Add filter type parameter for Query

Change-Id: If9554c67900cc854e3ba6912fefad19e043b1d62

server/src/main/java/com/vaadin/server/data/BackEndDataProvider.java

@@ -30,8 +30,8 @@ import com.vaadin.server.SerializableFunction;
  */
 public class BackEndDataProvider<T> extends AbstractDataProvider<T> {
 
-    private final SerializableFunction<Query, Stream<T>> request;
-    private final SerializableFunction<Query, Integer> sizeCallback;
+    private final SerializableFunction<Query<?>, Stream<T>> request;
+    private final SerializableFunction<Query<?>, Integer> sizeCallback;
 
     /**
      * Constructs a new DataProvider to request data from an arbitrary back end
@@ -42,8 +42,9 @@ public class BackEndDataProvider<T> extends AbstractDataProvider<T> {
      * @param sizeCallback
      *            function that return the amount of data in back end for query
      */
-    public BackEndDataProvider(SerializableFunction<Query, Stream<T>> request,
-                               SerializableFunction<Query, Integer> sizeCallback) {
+    public BackEndDataProvider(
+            SerializableFunction<Query<?>, Stream<T>> request,
+            SerializableFunction<Query<?>, Integer> sizeCallback) {
         Objects.requireNonNull(request, "Request function can't be null");
         Objects.requireNonNull(sizeCallback, "Size callback can't be null");
         this.request = request;
@@ -68,13 +69,14 @@ public class BackEndDataProvider<T> extends AbstractDataProvider<T> {
      *            directions
      * @return new data provider with modified sorting
      */
-    public BackEndDataProvider<T> sortingBy(List<SortOrder<String>> sortOrders) {
+    public BackEndDataProvider<T> sortingBy(
+            List<SortOrder<String>> sortOrders) {
         return new BackEndDataProvider<>(query -> {
             List<SortOrder<String>> queryOrder = new ArrayList<>(
                     query.getSortOrders());
             queryOrder.addAll(sortOrders);
-            return request.apply(new Query(query.getLimit(), query.getOffset(),
-                    queryOrder, query.getFilters()));
+            return request.apply(new Query<>(query.getLimit(),
+                    query.getOffset(), queryOrder, query.getFilter()));
         }, sizeCallback);
     }
 

server/src/main/java/com/vaadin/server/data/Query.java

@@ -18,20 +18,23 @@ package com.vaadin.server.data;
 import java.io.Serializable;
 import java.util.Collections;
 import java.util.List;
-import java.util.Set;
+import java.util.Optional;
 
 /**
- * Query object used to request data from a backend. Contains index limits,
- * sorting and filtering information.
+ * Immutable query object used to request data from a backend. Contains index
+ * limits, sorting and filtering information.
+ *
+ * @param <F>
+ *            filter type
  *
  * @since 8.0
  */
-public class Query implements Serializable {
+public class Query<F> implements Serializable {
 
     private final int offset;
     private final int limit;
     private final List<SortOrder<String>> sortOrders;
-    private final Set<Object> filters;
+    private final F filter;
 
     /**
      * Constructs a Query for all rows from 0 to {@link Integer#MAX_VALUE}
@@ -41,21 +44,21 @@ public class Query implements Serializable {
         offset = 0;
         limit = Integer.MAX_VALUE;
         sortOrders = Collections.emptyList();
-        filters = Collections.emptySet();
+        filter = null;
     }
 
     /**
      * Constructs a Query for all rows from 0 to {@link Integer#MAX_VALUE} with
      * filtering.
      *
-     * @param filters
-     *            set of back end filters
+     * @param filter
+     *            back end filter of a suitable type for the data provider
      */
-    public Query(Set<Object> filters) {
+    public Query(F filter) {
         offset = 0;
         limit = Integer.MAX_VALUE;
         sortOrders = Collections.emptyList();
-        this.filters = filters;
+        this.filter = filter;
     }
 
     /**
@@ -68,15 +71,15 @@ public class Query implements Serializable {
      *            fetched item count
      * @param sortOrders
      *            sorting order for fetching
-     * @param filters
+     * @param filter
      *            filtering for fetching
      */
     public Query(int offset, int limit, List<SortOrder<String>> sortOrders,
-            Set<Object> filters) {
+            F filter) {
         this.offset = offset;
         this.limit = limit;
         this.sortOrders = sortOrders;
-        this.filters = filters;
+        this.filter = filter;
     }
 
     /**
@@ -110,11 +113,11 @@ public class Query implements Serializable {
     }
 
     /**
-     * Gets the filters for items to fetch.
+     * Gets the filter for items to fetch.
      *
-     * @return set of filters
+     * @return optional filter
      */
-    public Set<Object> getFilters() {
-        return filters;
+    public Optional<F> getFilter() {
+        return Optional.ofNullable(filter);
     }
 }