Java邮件: NoClassDefFoundError: javax/activation/DataSource

Question

我编写了一个小型 Java 命令行程序来测试从远程服务器发送电子邮件。我收到了可怕的“NoClassDefFoundError”，但我不明白为什么。

服务器正在运行:

• SunOS 5.10 通用 2005 年 1 月
• Java 1.5.0_30-b03(Sun，标准)

我的java程序叫做

发送电子邮件ACME

错误信息是

Exception in thread "main" java.lang.NoClassDefFoundError: javax/activation/DataSource

程序运行的完整输出是:

bash-3.00$ javac SendEmailACME.java
bash-3.00$ java SendEmailACME
SendEmailACME: Classpath: .:/users/steve/TestProgramsLib/mail.jar:users/steve/TestProgramsLib/activation.jar
DEBUG: setDebug: JavaMail version 1.4.4
Exception in thread "main" java.lang.NoClassDefFoundError: javax/activation/DataSource
        at SendEmailACME.main(SendEmailACME.java:47)
bash-3.00$ 

我跑了

java -verbose SendEmailACME

输出对于 stackoverflow 来说太长。它包含的只是常规输出，加上一堆有关 java 加载所有常规库(来自 mail.jar 的库)的消息，但我没有看到来自 javax.activation.* 的任何消息。

“$ echo $CLASSPATH”的输出是:

bash-3.00$ echo $CLASSPATH
.:/users/steve/TestProgramsLib/mail.jar:users/steve/TestProgramsLib/activation.jar
bash-3.00$

我的主目录是

/users/steve

它包含这两个目录

1. 测试程序
2. 测试程序库

第一个是我的程序SendEmailACME.java，SendEmailACME.class/ 第二个里面有以下 jar :

bash-3.00$ ls -l
total 1102
-rw-r--r--   1 steve  acme      55932 Apr 19  2006 activation.jar
-rw-r--r--   1 steve  acme     494975 Jan 14  2011 mail.jar
bash-3.00$

这是我的命令行程序SendEmailACME的源代码:

import javax.mail.*;
import javax.mail.internet.*;
import javax.mail.Authenticator;
import javax.mail.PasswordAuthentication;

import java.util.Properties;

public class SendEmailACME {


    public static void main(String[] args) throws Exception{


        String smtpServer  = "msg.abc.acme.com";
        int port           = 25;        
        String userid      = "acme.staffdirectory"; 
        String password    = "password";  
        String contentType = "text/html";

        String subject     = "test: Send An Email, From A Java Client Using msg.abc.acme.com";
        String from        = "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="6e2f2d232b403d1a0f0808402a071c0b0d1a011c172e0f0d030b400d0103" rel="noreferrer noopener nofollow">[email protected]</a>";
        String to          = "<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="afdcdbcad9caefceccc2ca81ccc0c2" rel="noreferrer noopener nofollow">[email protected]</a>,<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="e68c8983949483d7d4d5a6818b878f8ac885898b" rel="noreferrer noopener nofollow">[email protected]</a>,<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="7b1d1a101e55161a12173b1a18161e55181416" rel="noreferrer noopener nofollow">[email protected]</a>,<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="563439312325163037232e3b373f3a7835393b" rel="noreferrer noopener nofollow">[email protected]</a>";
        String body        = "<h1>Test. An Email, From A Java Client Using msg.abc.acme.com.</hi>";

        System.out.println("SendEmailACME: Classpath: " + System.getProperty("java.class.path"));

        Properties props   = new Properties();
        props.put("mail.transport.protocol", "smtp");
        props.put("mail.smtp.auth", "true");
        props.put("mail.smtp.starttls.enable","true");
        props.put("mail.smtp.host", smtpServer);

        Session mailSession = Session.getInstance(props);

        // Get runtime more runtime output when attempting to send an email
        mailSession.setDebug(true);

        MimeMessage message = new MimeMessage(mailSession);
        message.setFrom(new InternetAddress(from));
        message.setRecipients(Message.RecipientType.TO, to);
        message.setSubject(subject);
        message.setContent(body,contentType);

        Transport transport = mailSession.getTransport();
        transport.connect(smtpServer, port, userid, password);
        transport.sendMessage(message,message.getRecipients(Message.RecipientType.TO));
        transport.close();
    }// end function main()

}// end class SendEmailACME

以下是运行命令查看activation.jar 内内容的输出:

bash-3.00$ jar -tf activation.jar
META-INF/MANIFEST.MF
META-INF/SUN_MICR.SF
META-INF/SUN_MICR.RSA
META-INF/
META-INF/mailcap.default
META-INF/mimetypes.default
javax/
javax/activation/
javax/activation/ActivationDataFlavor.class
javax/activation/MimeType.class
javax/activation/MimeTypeParameterList.class
javax/activation/MimeTypeParseException.class
javax/activation/CommandInfo.class
javax/activation/DataHandler$1.class
javax/activation/DataHandler.class
javax/activation/DataSource.class
javax/activation/CommandMap.class
javax/activation/DataContentHandler.class
javax/activation/DataContentHandlerFactory.class
javax/activation/CommandObject.class
javax/activation/DataHandlerDataSource.class
javax/activation/DataSourceDataContentHandler.class
javax/activation/ObjectDataContentHandler.class
javax/activation/FileDataSource.class
javax/activation/FileTypeMap.class
javax/activation/MailcapCommandMap.class
javax/activation/MimetypesFileTypeMap.class
javax/activation/SecuritySupport$1.class
javax/activation/SecuritySupport$2.class
javax/activation/SecuritySupport$3.class
javax/activation/SecuritySupport$4.class
javax/activation/SecuritySupport$5.class
javax/activation/SecuritySupport.class
javax/activation/URLDataSource.class
javax/activation/UnsupportedDataTypeException.class
com/
com/sun/
com/sun/activation/
com/sun/activation/registries/
com/sun/activation/registries/MailcapFile.class
com/sun/activation/registries/MailcapParseException.class
com/sun/activation/registries/MimeTypeFile.class
com/sun/activation/registries/MimeTypeEntry.class
com/sun/activation/registries/LineTokenizer.class
com/sun/activation/registries/LogSupport.class
com/sun/activation/registries/MailcapTokenizer.class
com/sun/activation/viewers/
com/sun/activation/viewers/ImageViewer.class
com/sun/activation/viewers/ImageViewerCanvas.class
com/sun/activation/viewers/TextEditor.class
com/sun/activation/viewers/TextViewer.class
bash-3.00$

一切都编译得很好，但尽管activation.jar位于类路径中，但似乎找不到javax.activation.DataSource

我无权访问 jdk_home/jre/lib/ext 目录。

我一直在尝试从我的目录执行 SendEmailACME /用户/史蒂夫/测试程序

预先感谢您的帮助

史蒂夫

Answer 1

bash-3.00$ echo $CLASSPATH
.:/users/steve/TestProgramsLib/mail.jar:users/steve/TestProgramsLib/activation.jar

您似乎在 mail.jar: 和 users/steve 之间缺少 /。这意味着 java 在错误的位置查找 activation.jar(在 ./users 而不是 /users )。