Configurable filename encoding in MimeMessageHelper

Closes gh-25755

spring-context-support/src/main/java/org/springframework/mail/javamail/MimeMessageHelper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 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.
@@ -159,8 +159,6 @@ public class MimeMessageHelper {
 
 	private static final String HEADER_PRIORITY = "X-Priority";
 
-	private static final String HEADER_CONTENT_ID = "Content-ID";
-
 
 	private final MimeMessage mimeMessage;
 
@@ -175,6 +173,8 @@ public class MimeMessageHelper {
 
 	private FileTypeMap fileTypeMap;
 
+	private boolean encodeFilenames = true;
+
 	private boolean validateAddresses = false;
 
 
@@ -464,7 +464,7 @@ protected FileTypeMap getDefaultFileTypeMap(MimeMessage mimeMessage) {
 	 * Set the Java Activation Framework {@code FileTypeMap} to use
 	 * for determining the content type of inline content and attachments
 	 * that get added to the message.
-	 * <p>Default is the {@code FileTypeMap} that the underlying
+	 * <p>The default is the {@code FileTypeMap} that the underlying
 	 * MimeMessage carries, if any, or the Activation Framework's default
 	 * {@code FileTypeMap} instance else.
 	 * @see #addInline
@@ -480,18 +480,40 @@ public void setFileTypeMap(@Nullable FileTypeMap fileTypeMap) {
 
 	/**
 	 * Return the {@code FileTypeMap} used by this MimeMessageHelper.
+	 * @see #setFileTypeMap
 	 */
 	public FileTypeMap getFileTypeMap() {
 		return this.fileTypeMap;
 	}
 
 
+	/**
+	 * Set whether to encode attachment filenames passed to this helper's
+	 * {@code #addAttachment} methods.
+	 * <p>The default is {@code true} for compatibility with older email clients;
+	 * turn this to {@code false} for standard MIME behavior. On a related note,
+	 * check out JavaMail's {@code mail.mime.encodefilename} system property.
+	 * @since 5.2.9
+	 * @see #addAttachment(String, DataSource)
+	 * @see MimeBodyPart#setFileName(String)
+	 */
+	public void setEncodeFilenames(boolean encodeFilenames) {
+		this.encodeFilenames = encodeFilenames;
+	}
+
+	/**
+	 * Return whether to encode attachment filenames passed to this helper's
+	 * {@code #addAttachment} methods.
+	 * @since 5.2.9
+	 * @see #setEncodeFilenames
+	 */
+	public boolean isEncodeFilenames() {
+		return this.encodeFilenames;
+	}
+
 	/**
 	 * Set whether to validate all addresses which get passed to this helper.
-	 * Default is "false".
-	 * <p>Note that this is by default just available for JavaMail >= 1.3.
-	 * You can override the default {@code validateAddress method} for
-	 * validation on older JavaMail versions (or for custom validation).
+	 * <p>The default is {@code false}.
 	 * @see #validateAddress
 	 */
 	public void setValidateAddresses(boolean validateAddresses) {
@@ -500,6 +522,7 @@ public void setValidateAddresses(boolean validateAddresses) {
 
 	/**
 	 * Return whether this helper will validate all addresses passed to it.
+	 * @see #setValidateAddresses
 	 */
 	public boolean isValidateAddresses() {
 		return this.validateAddresses;
@@ -508,10 +531,8 @@ public boolean isValidateAddresses() {
 	/**
 	 * Validate the given mail address.
 	 * Called by all of MimeMessageHelper's address setters and adders.
-	 * <p>Default implementation invokes {@code InternetAddress.validate()},
+	 * <p>The default implementation invokes {@link InternetAddress#validate()},
 	 * provided that address validation is activated for the helper instance.
-	 * <p>Note that this method will just work on JavaMail >= 1.3. You can override
-	 * it for validation on older JavaMail versions or for custom validation.
 	 * @param address the address to validate
 	 * @throws AddressException if validation failed
 	 * @see #isValidateAddresses()
@@ -525,7 +546,8 @@ protected void validateAddress(InternetAddress address) throws AddressException
 
 	/**
 	 * Validate all given mail addresses.
-	 * Default implementation simply delegates to validateAddress for each address.
+	 * <p>The default implementation simply delegates to {@link #validateAddress}
+	 * for each address.
 	 * @param addresses the addresses to validate
 	 * @throws AddressException if validation failed
 	 * @see #validateAddress(InternetAddress)
@@ -885,9 +907,7 @@ public void addInline(String contentId, DataSource dataSource) throws MessagingE
 		Assert.notNull(dataSource, "DataSource must not be null");
 		MimeBodyPart mimeBodyPart = new MimeBodyPart();
 		mimeBodyPart.setDisposition(MimeBodyPart.INLINE);
-		// We're using setHeader here to remain compatible with JavaMail 1.2,
-		// rather than JavaMail 1.3's setContentID.
-		mimeBodyPart.setHeader(HEADER_CONTENT_ID, "<" + contentId + ">");
+		mimeBodyPart.setContentID("<" + contentId + ">");
 		mimeBodyPart.setDataHandler(new DataHandler(dataSource));
 		getMimeMultipart().addBodyPart(mimeBodyPart);
 	}
@@ -997,7 +1017,8 @@ public void addAttachment(String attachmentFilename, DataSource dataSource) thro
 		try {
 			MimeBodyPart mimeBodyPart = new MimeBodyPart();
 			mimeBodyPart.setDisposition(MimeBodyPart.ATTACHMENT);
-			mimeBodyPart.setFileName(MimeUtility.encodeText(attachmentFilename));
+			mimeBodyPart.setFileName(isEncodeFilenames() ?
+					MimeUtility.encodeText(attachmentFilename) : attachmentFilename);
 			mimeBodyPart.setDataHandler(new DataHandler(dataSource));
 			getRootMimeMultipart().addBodyPart(mimeBodyPart);
 		}