From 175ab4e720266727f371e7f33381f2c6fecc5297 Mon Sep 17 00:00:00 2001
From: Jesse Rusak <me@jesserusak.com>
Date: Tue, 29 Aug 2017 11:00:23 -0400
Subject: [PATCH 1/2] Avoid possible GC issues in Java example code

This prevents the previously-set element value from being collected
before or during the call to setElement. Since C++ could still have
a reference to during that time, it could lead to misbehavior.
---
 Doc/Manual/Java.html | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/Doc/Manual/Java.html b/Doc/Manual/Java.html
index 85757d1cb..fd57fda25 100644
--- a/Doc/Manual/Java.html
+++ b/Doc/Manual/Java.html
@@ -8165,13 +8165,10 @@ public class Container {
   // Ensure that the GC doesn't collect any Element set from Java
   // as the underlying C++ class stores a shallow copy
   private Element elementReference;
-  private long getCPtrAndAddReference(Element element) {
-    elementReference = element;
-    return Element.getCPtr(element);
-  }
 
   public void setElement(Element e) {
-    exampleJNI.Container_setElement(swigCPtr, this, getCPtrAndAddReference(e), e);
+    exampleJNI.Container_setElement(swigCPtr, this, Element.getCPtr(e), e);
+    elementReference = e;
   }
 }
 </pre>
@@ -8179,22 +8176,20 @@ public class Container {
 
 <p>
 The following typemaps will generate the desired code.
-The 'javain' typemap matches the input parameter type for the <tt>setElement</tt> method.
+The 'javain' typemap matches the input parameter type for the <tt>setElement</tt> method and allows adding code after the call. 
 The 'javacode' typemap simply adds in the specified code into the Java proxy class.
 </p>
 
 <div class="code">
 <pre>
-%typemap(javain) Element *e "getCPtrAndAddReference($javainput)"
+%typemap(javain, 
+         post="elementReference = $javainput;\n"
+         ) Element *e "Element.getCPtr($javainput)"
 
 %typemap(javacode) Container %{
   // Ensure that the GC doesn't collect any element set from Java
   // as the underlying C++ class stores a shallow copy
   private Element elementReference;
-  private long getCPtrAndAddReference(Element element) {
-    elementReference = element;
-    return Element.getCPtr(element);
-  }
 %}
 </pre>
 </div>

From f674018126f7359e6e377ed4e623f45a3ad2118e Mon Sep 17 00:00:00 2001
From: William S Fulton <wsf@fultondesigns.co.uk>
Date: Tue, 19 Sep 2017 20:36:04 +0100
Subject: [PATCH 2/2] Improvements to Java Memory Management docs

---
 Doc/Manual/Java.html | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/Doc/Manual/Java.html b/Doc/Manual/Java.html
index fd57fda25..69cdc4eba 100644
--- a/Doc/Manual/Java.html
+++ b/Doc/Manual/Java.html
@@ -8175,25 +8175,42 @@ public class Container {
 </div>
 
 <p>
-The following typemaps will generate the desired code.
-The 'javain' typemap matches the input parameter type for the <tt>setElement</tt> method and allows adding code after the call. 
-The 'javacode' typemap simply adds in the specified code into the Java proxy class.
+The following typemaps can be used to generate this code:
 </p>
 
 <div class="code">
 <pre>
-%typemap(javain, 
-         post="elementReference = $javainput;\n"
-         ) Element *e "Element.getCPtr($javainput)"
-
 %typemap(javacode) Container %{
   // Ensure that the GC doesn't collect any element set from Java
   // as the underlying C++ class stores a shallow copy
   private Element elementReference;
 %}
+
+%typemap(javain, 
+         post="      elementReference = $javainput;"
+         ) Element *e "Element.getCPtr($javainput)"
 </pre>
 </div>
 
+<p>
+The 'javacode' typemap simply adds in the specified code into the Java proxy class.
+The 'javain' typemap matches the input parameter type and name for the <tt>setElement</tt> method and
+the 'post' typemap attribute allows adding code after the JNI call.
+The 'post' code is generated into a finally block after the JNI call so the resulting code isn't quite
+as mentioned earlier, <tt>setElement</tt> is actually:
+</p>
+
+<div class="code">
+<pre>
+  public void setElement(Element e) {
+    try {
+      exampleJNI.Container_setElement(swigCPtr, this, Element.getCPtr(e), e);
+    } finally {
+      elementReference = e;
+    }
+  }
+</pre>
+</div>
 
 <H3><a name="Java_date_marshalling">25.10.13 Date marshalling using the javain typemap and associated attributes</a></H3>