Java tutorial
// Copyright (C) 2016 The Android Open Source Project // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package com.google.gerrit.server.mail.receive; import static java.nio.charset.StandardCharsets.UTF_8; import com.google.common.base.Strings; import com.google.common.collect.ImmutableList; import com.google.common.collect.ImmutableSet; import com.google.common.io.CharStreams; import com.google.common.primitives.Ints; import com.google.gerrit.server.mail.Address; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStreamReader; import org.apache.james.mime4j.MimeException; import org.apache.james.mime4j.dom.Entity; import org.apache.james.mime4j.dom.Message; import org.apache.james.mime4j.dom.MessageBuilder; import org.apache.james.mime4j.dom.Multipart; import org.apache.james.mime4j.dom.TextBody; import org.apache.james.mime4j.dom.address.Mailbox; import org.apache.james.mime4j.message.DefaultMessageBuilder; import org.joda.time.DateTime; /** * RawMailParser parses raw email content received through POP3 or IMAP into an internal {@link * MailMessage}. */ public class RawMailParser { private static final ImmutableSet<String> MAIN_HEADERS = ImmutableSet.of("to", "from", "cc", "date", "message-id", "subject", "content-type"); /** * Parses a MailMessage from a string. * * @param raw String as received over the wire * @return Parsed MailMessage * @throws MailParsingException */ public static MailMessage parse(String raw) throws MailParsingException { MailMessage.Builder messageBuilder = MailMessage.builder(); messageBuilder.rawContentUTF(raw); Message mimeMessage; try { MessageBuilder builder = new DefaultMessageBuilder(); mimeMessage = builder.parseMessage(new ByteArrayInputStream(raw.getBytes(UTF_8))); } catch (IOException | MimeException e) { throw new MailParsingException("Can't parse email", e); } // Add general headers if (mimeMessage.getMessageId() != null) { messageBuilder.id(mimeMessage.getMessageId()); } if (mimeMessage.getSubject() != null) { messageBuilder.subject(mimeMessage.getSubject()); } messageBuilder.dateReceived(new DateTime(mimeMessage.getDate())); // Add From, To and Cc if (mimeMessage.getFrom() != null && mimeMessage.getFrom().size() > 0) { Mailbox from = mimeMessage.getFrom().get(0); messageBuilder.from(new Address(from.getName(), from.getAddress())); } if (mimeMessage.getTo() != null) { for (Mailbox m : mimeMessage.getTo().flatten()) { messageBuilder.addTo(new Address(m.getName(), m.getAddress())); } } if (mimeMessage.getCc() != null) { for (Mailbox m : mimeMessage.getCc().flatten()) { messageBuilder.addCc(new Address(m.getName(), m.getAddress())); } } // Add additional headers mimeMessage.getHeader().getFields().stream().filter(f -> !MAIN_HEADERS.contains(f.getName().toLowerCase())) .forEach(f -> messageBuilder.addAdditionalHeader(f.getName() + ": " + f.getBody())); // Add text and html body parts StringBuilder textBuilder = new StringBuilder(); StringBuilder htmlBuilder = new StringBuilder(); try { handleMimePart(mimeMessage, textBuilder, htmlBuilder); } catch (IOException e) { throw new MailParsingException("Can't parse email", e); } messageBuilder.textContent(Strings.emptyToNull(textBuilder.toString())); messageBuilder.htmlContent(Strings.emptyToNull(htmlBuilder.toString())); try { // build() will only succeed if all required attributes were set. We wrap // the IllegalStateException in a MailParsingException indicating that // required attributes are missing, so that the caller doesn't fall over. return messageBuilder.build(); } catch (IllegalStateException e) { throw new MailParsingException("Missing required attributes after email was parsed", e); } } /** * Parses a MailMessage from an array of characters. Note that the character array is int-typed. * This method is only used by POP3, which specifies that all transferred characters are US-ASCII * (RFC 6856). When reading the input in Java, io.Reader yields ints. These can be safely * converted to chars as all US-ASCII characters fit in a char. If emails contain non-ASCII * characters, such as UTF runes, these will be encoded in ASCII using either Base64 or * quoted-printable encoding. * * @param chars Array as received over the wire * @return Parsed MailMessage * @throws MailParsingException */ public static MailMessage parse(int[] chars) throws MailParsingException { StringBuilder b = new StringBuilder(chars.length); for (int c : chars) { b.append((char) c); } MailMessage.Builder messageBuilder = parse(b.toString()).toBuilder(); messageBuilder.rawContent(ImmutableList.copyOf(Ints.asList(chars))); return messageBuilder.build(); } /** * Traverses a mime tree and parses out text and html parts. All other parts will be dropped. * * @param part MimePart to parse * @param textBuilder StringBuilder to append all plaintext parts * @param htmlBuilder StringBuilder to append all html parts * @throws IOException */ private static void handleMimePart(Entity part, StringBuilder textBuilder, StringBuilder htmlBuilder) throws IOException { if (isPlainOrHtml(part.getMimeType()) && !isAttachment(part.getDispositionType())) { TextBody tb = (TextBody) part.getBody(); String result = CharStreams.toString(new InputStreamReader(tb.getInputStream(), tb.getMimeCharset())); if (part.getMimeType().equals("text/plain")) { textBuilder.append(result); } else if (part.getMimeType().equals("text/html")) { htmlBuilder.append(result); } } else if (isMixedOrAlternative(part.getMimeType())) { Multipart multipart = (Multipart) part.getBody(); for (Entity e : multipart.getBodyParts()) { handleMimePart(e, textBuilder, htmlBuilder); } } } private static boolean isPlainOrHtml(String mimeType) { return (mimeType.equals("text/plain") || mimeType.equals("text/html")); } private static boolean isMixedOrAlternative(String mimeType) { return mimeType.equals("multipart/alternative") || mimeType.equals("multipart/mixed"); } private static boolean isAttachment(String dispositionType) { return dispositionType != null && dispositionType.equals("attachment"); } }