From 29027f395792cfefec5e330fc0fc3dc06f0343b0 Mon Sep 17 00:00:00 2001
From: Kusal Kithul-Godage <git@kusal.io>
Date: Tue, 2 Jan 2024 21:21:35 +1100
Subject: [PATCH] WW-5379 Use ValueStackProvider marker interface for Velocity
 context implementation flexibility

---
 .../org/apache/struts2/util/ValueStackProvider.java  | 12 ++++++++++++
 .../views/velocity/StrutsVelocityContext.java        |  4 +++-
 .../views/velocity/components/AbstractDirective.java |  6 +++---
 3 files changed, 18 insertions(+), 4 deletions(-)
 create mode 100644 core/src/main/java/org/apache/struts2/util/ValueStackProvider.java

diff --git a/core/src/main/java/org/apache/struts2/util/ValueStackProvider.java b/core/src/main/java/org/apache/struts2/util/ValueStackProvider.java
new file mode 100644
index 0000000000..9136c4c858
--- /dev/null
+++ b/core/src/main/java/org/apache/struts2/util/ValueStackProvider.java
@@ -0,0 +1,12 @@
+package org.apache.struts2.util;
+
+import com.opensymphony.xwork2.util.ValueStack;
+
+/**
+ * @since 6.4.0
+ */
+public interface ValueStackProvider {
+
+    ValueStack getValueStack();
+
+}
diff --git a/plugins/velocity/src/main/java/org/apache/struts2/views/velocity/StrutsVelocityContext.java b/plugins/velocity/src/main/java/org/apache/struts2/views/velocity/StrutsVelocityContext.java
index 7ab4f24e78..d18ca6bcf4 100644
--- a/plugins/velocity/src/main/java/org/apache/struts2/views/velocity/StrutsVelocityContext.java
+++ b/plugins/velocity/src/main/java/org/apache/struts2/views/velocity/StrutsVelocityContext.java
@@ -19,6 +19,7 @@
 package org.apache.struts2.views.velocity;
 
 import com.opensymphony.xwork2.util.ValueStack;
+import org.apache.struts2.util.ValueStackProvider;
 import org.apache.velocity.VelocityContext;
 
 import java.util.ArrayList;
@@ -26,7 +27,7 @@
 import java.util.List;
 import java.util.function.Function;
 
-public class StrutsVelocityContext extends VelocityContext {
+public class StrutsVelocityContext extends VelocityContext implements ValueStackProvider {
 
     private final ValueStack stack;
     private final List<VelocityContext> chainedContexts;
@@ -104,6 +105,7 @@ protected Object chainedContextGet(String key) {
         return null;
     }
 
+    @Override
     public ValueStack getValueStack() {
         return stack;
     }
diff --git a/plugins/velocity/src/main/java/org/apache/struts2/views/velocity/components/AbstractDirective.java b/plugins/velocity/src/main/java/org/apache/struts2/views/velocity/components/AbstractDirective.java
index fd984a88da..539f64bdd9 100644
--- a/plugins/velocity/src/main/java/org/apache/struts2/views/velocity/components/AbstractDirective.java
+++ b/plugins/velocity/src/main/java/org/apache/struts2/views/velocity/components/AbstractDirective.java
@@ -22,8 +22,8 @@
 import com.opensymphony.xwork2.util.ValueStack;
 import org.apache.struts2.ServletActionContext;
 import org.apache.struts2.components.Component;
+import org.apache.struts2.util.ValueStackProvider;
 import org.apache.struts2.views.util.ContextUtil;
-import org.apache.struts2.views.velocity.StrutsVelocityContext;
 import org.apache.velocity.context.AbstractContext;
 import org.apache.velocity.context.Context;
 import org.apache.velocity.context.InternalContextAdapter;
@@ -86,8 +86,8 @@ public boolean render(InternalContextAdapter ctx, Writer writer, Node node) thro
 
     private ValueStack extractValueStack(Context context) {
         do {
-            if (context instanceof StrutsVelocityContext) {
-                return ((StrutsVelocityContext) context).getValueStack();
+            if (context instanceof ValueStackProvider) {
+                return ((ValueStackProvider) context).getValueStack();
             }
             context = extractContext(context);
         } while (context != null);