Ensure RedirectModel is initialized

This commit fixes an old bug in ModelAndViewContainer where getModel
returns a new ModelMap instance that isn't saved and re-used.

Issue: SPR-14045

spring-web/src/main/java/org/springframework/web/method/support/ModelAndViewContainer.java

@@ -134,7 +134,10 @@ public class ModelAndViewContainer {
 			return this.defaultModel;
 		}
 		else {
-			return (this.redirectModel != null) ? this.redirectModel : new ModelMap();
+			if (this.redirectModel == null) {
+				this.redirectModel = new ModelMap();
+			}
+			return this.redirectModel;
 		}
 	}
 

spring-web/src/test/java/org/springframework/web/method/support/ModelAndViewContainerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -76,4 +76,15 @@ public class ModelAndViewContainerTests {
 		assertTrue(this.mavContainer.getModel().isEmpty());
 	}
 
+	@Test // SPR-14045
+	public void ignoreDefaultModelAndWithoutRedirectModel() {
+		this.mavContainer.setIgnoreDefaultModelOnRedirect(true);
+		this.mavContainer.setRedirectModelScenario(true);
+		this.mavContainer.addAttribute("name", "value");
+
+		assertEquals(1, this.mavContainer.getModel().size());
+		assertEquals("value", this.mavContainer.getModel().get("name"));
+	}
+
+
 }

spring-webmvc/src/test/java/org/springframework/web/servlet/mvc/method/annotation/ModelAndViewMethodReturnValueHandlerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -143,6 +143,20 @@ public class ModelAndViewMethodReturnValueHandlerTests {
 		assertNotSame("RedirectAttributes should not be used if controller doesn't redirect", redirectAttributes, model);
 	}
 
+	@Test // SPR-14045
+	public void handleRedirectWithIgnoreDefaultModel() throws Exception {
+		mavContainer.setIgnoreDefaultModelOnRedirect(true);
+
+		RedirectView redirectView = new RedirectView();
+		ModelAndView mav = new ModelAndView(redirectView, "name", "value");
+		handler.handleReturnValue(mav, returnParamModelAndView, mavContainer, webRequest);
+
+		ModelMap model = mavContainer.getModel();
+		assertSame(redirectView, mavContainer.getView());
+		assertEquals(1, model.size());
+		assertEquals("value", model.get("name"));
+	}
+
 
 	private MethodParameter getReturnValueParam(String methodName) throws Exception {
 		Method method = getClass().getDeclaredMethod(methodName);