基於POP3的JAVA郵件接收程式！（與上次的發送程式配套）

有發送有接收才顯得完整一點。

同樣分兩部分寫：

一：POP3命令介紹（抄的）；二：執行個體。

一：POP3命令介紹

telnet 119.119.119.212 110 ----------------------------- 使用 telnet 命令串連伺服器 110 連接埠      
Trying 119.119.119.212... ------------------------------ 正在串連伺服器 110 連接埠      
Connected to 119.119.119.212. -------------------------- 串連伺服器 110 連接埠成功      
+OK Winmail Mail Server POP3 ready        
user username ------------------------------------------ 輸入使用者名稱, username 為具體的使用者名稱      
+OK ---------------------------------------------------- 執行命令成功
pass password ------------------------------------------ 輸入使用者密碼，password 為具體的密碼
+OK 2 messages ----------------------------------------- 密碼認證通過
(-ERR authorization failed ----------------------------- 密碼認證失敗)      
stat --------------------------------------------------- 郵箱狀態
+OK 2 6415 --------------------------------------------- 2 為該信箱總郵件數，6415 為總位元組數      
list --------------------------------------------------- 列出每封郵件的位元組數
+OK ---------------------------------------------------- 執行命令成功，開始顯示，左邊為郵件的序號，右邊為該郵件的大小
1 537 -------------------------------------------------- 第 1 封郵件，大小為 537 位元組      
2 5878 ------------------------------------------------- 第 2 封郵件，大小為 5878 位元組      
.
top 1 -------------------------------------------------- 接收第 1 封郵件
+OK ---------------------------------------------------- 接收成功, 返回第 1 封郵件標頭
Return-Path: <test1@look.com>
Delivered-To: test2@look.com
Received: (winmail server invoked for smtp delivery); Mon, 25 Oct 2004 14:24:27 +0800
From: test1@look.com
To: test2@look.com
Date: Mon, 25 Oct 2004 14:24:27 +0800
Subject: test mail
.    
retr 1 ------------------------------------------------- 接收第 1 封郵件    
+OK ---------------------------------------------------- 接收成功, 返回第 1 封郵件全部內容
Return-Path: <test1@look.com>
Delivered-To: test2@look.com
Received: (winmail server invoked for smtp delivery); Mon, 25 Oct 2004 14:24:27 +0800
 
From: test1@look.com
To: test2@look.com
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 ------------------------------------------------- 刪除第 1 封郵件  
+OK ---------------------------------------------------- 刪除成功    
dele 2 ------------------------------------------------- 刪除第 2 封郵件  
+OK ---------------------------------------------------- 刪除成功    
quit --------------------------------------------------- 結束會話
+OK ---------------------------------------------------- 執行命令成功

二：發送郵件執行個體 

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伺服器位址
  String user="wasingmon";//使用者名稱
  String password="";//密碼
  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("建立串連！");
  }
 }
 
 //得到伺服器返回的一行命令
 public String getReturn(BufferedReader in){
  String line="";
  try{
   line=in.readLine();
   if(debug){
    System.out.println("伺服器返回狀態:"+line);
   }
  }catch(Exception e){
   e.printStackTrace();
  }
  return line;
 }
 
 //從返回的命令中得到第一個欄位,也就是伺服器的返回狀態代碼(+OK或者-ERR)
 public String getResult(String line){
  StringTokenizer st=new StringTokenizer(line," ");
  return st.nextToken();
 }
 

 
 //發送命令
 private String sendServer(String str,BufferedReader in,BufferedWriter out) throws IOException{
  out.write(str);
  out.newLine();
  out.flush();
  if(debug)
  {
   System.out.println("已發送命令:"+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("串連伺服器失敗!");
  }
  result=getResult(sendServer("user "+user,in,out)); 
  if(!"+OK".equals(result)){
   throw new IOException("使用者名稱錯誤!");
  }
 }
 
 //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("密碼錯誤!");
  }
 }
 //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("查看郵箱狀態出錯!");
  }
  System.out.println("共有郵件"+mailNum+"封");
  return mailNum;
  
 }
 
 //得到郵件詳細資料
 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("內送郵件出錯!");
  }
  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("未能正確退出");
  }
 }
 
 //內送郵件程式
 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;
 }
 
}