java mail 纯文本附件乱码的解决方案
java mail在发送纯文本附件时，当附件内容的编码和jvm缺省的编码不一致时，出现乱码。原因时java mail处理纯文本附件，使用text_plain这个datacontenthandler来处理，而text_plain又简单的使用jvm缺省编码来读取文件内容（可以使用file.encode和mail.mime.charset系统属性来更改），两者不一致时，自然就乱码了
找到的问题的原因，也就容易解决了，一种方法就是把所有的附件类新全部设成application/octet-stream，把附件作为二进制流，还有一种就是当附件是存文本时，通过BOM（byte order mark）来探测文件的编码类型。
扩展FileDataSource，处理ContentType类型：
public class MyFileDataSource extends FileDataSource {
private static final String DEFAULT_CONTENT_TYPE = "application/octet-stream";
private final static Pattern pattern = Pattern.compile("^text/");
private String contentType ;
private int head_count=0;
public MyFileDataSource(File file) {
super(file);
determinateType();
}
private void determinateType(){
contentType = super.getContentType();
Matcher m = pattern.matcher(contentType);
if(m.find() && getFile().exists() && getFile().isFile()){
InputStream in = null;
try {
in = new FileInputStream(getFile());
if(is_utf_8(in)){
contentType = contentType + "; charset=utf-8";
head_count = 3;
} else {
contentType = DEFAULT_CONTENT_TYPE;
}
} catch (IOException e) {
contentType = DEFAULT_CONTENT_TYPE;
} finally {
try {
if(in!=null) {
in.close();
}
} catch (IOException e1) {
}
}
}
}
public MyFileDataSource(String s) {
this(new File(s));
}
@Override
public InputStream getInputStream() throws IOException {
InputStream in = super.getInputStream();
for(int i=0;i<head_count;i++) in.read();
return in;
}
@Override
public String getContentType() {
return contentType;
}
private boolean is_utf_8(InputStream in) throws IOException{
byte[] b3 = new byte[3];
int count = in.read(b3, 0, 3);
if(count<3) return false;
int b0 = b3[0] & 0xFF;
int b1 = b3[1] & 0xFF;
int b2 = b3[2] & 0xFF;
if (b0 == 0xEF && b1 == 0xBB && b2 == 0xBF){
return true;
}
return false;
}
}
使用：
public static void main(String[] args) throws Exception {
String host = "your host";
String from = "mail from addr";
String to = "to addr";
Properties props = new Properties();
props.put("mail.smtp.host", host);
props.put("mail.smtp.auth", "true");
props.put("mail.transport.protocol", "smtp");
Session session = Session.getInstance(props, null);
session.setDebug(true);
System.setProperty("mail.mime.charset", "utf-8");
MimeMessage message = new MimeMessage(session);
message.setSentDate(new Date());
message.setFrom(new InternetAddress(from,"test"));
message.setRecipients(Message.RecipientType.TO, new InternetAddress[] {new InternetAddress(to)});
message.setSubject("测试");
String html="<html><head></head>\r\n\r\n <body><h1>测试htmlmail</h1><img src=\"cid:aaaaaaa\"></body></html>";
MimeMultipart multipart = new MimeMultipart("related");
MimeBodyPart html_body = new MimeBodyPart();
html_body.setContent(html,"text/html; charset=utf-8");
multipart.addBodyPart(html_body);
MimeBodyPart file = new MimeBodyPart();
//file.attachFile("d:\\aa.txt");
FileDataSource fds = new MyFileDataSource("d:\\test.txt");
file.setDataHandler(new DataHandler(fds));
multipart.addBodyPart(file);
message.setContent(multipart);
Transport transport = session.getTransport();
try {
transport.connect(host, 25, "×××", "×××");
transport.sendMessage(message, message.getAllRecipients());
} finally {
transport.close();
}
}