Package org.apache.commons.net.smtp

Class SMTPClient

  • Direct Known Subclasses:
    SMTPSClient
    public class SMTPClient
extends SMTP
    SMTPClient encapsulates all the functionality necessary to send files through an SMTP server. This class takes care of all low level details of interacting with an SMTP server and provides a convenient higher level interface. As with all classes derived from SocketClient, you must first connect to the server with connect before doing anything, and finally disconnect after you're completely finished interacting with the server. Then you need to check the SMTP reply code to see if the connection was successful. For example: 
        try {
      int reply;
      client.connect("mail.foobar.com");
      System.out.print(client.getReplyString());

      // After connection attempt, you should check the reply code to verify
      // success.
      reply = client.getReplyCode();

      if(!SMTPReply.isPositiveCompletion(reply)) {
        client.disconnect();
        System.err.println("SMTP server refused connection.");
        System.exit(1);
      }

      // Do useful stuff here.
      ...
    } catch(IOException e) {
      if(client.isConnected()) {
        try {
          client.disconnect();
        } catch(IOException f) {
          // do nothing
        }
      }
      System.err.println("Could not connect to server.");
      e.printStackTrace();
      System.exit(1);
    }

    Immediately after connecting is the only real time you need to check the reply code (because connect is of type void). The convention for all the SMTP command methods in SMTPClient is such that they either return a boolean value or some other value. The boolean methods return true on a successful completion reply from the SMTP server and false on a reply resulting in an error condition or failure. The methods returning a value other than boolean return a value containing the higher level data produced by the SMTP command, or null if a reply resulted in an error condition or failure. If you want to access the exact SMTP reply code causing a success or failure, you must call getReplyCode after a success or failure.

    You should keep in mind that the SMTP server may choose to prematurely close a connection for various reasons. The SMTPClient class will detect a premature SMTP server connection closing when it receives a SMTPReply.SERVICE_NOT_AVAILABLE response to a command. When that occurs, the method encountering that reply will throw an SMTPConnectionClosedException . SMTPConectionClosedException is a subclass of IOException and therefore need not be caught separately, but if you are going to catch it separately, its catch block must appear before the more general IOException catch block. When you encounter an SMTPConnectionClosedException , you must disconnect the connection with disconnect() to properly clean up the system resources used by SMTPClient. Before disconnecting, you may check the last reply code and text with getReplyCode , getReplyString , and getReplyStrings.

    Rather than list it separately for each method, we mention here that every method communicating with the server and throwing an IOException can also throw a MalformedServerReplyException , which is a subclass of IOException. A MalformedServerReplyException will be thrown when the reply received from the server deviates enough from the protocol specification that it cannot be interpreted in a useful manner despite attempts to be as lenient as possible.

    See Also:
    SMTP, SimpleSMTPHeader, RelayPath, SMTPConnectionClosedException, MalformedServerReplyException

    • Constructor Detail

      • SMTPClient

        public SMTPClient()
        Default SMTPClient constructor. Creates a new SMTPClient instance.

      • SMTPClient

        public SMTPClient​(java.lang.String encoding)
        Overloaded constructor that takes an encoding specification
        Parameters:
        encoding - The encoding to use
        Since:
        2.0

    • Method Detail

      • completePendingCommand

        public boolean completePendingCommand()
                               throws java.io.IOException
        At least one SMTPClient method (sendMessageData ) does not complete the entire sequence of SMTP commands to complete a transaction. These types of commands require some action by the programmer after the reception of a positive intermediate command. After the programmer's code completes its actions, it must call this method to receive the completion reply from the server and verify the success of the entire transaction.

        For example, 

         writer = client.sendMessageData();
 if(writer == null) // failure
   return false;
 header =
  new SimpleSMTPHeader("foobar@foo.com", "foo@foobar.com", "Re: Foo");
 writer.write(header.toString());
 writer.write("This is just a test");
 writer.close();
 if(!client.completePendingCommand()) // failure
   return false;

        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • login

        public boolean login​(java.lang.String hostname)
              throws java.io.IOException
        Login to the SMTP server by sending the HELO command with the given hostname as an argument. Before performing any mail commands, you must first login.

        Parameters:
        hostname - The hostname with which to greet the SMTP server.
        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • login

        public boolean login()
              throws java.io.IOException
        Login to the SMTP server by sending the HELO command with the client hostname as an argument. Before performing any mail commands, you must first login.

        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • setSender

        public boolean setSender​(RelayPath path)
                  throws java.io.IOException
        Set the sender of a message using the SMTP MAIL command, specifying a reverse relay path. The sender must be set first before any recipients may be specified, otherwise the mail server will reject your commands.

        Parameters:
        path - The reverse relay path pointing back to the sender.
        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • setSender

        public boolean setSender​(java.lang.String address)
                  throws java.io.IOException
        Set the sender of a message using the SMTP MAIL command, specifying the sender's email address. The sender must be set first before any recipients may be specified, otherwise the mail server will reject your commands.

