Add APIs to inform components of stale objects in DataProvider (#8271)

* Add DataProvider refreshItem for single item update

* Add 'id' concept for DataProviders

This patch also adds a simplified data provider that can replace items
based on their id. This can be used to simulate stale objects from an actual
backend.

* Add refresh logic to Grid SelectionModels

* Remove broken equals and hashCode

* Refresh KeyMapper, clean up some methods

* Fix UI.access in test

* Fix tests and Grid single selection model

* Do clean up before replacing data provider

* Check correct variable for null value

* Fix other selects, add generic tests

* Code style fixes, removed assert

* Merge remote-tracking branch 'origin/master' into 286_refresh_items

* Fix documentation for refreshing an item

* Improve introduction chapter, minor clarifications

* Merge remote-tracking branch 'origin/master' into 287_refresh_items

* Add missing parameters in unit tests

1 files changed, 14 insertions, 0 deletions

diff --git a/server/src/main/java/com/vaadin/data/provider/DataKeyMapper.java b/server/src/main/java/com/vaadin/data/provider/DataKeyMapper.java
index 63bd2d92f8..0ec6748a85 100644
--- a/server/src/main/java/com/vaadin/data/provider/DataKeyMapper.java
+++ b/server/src/main/java/com/vaadin/data/provider/DataKeyMapper.java
@@ -17,6 +17,8 @@ package com.vaadin.data.provider;
 
 import java.io.Serializable;
 
+import com.vaadin.data.ValueProvider;
+
 /**
  * DataKeyMapper to map data objects to key strings.
  *
@@ -59,4 +61,16 @@ public interface DataKeyMapper<T> extends Serializable {
      * Dropped keys are not reused.
      */
     void removeAll();
+
+    /**
+     * Updates any existing mappings of given data object. The equality of two
+     * data objects is determined by the equality of their identifiers provided
+     * by the given value provider.
+     *
+     * @param dataObject
+     *            the data object to update
+     * @param identifierGetter
+     *            the function to get an identifier from a data object
+     */
+    void refresh(T dataObject, ValueProvider<T, Object> identifierGetter);
 }