Add RequestPath tests for modifying the contextPath

spring-web/src/main/java/org/springframework/http/server/DefaultRequestPath.java

@@ -55,8 +55,7 @@ class DefaultRequestPath implements RequestPath {
 			return PathContainer.parseUrlPath("");
 		}
 
-		Assert.isTrue(contextPath.startsWith("/") && !contextPath.endsWith("/") &&
-				path.value().startsWith(contextPath), "Invalid contextPath: " + contextPath);
+		validateContextPath(path.value(), contextPath);
 
 		int length = contextPath.length();
 		int counter = 0;
@@ -70,8 +69,24 @@ class DefaultRequestPath implements RequestPath {
 		}
 
 		// Should not happen..
-		throw new IllegalStateException("Failed to initialize contextPath='" + contextPath + "'" +
-				" given path='" + path.value() + "'");
+		throw new IllegalStateException("Failed to initialize contextPath '" + contextPath + "'" +
+				" for requestPath '" + path.value() + "'");
+	}
+
+	private static void validateContextPath(String fullPath, String contextPath) {
+		int length = contextPath.length();
+		if (contextPath.charAt(0) != '/' || contextPath.charAt(length - 1) == '/') {
+			throw new IllegalArgumentException("Invalid contextPath: '" + contextPath + "': " +
+					"must start with '/' and not end with '/'");
+		}
+		if (!fullPath.startsWith(contextPath)) {
+			throw new IllegalArgumentException("Invalid contextPath '" + contextPath + "': " +
+					"must match the start of requestPath: '" + fullPath + "'");
+		}
+		if (fullPath.length() > length && fullPath.charAt(length) != '/') {
+			throw new IllegalArgumentException("Invalid contextPath '" + contextPath + "': " +
+					"must match to full path segments for requestPath: '" + fullPath + "'");
+		}
 	}
 
 	private static PathContainer extractPathWithinApplication(PathContainer fullPath, PathContainer contextPath) {

spring-web/src/main/java/org/springframework/http/server/RequestPath.java

@@ -46,7 +46,7 @@ public interface RequestPath extends PathContainer {
 
 	/**
 	 * Return a new {@code RequestPath} instance with a modified context path.
-	 * The new context path must match the beginning of this request path.
+	 * The new context path must match 0 or more path segments at the start.
 	 * @param contextPath the new context path
 	 * @return a new {@code RequestPath} instance
 	 */

spring-web/src/test/java/org/springframework/http/server/DefaultRequestPathTests.java

@@ -59,4 +59,19 @@ public class DefaultRequestPathTests {
 		assertEquals(pathWithinApplication, requestPath.pathWithinApplication().value());
 	}
 
+	@Test
+	public void updateRequestPath() throws Exception {
+
+		URI uri = URI.create("http://localhost:8080/aA/bB/cC");
+		RequestPath requestPath = RequestPath.parse(uri, null);
+
+		assertEquals("", requestPath.contextPath().value());
+		assertEquals("/aA/bB/cC", requestPath.pathWithinApplication().value());
+
+		requestPath = requestPath.modifyContextPath("/aA");
+
+		assertEquals("/aA", requestPath.contextPath().value());
+		assertEquals("/bB/cC", requestPath.pathWithinApplication().value());
+	}
+
 }