Class QueryContext
- java.lang.Object
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- org.eclipse.rdf4j.query.algebra.evaluation.QueryContext
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public class QueryContext extends java.lang.Object
AQueryContext
provides a means to pass arbitrary local state to aFunction
orTupleFunction
. The implementation oforg.eclipse.rdf4j.sail.SailConnection#evaluate()
is responsible for initialising a QueryContext and making it available during evaluation viaQueryContextIteration
. A QueryContext is commonly used to provide aQueryPreparer
for the current SailConnection. This allows, for example, Functions to be written that conveniently express more complex queries.
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Field Summary
Fields Modifier and Type Field Description private java.util.Map<java.lang.String,java.lang.Object>
attributes
private QueryContext
previous
private static java.lang.String
QUERY_PREPARER_ATTRIBUTE
private static java.lang.ThreadLocal<QueryContext>
queryContext
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Constructor Summary
Constructors Constructor Description QueryContext()
QueryContext(QueryPreparer qp)
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
begin()
void
end()
<T> T
getAttribute(java.lang.String name)
static QueryContext
getQueryContext()
QueryPreparer
getQueryPreparer()
void
setAttribute(java.lang.String name, java.lang.Object value)
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Field Detail
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QUERY_PREPARER_ATTRIBUTE
private static final java.lang.String QUERY_PREPARER_ATTRIBUTE
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queryContext
private static final java.lang.ThreadLocal<QueryContext> queryContext
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attributes
private final java.util.Map<java.lang.String,java.lang.Object> attributes
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previous
private QueryContext previous
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Constructor Detail
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QueryContext
public QueryContext()
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QueryContext
public QueryContext(QueryPreparer qp)
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Method Detail
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getQueryContext
public static QueryContext getQueryContext()
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begin
public void begin()
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getQueryPreparer
public QueryPreparer getQueryPreparer()
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setAttribute
public void setAttribute(java.lang.String name, java.lang.Object value)
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getAttribute
public <T> T getAttribute(java.lang.String name)
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end
public void end()
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