Fix NPE sorting columns with null values (#8610)

* Fix NPE sorting columns with null values

Sorting a column in Grid throws a NullPointerException if there are null values and we are using the default TextRenderer

* Test for #8610

* Update Grid.java

* Update GridNullValueSortTest.java

* Update GridNullValueSortTest.java

2 files changed, 50 insertions, 1 deletions

diff --git a/server/src/main/java/com/vaadin/ui/Grid.java b/server/src/main/java/com/vaadin/ui/Grid.java
index c3456075c3..c464acb8fc 100644
--- a/server/src/main/java/com/vaadin/ui/Grid.java
+++ b/server/src/main/java/com/vaadin/ui/Grid.java
@@ -887,7 +887,7 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
             if (hasCommonComparableBaseType(a, b)) {
                 return compareComparables(a, b);
             } else {
-                return compareComparables(a.toString(), b.toString());
+                return compareComparables(Objects.toString(a, ""), Objects.toString(b, ""));
             }
         }
 
@@ -906,6 +906,10 @@ public class Grid<T> extends AbstractListing<T> implements HasComponents,
                     return true;
                 }
             }
+            if ((a == null && b instanceof Comparable<?>)
+                || (b == null && a instanceof Comparable<?>)) {
+                return true;
+            }
 
             return false;
         }
diff --git a/server/src/test/java/com/vaadin/tests/components/grid/GridNullValueSortTest.java b/server/src/test/java/com/vaadin/tests/components/grid/GridNullValueSortTest.java
new file mode 100644
index 0000000000..ddf4844490
--- /dev/null
+++ b/server/src/test/java/com/vaadin/tests/components/grid/GridNullValueSortTest.java
@@ -0,0 +1,45 @@
+package com.vaadin.tests.components.grid;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import com.vaadin.server.VaadinSession;
+import com.vaadin.tests.util.MockUI;
+import com.vaadin.ui.Grid;
+import com.vaadin.ui.Grid.Column;
+
+public class GridNullValueSortTest {
+
+    private Grid<TestClass> grid;
+    private Column<TestClass, String> stringColumn;
+    private Column<TestClass, Object> nonComparableColumn;
+
+    @Test
+    public void sortWithNullValues() {
+        this.grid.sort(this.stringColumn);
+        this.grid.sort(this.nonComparableColumn);
+        this.grid.getDataCommunicator().beforeClientResponse(true);
+    }
+
+    @Before
+    public void setup() {
+        VaadinSession.setCurrent(null);
+        this.grid = new Grid<TestClass>();
+        this.stringColumn = this.grid.addColumn(bean -> bean.stringField);
+        this.nonComparableColumn = this.grid.addColumn(bean -> bean.nonComparableField);
+
+        this.grid.setItems(new TestClass(null, new Object()), new TestClass("something", null));
+        new MockUI().setContent(grid);
+    }
+
+    private static class TestClass {
+
+        private final String stringField;
+        private final Object nonComparableField;
+
+        TestClass(final String stringField, final Object nonComparableField) {
+            this.stringField = stringField;
+            this.nonComparableField = nonComparableField;
+        }
+    }
+}