query . |
Query |
orderAscending()
adds an ascending ordering criteria to this node of the query graph. |
Query |
orderDescending()
adds a descending order criteria to this node of the query graph. |
Query |
sortBy(java.util.Comparator comparator)
Sort the resulting ObjectSet by the given comparator. |
Query |
sortBy(QueryComparator comparator)
Sort the resulting ObjectSet by the given comparator. |
Method Detail |
---|
Constraint constrain(java.lang.Object constraint)
Class
: confine the result to objects of one
class or to objects implementing an interface.Evaluation
: run
evaluation callbacks against all candidates.
constraint
- the constraint to be added to this Query.
Constraint
a new Constraint
for this
query node or null
for objects implementing the
Evaluation
interface.Constraints constraints()
Constraints
object that holds an array of all constraints on this node.
Constraints
on this query node.Query descend(java.lang.String fieldName)
fieldName
- path to the descendant.
Query
nodeObjectSet execute()
Query
.
ObjectSet
- the result of the Query
.Query orderAscending()
Query
object to allow the chaining of method calls.Query orderDescending()
Query
object to allow the chaining of method calls.Query sortBy(QueryComparator comparator)
comparator
- The comparator to apply.
Query
object to allow the chaining of method calls.Query sortBy(java.util.Comparator comparator)
comparator
- The comparator to apply.
Query
object to allow the chaining of method calls.
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