java实现后台自动发邮件功能

web.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN" "http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
  <servlet>
    <servlet-name>mailsenderservlet</servlet-name><!--邮件发送程序-->
    <servlet-class>com.email.MailSenderServlet</servlet-class>
    <init-param>
      <param-name>server</param-name><!--邮件服务器SMTP地址-->
      <param-value>smtp.163.com</param-value>
    </init-param>
    <init-param>
      <param-name>port</param-name><!--邮件服务器SMTP端口-->
      <param-value>25</param-value>
    </init-param>
    <init-param>
      <param-name>address</param-name><!--邮件地址-->
      <param-value>[e-mail]</param-value>
    </init-param>
    <init-param>
      <param-name>username</param-name><!--邮件账号-->
      <param-value>username</param-value>
    </init-param>
    <init-param>
      <param-name>password</param-name><!--密码-->
      <param-value>******</param-value>
    </init-param>
    <init-param>
      <param-name>validate</param-name><!--SMTP服务器是否要求验证-->
      <param-value>true</param-value>
    </init-param>
    <init-param>
      <param-name>time</param-name><!--扫描数据库时间间隔（分钟）-->
      <param-value>5</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
</web-app>
servlet:
package com.email;
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
public class MailSenderServlet
    extends HttpServlet {
  private MailSender sender;
  private Thread t;
  public void init() throws ServletException {
    sender = new MailSender();
    sender.setRoot(root);
    String server = getInitParameter("server");
String port = getInitParameter("port");
    String address = getInitParameter("address");
    String username = getInitParameter("username");
    String password = getInitParameter("password");
    if (server == null || port == null || address == null || username == null ||
        password == null) {
      System.out.println("系统文件web.xml错误：邮件发送程序初始化失败！");
      return;
    }
    sender.setServer(server);
    sender.setPort(port);
    sender.setAddress(address);
    sender.setUsername(username);
    sender.setPassword(password);
    String time = getInitParameter("time");
    if (time != null) {
      sender.setTime(Integer.parseInt(time));
    }
    String validate = getInitParameter("validate");
    if (validate != null) {
      sender.setValidate(Boolean.valueOf(validate).booleanValue());
    }
    t = new Thread(sender);
    t.start(); //启动邮件发送线程
  }
  public void destroy() {
    sender.stop(); //停止邮件发送线程
    try {
      t.join(1000);
      if (t.isAlive()) {
        System.out.println("邮件发送线程未停止。");
      }
    }
    catch (Exception e) {}
  }
}
邮件发送程序
package com.email;
import java.io.*;
import java.sql.*;
import java.util.*;
import java.util.Date;
import javax.activation.*;
import javax.mail.*;
import javax.mail.Message.*;
import javax.mail.internet.*;
/**
 * <p>Copyright: Copyright (c) 2004</p>
 * @author [e-mail]
 * @version 1.0
 */
public class MailSender
    implements Runnable {
private int time = 5 * 60 * 1000; //扫描数据库时间间隔
  private boolean flag = true; //停止线程标记
  private String server = "smtp.163.com"; //SMTP服务器地址
  private String port = "25"; //SMTP服务器端口
  private String address; //用于发送EMAIL的发送者地址
  private String username; //发送者的用户名
  private String password; //发送者的密码
  private boolean validate = true; //邮件服务器是否要求验证
  private File root = null; //WEB根目录
  MailConfigManager manager = MailConfigManager.getInstance();
  public MailSender() {
  }
  public void setAddress(String address) {
    this.address = address;
  }
  public void setPassword(String password) {
    this.password = password;
  }
  public void setPort(String port) {
    if (port != null && port.length() > 0) {
      this.port = port;
    }
  }
