需求

因为某些特定的业务需要，要从邮件中获取附件。花了一些时间，最终业务需求实现了，但是也遇到一些坑，所以记录一下。

JavaMail

使用JavaMail来实现邮件的一系列操作（发送、接收），我使用的版本是1.6.2（maven仓库里有），不多说，上代码

工具类

package com.xxx.xxx;import com.sun.mail.imap.IMAPFolder;
import com.sun.mail.imap.IMAPStore;
import com.sun.mail.pop3.POP3Folder;
import com.sun.mail.pop3.POP3Store;
import org.castor.util.Base64Decoder;import javax.activation.DataHandler;
import javax.activation.FileDataSource;
import javax.mail.*;
import javax.mail.internet.*;
import javax.mail.search.*;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.security.Security;
import java.util.Date;
import java.util.List;
import java.util.Properties;/*** @author jiangyw* @date 2019/1/7 19:29* <p>* 处理邮件工具类* 接收/发送服务器根据不同邮箱有不同的地址* 在邮箱设置里都可找到*/
public class MailUtil {// 发送服务器private static final String SEND_SMTP_HOST = "smtp.exmail.qq.com";private static final int SEND_SMTP_PORT = 465;// 接收服务器private static final String RECEIVE_IMAP_HOST = "imap.exmail.qq.com";private static final int RECEIVE_IMAP_PORT = 993;private static final String RECEIVE_POP_HOST = "pop.exmail.qq.com";private static final int RECEIVE_POP_PORT = 110;// 账号private String user;// 密码private String password;private IMAPFolder imapFolder = null;private IMAPStore imapStore = null;private POP3Store pop3Store = null;private POP3Folder pop3Folder = null;public MailUtil() {this("your email address", "your email password");}private MailUtil(String user, String password) {this.user = user;this.password = password;}/*** 发送邮件** @param toEmail 收件人邮箱地址* @param subject 邮件标题* @param content 邮件内容 可以是html内容*/public void send(String toEmail, String subject, String content) {Session session = loadSendSession();// session.setDebug(true);// 创建邮件消息MimeMessage message = new MimeMessage(session);try {// 设置发件人message.setFrom(new InternetAddress(user));Address[] a = new Address[1];a[0] = new InternetAddress(user);message.setReplyTo(a);// 设置收件人InternetAddress to = new InternetAddress(toEmail);message.setRecipient(MimeMessage.RecipientType.TO, to);// 设置邮件标题message.setSubject(subject);// 设置邮件的内容体message.setContent(content, "text/html;charset=UTF-8");// 发送邮件Transport.send(message);} catch (MessagingException e) {e.printStackTrace();String err = e.getMessage();// 在这里处理message内容， 格式是固定的System.out.println(err);}}/*** 发送邮件 带附件** @param toEmail    收件人邮箱地址* @param subject    邮件标题* @param content    邮件内容 可以是html内容* @param attachPath 附件路径*/public void send(String toEmail, String subject, String content, String attachPath) {Session session = loadSendSession();MimeMessage mm = new MimeMessage(session);try {//发件人mm.setFrom(new InternetAddress(user));//收件人mm.setRecipient(Message.RecipientType.TO, new InternetAddress(toEmail)); // 设置收件人// mm.setRecipient(Message.RecipientType.CC, new// InternetAddress("XXXX@qq.com")); //设置抄送人//标题mm.setSubject(subject);//内容Multipart multipart = new MimeMultipart();//body部分BodyPart contentPart = new MimeBodyPart();contentPart.setContent(content, "text/html;charset=utf-8");multipart.addBodyPart(contentPart);//附件部分BodyPart attachPart = new MimeBodyPart();FileDataSource fileDataSource = new FileDataSource(attachPath);attachPart.setDataHandler(new DataHandler(fileDataSource));attachPart.setFileName(MimeUtility.encodeText(fileDataSource.getName()));multipart.addBodyPart(attachPart);mm.setContent(multipart);Transport.send(mm);} catch (Exception e) {e.printStackTrace();String err = e.getMessage();// 在这里处理message内容， 格式是固定的System.out.println(err);}}private Session loadSendSession() {try {// 配置发送邮件的环境属性final Properties props = new Properties();// 表示SMTP发送邮件，需要进行身份验证props.put("mail.smtp.auth", "true");props.put("mail.smtp.host", SEND_SMTP_HOST);// props.put("mail.smtp.port", SEND_SMTP_PORT);// 