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Java > Open Source Codes > org > apache > cayenne > query > QueryRouter


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19
20 package org.apache.cayenne.query;
21
22 import org.apache.cayenne.access.QueryEngine;
23 import org.apache.cayenne.map.DataMap;
24
25 /**
26  * An interface used by Queries to route themselves to an appropriate QueryEngine. As of
27  * 1.2 QueryRouter only supports routing by DataMap.
28  *
29  * @since 1.2
30  * @author Andrus Adamchik
31  */
32 public interface QueryRouter {
33
34     /**
35      * A callback method that allows a query to set its preferred engine during the
36      * routing phase. It allows query to further customize its routing, e.g. it is
37      * possible to implement query chains that pass multiple queries for execution.
38      *
39      * @param engine engine to use for query execution
40      * @param query A query to execute.
41      * @param substitutedQuery a query that was substituted for "query". Results must be
42      * mapped back to substituted query.
43      */
44     void route(QueryEngine engine, Query query, Query substitutedQuery);
45
46     /**
47      * Returns a QueryEngine that is configured to handle a given DataMap.
48      *
49      * @throws CayenneRuntimeException if an engine can't be found.
50      * @throws NullPointerException if a map parameter is null.
51      */
52     QueryEngine engineForDataMap(DataMap map);
53 }
54
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