一个发邮件的类，带验证功能，可以发html内容，可以添加附件，并解决附件乱码问题。

//文件Mail.java 该文件内容部分综合网上的资源，自己进行了改进，转载请注明 汪建伟。

package sendmail;

import java.io.UnsupportedEncodingException;
import java.util.Properties;
import java.util.Date;
import java.util.ArrayList;
import javax.mail.*;
import javax.mail.internet.*;
import javax.activation.*;
import java.net.MalformedURLException;
import java.net.URL;
/**
* <p>Title: </p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2005</p>
* <p>Company: Peking University </p>
* @author 汪建伟
* @version 1.0
*/

public class Mail{

protected ArrayList bodypartArrayList=null;
protected Multipart multipart = null;
protected MimeMessage mailMessage = null;
protected Session mailSession = null;
protected Properties mailProperties = System.getProperties();
protected InternetAddress mailFromAddress = null;
protected InternetAddress mailToAddress = null;
protected String mailSubject ="";
protected Date mailSendDate = null;
private String smtpserver="";
private String name="";
private String password="";

public Mail(String smtpHost,String username,String password){
smtpserver=smtpHost;
name=username;
this.password=password;
mailProperties.put("mail.smtp.host",smtpHost);
mailProperties.put("mail.smtp.auth","true"); //设置smtp认证，很关键的一句
mailSession = Session.getDefaultInstance(mailProperties);
//mailSession.setDebug(true);

mailMessage = new MimeMessage(mailSession);
multipart = new MimeMultipart();
bodypartArrayList=new ArrayList();//用来存放BodyPart，可以有多个BodyPart！
}
//设置邮件主题
public void setSubject(String mailSubject)throws MessagingException{
this.mailSubject = mailSubject;
mailMessage.setSubject(mailSubject);
}
//设置邮件发送日期
public void setSendDate(Date sendDate)throws MessagingException{
this.mailSendDate = sendDate;
mailMessage.setSentDate(sendDate);
}
//发送纯文本
public void addTextContext(String textcontent)throws MessagingException{
BodyPart bodypart=new MimeBodyPart();
bodypart.setContent(textcontent,"text/plain;charset=GB2312");
bodypartArrayList.add(bodypart);
}
//发送Html邮件
public void addHtmlContext(String htmlcontent)throws MessagingException{
BodyPart bodypart=new MimeBodyPart();
bodypart.setContent(htmlcontent,"text/html;charset=GB2312");
bodypartArrayList.add(bodypart);
}
//将文件添加为附件
public void addAttachment(String FileName/*附件文件名*/,String DisplayFileName/*在邮件中想要显示的文件名*/)
throws MessagingException,UnsupportedEncodingException{
BodyPart bodypart=new MimeBodyPart();
FileDataSource fds=new FileDataSource(FileName);

DataHandler dh=new DataHandler(fds);
String displayfilename="";
displayfilename = MimeUtility.encodeWord(DisplayFileName,"gb2312", null);//对显示名称进行编码，否则会出现乱码！

bodypart.setFileName(displayfilename);//可以和原文件名不一致
bodypart.setDataHandler(dh);
bodypartArrayList.add(bodypart);
}
//将byte[]作为文件添加为附件
public void addAttachmentFrombyte(byte[] filebyte/*附件文件的字节数组*/,String DisplayFileName/*在邮件中想要显示的文件名*/)
throws MessagingException,UnsupportedEncodingException{
BodyPart bodypart=new MimeBodyPart();
ByteDataSource fds=new ByteDataSource(filebyte,DisplayFileName);

DataHandler dh=new DataHandler(fds);
String displayfilename="";
displayfilename = MimeUtility.encodeWord(DisplayFileName,"gb2312", null);//对显示名称进行编码，否则会出现乱码！

bodypart.setFileName(displayfilename);//可以和原文件名不一致
bodypart.setDataHandler(dh);
bodypartArrayList.add(bodypart);
}

//使用远程文件（使用URL）作为信件的附件
public void addAttachmentFromUrl(String url/*附件URL地址*/,String DisplayFileName/*在邮件中想要显示的文件名*/)
throws MessagingException,MalformedURLException,UnsupportedEncodingException{
BodyPart bodypart=new MimeBodyPart();
//用远程文件作为信件的附件
URLDataSource ur= new URLDataSource(new URL(url));
//注:这里用的参数只能为URL对象,不能为URL字串
DataHandler dh=new DataHandler(ur);
String displayfilename="";
displayfilename=MimeUtility.encodeWord(DisplayFileName,"gb2312", null);
bodypart.setFileName(displayfilename);//可以和原文件名不一致
bodypart.setDataHandler(dh);
bodypartArrayList.add(bodypart);
}