如果使用ssl，则去掉使用25端口的配置，进行如下配置,props.put("mail.smtp.socketFactory.class", "javax.net.ssl.SSLSocketFactory");props.put("mail.smtp.socketFactory.port", SEND_SMTP_PORT);props.put("mail.smtp.port", SEND_SMTP_PORT);// 发件人的账号props.put("mail.user", user);// 访问SMTP服务时需要提供的密码props.put("mail.password", password);// 构建授权信息，用于进行SMTP进行身份验证Authenticator authenticator = new Authenticator() {@Overrideprotected PasswordAuthentication getPasswordAuthentication() {// 用户名、密码String userName = props.getProperty("mail.user");String password = props.getProperty("mail.password");return new PasswordAuthentication(userName, password);}};// 使用环境属性和授权信息，创建邮件会话return Session.getInstance(props, authenticator);} catch (Exception e) {e.printStackTrace();System.out.println("mail session is null");}return null;}public void saveFile(List<MailAttachment> list) throws IOException {for (MailAttachment mailAttachment : list) {InputStream inputStream = mailAttachment.getInputStream();FileOutputStream outputStream = new FileOutputStream(new File("C:\\Users\\jiangyw\\Desktop\\test.pdf"));int len;byte[] bytes = new byte[1024];while ((len = inputStream.read(bytes)) != -1) {outputStream.write(bytes, 0, len);outputStream.flush();}inputStream.close();outputStream.close();}}/*** 获取附件* 只获取附件里的* 邮件内容里的附件（图片等）忽略* @param part 邮件中多个组合体中的其中一个组合体* @param list 附件容器* @throws UnsupportedEncodingException* @throws MessagingException* @throws FileNotFoundException* @throws IOException*/public void getAttachment(Part part, List<MailAttachment> list) throws UnsupportedEncodingException, MessagingException,FileNotFoundException, IOException {if (part.isMimeType("multipart/*")) {Multipart multipart = (Multipart) part.getContent();    //复杂体邮件//复杂体邮件包含多个邮件体int partCount = multipart.getCount();for (int i = 0; i < partCount; i++) {//获得复杂体邮件中其中一个邮件体BodyPart bodyPart = multipart.getBodyPart(i);//某一个邮件体也有可能是由多个邮件体组成的复杂体String disposition = bodyPart.getDisposition();if (disposition != null && (disposition.equalsIgnoreCase(Part.ATTACHMENT) || disposition.equalsIgnoreCase(Part.INLINE))) {InputStream is = bodyPart.getInputStream();// 附件名通过MimeUtility解码，否则是乱码String name = MimeUtility.decodeText(bodyPart.getFileName());list.add(new MailAttachment(name, is));} else if (bodyPart.isMimeType("multipart/*")) {getAttachment(bodyPart, list);} else {String contentType = bodyPart.getContentType();if (contentType.contains("name") || contentType.contains("application")) {}}}} else if (part.isMimeType("message/rfc822")) {getAttachment((Part) part.getContent(), list);}}/*** 判断邮件中是否包含附件** @return 邮件中是否存在附件* @throws MessagingException* @throws IOException*/public boolean hasAttachment(Part part) throws MessagingException, IOException {boolean flag = false;if (part.isMimeType("multipart/*")) {MimeMultipart multipart = (MimeMultipart) part.getContent();int partCount = multipart.getCount();for (int i = 0; i < partCount; i++) {BodyPart bodyPart = multipart.getBodyPart(i);String disp = bodyPart.getDisposition();if (disp != null && (disp.equalsIgnoreCase(Part.ATTACHMENT) || disp.equalsIgnoreCase(Part.INLINE))) {flag = true;} else if (bodyPart.isMimeType("multipart/*")) {flag = hasAttachment(bodyPart);} else {String contentType = bodyPart.getContentType();if (contentType.contains("application")) {flag = true;}if (contentType.contains("name")) {flag = true;}}if (flag) break;}} else if (part.isMimeType("message/rfc822")) {flag = hasAttachment((Part) part.getContent());}return flag;}/*** 获得邮件文本内容** @param part        邮件体* @param textContent 存储邮件文本内容的字符串* @param htmlContent 存储邮件html内容的字符串* @throws MessagingException* @throws IOException*/public void getMailTextContent(Part part, StringBuffer textContent, StringBuffer htmlContent) throws MessagingException, IOException {//如果是文本类型的附件，通过getContent方法可以取到文本内容，但这不是我们需要的结果，所以在这里要做判断boolean