From f777b14fdce26b37ad63b21159a3de46b878a8a8 Mon Sep 17 00:00:00 2001
From: Paul Hoadley <paulh@logicsquad.net>
Date: Thu, 21 May 2015 11:48:02 +0930
Subject: [PATCH] Makes ERXDisplayGroup serializable. #651

The java.lang.reflect.Field ivar displayedObjectsField was not
serializable. Here we make that field transient, and add a method to
lazily fetch its value from the parent object as required.
---
 .../extensions/appserver/ERXDisplayGroup.java | 38 +++++++++++++------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/Frameworks/Core/ERExtensions/Sources/er/extensions/appserver/ERXDisplayGroup.java b/Frameworks/Core/ERExtensions/Sources/er/extensions/appserver/ERXDisplayGroup.java
index 25f403638c2..31fd6ac10d3 100644
--- a/Frameworks/Core/ERExtensions/Sources/er/extensions/appserver/ERXDisplayGroup.java
+++ b/Frameworks/Core/ERExtensions/Sources/er/extensions/appserver/ERXDisplayGroup.java
@@ -38,7 +38,10 @@
  * @param <T> data type of the displaygroup's objects
  */
 public class ERXDisplayGroup<T> extends WODisplayGroup {
-	private Field displayedObjectsField;
+	/**
+	 * {@code _displayedObjects} field in parent object
+	 */
+	private transient Field displayedObjectsField;
 	
 	/**
 	 * Do I need to update serialVersionUID?
@@ -52,16 +55,29 @@ public class ERXDisplayGroup<T> extends WODisplayGroup {
 
 	public ERXDisplayGroup() {
 		super();
-		try {
-			displayedObjectsField = WODisplayGroup.class.getDeclaredField("_displayedObjects");
-			displayedObjectsField.setAccessible(true);
-		}
-		catch (SecurityException e) {
-			throw NSForwardException._runtimeExceptionForThrowable(e);
-		}
-		catch (NoSuchFieldException e) {
-			throw NSForwardException._runtimeExceptionForThrowable(e);
+	}
+
+	/**
+	 * Fetches the {@code _displayedObjects} field from the parent
+	 * {@link WODisplayGroup}. This is used in the overriden
+	 * {@link #setSelectedObjects(NSArray)} method.
+	 * 
+	 * @return {@code _displayedObjects} field from parent object
+	 */
+	private Field displayedObjectsField() {
+		if (displayedObjectsField == null) {
+			try {
+				displayedObjectsField = WODisplayGroup.class.getDeclaredField("_displayedObjects");
+				displayedObjectsField.setAccessible(true);
+			}
+			catch (SecurityException e) {
+				throw NSForwardException._runtimeExceptionForThrowable(e);
+			}
+			catch (NoSuchFieldException e) {
+				throw NSForwardException._runtimeExceptionForThrowable(e);
+			}
 		}
+		return displayedObjectsField;
 	}
 	
 	/**
@@ -222,7 +238,7 @@ public void setSelectedObjects(NSArray objects) {
 			// wrong indexes when calling displayedObjects()
 			NSMutableArray displayedObjects;
 			try {
-				displayedObjects = (NSMutableArray) displayedObjectsField.get(this);
+				displayedObjects = (NSMutableArray) displayedObjectsField().get(this);
 			}
 			catch (IllegalArgumentException e) {
 				throw NSForwardException._runtimeExceptionForThrowable(e);