From 8ab0471d8aa478b72789739d963fb431ebadcef3 Mon Sep 17 00:00:00 2001
From: Bauke Scholtz <balusc@gmail.com>
Date: Sat, 17 Dec 2022 08:07:30 -0400
Subject: [PATCH] https://github.com/eclipse-ee4j/mojarra/issues/5190 Add
 EmptyStringToNullELResolver to work around a misinterpreted change in EL3
 spec

---
 .../main/java/com/sun/faces/el/ELUtils.java   |  9 +++
 .../faces/el/EmptyStringToNullELResolver.java | 66 +++++++++++++++++++
 2 files changed, 75 insertions(+)
 create mode 100644 impl/src/main/java/com/sun/faces/el/EmptyStringToNullELResolver.java

diff --git a/impl/src/main/java/com/sun/faces/el/ELUtils.java b/impl/src/main/java/com/sun/faces/el/ELUtils.java
index 0acbac12c2..17468e5f1d 100644
--- a/impl/src/main/java/com/sun/faces/el/ELUtils.java
+++ b/impl/src/main/java/com/sun/faces/el/ELUtils.java
@@ -18,6 +18,7 @@
 
 import static com.sun.faces.RIConstants.EMPTY_CLASS_ARGS;
 import static com.sun.faces.cdi.CdiUtils.getBeanReference;
+import static com.sun.faces.config.WebConfiguration.BooleanWebContextInitParameter.InterpretEmptyStringSubmittedValuesAsNull;
 import static com.sun.faces.el.FacesCompositeELResolver.ELResolverChainType.Faces;
 import static com.sun.faces.el.FacesCompositeELResolver.ELResolverChainType.JSP;
 import static com.sun.faces.util.MessageUtils.NULL_PARAMETERS_ERROR_MESSAGE_ID;
@@ -62,6 +63,7 @@
 
 import com.sun.faces.application.ApplicationAssociate;
 import com.sun.faces.cdi.CdiExtension;
+import com.sun.faces.config.WebConfiguration;
 import com.sun.faces.context.flash.FlashELResolver;
 import com.sun.faces.mgbean.BeanManager;
 import com.sun.faces.util.MessageUtils;
@@ -178,6 +180,8 @@ public String toString() {
 
     public static final ListELResolver LIST_RESOLVER = new ListELResolver();
 
+    public static final EmptyStringToNullELResolver EMPTY_STRING_TO_NULL_RESOLVER = new EmptyStringToNullELResolver();
+
     public static final ManagedBeanELResolver MANAGED_BEAN_RESOLVER =
         new ManagedBeanELResolver();
 
@@ -266,6 +270,11 @@ public static void buildFacesResolver(FacesCompositeELResolver composite, Applic
         addVariableResolvers(composite, Faces, associate);
         addPropertyResolvers(composite, associate);
         composite.add(associate.getApplicationELResolvers());
+
+        if (WebConfiguration.getInstance().isOptionEnabled(InterpretEmptyStringSubmittedValuesAsNull)) {
+            composite.addPropertyELResolver(EMPTY_STRING_TO_NULL_RESOLVER);
+        }
+
         composite.addRootELResolver(MANAGED_BEAN_RESOLVER);
         composite.addPropertyELResolver(RESOURCE_RESOLVER);
         composite.addPropertyELResolver(BUNDLE_RESOLVER);
diff --git a/impl/src/main/java/com/sun/faces/el/EmptyStringToNullELResolver.java b/impl/src/main/java/com/sun/faces/el/EmptyStringToNullELResolver.java
new file mode 100644
index 0000000000..abd71087e5
--- /dev/null
+++ b/impl/src/main/java/com/sun/faces/el/EmptyStringToNullELResolver.java
@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 1997, 2022 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0, which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the
+ * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
+ * version 2 with the GNU Classpath Exception, which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ */
+
+package com.sun.faces.el;
+
+import java.beans.FeatureDescriptor;
+import java.util.Iterator;
+
+import javax.el.ELContext;
+import javax.el.ELResolver;
+
+public class EmptyStringToNullELResolver extends ELResolver {
+
+    @Override
+    public Class<?> getCommonPropertyType(ELContext context, Object base) {
+        return String.class;
+    }
+
+    @Override
+    public Object convertToType(ELContext context, Object value, Class<?> targetType) {
+        if (value == null && targetType == String.class) {
+            context.setPropertyResolved(true);
+        }
+
+        return value;
+    }
+
+    @Override
+    public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {
+        return null;
+    }
+
+    @Override
+    public Class<?> getType(ELContext context, Object base, Object property) {
+        return null;
+    }
+
+    @Override
+    public Object getValue(ELContext context, Object base, Object property) {
+        return null;
+    }
+
+    @Override
+    public boolean isReadOnly(ELContext context, Object base, Object property) {
+        return true;
+    }
+
+    @Override
+    public void setValue(ELContext context, Object base, Object property, Object value) {
+        // NOOP.
+    }
+
+}
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