Add support for changing context path in ServletRequestPath

This commit implements modifyContextPath in ServletRequestPath and
apply the same logic of concatenating the servlet path with the
context path.

Closes gh-33251

Author: snicoll

spring-web/src/main/java/org/springframework/web/util/ServletRequestPathUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2023 the original author or authors.
+ * Copyright 2002-2024 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 @@
  * {@link org.springframework.util.PathMatcher} otherwise.
  *
  * @author Rossen Stoyanchev
+ * @author Stephane Nicoll
  * @since 5.3
  */
 public abstract class ServletRequestPathUtils {
@@ -186,14 +187,16 @@ public static boolean hasCachedPath(ServletRequest request) {
 	 */
 	private static final class ServletRequestPath implements RequestPath {
 
+		private final PathElements pathElements;
+
 		private final RequestPath requestPath;
 
 		private final PathContainer contextPath;
 
-		private ServletRequestPath(String rawPath, @Nullable String contextPath, String servletPathPrefix) {
-			Assert.notNull(servletPathPrefix, "`servletPathPrefix` is required");
-			this.requestPath = RequestPath.parse(rawPath, contextPath + servletPathPrefix);
-			this.contextPath = PathContainer.parsePath(StringUtils.hasText(contextPath) ? contextPath : "");
+		private ServletRequestPath(PathElements pathElements) {
+			this.pathElements = pathElements;
+			this.requestPath = pathElements.createRequestPath();
+			this.contextPath = pathElements.createContextPath();
 		}
 
 		@Override
@@ -218,7 +221,7 @@ public PathContainer pathWithinApplication() {
 
 		@Override
 		public RequestPath modifyContextPath(String contextPath) {
-			throw new UnsupportedOperationException();
+			return new ServletRequestPath(this.pathElements.withContextPath(contextPath));
 		}
 
 
@@ -249,7 +252,7 @@ public static RequestPath parse(HttpServletRequest request) {
 			requestUri = (requestUri != null ? requestUri : request.getRequestURI());
 			String servletPathPrefix = getServletPathPrefix(request);
 			return (StringUtils.hasText(servletPathPrefix) ?
-					new ServletRequestPath(requestUri, request.getContextPath(), servletPathPrefix) :
+					new ServletRequestPath(new PathElements(requestUri, request.getContextPath(), servletPathPrefix)) :
 					RequestPath.parse(requestUri, request.getContextPath()));
 		}
 
@@ -265,6 +268,38 @@ private static String getServletPathPrefix(HttpServletRequest request) {
 			}
 			return null;
 		}
+
+		record PathElements(String rawPath, @Nullable String contextPath, String servletPathPrefix) {
+
+			PathElements {
+				Assert.notNull(servletPathPrefix, "`servletPathPrefix` is required");
+			}
+
+			private RequestPath createRequestPath() {
+				return RequestPath.parse(this.rawPath, this.contextPath + this.servletPathPrefix);
+			}
+
+			private PathContainer createContextPath() {
+				return PathContainer.parsePath(StringUtils.hasText(this.contextPath) ? this.contextPath : "");
+			}
+
+			PathElements withContextPath(String contextPath) {
+				if (!contextPath.startsWith("/") || contextPath.endsWith("/")) {
+					throw new IllegalArgumentException("Invalid contextPath '" + contextPath + "': " +
+							"must start with '/' and not end with '/'");
+				}
+				String contextPathToUse = this.servletPathPrefix + contextPath;
+				if (StringUtils.hasText(this.contextPath())) {
+					throw new IllegalStateException("Could not change context path to '" + contextPathToUse +
+							"': a context path is already specified");
+				}
+				if (!this.rawPath.startsWith(contextPathToUse)) {
+					throw new IllegalArgumentException("Invalid contextPath '" + contextPathToUse + "': " +
+							"must match the start of requestPath: '" + this.rawPath + "'");
+				}
+				return new PathElements(this.rawPath, contextPathToUse, "");
+			}
+		}
 	}
 