        Parameters:
        address - The sender's email address.
        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • addRecipient

        public boolean addRecipient​(RelayPath path)
                     throws java.io.IOException
        Add a recipient for a message using the SMTP RCPT command, specifying a forward relay path. The sender must be set first before any recipients may be specified, otherwise the mail server will reject your commands.

        Parameters:
        path - The forward relay path pointing to the recipient.
        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • addRecipient

        public boolean addRecipient​(java.lang.String address)
                     throws java.io.IOException
        Add a recipient for a message using the SMTP RCPT command, the recipient's email address. The sender must be set first before any recipients may be specified, otherwise the mail server will reject your commands.

        Parameters:
        address - The recipient's email address.
        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • sendMessageData

        public java.io.Writer sendMessageData()
                               throws java.io.IOException
        Send the SMTP DATA command in preparation to send an email message. This method returns a DotTerminatedMessageWriter instance to which the message can be written. Null is returned if the DATA command fails.

        You must not issue any commands to the SMTP server (i.e., call any (other methods) until you finish writing to the returned Writer instance and close it. The SMTP protocol uses the same stream for issuing commands as it does for returning results. Therefore the returned Writer actually writes directly to the SMTP connection. After you close the writer, you can execute new commands. If you do not follow these requirements your program will not work properly.

        You can use the provided SimpleSMTPHeader class to construct a bare minimum header. To construct more complicated headers you should refer to RFC 5322. When the Java Mail API is finalized, you will be able to use it to compose fully compliant Internet text messages. The DotTerminatedMessageWriter takes care of doubling line-leading dots and ending the message with a single dot upon closing, so all you have to worry about is writing the header and the message.

        Upon closing the returned Writer, you need to call completePendingCommand() to finalize the transaction and verify its success or failure from the server reply.

        Returns:
        A DotTerminatedMessageWriter to which the message (including header) can be written. Returns null if the command fails.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.
        See Also:
        sendShortMessageData(String)

      • sendShortMessageData

        public boolean sendShortMessageData​(java.lang.String message)
                             throws java.io.IOException
        A convenience method for sending short messages. This method fetches the Writer returned by sendMessageData() and writes the specified String to it. After writing the message, this method calls completePendingCommand() to finalize the transaction and returns its success or failure.

        Parameters:
        message - The short email message to send. This must include the headers and the body, but not the trailing "."
        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • sendSimpleMessage

        public boolean sendSimpleMessage​(java.lang.String sender,
                                 java.lang.String recipient,
                                 java.lang.String message)
                          throws java.io.IOException
        A convenience method for a sending short email without having to explicitly set the sender and recipient(s). This method sets the sender and recipient using setSender and addRecipient , and then sends the message using sendShortMessageData .

        Parameters:
        sender - The email address of the sender.
        recipient - The email address of the recipient.
        message - The short email message to send. This must include the headers and the body, but not the trailing "."
        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • sendSimpleMessage

        public boolean sendSimpleMessage​(java.lang.String sender,
                                 java.lang.String[] recipients,
                                 java.lang.String message)
                          throws java.io.IOException
        A convenience method for a sending short email without having to explicitly set the sender and recipient(s). This method sets the sender and recipients using setSender and addRecipient, and then sends the message using sendShortMessageData.

        Note that the method ignores failures when calling addRecipient so long as at least one call succeeds. If no recipients can be successfully added then the method will fail (and does not attempt to send the message)

        Parameters:
        sender - The email address of the sender.
        recipients - An array of recipient email addresses.
        message - The short email message to send. This must include the headers and the body, but not the trailing "."
        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • logout

        public boolean logout()
               throws java.io.IOException
        Logout of the SMTP server by sending the QUIT command.

        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • reset

        public boolean reset()
              throws java.io.IOException
        Aborts the current mail transaction, resetting all server stored sender, recipient, and mail data, cleaing all buffers and tables.

        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • verify

        public boolean verify​(java.lang.String username)
               throws java.io.IOException
        Verify that a username or email address is valid, i.e., that mail can be delivered to that mailbox on the server.

        Parameters:
        username - The username or email address to validate.
        Returns:
        True if the username is valid, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • listHelp

        public java.lang.String listHelp()
                          throws java.io.IOException
        Fetches the system help information from the server and returns the full string.

        Returns:
        The system help string obtained from the server. null if the information could not be obtained.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • listHelp

        public java.lang.String listHelp​(java.lang.String command)
                          throws java.io.IOException
        Fetches the help information for a given command from the server and returns the full string.

        Parameters:
        command - The command on which to ask for help.
        Returns:
        The command help string obtained from the server. null if the information could not be obtained.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.

      • sendNoOp

        public boolean sendNoOp()
                 throws java.io.IOException
        Sends a NOOP command to the SMTP server. This is useful for preventing server timeouts.

        Returns:
        True if successfully completed, false if not.
        Throws:
        SMTPConnectionClosedException - If the SMTP server prematurely closes the connection as a result of the client being idle or some other reason causing the server to send SMTP reply code 421. This exception may be caught either as an IOException or independently as itself.
        java.io.IOException - If an I/O error occurs while either sending a command to the server or receiving a reply from the server.