关于java.lang.NoClassDefFoundError: com/sun/mail/util/LineInputStream

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;

}

}