（本文基于MyEclipse6.5其他IDE不知）
接收邮件：
Exception in thread "main" java.lang.NoClassDefFoundError: com/sun/mail/util/LineInputStream
当出现以上错误时，恭喜您已经离接收邮件不远了，否则请您解决好所有的异常后再来看这个帖子。
javax.mail和javax.activation这两个包已经在javaEE5当中属于基础包了，就是JDK中自带了已经，但是里面的方法与现在外面的mail.jar和activation.jar有一些出入，所以初学者在直接copy别人代码的时候往往会出现上面的错误。
废话不多说下面是解决方法
进到
X:\Program Files\MyEclipse 6.5\myeclipse\eclipse\plugins\com.genuitec.eclipse.j2eedt.core_6.5.0.zmyeclipse650200806\data\libraryset\EE_5
这个路径里,可以看到javaee.jar,用rar把这个文件打开,然后进到javax文件夹里,删除mail.jar和activation.jar(我的javaee.jar里，这两个东西是文件夹，总之删掉就OK，不过要注意备份一下)
删掉之后运行下面的代码，经行简单的修改以后就可以实现接收邮件的功能了！我已经测试过完全可行。
package com.oa.mail;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.util.Properties;
import javax.mail.BodyPart;
import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.Multipart;
import javax.mail.Part;
import javax.mail.Session;
import javax.mail.Store;
import sun.misc.BASE64Decoder;
public class MailReceiver{
public static void main(String[] args){
MailReceiver receiver = new MailReceiver();
receiver.setHost("pop3.pchome.com.tw");
receiver.setUsername("xxxxxx");//您的邮箱账号
receiver.setPassword("yyyyyy");//您的邮箱密码
receiver.setAttachPath("f:\\email");//您要存放附件在什么位置？绝对路径
try{
receiver.reveiveMail();
} catch (Exception e){
e.printStackTrace();
}
}
public void reveiveMail() throws Exception {
Properties props = new Properties();
Session session = Session.getDefaultInstance(props, null);
Store store = session.getStore("pop3");
store.connect(getHost(), getUsername(), getPassword());
Folder folder = store.getFolder("INBOX");
folder.open(Folder.READ_ONLY);
Message message[] = folder.getMessages();
System.out.println("Messages''s length: " + message.length);
//FetchProfile profile = new FetchProfile();
//profile.add(FetchProfile.Item.ENVELOPE);
//folder.fetch(message, profile);
for (int i = 0; i < message.length; i++) {
//message[i].setFlag(Flags.Flag.DELETED, true);//必须先设置：folder.open(Folder.READ_WRITE);
handleMultipart(message[i]);
}
if (folder != null) {
folder.close(true);
}
if (store != null) {
store.close();
}
}
private void handleMultipart(Message msg) throws Exception {
String disposition;
Multipart mp = (Multipart) msg.getContent();
int mpCount = mp.getCount();
for (int m = 0; m < mpCount; m++) {
handle(msg);
BodyPart part = mp.getBodyPart(m);
disposition = part.getDisposition();
if (disposition != null && disposition.equals(Part.ATTACHMENT)) {
saveAttach(part, getAttachPath());
} else {
System.out.println(part.getContent());
}
}
}
private static void handle(Message msg) throws Exception {
System.out.println("邮件主题:" + msg.getSubject());//测试
System.out.println("邮件作者:" + msg.getFrom()[0].toString());
System.out.println("发送日期:" + msg.getSentDate());
}
private static void saveAttach(BodyPart part, String filePath) throws Exception {
String temp = part.getFileName();
String s = temp.substring(8, temp.indexOf("?="));
String fileName = base64Decoder(s);
System.out.println("有附件:" + fileName);
InputStream in = part.getInputStream();
FileOutputStream writer = new FileOutputStream(new File(filePath+"\\" + fileName));
byte[] content = new byte[255];
while ((in.read(content)) != -1) {
writer.write(content);
}
writer.close();
in.close();
}
private static String base64Decoder(String s) throws Exception {
BASE64Decoder decoder = new BASE64Decoder();
byte[] b = decoder.decodeBuffer(s);
return (new String(b));
}
private String host = null;
private String username = null;
private String password = null;
private String attachPath = null;
public String getAttachPath() {
return attachPath;
}
public void setAttachPath(String attachPath) {
this.attachPath = attachPath;
}
public String getHost() {
return host;
}
public void setHost(String host) {
this.host = host;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
--文章转自http://hi.baidu.com/576699909/item/c42b4e1461b20923f6625c8d