我试图在javamail示例包中使用showmsg.java读取gmail消息，并且在运行时我一直收到此错误。该程序编译得很好。
以下是错误消息：
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: javax/mail/internet/ParseException
at java.lang.Class.getDeclaredMethods0(Native Method)
at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
at java.lang.Class.getMethod0(Class.java:3018)
at java.lang.Class.getMethod(Class.java:1784)
at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)
Caused by: java.lang.ClassNotFoundException: javax.mail.internet.ParseException
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 7 more
以下是代码：
import java.util.*;
import java.io.*;
import javax.mail.*;
import javax.mail.event.*;
import javax.mail.internet.*;
/*
* Demo app that exercises the Message interfaces.
* Show information about and contents of messages.
*
* @author John Mani
* @author Bill Shannon
*/
public class msgshow {
static String protocol;
static String host = null;
static String user = null;
static String password = null;
static String mbox = null;
static String url = null;
static int port = -1;
static boolean verbose = false;
static boolean debug = false;
static boolean showStructure = false;
static boolean showMessage = false;
static boolean showAlert = false;
static boolean saveAttachments = false;
static int attnum = 1;
public static void main(String argv[]) {
int optind;
InputStream msgStream = System.in;
for (optind = 0; optind < argv.length; optind++) {
if (argv[optind].equals("-T")) {
protocol = argv[++optind];
} else if (argv[optind].equals("-H")) {
host = argv[++optind];
} else if (argv[optind].equals("-U")) {
user = argv[++optind];
} else if (argv[optind].equals("-P")) {
password = argv[++optind];
} else if (argv[optind].equals("-v")) {
verbose = true;
} else if (argv[optind].equals("-D")) {
debug = true;
} else if (argv[optind].equals("-f")) {
mbox = argv[++optind];
} else if (argv[optind].equals("-L")) {
url = argv[++optind];
} else if (argv[optind].equals("-p")) {
port = Integer.parseInt(argv[++optind]);
} else if (argv[optind].equals("-s")) {
showStructure = true;
} else if (argv[optind].equals("-S")) {
saveAttachments = true;
} else if (argv[optind].equals("-m")) {
showMessage = true;
} else if (argv[optind].equals("-a")) {
showAlert = true;
} else if (argv[optind].equals("--")) {
optind++;
break;
} else if (argv[optind].startsWith("-")) {
System.out.println(
"Usage: msgshow [-L url] [-T protocol] [-H host] [-p port] [-U user]");
System.out.println(
"\t[-P password] [-f mailbox] [msgnum ...] [-v] [-D] [-s] [-S] [-a]");
System.out.println(
"or msgshow -m [-v] [-D] [-s] [-S] [-f msg-file]");
System.exit(1);
} else {
break;
}
}
try {
// Get a Properties object
Properties props = System.getProperties();
// Get a Session object
Session session = Session.getInstance(props, null);
session.setDebug(debug);
if (showMessage) {
MimeMessage msg;
if (mbox != null)
msg = new MimeMessage(session,
new BufferedInputStream(new FileInputStream(mbox)));
else
msg = new MimeMessage(session, msgStream);
dumpPart(msg);
System.exit(0);
}
// Get a Store object
Store store = null;
if (url != null) {
URLName urln = new URLName(url);
store = session.getStore(urln);
if (showAlert) {
store.addStoreListener(new StoreListener() {
public void notification(StoreEvent e) {
String s;
if (e.getMessageType() == StoreEvent.ALERT)
s = "ALERT: ";
else
s = "NOTICE: ";
System.out.println(s + e.getMessage());
}
});
}
store.connect();
} else {
if (protocol != null)
store = session.getStore(protocol);
else
store = session.getStore();
// Connect
if (host != null || user != null || password != null)
store.connect(host, port, user, password);
else
store.connect();
}
// Open the Folder
Folder folder = store.getDefaultFolder();
if (folder == null) {
System.out.println("No default folder");
System.exit(1);
}
if (mbox == null)
mbox = "INBOX";
folder = folder.getFolder(mbox);
if (folder == null) {
System.out.println("Invalid folder");
System.exit(1);
}
// try to open read/write and if that fails try read-only
try {
folder.open(Folder.READ_WRITE);
} catch (MessagingException ex) {
folder.open(Folder.READ_ONLY);
}
int totalMessages = folder.getMessageCount();
if (totalMessages == 0) {
System.out.println("Empty folder");
folder.close(false);
store.close();
System.exit(1);
}
if (verbose) {
int newMessages = folder.getNewMessageCount();
System.out.println("Total messages = " + totalMessages);
System.out.println("New messages = " + newMessages);
System.out.println("-------------------------------");
}
if (optind >= argv.length) {
// Attributes & Flags for all messages ..