isContainTextAttach = part.getContentType().indexOf("name") > 0;if (part.isMimeType("text/*") && !isContainTextAttach) {String contentType = part.getContentType();if (contentType.startsWith("TEXT/PLAIN") || contentType.startsWith("text/plain")) {textContent.append(part.getContent().toString());}if (contentType.startsWith("TEXT/HTML") || contentType.startsWith("text/html")) {htmlContent.append(part.getContent().toString());}} else if (part.isMimeType("message/rfc822")) {getMailTextContent((Part) part.getContent(), textContent, htmlContent);} else if (part.isMimeType("multipart/*")) {Multipart multipart = (Multipart) part.getContent();int partCount = multipart.getCount();for (int i = 0; i < partCount; i++) {BodyPart bodyPart = multipart.getBodyPart(i);getMailTextContent(bodyPart, textContent, htmlContent);}}}public String getSubject(Message message) throws MessagingException {return message.getSubject();}/*** 获取邮件信息* IMAP协议* 下载附件的时候巨慢* 如果需要获取附件的时候不推荐使用* 该协议下只能查询receivedDate* sentDate都为null** @throws MessagingException*/public Message[] getImapMessages() throws MessagingException {String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory";Security.addProvider(new com.sun.net.ssl.internal.ssl.Provider());System.setProperty("mail.mime.splitlongparameters", "false");Properties props = System.getProperties();props.setProperty("mail.imap.socketFactory.class", SSL_FACTORY);props.setProperty("mail.imap.socketFactory.port", "993");props.setProperty("mail.imapStore.protocol", "imap");props.setProperty("mail.imap.host", RECEIVE_IMAP_HOST);props.setProperty("mail.imap.port", "993");props.setProperty("mail.imap.auth.login.disable", "true");Session session = Session.getDefaultInstance(props, null);session.setDebug(false);imapStore = (IMAPStore) session.getStore("imap");  // 使用imap会话机制，连接服务器imapStore.connect(RECEIVE_IMAP_HOST, RECEIVE_IMAP_PORT, user, password);imapFolder = (IMAPFolder) imapStore.getFolder("INBOX"); //收件箱imapFolder.open(Folder.READ_WRITE);// 获取前一天的邮件信息SearchTerm endTerm = new ReceivedDateTerm(ComparisonTerm.LE, new Date(System.currentTimeMillis() + 24 * 60 * 60 * 1000L));SearchTerm startTerm = new ReceivedDateTerm(ComparisonTerm.GE, new Date(System.currentTimeMillis() - 24 * 60 * 60 * 1000L));SearchTerm searchTerm = new AndTerm(startTerm, endTerm);return imapFolder.search(searchTerm);}/*** 通过pop3协议获取邮件信息* pop3协议下只能通过sentDate来查询* receivedDate都为null** @return Message[]* @throws MessagingException*/public Message[] getPopMessages() throws MessagingException {Properties props = new Properties();props.setProperty("mail.imapStore.protocol", "pop3");       // 使用pop3协议props.setProperty("mail.pop3.port", "110");           // 端口props.setProperty("mail.pop3.host", RECEIVE_POP_HOST);       // pop3服务器Session session = Session.getInstance(props);pop3Store = (POP3Store) session.getStore("pop3");pop3Store.connect(RECEIVE_POP_HOST, RECEIVE_POP_PORT, user, password);// 获得收件箱pop3Folder = (POP3Folder) pop3Store.getFolder("INBOX");/* Folder.READ_ONLY：只读权限* Folder.READ_WRITE：可读可写（可以修改邮件的状态）*/pop3Folder.open(Folder.READ_ONLY); //打开收件箱// 获取前一天的邮件信息SearchTerm endTerm = new SentDateTerm(ComparisonTerm.LE, new Date(System.currentTimeMillis() + 24 * 60 * 60 * 1000L));SearchTerm startTerm = new SentDateTerm(ComparisonTerm.GE, new Date(System.currentTimeMillis() - 24 * 60 * 60 * 1000L));SearchTerm searchTerm = new AndTerm(startTerm, endTerm);
//         得到收件箱中的所有邮件,并解析return pop3Folder.search(searchTerm);}/*** 关闭folder和store资源** @throws MessagingException*/public void close() throws MessagingException {if (imapFolder != null) {imapFolder.close(false);}if (imapStore != null) {imapStore.close();}if (pop3Folder != null) {pop3Folder.close(false);}if (pop3Store != null) {pop3Store.close();}}}

