打开javamail文件夹失败

Question

我开发了一个使用javamail和apache-james的电子邮件网站，并且它主要工作得很好。但是一些用户得到了“打开失败例外”并且无法接收新邮件。 的代码接收电子邮件：

Session mailSession = Session.getInstance(System.getProperties(), null); 
mailSession.setDebug(false); 
Store store = null; 
Folder folder = null; //javax.mail.Folder 
try { 
    store = mailSession.getStore(SParam.PROTOCOL); 
    store.connect(Property.getPop3(), userName, password); 
    logger.info("trying to receive emails from james server..."); 
    folder = store.getFolder("INBOX"); 
    try { 
     if (!folder.isOpen()) { 
      folder.open(Folder.READ_WRITE); //the point of throwing the exception 
     } 
    } catch (Exception e) { 
     // TODO: handle exception 
     e.printStackTrace(); 
    } 
    //receive email from james server. 
} catch (Exception e) { 
    logger.error("Email Receive Error!" + StackTraceStr.st2str(e)); 
    try { 
     folder.close(true); 
    } catch (Exception e2) { 
} 
} finally { 
    try { 
     store.close(); 
    } catch (Exception cloex) { 
    } 
} 

在大多数情况下，它工作得很好。但偶尔还是有错误的：

javax.mail.MessagingException: Open failed; 
nested exception is: 
java.io.IOException: STAT command failed: null 
at com.sun.mail.pop3.POP3Folder.open(POP3Folder.java:228) 
at com.csc.mail.jsh.mail.core.ReceiveMail.receive(ReceiveMail.java:82) 
at com.csc.mail.jsh.mail.core.ReceiveMail.run(ReceiveMail.java:222) 
at java.lang.Thread.run(Thread.java:619) 
Caused by: java.io.IOException: STAT command failed: null 
at com.sun.mail.pop3.Protocol.stat(Protocol.java:366) 
at com.sun.mail.pop3.POP3Folder.open(POP3Folder.java:203) 
... 3 more 

等待你的帮助，多谢！

我调试和调试，终于发现STAT命令失败！当STAT命令出现错误时，有一个詹姆斯的例外，但这没有意义！

21/11/12 14:39:16 ERROR pop3server: Exception during connection from 127.0.0.1  
    (127.0.0.1) : An exception occurred getting a database connection. 
    org.apache.avalon.framework.CascadingRuntimeException: An exception occurred getting a database connection. 
at org.apache.james.userrepository.AbstractJdbcUsersRepository.openConnection(AbstractJdbcUsersRepository.java:617) 
    at org.apache.james.userrepository.AbstractJdbcUsersRepository.getUserByName(AbstractJdbcUsersRepository.java:521) 
    at org.apache.james.userrepository.AbstractUsersRepository.test(AbstractUsersRepository.java:270) 
    at org.apache.james.core.LocalUsersRepository.test(LocalUsersRepository.java:90) 
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) 
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) 
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) 
    at java.lang.reflect.Method.invoke(Method.java:597) 
    at org.apache.avalon.phoenix.components.application.BlockInvocationHandler.invoke(BlockInvocationHandler.java:134) 
    at $Proxy4.test(Unknown Source) 
    at org.apache.james.pop3server.POP3Handler.doPASS(POP3Handler.java:537) 
    at org.apache.james.pop3server.POP3Handler.parseCommand(POP3Handler.java:479) 
    at org.apache.james.pop3server.POP3Handler.handleConnection(POP3Handler.java:277) 
    at org.apache.james.util.connection.ServerConnection$ClientConnectionRunner.run(ServerConnection.java:432) 
    at org.apache.excalibur.thread.impl.ExecutableRunnable.execute(ExecutableRunnable.java:55) 
    at org.apache.excalibur.thread.impl.WorkerThread.run(WorkerThread.java:116) 
Caused by: java.sql.SQLException: Listener refused the connection with the following error: 
    ORA-12519, TNS:no appropriate service handler found 
    The Connection descriptor used by the client was: 192.168.250.23:1521:csmis 
    at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:112) 
    at oracle.jdbc.driver.DatabaseError.throwSqlException(DatabaseError.java:261) 
    at oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:387) 
    at oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:439) 
    at oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:165) 
    at oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:35) 
    at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:801) 
    at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:37) 
    at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:290) 
    at org.apache.commons.pool.impl.GenericObjectPool.borrowObject(GenericObjectPool.java:771) 
    at org.apache.commons.dbcp.PoolingDataSource.getConnection(PoolingDataSource.java:95) 
    at org.apache.commons.dbcp.BasicDataSource.getConnection(BasicDataSource.java:540) 
    at org.apache.james.util.dbcp.JdbcDataSource.getConnection(JdbcDataSource.java:220) 
    at org.apache.james.userrepository.AbstractJdbcUsersRepository.openConnection(AbstractJdbcUsersRepository.java:614) 
... 15 more 

所有应用程序运行在同一台服务器上，并且只有少数用户在线（当我测试它时，只有我使用它）。这个错误偶尔会出现。为什么？

Answer 1

我曾与Apache James联系过，最后找到答案。你可以在这里找到它：STAT command failed occasionally。在页面结尾处，该线程已被列出。

Answer 2

这似乎是一个邮件服务器问题。 STAT命令用于显示消息的数量。通常，STAT是成功连接到邮件服务器后运行的第一个命令。

尝试使用mailSession.setDebug(true)进入调试模式以获取更多错误日志。