Do not derive DataSource from Function and replace apply method #307.

Change-Id: Ic0587e75c9a50c802a64673b1db0b8828b37889c

4 files changed, 20 insertions, 12 deletions

diff --git a/server/src/main/java/com/vaadin/server/data/BackEndDataSource.java b/server/src/main/java/com/vaadin/server/data/BackEndDataSource.java
index e0cfc8f48b..c792ebd23e 100644
--- a/server/src/main/java/com/vaadin/server/data/BackEndDataSource.java
+++ b/server/src/main/java/com/vaadin/server/data/BackEndDataSource.java
@@ -50,13 +50,13 @@ public class BackEndDataSource<T> extends AbstractDataSource<T> {
     }
 
     @Override
-    public Stream<T> apply(Query t) {
-        return request.apply(t);
+    public Stream<T> fetch(Query query) {
+        return request.apply(query);
     }
 
     @Override
-    public int size(Query t) {
-        return sizeCallback.apply(t);
+    public int size(Query query) {
+        return sizeCallback.apply(query);
     }
 
     /**
diff --git a/server/src/main/java/com/vaadin/server/data/DataCommunicator.java b/server/src/main/java/com/vaadin/server/data/DataCommunicator.java
index 5fc11bb15d..8238777c64 100644
--- a/server/src/main/java/com/vaadin/server/data/DataCommunicator.java
+++ b/server/src/main/java/com/vaadin/server/data/DataCommunicator.java
@@ -228,7 +228,7 @@ public class DataCommunicator<T> extends AbstractExtension {
         if (initial || reset) {
             int dataSourceSize;
             if (getDataSource().isInMemory() && inMemoryFilter != null) {
-                dataSourceSize = (int) getDataSource().apply(new Query())
+                dataSourceSize = (int) getDataSource().fetch(new Query())
                         .filter(inMemoryFilter).count();
             } else {
                 dataSourceSize = getDataSource().size(new Query(filters));
@@ -244,7 +244,7 @@ public class DataCommunicator<T> extends AbstractExtension {
 
             if (getDataSource().isInMemory()) {
                 // We can safely request all the data when in memory
-                rowsToPush = getDataSource().apply(new Query());
+                rowsToPush = getDataSource().fetch(new Query());
                 if (inMemoryFilter != null) {
                     rowsToPush = rowsToPush.filter(inMemoryFilter);
                 }
@@ -254,7 +254,7 @@ public class DataCommunicator<T> extends AbstractExtension {
                 rowsToPush = rowsToPush.skip(offset).limit(limit);
             } else {
                 Query query = new Query(offset, limit, backEndSorting, filters);
-                rowsToPush = getDataSource().apply(query);
+                rowsToPush = getDataSource().fetch(query);
             }
             pushData(offset, rowsToPush);
         }
diff --git a/server/src/main/java/com/vaadin/server/data/DataSource.java b/server/src/main/java/com/vaadin/server/data/DataSource.java
index f767f60cf0..c4042ecc11 100644
--- a/server/src/main/java/com/vaadin/server/data/DataSource.java
+++ b/server/src/main/java/com/vaadin/server/data/DataSource.java
@@ -18,7 +18,6 @@ package com.vaadin.server.data;
 import java.io.Serializable;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.function.Function;
 import java.util.stream.Stream;
 
 import com.vaadin.shared.Registration;
@@ -37,8 +36,7 @@ import com.vaadin.shared.Registration;
  *
  * @since 8.0
  */
-public interface DataSource<T>
-        extends Function<Query, Stream<T>>, Serializable {
+public interface DataSource<T> extends Serializable {
 
     /**
      * Gets whether the DataSource content all available in memory or does it
@@ -58,6 +56,16 @@ public interface DataSource<T>
     int size(Query t);
 
     /**
+     * Fetches data from this DataSource using given {@code query}.
+     * 
+     * @param query
+     *            given query to request data
+     * @return the result of the query request: a stream of data objects, not
+     *         {@code null}
+     */
+    Stream<T> fetch(Query query);
+
+    /**
      * Refreshes all data based on currently available data in the underlying
      * provider.
      */
diff --git a/server/src/main/java/com/vaadin/server/data/ListDataSource.java b/server/src/main/java/com/vaadin/server/data/ListDataSource.java
index 64b7c03cb1..1e2724dc5b 100644
--- a/server/src/main/java/com/vaadin/server/data/ListDataSource.java
+++ b/server/src/main/java/com/vaadin/server/data/ListDataSource.java
@@ -63,7 +63,7 @@ public class ListDataSource<T> extends AbstractDataSource<T> {
     }
 
     @Override
-    public Stream<T> apply(Query query) {
+    public Stream<T> fetch(Query query) {
         Stream<T> stream = backend.stream();
         if (sortOrder != null) {
             stream = stream.sorted(sortOrder);
@@ -117,7 +117,7 @@ public class ListDataSource<T> extends AbstractDataSource<T> {
      * return the full size.
      */
     @Override
-    public int size(Query t) {
+    public int size(Query query) {
         return backend.size();
     }