Support Windows path in ContentDisposition::parse

This commit makes sure that ContentDisposition::parse supports Windows
path with a backslash.

Closes gh-30111

Author: poutsma

spring-web/src/main/java/org/springframework/http/ContentDisposition.java

@@ -624,7 +624,11 @@ private static String decodeQuotedPairs(String filename) {
 			char c = filename.charAt(i);
 			if (filename.charAt(i) == '\\' && i + 1 < length) {
 				i++;
-				sb.append(filename.charAt(i));
+				char next = filename.charAt(i);
+				if (next != '"' && next != '\\') {
+					sb.append(c);
+				}
+				sb.append(next);
 			}
 			else {
 				sb.append(c);

spring-web/src/test/java/org/springframework/http/ContentDispositionTests.java

@@ -169,6 +169,14 @@ void parseBackslashInLastPosition() {
 		assertThat(cd.toString()).isEqualTo("form-data; name=\"foo\"; filename=\"bar\\\\\"");
 	}
 
+	@Test
+	void parseWindowsPath() {
+		ContentDisposition cd = ContentDisposition.parse("form-data; name=\"foo\"; filename=\"D:\\foo\\bar.txt\"");
+		assertThat(cd.getName()).isEqualTo("foo");
+		assertThat(cd.getFilename()).isEqualTo("D:\\foo\\bar.txt");
+		assertThat(cd.toString()).isEqualTo("form-data; name=\"foo\"; filename=\"D:\\\\foo\\\\bar.txt\"");
+	}
+
 
 	@SuppressWarnings("deprecation")
 	@Test