//设置发件人地址
public void setMailFrom(String mailFrom)throws MessagingException{
mailFromAddress = new InternetAddress(mailFrom);
mailMessage.setFrom(mailFromAddress);
}
//设置收件人地址，收件人类型为to,cc,bcc(大小写不限)
public void setMailTo(String[] mailTo,String mailType)throws Exception{
for(int i=0;i<mailTo.length;i++){
mailToAddress = new InternetAddress(mailTo[i]);
if(mailType.equalsIgnoreCase("to")){
mailMessage.addRecipient(Message.RecipientType.TO,mailToAddress);
}
else if(mailType.equalsIgnoreCase("cc")){
mailMessage.addRecipient(Message.RecipientType.CC,mailToAddress);
}
else if(mailType.equalsIgnoreCase("bcc")){
mailMessage.addRecipient(Message.RecipientType.BCC,mailToAddress);
}
else{
throw new Exception("Unknown mailType: "+mailType+"!");
}
}
}
//开始投递邮件
public void sendMail()throws MessagingException,SendFailedException{
for (int i=0;i<bodypartArrayList.size();i++) {
multipart.addBodyPart((BodyPart)bodypartArrayList.get(i));
}
mailMessage.setContent(multipart);
mailMessage.saveChanges();
Transport transport=mailSession.getTransport("smtp");
transport.connect(smtpserver,name,password);//以smtp方式登录邮箱
transport.sendMessage(mailMessage,mailMessage.getAllRecipients());
//发送邮件,其中第二个参数是所有已设好的收件人地址
transport.close();
}

}

//文件 ByteDataSource.java 该文件内容由汪建伟原创。转载请注明！

package sendmail;

/**
* <p>Title: </p>
* <p>Description: 发邮件</p>
* <p>Copyright: Copyright (c) 2005</p>
* <p>Company: Peking University </p>
* @author 汪建伟
* @version 1.0
*/
import javax.activation.DataSource;
import java.io.*;
public class ByteDataSource implements DataSource{
private byte[] filebyte=null;
private String filetype="application/octet-stream";
private String filename="";
private OutputStream outputstream=null;
private InputStream inputstream=null;
public ByteDataSource() {
}
public ByteDataSource(String FileName) {
File f=new File(FileName);
filename=f.getName();
try {
inputstream = new FileInputStream(f);
inputstream.read(filebyte);

} catch (Exception e) {
}

}

public ByteDataSource(byte[] filebyte,String displayfilename) {
this.filebyte=filebyte;
this.filename=displayfilename;
}
public String getContentType() {
return filetype;
}

public InputStream getInputStream() throws IOException {
InputStream input=new ByteArrayInputStream(filebyte);
return input;
}

public String getName() {
return filename;
}

public OutputStream getOutputStream() throws IOException {

outputstream.write(filebyte);
return outputstream;
}
}
//newSendMail.java 发邮件示例

package sendmail;

/**
* <p>Title: </p>
* <p>Description: 发邮件示例</p>
* <p>Copyright: Copyright (c) 2005</p>
* <p>Company: Peking University </p>
* @author 汪建伟
* @version 1.0
*/

import java.io.FileWriter;
import java.io.IOException;
import java.util.Date;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.io.PrintWriter;
import java.io.BufferedWriter;
import java.io.*;
public class newSendMail {
public static void main(String[] args) {
Mainprogram1 w1= new Mainprogram1();

w1.sendmail() ;

}
}

class Mainprogram1{

private java.util.Date sysdate;
Mainprogram1(){
//获取要查询的起止时间
sysdate = new java.util.Date();
}

public void sendmail(){ //创建邮件发送实例，发送邮件
String smtp = "smtp.163.com";//邮件服务器地址
String mailname = "";//连接邮件服务器的用户名
String mailpsw = "";//连连接邮件服务器的用户密码
String mailto = "";// 接收邮件的地址
String copyto = "";// 抄送邮件的地址
String mailfrom = "";// 发送邮件的地址
String mailtitle = "测试邮件标题";// 邮件的标题
//请根据实际情况赋值
Mail mymail= new Mail(smtp,mailname, mailpsw);
String mto[]={mailto};
String mcc[]={copyto};
try{
mymail.setMailFrom(mailfrom);
mymail.setSendDate(new Date());
mymail.setMailTo(mto,"to");
if (!copyto.matches("")){ //如果抄送不为空，则将信件抄送给copyto
mymail.setMailTo(mcc,"cc");
}
mymail.setSubject(mailtitle);
mymail.addTextContext("邮件内容");
mymail.addHtmlContext("html内容");
mymail.addAttachment("c://测试附件.doc","测试附件.doc");
mymail.addAttachmentFromUrl("http://162.105.109.163/getimg?imgid=148","图片文件.jpg");
mymail.addAttachmentFromUrl("http://www.pku.edu.cn","北大主页.htm");

//下面的附件内容来自一个byte[]类型，增加这个方法的意图在于如果在web模式下发邮件，就不用生成临时文件
//直接将上载的文件保存成byte[]格式，然后使用该方法添加到邮件的附件中，进行发送
InputStream inputStream=null;
try {
File imageFile = new File("c://1.jpg");
inputStream = new FileInputStream(imageFile);
} catch(IOException ei){}

try {
byte[] b=new byte[inputStream.available()];

inputStream.read(b);
mymail.addAttachmentFrombyte(b,"来自byte的附件.jpg");

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

mymail.sendMail() ;
WriteinfoToFile("邮件发出！");
}
catch (Exception ex){ WriteinfoToFile("邮件发送失败！"+ex.toString());}
}

//向ini文件中写提示信息
private void WriteinfoToFile(String info){
try{
PrintWriter pw = new PrintWriter(new BufferedWriter(new FileWriter("mailinfo.txt",true)));
pw.println(sysdate.toString()+" "+info);
pw.close();
}
catch(IOException ei){
System.out.println(sysdate.toString()+ " 向mailinfo.txt文件中写数据错误:"+ei.toString());
System.exit(0);
}
}
}