 }

spring-web/src/test/java/org/springframework/web/util/ServletRequestPathUtilsTests.java

@@ -24,11 +24,14 @@
 import org.springframework.web.testfixture.servlet.MockHttpServletRequest;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 
 /**
  * Tests for {@link ServletRequestPathUtils}.
  *
  * @author Rossen Stoyanchev
+ * @author Stephane Nicoll
  */
 class ServletRequestPathUtilsTests {
 
@@ -47,19 +50,63 @@ void parseAndCache() {
 		testParseAndCache("/app/servlet/a//", "/app", "/servlet", "/a//");
 	}
 
+	@Test
+	void modifyPathContextWithExistingContextPath() {
+		RequestPath requestPath = createRequestPath("/app/api/persons/42", "/app", "/api", "/persons/42");
+		assertThatIllegalStateException().isThrownBy(() -> requestPath.modifyContextPath("/persons"))
+				.withMessage("Could not change context path to '/api/persons': a context path is already specified");
+	}
+
+	@Test
+	void modifyPathContextWhenContextPathIsNotInThePath() {
+		RequestPath requestPath = createRequestPath("/api/persons/42", "", "/api", "/persons/42");
+		assertThatIllegalArgumentException().isThrownBy(() -> requestPath.modifyContextPath("/something"))
+				.withMessage("Invalid contextPath '/api/something': " +
+						"must match the start of requestPath: '/api/persons/42'");
+	}
+
+	@Test
+	void modifyPathContextReplacesServletPath() {
+		RequestPath requestPath = createRequestPath("/api/persons/42", "", "/api", "/persons/42");
+		RequestPath updatedRequestPath = requestPath.modifyContextPath("/persons");
+		assertThat(updatedRequestPath.contextPath().value()).isEqualTo("/api/persons");
+		assertThat(updatedRequestPath.pathWithinApplication().value()).isEqualTo("/42");
+		assertThat(updatedRequestPath.value()).isEqualTo("/api/persons/42");
+	}
+
+	@Test
+	void modifyPathContextWithContextPathNotStartingWithSlash() {
+		RequestPath requestPath = createRequestPath("/api/persons/42", "", "/api", "/persons/42");
+		assertThatIllegalArgumentException().isThrownBy(() -> requestPath.modifyContextPath("persons"))
+				.withMessage("Invalid contextPath 'persons': must start with '/' and not end with '/'");
+	}
+
+	@Test
+	void modifyPathContextWithContextPathEndingWithSlash() {
+		RequestPath requestPath = createRequestPath("/api/persons/42", "", "/api", "/persons/42");
+		assertThatIllegalArgumentException().isThrownBy(() -> requestPath.modifyContextPath("/persons/"))
+				.withMessage("Invalid contextPath '/persons/': must start with '/' and not end with '/'");
+	}
+
 	private void testParseAndCache(
 			String requestUri, String contextPath, String servletPath, String pathWithinApplication) {
 
+		RequestPath requestPath = createRequestPath(requestUri, contextPath, servletPath, pathWithinApplication);
+
+		assertThat(requestPath.contextPath().value()).isEqualTo(contextPath);
+		assertThat(requestPath.pathWithinApplication().value()).isEqualTo(pathWithinApplication);
+	}
+
+	private static RequestPath createRequestPath(
+			String requestUri, String contextPath, String servletPath, String pathWithinApplication) {
+
 		MockHttpServletRequest request = new MockHttpServletRequest("GET", requestUri);
 		request.setContextPath(contextPath);
 		request.setServletPath(servletPath);
 		request.setHttpServletMapping(new MockHttpServletMapping(
 				pathWithinApplication, contextPath, "myServlet", MappingMatch.PATH));
 
-		RequestPath requestPath = ServletRequestPathUtils.parseAndCache(request);
-
-		assertThat(requestPath.contextPath().value()).isEqualTo(contextPath);
-		assertThat(requestPath.pathWithinApplication().value()).isEqualTo(pathWithinApplication);
+		return ServletRequestPathUtils.parseAndCache(request);
 	}
 
 }