Support empty target request path in FlashMap

Prior to this commit, if the user configured an empty path for the
targetRequestPath property of a FlashMap, the FlashMapManager threw a
StringIndexOutOfBoundsException when saving the output FlashMap for the
next request.

This commit fixes this by skipping the decoding and normalization of an
empty target request path. An empty target request path is therefore
effectively treated as the root path.

Fixes gh-23240

spring-webmvc/src/main/java/org/springframework/web/servlet/support/AbstractFlashMapManager.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -41,6 +41,7 @@
  *
  * @author Rossen Stoyanchev
  * @author Juergen Hoeller
+ * @author Sam Brannen
  * @since 3.1.1
  */
 public abstract class AbstractFlashMapManager implements FlashMapManager {
@@ -228,7 +229,7 @@ public final void saveOutputFlashMap(FlashMap flashMap, HttpServletRequest reque
 
 	@Nullable
 	private String decodeAndNormalizePath(@Nullable String path, HttpServletRequest request) {
-		if (path != null) {
+		if (path != null && !path.isEmpty()) {
 			path = getUrlPathHelper().decodeRequestString(request, path);
 			if (path.charAt(0) != '/') {
 				String requestUri = getUrlPathHelper().getRequestUri(request);

spring-webmvc/src/test/java/org/springframework/web/servlet/support/FlashMapManagerTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -16,47 +16,37 @@
 
 package org.springframework.web.servlet.support;
 
-import static org.junit.Assert.*;
-
 import java.net.URLEncoder;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
-
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
-import org.junit.Before;
 import org.junit.Test;
 
 import org.springframework.mock.web.test.MockHttpServletRequest;
 import org.springframework.mock.web.test.MockHttpServletResponse;
 import org.springframework.web.servlet.FlashMap;
 import org.springframework.web.util.WebUtils;
 
+import static org.junit.Assert.*;
 
 /**
  * Test fixture for testing {@link AbstractFlashMapManager} methods.
  *
  * @author Rossen Stoyanchev
+ * @author Sam Brannen
  */
 public class FlashMapManagerTests {
 
-	private TestFlashMapManager flashMapManager;
-
-	private MockHttpServletRequest request;
+	private final TestFlashMapManager flashMapManager = new TestFlashMapManager();
 
-	private MockHttpServletResponse response;
+	private final MockHttpServletRequest request = new MockHttpServletRequest();
 
-
-	@Before
-	public void setup() {
-		this.flashMapManager = new TestFlashMapManager();
-		this.request = new MockHttpServletRequest();
-		this.response = new MockHttpServletResponse();
-	}
+	private final MockHttpServletResponse response = new MockHttpServletResponse();
 
 
 	@Test
@@ -73,9 +63,7 @@ public void retrieveAndUpdateMatchByPath() {
 		assertEquals(flashMap, inputFlashMap);
 	}
 
-	// SPR-8779
-
-	@Test
+	@Test // SPR-8779
 	public void retrieveAndUpdateMatchByOriginatingPath() {
 		FlashMap flashMap = new FlashMap();
 		flashMap.put("key", "value");
@@ -133,9 +121,7 @@ public void retrieveAndUpdateMatchByParams() {
 		assertEquals("Input FlashMap should have been removed", 0, this.flashMapManager.getFlashMaps().size());
 	}
 
-	// SPR-8798
-
-	@Test
+	@Test // SPR-8798
 	public void retrieveAndUpdateMatchWithMultiValueParam() {
 		FlashMap flashMap = new FlashMap();
 		flashMap.put("name", "value");
@@ -180,7 +166,7 @@ public void retrieveAndUpdateSortMultipleMatches() {
 	}
 
 	@Test
-	public void retrieveAndUpdateRemoveExpired() throws InterruptedException {
+	public void retrieveAndUpdateRemoveExpired() {
 		List<FlashMap> flashMaps = new ArrayList<>();
 		for (int i = 0; i < 5; i++) {
 			FlashMap expiredFlashMap = new FlashMap();
@@ -195,7 +181,7 @@ public void retrieveAndUpdateRemoveExpired() throws InterruptedException {
 	}
 
 	@Test
-	public void saveOutputFlashMapEmpty() throws InterruptedException {
+	public void saveOutputFlashMapEmpty() {
 		FlashMap flashMap = new FlashMap();
 
 		this.flashMapManager.saveOutputFlashMap(flashMap, this.request, this.response);
@@ -205,7 +191,7 @@ public void saveOutputFlashMapEmpty() throws InterruptedException {
 	}
 
 	@Test
-	public void saveOutputFlashMap() throws InterruptedException {
+	public void saveOutputFlashMap() {
 		FlashMap flashMap = new FlashMap();
 		flashMap.put("name", "value");
 
@@ -219,7 +205,7 @@ public void saveOutputFlashMap() throws InterruptedException {
 	}
 
 	@Test
-	public void saveOutputFlashMapDecodeTargetPath() throws InterruptedException {
+	public void saveOutputFlashMapDecodeTargetPath() {
 		FlashMap flashMap = new FlashMap();
 		flashMap.put("key", "value");
 
@@ -230,7 +216,7 @@ public void saveOutputFlashMapDecodeTargetPath() throws InterruptedException {
 	}
 
 	@Test
-	public void saveOutputFlashMapNormalizeTargetPath() throws InterruptedException {
+	public void saveOutputFlashMapNormalizeTargetPath() {
 		FlashMap flashMap = new FlashMap();
 		flashMap.put("key", "value");
 
@@ -265,11 +251,19 @@ public void saveOutputFlashMapNormalizeTargetPath() throws InterruptedException
 		assertEquals("/once/only", flashMap.getTargetRequestPath());
 	}
 
-	// SPR-9657, SPR-11504
+	@Test // gh-23240
+	public void saveOutputFlashMapAndNormalizeEmptyTargetPath() {
+		FlashMap flashMap = new FlashMap();
+		flashMap.put("key", "value");
 
-	@Test
-	public void saveOutputFlashMapDecodeParameters() throws Exception {
+		flashMap.setTargetRequestPath("");
+		this.flashMapManager.saveOutputFlashMap(flashMap, this.request, this.response);
 
+		assertEquals("", flashMap.getTargetRequestPath());
+	}
+
+	@Test // SPR-9657, SPR-11504
+	public void saveOutputFlashMapDecodeParameters() throws Exception {
 		FlashMap flashMap = new FlashMap();
 		flashMap.put("key", "value");
 		flashMap.setTargetRequestPath("/path");
@@ -295,11 +289,8 @@ public void saveOutputFlashMapDecodeParameters() throws Exception {
 		assertEquals("value", flashMap.get("key"));
 	}
 
-	// SPR-12569
-
-	@Test
+	@Test // SPR-12569
 	public void flashAttributesWithQueryParamsWithSpace() throws Exception {
-
 		String encodedValue = URLEncoder.encode("1 2", "UTF-8");
 
 		FlashMap flashMap = new FlashMap();