NullPointerException尝试在Android中使用OAuth发送电子邮件

Question

我试图使用Google的Gmail API和OAuth 2.0发送电子邮件。我设法得到看起来是有效的SMTPTransport（不完全确定它是否有效），但是当我尝试发送电子邮件时，sendMessage发生的线路上会出现NullPointerException。实际上，这个例外并不是完全在这条线上发生的。奇怪的是，在Eclipse中，调试器中的当前行返回到sendMail方法的第一行，然后返回给调用客户端，并发生NullPointerException异常。我不知道是什么导致了空例外。该smtpTransport和味精的变量是不是空：

private Session session; 

    public SMTPTransport connectToSmtp(String host, int port, String userEmail, String oauthToken, boolean debug) throws Exception 
    { 
    try 
    { 
     Properties props = new Properties(); 
     props.put("mail.smtp.starttls.enable", "true"); 
     props.put("mail.smtp.starttls.required", "true"); 
     props.put("mail.smtp.sasl.enable", "false"); 
     session = Session.getInstance(props); 
     session.setDebug(debug); 

     final URLName unusedUrlName = null; 
     SMTPTransport transport = new SMTPTransport(session, unusedUrlName); 

     // If the password is non-null, SMTP tries to do AUTH LOGIN. 
     final String emptyPassword = null; 
     transport.connect(host, port, userEmail, emptyPassword); 

     byte[] response = String.format("user=%s\1auth=Bearer %s\1\1", userEmail, oauthToken).getBytes(); 
     response = BASE64EncoderStream.encode(response); 

     transport.issueCommand("AUTH XOAUTH2 " + new String(response), 235); 

     return transport; 
    } 
    catch (Exception ex) 
    { 
     return null; 
    } 
    } 

    public synchronized void sendMail(String subject, String body, String user, String oauthToken, String recipients) 
    { 
    try 
    { 
     SMTPTransport smtpTransport = connectToSmtp("smtp.gmail.com", 587, user, oauthToken, true); 

     MimeMessage message = new MimeMessage(session); 
     DataHandler handler = new DataHandler(new ByteArrayDataSource(body.getBytes(), "text/plain")); 
     message.setSender(new InternetAddress(user)); 
     message.setSubject(subject); 
     message.setDataHandler(handler); 

     if (recipients.indexOf(',') > 0) 
     message.setRecipients(Message.RecipientType.TO, InternetAddress.parse(recipients)); 
     else 
     message.setRecipient(Message.RecipientType.TO, new InternetAddress(recipients)); 

     smtpTransport.sendMessage(message, message.getAllRecipients()); 
    } 
    catch (Exception e) 
    { 
    } 
    } 

编辑： 我更新Sendmail中的代码，但仍然有同样的问题。 logcat根本没有显示任何异常。实际上，接受服务器的连接。但是，如果我运行代码多次，我终于做logcat中得到一个异常如下：

