基于POP3的JAVA邮件接收程序

有发送有接收才显得完整一点。

同样分两部分写：

一：POP3命令介绍（抄的）；二：实例。

一：POP3命令介绍

telnet 119.119.119.212 110 ----------------------------- 使用 telnet 命令连接服务器 110 端口      
Trying 119.119.119.212... ------------------------------ 正在连接服务器 110 端口      
Connected to 119.119.119.212. -------------------------- 连接服务器 110 端口成功      
+OK Winmail Mail Server POP3 ready        
user username ------------------------------------------ 输入用户名, username 为具体的用户名      
+OK ---------------------------------------------------- 执行命令成功
pass password ------------------------------------------ 输入用户密码，password 为具体的密码
+OK 2 messages ----------------------------------------- 密码认证通过
(-ERR authorization failed ----------------------------- 密码认证失败)      
stat --------------------------------------------------- 邮箱状态
+OK 2 6415 --------------------------------------------- 2 为该信箱总邮件数，6415 为总字节数      
list --------------------------------------------------- 列出每封邮件的字节数
+OK ---------------------------------------------------- 执行命令成功，开始显示，左边为邮件的序号，右边为该邮件的大小
1 537 -------------------------------------------------- 第 1 封邮件，大小为 537 字节      
2 5878 ------------------------------------------------- 第 2 封邮件，大小为 5878 字节      
.
top 1 -------------------------------------------------- 接收第 1 封邮件
+OK ---------------------------------------------------- 接收成功, 返回第 1 封邮件头
Return-Path: <[e-mail]>
Delivered-To: [e-mail]
Received: (winmail server invoked for smtp delivery); Mon, 25 Oct 2004 14:24:27 +0800
From: [e-mail]
To: [e-mail]
Date: Mon, 25 Oct 2004 14:24:27 +0800
Subject: test mail
.    
retr 1 ------------------------------------------------- 接收第 1 封邮件    
+OK ---------------------------------------------------- 接收成功, 返回第 1 封邮件全部内容
Return-Path: <[e-mail]>
Delivered-To: [e-mail]
Received: (winmail server invoked for smtp delivery); Mon, 25 Oct 2004 14:24:27 +0800
 
From: [e-mail]
To: [e-mail]
Date: Mon, 25 Oct 2004 14:24:27 +0800
Subject: test mail
 
Hi, test2
This is a test mail, you don't reply it.
 
.
 
dele 1 ------------------------------------------------- 删除第 1 封邮件  
+OK ---------------------------------------------------- 删除成功    
dele 2 ------------------------------------------------- 删除第 2 封邮件  
+OK ---------------------------------------------------- 删除成功    
quit --------------------------------------------------- 结束会话
+OK ---------------------------------------------------- 执行命令成功

二：发送邮件实例 

package mail;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.StringTokenizer;

public class POP3Client {

 private Socket socket;
 private boolean debug=true;
 public static void main(String[] args) throws UnknownHostException, IOException {
  
  String server="pop3.126.com";//POP3服务器地址
  String user="wasingmon";//用户名
  String password="";//密码
  POP3Client pop3Client=new POP3Client(server,110);
  pop3Client.recieveMail(user,password);

 }
 
 public POP3Client(String server,int port) throws UnknownHostException, IOException{
  try{
   socket=new Socket(server,port);
  }catch(Exception e){
   e.printStackTrace();
  }finally{
   System.out.println("建立连接！");
  }
 }
 
 //得到服务器返回的一行命令
 public String getReturn(BufferedReader in){
  String line="";
  try{
   line=in.readLine();
   if(debug){
    System.out.println("服务器返回状态:"+line);
   }
  }catch(Exception e){
   e.printStackTrace();
  }
  return line;
 }
 
 //从返回的命令中得到第一个字段,也就是服务器的返回状态码(+OK或者-ERR)
 public String getResult(String line){
  StringTokenizer st=new StringTokenizer(line," ");
  return st.nextToken();
 }
 

 
 //发送命令
 private String sendServer(String str,BufferedReader in,BufferedWriter out) throws IOException{
  out.write(str);
  out.newLine();
  out.flush();
  if(debug)
  {
   System.out.println("已发送命令:"+str);
  }
  return getReturn(in);
 }
 
 //user命令
 public void user(String user,BufferedReader in,BufferedWriter out) throws IOException{
  String result;
  result=getResult(getReturn(in));
  if(!"+OK".equals(result)){
   throw new IOException("连接服务器失败!");
  }
  result=getResult(sendServer("user "+user,in,out)); 
  if(!"+OK".equals(result)){
   throw new IOException("用户名错误!");
  }
 }
 
 //pass命令
 public void pass(String password,BufferedReader in,BufferedWriter out) throws IOException{
  String result;
  result=getResult(sendServer("pass "+password,in,out)); 
  if(!"+OK".equals(result)){
   throw new IOException("密码错误!");
  }
 }
 //stat命令
 public int stat(BufferedReader in,BufferedWriter out) throws IOException{
  String result;
  String line;
  int mailNum;
  line=sendServer("stat",in,out); 
  StringTokenizer st=new StringTokenizer(line," ");
  result=st.nextToken();
  if(st.hasMoreTokens())
  mailNum=Integer.parseInt(st.nextToken());
  else
   mailNum=0;
  if(!"+OK".equals(result)){
   throw new IOException("查看邮箱状态出错!");
  }
  System.out.println("共有邮件"+mailNum+"封");
  return mailNum;
  
 }
 
 //得到邮件详细信息
 public String getMessagedetail(BufferedReader in){
  String message="";
  String line;
  try{
   line=in.readLine();
   while(!".".equalsIgnoreCase(line)){
    message=message+line+"/n";
    line=in.readLine();
   }
  }catch(Exception e){
   e.printStackTrace();
  }
  return message;
 }
 
 //retr命令
 public void retr(int mailNum,BufferedReader in,BufferedWriter out) throws IOException{
  String result;
  for(int i=1;i<=mailNum;i++){
   result=getResult(sendServer("retr "+i,in,out));
  if(!"+OK".equals(result)){
   throw new IOException("接收邮件出错!");
  }
  System.out.println("第"+i+"封");
  System.out.println(getMessagedetail(in));
  }
 }
 
 //退出
 public void quit(BufferedReader in,BufferedWriter out) throws IOException{
  String result;
  result=getResult(sendServer("QUIT",in,out));
  if(!"+OK".equals(result)){
   throw new IOException("未能正确退出");
  }
 }
 
 //接收邮件程序
 public boolean recieveMail(String user,String password){
  try{
   BufferedReader in=new BufferedReader(new InputStreamReader(socket.getInputStream()));
   BufferedWriter out=new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
   user(user,in,out);
   pass(password,in,out);
   int mailNum;
   mailNum=stat(in,out);
   retr(mailNum,in,out);
   quit(in,out);
  }catch(Exception e){
   e.printStackTrace();
   return false;
  }
  return true;
 }
 
}