AbstractMessageSource properly interacts with non-AbstractMessageSource parent

Issue: SPR-16047

Author: jhoeller

spring-context/src/main/java/org/springframework/context/support/AbstractMessageSource.java

@@ -263,7 +263,9 @@ protected String getMessageFromParent(String code, @Nullable Object[] args, Loca
 			}
 			else {
 				// Check parent MessageSource, returning null if not found there.
-				return parent.getMessage(code, args, null, locale);
+				// Covers custom MessageSource impls and DelegatingMessageSource.
+				String msg = parent.getMessage(code, args, null, locale);
+				return ("".equals(msg) ? null : msg);
 			}
 		}
 		// Not found in parent either.

spring-context/src/test/java/org/springframework/context/support/ResourceBundleMessageSourceTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -210,6 +210,39 @@ public void testDefaultApplicationContextMessageSource() {
 		assertEquals("default value", ac.getMessage("code1", new Object[] {"value"}, "default {0}", Locale.ENGLISH));
 	}
 
+	@Test
+	public void testDefaultApplicationContextMessageSourceWithParent() {
+		GenericApplicationContext ac = new GenericApplicationContext();
+		GenericApplicationContext parent = new GenericApplicationContext();
+		parent.refresh();
+		ac.setParent(parent);
+		ac.refresh();
+		assertEquals("default", ac.getMessage("code1", null, "default", Locale.ENGLISH));
+		assertEquals("default value", ac.getMessage("code1", new Object[] {"value"}, "default {0}", Locale.ENGLISH));
+	}
+
+	@Test
+	public void testStaticApplicationContextMessageSourceWithStaticParent() {
+		StaticApplicationContext ac = new StaticApplicationContext();
+		StaticApplicationContext parent = new StaticApplicationContext();
+		parent.refresh();
+		ac.setParent(parent);
+		ac.refresh();
+		assertEquals("default", ac.getMessage("code1", null, "default", Locale.ENGLISH));
+		assertEquals("default value", ac.getMessage("code1", new Object[] {"value"}, "default {0}", Locale.ENGLISH));
+	}
+
+	@Test
+	public void testStaticApplicationContextMessageSourceWithDefaultParent() {
+		StaticApplicationContext ac = new StaticApplicationContext();
+		GenericApplicationContext parent = new GenericApplicationContext();
+		parent.refresh();
+		ac.setParent(parent);
+		ac.refresh();
+		assertEquals("default", ac.getMessage("code1", null, "default", Locale.ENGLISH));
+		assertEquals("default value", ac.getMessage("code1", new Object[] {"value"}, "default {0}", Locale.ENGLISH));
+	}
+
 	@Test
 	public void testResourceBundleMessageSourceStandalone() {
 		ResourceBundleMessageSource ms = new ResourceBundleMessageSource();