找不到类“的javax.activation.DataHandler”，从 方法myapp.sendMail引用

不知道为什么找不到DataHandler。潜在的东西缺少一个jar文件，在编译期间没有检测到，但只在运行时检测到？

02-28 14:33:14.619: I/ActivityManager(199): Starting: Intent { act=com.google.android.gms.common.account.CHOOSE_ACCOUNT cmp=com.google.android.gms/.common.account.AccountPickerActivity (has extras) } from pid 967 
02-28 14:33:14.619: E/ActivityManager(199): exception bw.write()java.io.IOException: Transport endpoint is not connected 
02-28 14:33:14.619: D/PowerManagerService(199): acquireWakeLock flags=0x1 tag=ActivityManager-Launch 
02-28 14:33:14.899: E/ActivityRecord(199): sendActivityPerformanceInfo exception occurs: java.io.IOException: Transport endpoint is not connected 
02-28 14:33:14.899: I/ActivityManager(199): Displayed com.google.android.gms/.common.account.AccountPickerActivity: +260ms 
02-28 14:33:14.909: D/PowerManagerService(199): releaseWakeLock flags=0x1 tag=ActivityManager-Launch 
02-28 14:33:16.879: E/ActivityManager(199): exception bw.write()java.io.IOException: Transport endpoint is not connected 
02-28 14:33:16.879: D/PowerManagerService(199): acquireWakeLock flags=0x1 tag=ActivityManager-Launch 
02-28 14:33:17.089: I/ActivityManager(199): Process com.google.android.gms (pid 642) has died. 
02-28 14:33:18.629: D/PowerManagerService(199): acquireWakeLock flags=0xa tag=KEEP_SCREEN_ON_FLAG 
02-28 14:33:18.649: W/InputManagerService(199): Starting input on non-focused client com.android.internal.view.IInputMethodClient$Stub$Proxy@40928628 (uid=10025 pid=1085) 
02-28 14:33:18.719: D/PowerManagerService(199): releaseWakeLock flags=0x1 tag=ActivityManager-Launch 
02-28 14:33:22.139: D/PowerManagerService(199): releaseWakeLock flags=0xa tag=KEEP_SCREEN_ON_FLAG 
02-28 14:33:23.969: I/System.out(967): DEBUG: setDebug: JavaMail version 1.4.6 
02-28 14:33:23.989: I/System.out(967): DEBUG SMTP: useEhlo true, useAuth false 
02-28 14:33:24.009: I/System.out(967): DEBUG SMTP: trying to connect to host "smtp.gmail.com", port 587, isSSL false 
02-28 14:33:24.139: I/System.out(967): 220 mx.google.com ESMTP 44sm11905543eek.5 - gsmtp 
02-28 14:33:24.139: I/System.out(967): DEBUG SMTP: connected to host "smtp.gmail.com", port: 587 
02-28 14:33:24.149: I/System.out(967): EHLO localhost 
02-28 14:33:24.219: I/System.out(967): 250-mx.google.com at your service, [217.238.138.215] 
02-28 14:33:24.239: I/System.out(967): 250-SIZE 35882577 
02-28 14:33:24.239: I/System.out(967): 250-8BITMIME 
02-28 14:33:24.239: I/System.out(967): 250-STARTTLS 
02-28 14:33:24.259: I/System.out(967): 250 ENHANCEDSTATUSCODES 
02-28 14:33:24.269: I/System.out(967): DEBUG SMTP: Found extension "SIZE", arg "35882577" 
02-28 14:33:24.269: I/System.out(967): DEBUG SMTP: Found extension "8BITMIME", arg "" 
02-28 14:33:24.269: I/System.out(967): DEBUG SMTP: Found extension "STARTTLS", arg "" 
02-28 14:33:24.279: I/System.out(967): DEBUG SMTP: Found extension "ENHANCEDSTATUSCODES", arg "" 
02-28 14:33:24.289: I/System.out(967): STARTTLS 
02-28 14:33:24.359: I/System.out(967): 220 2.0.0 Ready to start TLS 
02-28 14:33:25.319: I/System.out(967): EHLO localhost 
02-28 14:33:25.589: I/System.out(967): 250-mx.google.com at your service, [217.238.138.215] 
02-28 14:33:25.599: I/System.out(967): 250-SIZE 35882577 
02-28 14:33:25.609: I/System.out(967): 250-8BITMIME 
02-28 14:33:25.609: I/System.out(967): 250-AUTH LOGIN PLAIN XOAUTH XOAUTH2 
02-28 14:33:25.619: I/System.out(967): 250 ENHANCEDSTATUSCODES 
02-28 14:33:25.629: I/System.out(967): DEBUG SMTP: Found extension "SIZE", arg "35882577" 
02-28 14:33:25.639: I/System.out(967): DEBUG SMTP: Found extension "8BITMIME", arg "" 
02-28 14:33:25.639: I/System.out(967): DEBUG SMTP: Found extension "AUTH", arg "LOGIN PLAIN XOAUTH XOAUTH2" 
02-28 14:33:25.639: I/System.out(967): DEBUG SMTP: Found extension "ENHANCEDSTATUSCODES", arg "" 
02-28 14:33:25.679: I/System.out(967): AUTH XOAUTH2 ??????????????????????????????== 
02-28 14:33:26.309: I/System.out(967): 235 2.7.0 Accepted 

Answer 1

原来，与用于邮件的jar文件不兼容。需要为Android的jar文件可以下载在：

https://code.google.com/p/javamail-android/downloads/list