Message[] msgs = folder.getMessages();
// Use a suitable FetchProfile
FetchProfile fp = new FetchProfile();
fp.add(FetchProfile.Item.ENVELOPE);
fp.add(FetchProfile.Item.FLAGS);
fp.add("X-Mailer");
folder.fetch(msgs, fp);
for (int i = 0; i < msgs.length; i++) {
System.out.println("--------------------------");
System.out.println("MESSAGE #" + (i + 1) + ":");
dumpEnvelope(msgs[i]);
// dumpPart(msgs[i]);
}
} else {
while (optind < argv.length) {
int msgnum = Integer.parseInt(argv[optind++]);
System.out.println("Getting message number: " + msgnum);
Message m = null;
try {
m = folder.getMessage(msgnum);
dumpPart(m);
} catch (IndexOutOfBoundsException iex) {
System.out.println("Message number out of range");
}
}
}
folder.close(false);
store.close();
} catch (Exception ex) {
System.out.println("Oops, got exception! " + ex.getMessage());
ex.printStackTrace();
System.exit(1);
}
System.exit(0);
}
public static void dumpPart(Part p) throws Exception {
if (p instanceof Message)
dumpEnvelope((Message)p);
/** Dump input stream ..
InputStream is = p.getInputStream();
// If "is" is not already buffered, wrap a BufferedInputStream
// around it.
if (!(is instanceof BufferedInputStream))
is = new BufferedInputStream(is);
int c;
while ((c = is.read()) != -1)
System.out.write(c);
**/
String ct = p.getContentType();
try {
pr("CONTENT-TYPE: " + (new ContentType(ct)).toString());
} catch (ParseException pex) {
pr("BAD CONTENT-TYPE: " + ct);
}
String filename = p.getFileName();
if (filename != null)
pr("FILENAME: " + filename);
/*
* Using isMimeType to determine the content type avoids
* fetching the actual content data until we need it.
*/
if (p.isMimeType("text/plain")) {
pr("This is plain text");
pr("---------------------------");
if (!showStructure && !saveAttachments)
System.out.println((String)p.getContent());
} else if (p.isMimeType("multipart/*")) {
pr("This is a Multipart");
pr("---------------------------");
Multipart mp = (Multipart)p.getContent();
level++;
int count = mp.getCount();
for (int i = 0; i < count; i++)
dumpPart(mp.getBodyPart(i));
level--;
} else if (p.isMimeType("message/rfc822")) {
pr("This is a Nested Message");
pr("---------------------------");
level++;
dumpPart((Part)p.getContent());
level--;
} else {
if (!showStructure && !saveAttachments) {
/*
* If we actually want to see the data, and it's not a
* MIME type we know, fetch it and check its Java type.
*/
Object o = p.getContent();
if (o instanceof String) {
pr("This is a string");
pr("---------------------------");
System.out.println((String)o);
} else if (o instanceof InputStream) {
pr("This is just an input stream");
pr("---------------------------");
InputStream is = (InputStream)o;
int c;
while ((c = is.read()) != -1)
System.out.write(c);
} else {
pr("This is an unknown type");
pr("---------------------------");
pr(o.toString());
}
} else {
// just a separator
pr("---------------------------");
}
}
/*
* If we're saving attachments, write out anything that
* looks like an attachment into an appropriately named
* file. Don't overwrite existing files to prevent
* mistakes.
