现在大多数smtp服务器都需要身份认证，若用javamail写一个邮件收发客户端，怎么来实现这种功能呢？下面是一个简单的列子，模拟foxmail对认证功能的实现。

package jmail;

import javax.mail.*;

import java.util.*;

import java.sql.*;

import javax.swing.*;

import java.awt.*;

public class MailAuthenticator extends Authenticator{

String authenName; //用户名

String authenPass; //密码

public MailAuthenticator(String authenName,String authenPass) {

super();

this.authenName=authenName;

this.authenPass=authenPass;

}

public PasswordAuthentication getPasswordAuthentication(){ /*若服务器需要身份认证，Sission会自动调用这个方法

String temp=null;

if(authenPass.equals("")||authenPass==null){ /*若密码为空*/

Option op=new Option(null,"身份验证",true); /*弹出要求用户输入密码的对话框，Option是自定义的JDialog，包含一个密码域*/

temp=op.showDialog(); /*Option的返回输入的密码*/

authenPass=temp;

}

return new PasswordAuthentication(authenName,authenPass);

}

}

/* 下面是Option 类，jbuilder里写的，无须解释*/

package jmail;

import java.awt.*;

import javax.swing.*;

import com.borland.jbcl.layout.*;

import java.awt.event.*;

public class Option extends JDialog {

JPanel panel1 = new JPanel();

JLabel jLabel1 = new JLabel();

XYLayout xYLayout1 = new XYLayout();

JButton jButton1 = new JButton();

JButton jButton2 = new JButton();

JPasswordField jPasswordField1 = new JPasswordField();

JLabel jLabel2 = new JLabel();

JLabel jLabel3 = new JLabel();

Icon forget=new ImageIcon(".\images\forget.gif");

boolean ok=false;

JLabel jLabel4 = new JLabel();

JLabel jLabel5 = new JLabel();

public Option(Frame frame, String title, boolean modal) {

super(frame, title, modal);

try {

jbInit();

pack();

}

catch(Exception ex) {

ex.printStackTrace();

}

}

public Option() {

this(null, "", false);

}

private void jbInit() throws Exception {

panel1.setLayout(xYLayout1);

jLabel1.setFont(new java.awt.Font("Dialog", 0, 12));

jLabel1.setText("密码:");

jButton1.setFont(new java.awt.Font("Dialog", 0, 12));

jButton1.setDoubleBuffered(false);

jButton1.setText("确定");

jButton1.addActionListener(new Option_jButton1_actionAdapter(this));

jButton2.setFont(new java.awt.Font("Dialog", 0, 12));

jButton2.setText("取消");

jButton2.addActionListener(new Option_jButton2_actionAdapter(this));

jLabel2.setFont(new java.awt.Font("Dialog", 0, 12));

jLabel2.setHorizontalTextPosition(SwingConstants.TRAILING);

jLabel2.setIcon(forget);

jLabel2.setText("");

jLabel3.setFont(new java.awt.Font("Dialog", 0, 12));

jLabel3.setText("服务器需要身份认证, 请输入密码");

panel1.setToolTipText("");

jLabel4.setText(" ");

jLabel5.setText(" ");

getContentPane().add(panel1, BorderLayout.CENTER);

panel1.add(jLabel4, new XYConstraints(189, 61, -1, -1));

panel1.add(jLabel2, new XYConstraints(15, 1, 67, 19));

panel1.add(jLabel3, new XYConstraints(15, 22, -1, -1));

panel1.add(jPasswordField1, new XYConstraints(48, 46, 140, -1));

panel1.add(jLabel1, new XYConstraints(15, 48, -1, -1));

panel1.add(jButton1, new XYConstraints(46, 79, 58, 22));

panel1.add(jButton2, new XYConstraints(112, 79, 58, 22));

panel1.add(jLabel5, new XYConstraints(85, 102, -1, 12));

this.getRootPane().setDefaultButton(jButton1);

this.setSize(220,130);

Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();

this.setLocation((int)screenSize.getWidth()/2-80,(int)screenSize.getHeight()/2-50);

}

void jButton1_actionPerformed(ActionEvent e) {

ok=true;

this.dispose();

}

void jButton2_actionPerformed(ActionEvent e) {

ok=false;

this.dispose();

}

public String showDialog(){

show();

if(ok)return new String(jPasswordField1.getPassword());

else return null;

}

}

class Option_jButton1_actionAdapter implements java.awt.event.ActionListener {

Option adaptee;

Option_jButton1_actionAdapter(Option adaptee) {

this.adaptee = adaptee;

}

public void actionPerformed(ActionEvent e) {

adaptee.jButton1_actionPerformed(e);

}

}

class Option_jButton2_actionAdapter implements java.awt.event.ActionListener {

Option adaptee;

Option_jButton2_actionAdapter(Option adaptee) {

this.adaptee = adaptee;

}

public void actionPerformed(ActionEvent e) {

adaptee.jButton2_actionPerformed(e);

}

}

/*下面写一个发送邮件主类，利用上面的MailAuthenticator类来提供身份验证 */

package jmail;

import javax.mail.*;

import javax.mail.internet.*;

import javax.swing.*;

import java.io.*;

import javax.activation.*;

import java.util.*;

public class SendMail{

public static void main(String[] args) {

String host="";

String from="";

String to="";

String name="";

String pass=null；

String subject="";

String content="";

MailAuthenticator ma;

if(args.length<6){ /*小于6，先不输入密码，发送过程服务器要求认证时就会跳出密码输入框（Option类）*/

System.out.println("enter");

System.exit(0);

}

else {

host=args[0]; /*smtp服务器*/

from=args[1]; /*发件人*/

to=args[2]; /收件人*/

name=args[3]; /*smtp认证用户名，一般跟pop3登录相同*/

subject=args[4]; /*邮件主题*/

content=args[5]; /*邮件内容*/

}

try{

ma=new MailAuthenticator(name,pass);

Properties props=System.getProperties();

props.put("mail.smtp.host",host);

props.put("mail.smtp.auth","true"); /*服务器需要认证*/

Session session=Session.getInstance(props,ma); /*Session会自动调用getPasswordAuthentication()方法*/

MimeMessage msg=new MimeMessage(session);

msg.setFrom(new InternetAddress(from));

msg.setRecipient(Message.RecipientType.TO,new InternetAddress(to));

msg.setSubject(subject);

msg.setText(content);

msg.setSentDate(new java.util.Date());

Transport.send(msg);

System.out.println("Send Email Success");

}catch(Exception e){

System.out.println(e.getMessage());

}

}

}

可以自己写个UI界面的SendMail()主类，再加入发送附件和群发邮件的功能，那么将是一个完整的邮件发送客户端程序。