Polish contribution & Support multiple quoted printable segments in Content-Disposition

This commit polishes the contribution for support of multiple
base64 segments, and adds supports for multiple quoted printable
segments in Content-Disposition.

Closes gh-28236

Author: poutsma

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

@@ -53,7 +53,7 @@ public final class ContentDisposition {
 			Pattern.compile("=\\?([0-9a-zA-Z-_]+)\\?B\\?([+/0-9a-zA-Z]+=*)\\?=");
 
 	private final static Pattern QUOTED_PRINTABLE_ENCODED_PATTERN =
-			Pattern.compile("=\\?([0-9a-zA-Z-_]+)\\?Q\\?(\\p{Print}+)\\?=");
+			Pattern.compile("=\\?([0-9a-zA-Z-_]+)\\?Q\\?([!->@-~]+)\\?="); // Printable ASCII other than "?" or SPACE
 
 	private static final String INVALID_HEADER_FIELD_PARAMETER_FORMAT =
 			"Invalid header field parameter format (as defined in RFC 5987)";
@@ -375,22 +375,29 @@ else if (attribute.equals("filename") && (filename == null)) {
 					if (value.startsWith("=?") ) {
 						Matcher matcher = BASE64_ENCODED_PATTERN.matcher(value);
 						if (matcher.find()) {
-							charset = Charset.forName(matcher.group(1));
-							String encodedValue = matcher.group(2);
-							StringBuilder sb = new StringBuilder(new String(Base64.getDecoder().decode(encodedValue), charset));
-							while (matcher.find()){
+							Base64.Decoder decoder = Base64.getDecoder();
+							StringBuilder builder = new StringBuilder();
+							do {
 								charset = Charset.forName(matcher.group(1));
-								encodedValue = matcher.group(2);
-								sb.append(new String(Base64.getDecoder().decode(encodedValue), charset));
+								byte[] decoded = decoder.decode(matcher.group(2));
+								builder.append(new String(decoded, charset));
 							}
-							filename = sb.toString();
+							while (matcher.find());
+
+							filename = builder.toString();
 						}
 						else {
 							matcher = QUOTED_PRINTABLE_ENCODED_PATTERN.matcher(value);
 							if (matcher.find()) {
-								charset = Charset.forName(matcher.group(1));
-								String encodedValue = matcher.group(2);
-								filename = decodeQuotedPrintableFilename(encodedValue, charset);
+								StringBuilder builder = new StringBuilder();
+								do {
+									charset = Charset.forName(matcher.group(1));
+									String decoded = decodeQuotedPrintableFilename(matcher.group(2), charset);
+									builder.append(decoded);
+								}
+								while (matcher.find());
+
+								filename = builder.toString();
 							}
 							else {
 								filename = value;

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

@@ -87,10 +87,11 @@ void parseBase64EncodedFilename() {
 	}
 
 	@Test
-	void parseBase64EncodedFilenameHasMoreSegments() {
-		/* https://datatracker.ietf.org/doc/html/rfc2047#section-2
-		* An 'encoded-word' may not be more than 75 characters long */
-		String input = "attachment; filename=\"=?utf-8?B?U3ByaW5n5qGG5p625Li65Z+65LqOSmF2YeeahOeOsOS7o+S8geS4muW6lA==?= =?utf-8?B?55So56iL5bqP5o+Q5L6b5LqG5YWo6Z2i55qE57yW56iL5ZKM6YWN572u5qih?= =?utf-8?B?5Z6LLnR4dA==?=\"";
+	void parseBase64EncodedFilenameMultipleSegments() {
+		String input =
+				"attachment; filename=\"=?utf-8?B?U3ByaW5n5qGG5p625Li65Z+65LqOSmF2YeeahOeOsOS7o+S8geS4muW6lA==?= " +
+				"=?utf-8?B?55So56iL5bqP5o+Q5L6b5LqG5YWo6Z2i55qE57yW56iL5ZKM6YWN572u5qih?= " +
+				"=?utf-8?B?5Z6LLnR4dA==?=\"";
 		assertThat(parse(input).getFilename()).isEqualTo("Spring框架为基于Java的现代企业应用程序提供了全面的编程和配置模型.txt");
 	}
 
@@ -106,6 +107,18 @@ void parseQuotedPrintableFilename() {
 		assertThat(parse(input).getFilename()).isEqualTo("日本語.csv");
 	}
 
+	@Test
+	void parseQuotedPrintableFilenameMultipleSegments() {
+		String input =
+				"attachment; filename=\"=?utf-8?Q?Spring=E6=A1=86=E6=9E=B6=E4=B8=BA=E5=9F=BA=E4=BA=8E?=" +
+						"=?utf-8?Q?Java=E7=9A=84=E7=8E=B0=E4=BB=A3=E4=BC=81=E4=B8=9A=E5=BA=94?=" +
+						"=?utf-8?Q?=E7=94=A8=E7=A8=8B=E5=BA=8F=E6=8F=90=E4=BE=9B=E4=BA=86=E5=85=A8?=" +
+						"=?utf-8?Q?=E9=9D=A2=E7=9A=84=E7=BC=96=E7=A8=8B=E5=92=8C=E9=85=8D=E7=BD=AE?=" +
+						"=?utf-8?Q?=E6=A8=A1=E5=9E=8B.txt?=\"";
+		assertThat(parse(input).getFilename()).isEqualTo("Spring框架为基于Java的现代企业应用程序提供了全面的编程和配置模型.txt");
+
+	}
+
 	@Test
 	void parseQuotedPrintableShiftJISFilename() {
 		String input = "attachment; filename=\"=?SHIFT_JIS?Q?=93=FA=96{=8C=EA.csv?=\"";