*/
if (saveAttachments && level != 0 && p instanceof MimeBodyPart &&
!p.isMimeType("multipart/*")) {
String disp = p.getDisposition();
// many mailers don't include a Content-Disposition
if (disp == null || disp.equalsIgnoreCase(Part.ATTACHMENT)) {
if (filename == null)
filename = "Attachment" + attnum++;
pr("Saving attachment to file " + filename);
try {
File f = new File(filename);
if (f.exists())
// XXX - could try a series of names
throw new IOException("file exists");
((MimeBodyPart)p).saveFile(f);
} catch (IOException ex) {
pr("Failed to save attachment: " + ex);
}
pr("---------------------------");
}
}
}
public static void dumpEnvelope(Message m) throws Exception {
pr("This is the message envelope");
pr("---------------------------");
Address[] a;
// FROM
if ((a = m.getFrom()) != null) {
for (int j = 0; j < a.length; j++)
pr("FROM: " + a[j].toString());
}
// REPLY TO
if ((a = m.getReplyTo()) != null) {
for (int j = 0; j < a.length; j++)
pr("REPLY TO: " + a[j].toString());
}
// TO
if ((a = m.getRecipients(Message.RecipientType.TO)) != null) {
for (int j = 0; j < a.length; j++) {
pr("TO: " + a[j].toString());
InternetAddress ia = (InternetAddress)a[j];
if (ia.isGroup()) {
InternetAddress[] aa = ia.getGroup(false);
for (int k = 0; k < aa.length; k++)
pr(" GROUP: " + aa[k].toString());
}
}
}
// SUBJECT
pr("SUBJECT: " + m.getSubject());
// DATE
Date d = m.getSentDate();
pr("SendDate: " +
(d != null ? d.toString() : "UNKNOWN"));
// FLAGS
Flags flags = m.getFlags();
StringBuffer sb = new StringBuffer();
Flags.Flag[] sf = flags.getSystemFlags(); // get the system flags
boolean first = true;
for (int i = 0; i < sf.length; i++) {
String s;
Flags.Flag f = sf[i];
if (f == Flags.Flag.ANSWERED)
s = "\\Answered";
else if (f == Flags.Flag.DELETED)
s = "\\Deleted";
else if (f == Flags.Flag.DRAFT)
s = "\\Draft";
else if (f == Flags.Flag.FLAGGED)
s = "\\Flagged";
else if (f == Flags.Flag.RECENT)
s = "\\Recent";
else if (f == Flags.Flag.SEEN)
s = "\\Seen";
else
continue; // skip it
if (first)
first = false;
else
sb.append(' ');
sb.append(s);
}
String[] uf = flags.getUserFlags(); // get the user flag strings
for (int i = 0; i < uf.length; i++) {
if (first)
first = false;
else
sb.append(' ');
sb.append(uf[i]);
}
pr("FLAGS: " + sb.toString());
// X-MAILER
String[] hdrs = m.getHeader("X-Mailer");
if (hdrs != null)
pr("X-Mailer: " + hdrs[0]);
else
pr("X-Mailer NOT available");
}
static String indentStr = " ";
static int level = 0;
/**
* Print a, possibly indented, string.
*/
public static void pr(String s) {
if (showStructure)
System.out.print(indentStr.substring(0, level * 2));
System.out.println(s);
}
}
我用来运行的命令是java msgshow -D -T imaps -H imap.gmail.com -U [USER] -P [PASS]，我用来编译的命令是javac -cp ".:./:./lib:./lib/*" msgshow.java。 javax.mail.jar包含在lib文件夹
这是一些替代代码，它们更短并且得到相同的错误：
import java.util.*;
import java.io.*;
import javax.mail.*;
import smtp;
import imaps;
//import java.mail.*;
//import com.sun.mail.*;
public class AccessGmail {
public static void main (String[] args) {
Scanner scan = new Scanner(System.in);
try
{
Properties prop = new Properties();
prop.load(new FileInputStream(new File("smtp.properties")));
Session session = Session.getDefaultInstance(prop, null);
String pass = scan.next();
Store store = session.getStore("imaps");
store.connect("smtp.gmail.com","shane.l.gvoice@gmail.com",pass);
Folder inbox = store.getFolder("inbox");
inbox.open(Folder.READ_ONLY);
int messageCount = inbox.getMessageCount();
System.out.println("Message Count: "+messageCount);
}
catch (FileNotFoundException e){}
catch (IOException e){}
catch(NoSuchProviderException e){}
catch(MessagingException e){}
}
}
答案 0 :(得分：4)
当您运行程序时，您没有设置CLASSPATH，因此它找不到javax.mail.jar文件：
java -cp ".:lib/javax.mail.jar" msgshow -D -T imaps -H imap.gmail.com -U [USER] -P [PASS]