附件类

很简单的容器类：

package com.xxx.xxx;import java.io.InputStream;/*** @author jiangyw* @date 2019/1/10 21:14** 邮件附件类*/
public class MailAttachment {private String name;private InputStream inputStream;public String getName() {return name;}public void setName(String name) {this.name = name;}public InputStream getInputStream() {return inputStream;}public void setInputStream(InputStream inputStream) {this.inputStream = inputStream;}public MailAttachment(String name, InputStream inputStream) {this.name = name;this.inputStream = inputStream;}
}

使用

public void readMail() throws MessagingException {long startTime = System.currentTimeMillis();MailUtil mailUtil = new MailUtil();Message[] messages = mailUtil.getPopMessages();for (Message message : messages) {String subject = mailUtil.getSubject(message);try {List<MailAttachment> mailAttachments = new ArrayList<>();mailUtil.getAttachment(message, mailAttachments);saveAttachment(mailAttachments);}} catch (Exception ignore) {}}mailUtil.close();System.out.println("解析邮件共耗时：" + (System.currentTimeMillis() - startTime) + "毫秒");}private void saveAttachment(List<MailAttachment> list) throws IOException {for (MailAttachment mailAttachment : list) {InputStream inputStream = mailAttachment.getInputStream();FileOutputStream outputStream = new FileOutputStream(new File( "your path");int len;byte[] bytes = new byte[1024 * 1024];while ((len = inputStream.read(bytes)) != -1) {outputStream.write(bytes, 0, len);outputStream.flush();}inputStream.close();outputStream.close();}}

遇到的一些意外

下载附件速度慢到令人发指！！！（看图）

两个一共不到4M的附件，下载总共用了1000多秒！！！
解决方法：不要用IMAP协议接收邮件信息，用POP3协议，换了协议之后的速度（看图）

速度差了两个数量级！！！
在代码里也注释了，用IMAP协议时没有SentDate，用POP3协议时没有ReceivedDate；这两个协议具体的区别百度一下你就知道，我是因为要获取前一天的邮件，所以是根据日期来搜索。
附件名乱码，这个其实很简单，用JavaMail自带的MimeUtility解码一下就好。

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通过JavaMail下载邮件附件

通过JavaMail下载邮件附件

需求

JavaMail

工具类

附件类

使用

遇到的一些意外

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