From dda6e0c4ddf6e4bb4cd777e24ccb22acbb3790a7 Mon Sep 17 00:00:00 2001
From: Denis Anisimov <denis@vaadin.com>
Date: Sun, 21 Sep 2014 19:32:13 +0300
Subject: [PATCH] Make DefaultFieldGroupFieldFactory singleton (#11038).

Change-Id: I40250fadfe78d663d1cb7614f4f8818216e773a4
---
 .../DefaultFieldGroupFieldFactory.java        | 16 ++++++++++++
 .../vaadin/data/fieldgroup/FieldGroup.java    |  3 ++-
 .../DefaultFieldGroupFieldFactoryTest.java    | 26 ++++++++++++++++++-
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/server/src/com/vaadin/data/fieldgroup/DefaultFieldGroupFieldFactory.java b/server/src/com/vaadin/data/fieldgroup/DefaultFieldGroupFieldFactory.java
index b1bf58199a..9c2e4b2f83 100644
--- a/server/src/com/vaadin/data/fieldgroup/DefaultFieldGroupFieldFactory.java
+++ b/server/src/com/vaadin/data/fieldgroup/DefaultFieldGroupFieldFactory.java
@@ -36,10 +36,26 @@ import com.vaadin.ui.RichTextArea;
 import com.vaadin.ui.Table;
 import com.vaadin.ui.TextField;
 
+/**
+ * This class contains a basic implementation for {@link FieldGroupFieldFactory}
+ * .The class is singleton, use {@link #get()} method to get reference to the
+ * instance.
+ * 
+ * @author Vaadin Ltd
+ */
 public class DefaultFieldGroupFieldFactory implements FieldGroupFieldFactory {
 
+    private static final DefaultFieldGroupFieldFactory INSTANCE = new DefaultFieldGroupFieldFactory();
+
     public static final Object CAPTION_PROPERTY_ID = "Caption";
 
+    protected DefaultFieldGroupFieldFactory() {
+    }
+
+    public static DefaultFieldGroupFieldFactory get() {
+        return INSTANCE;
+    }
+
     @Override
     public <T extends Field> T createField(Class<?> type, Class<T> fieldType) {
         if (Enum.class.isAssignableFrom(type)) {
diff --git a/server/src/com/vaadin/data/fieldgroup/FieldGroup.java b/server/src/com/vaadin/data/fieldgroup/FieldGroup.java
index 27515d15af..c5aab5a053 100644
--- a/server/src/com/vaadin/data/fieldgroup/FieldGroup.java
+++ b/server/src/com/vaadin/data/fieldgroup/FieldGroup.java
@@ -68,7 +68,8 @@ public class FieldGroup implements Serializable {
     /**
      * The field factory used by builder methods.
      */
-    private FieldGroupFieldFactory fieldFactory = new DefaultFieldGroupFieldFactory();
+    private FieldGroupFieldFactory fieldFactory = DefaultFieldGroupFieldFactory
+            .get();
 
     /**
      * Constructs a field binder. Use {@link #setItemDataSource(Item)} to set a
diff --git a/server/tests/src/com/vaadin/data/DefaultFieldGroupFieldFactoryTest.java b/server/tests/src/com/vaadin/data/DefaultFieldGroupFieldFactoryTest.java
index a5fee5175e..bbf74bfb21 100644
--- a/server/tests/src/com/vaadin/data/DefaultFieldGroupFieldFactoryTest.java
+++ b/server/tests/src/com/vaadin/data/DefaultFieldGroupFieldFactoryTest.java
@@ -15,6 +15,7 @@
  */
 package com.vaadin.data;
 
+import java.lang.reflect.Constructor;
 import java.util.Date;
 
 import org.junit.Assert;
@@ -34,7 +35,30 @@ public class DefaultFieldGroupFieldFactoryTest {
 
     @Before
     public void setupFieldFactory() {
-        fieldFactory = new DefaultFieldGroupFieldFactory();
+        fieldFactory = DefaultFieldGroupFieldFactory.get();
+    }
+
+    @Test
+    public void noPublicConstructor() {
+        Class<DefaultFieldGroupFieldFactory> clazz = DefaultFieldGroupFieldFactory.class;
+        Constructor<?>[] constructors = clazz.getConstructors();
+        Assert.assertEquals(
+                "DefaultFieldGroupFieldFactory contains public constructors",
+                0, constructors.length);
+    }
+
+    @Test
+    public void testSameInstance() {
+        DefaultFieldGroupFieldFactory factory1 = DefaultFieldGroupFieldFactory
+                .get();
+        DefaultFieldGroupFieldFactory factory2 = DefaultFieldGroupFieldFactory
+                .get();
+        Assert.assertTrue(
+                "DefaultFieldGroupFieldFactory.get() method returns different instances",
+                factory1 == factory2);
+        Assert.assertNotNull(
+                "DefaultFieldGroupFieldFactory.get() method returns null",
+                factory1);
     }
 
     @Test
-- 
2.39.5