  public void setServer(String server) {
    this.server = server;
  }
  public void setUsername(String username) {
    this.username = username;
  }
  public void setValidate(boolean validate) {
    this.validate = validate;
  }
  public void setTime(int minute) {
    this.time = minute * 60 * 1000;
  }
  public void run() {
    long lastTime = new Date().getTime(); //保存前一次发送邮件的时间
    while (flag) { //服务器停止时退出线程
      long k = new Date().getTime() - lastTime;
      if (k < -1000) { //防止系统修改时间
        lastTime = new Date().getTime();
        continue;
      }
      if (k > time) { //超过设定时间间隔开始发送邮件
        sendData();
        lastTime = new Date().getTime();
      }
      try {
        Thread.sleep(100);
      }
      catch (Exception e) {}
    }
  }
  public void stop() {
    flag = false;
}
/**
  * 检索数据库，并发送邮件
  * @throws Exception
  */
 private void sendData() throws Exception {
  
  Connection con=null;
  Statement stmt =null;
  ResultSet rs = null;// 读取数据库数据
  con = DBUtils.getConnection();
  stmt=con.createStatement();
        String sql="select email from Lp_teacher  ";
        rs=stmt.executeQuery(sql);
      try {
        while(rs.next()){
       Session session = Session.getInstance(getProperties(),
     new Authentic());
   /*while (flag) {*/// 服务器停止时退出线程
    String toAddress =rs.getString("email"); ;// 发送地址（从rs中得到）
    System.out.println("toAddress:"+toAddress);
    String subject = "我是测试用户";// 邮件主题(也可以从数据字段中拿到)
    String content = "我要测试！";// 邮件内容
    String file[] = null;// 所有附件（绝对路径）(也可以从数据字段中拿到)
      sendMail(session, toAddress, subject, content, file);// 发送邮件
         }      
  } catch (Exception e) {
   e.printStackTrace();
  } finally {
   if (rs != null) {
    try {
     rs.close();
    } catch (SQLException e) {
    }
   }
  }
   }  /**
   * 发送邮件
   * @param session 会话
   * @param toAddress 目的地址
   * @param subject 邮件主题
   * @param content 邮件内容（HTML）
   * @param files 邮件附件
   * @return 是否发送成功
   */
  private boolean sendMail(Session session, String toAddress, String subject,
                           String content, String[] files) {
    toAddress = [e-mail];
    try {
      Message rs = new MimeMessage(session);
      Address from = new InternetAddress(address);
      rs.setFrom(from); //发送地址
      rs.setRecipient(RecipientType.TO, new InternetAddress(toAddress)); //接收地址
      rs.setSubject(subject); //邮件主题
      Multipart mp = new MimeMultipart();
      BodyPart html = new MimeBodyPart();
      html.setContent(content, "text/html; charset=GBK"); //邮件HTML内容
      mp.addBodyPart(html);
      if (files != null && files.length > 0) { //邮件附件
        for (int i = 0; i < files.length; i++) {
          MimeBodyPart mbp = new MimeBodyPart();
          FileDataSource fds = new FileDataSource(files[i]);
          mbp.setDataHandler(new DataHandler(fds));
          mbp.setFileName(MimeUtility.encodeWord(files[i]), "GBK", null));
          mp.addBodyPart(mbp);
        }
      }
      rs.setContent(mp); //邮件全部内容
      rs.setSentDate(new Date()); //发送时间
      Transport.send(rs); //发送
      return true;
    }
    catch (Exception e) {
      e.printStackTrace();
      return false;
    }
  }
  /**
   * 邮件会话属性
   * @return 会话属性
   */
  private Properties getProperties() {
    Properties rs = new Properties();
    rs.put("mail.smtp.host", server);
    rs.put("mail.smtp.port", port);
    rs.put("mail.smtp.auth", validate ? "true" : "false");
    return rs;
  }
  public void setRoot(File root) {
    this.root = root;
  }
  class Authentic
      extends Authenticator { //验证密码
    public Authentic() {
    }
    public PasswordAuthentication getPasswordAuthentication() {
      return new PasswordAuthentication(username, password);
    }
  }
}