Sending Email Through a URLConnection using Java

是 否 +2 论坛币

k人 参与回答

经管之家送您一份

应届毕业生专属福利!

求职就业群

赵安豆老师微信：zhaoandou666

经管之家联合CDA

送您一个全额奖学金名额~ !

立即领取

感谢您参与论坛问题回答

经管之家送您两个论坛币！

+2 论坛币

Sending Email Through a URLConnection using Java

As mentioned earlier, Java includes support for different URL protocols through protocol handlers that are implemented internally to the Java SDK. These handlers include support for the mailto: protocol. Example 5-3 shows a program that uses a mailto: URL to send email. The program prompts the user to enter the sender, recipient or recipients, subject, and body of the message, and then creates an appropriatemailto: URL and obtains a URLConnection object for it. The program uses the setDoInput( ) and setDoOutput( ) methods to specify that it is writing data to the URLConnection. It obtains the appropriate stream with getOutputStream( ) and then writes the message headers and body to that stream, closing the stream when the message body is complete. The program uses the user.name system property and theInetAddress class to attempt to create a valid return address for the sender of the email, though this doesn’t actually work correctly on all platforms.

In order for the mailto: protocol handler to send mail, it must know what computer, or mailhost, to send it to. By default, it attempts to send it to the machine on which it is running. Some computers, particularly Unix machines on intranets, work as mailhosts, so this works fine. Other computers, such as PCs connected to the Internet by a dialup connection, have to specify a mailhost explicitly on the command line. For example, if your Internet service provider has the domain name isp.net, the appropriate mailhost is often mail.isp.net or smtp.isp.net. If you specify a mailhost, it is stored in the system property mail.host, which is read by the internal mailto: protocol handler.

Note that Example 5-3 uses the println( ) method to display messages to the console but uses the print( ) method and explicit “\r\n” line terminator characters to send text over the network. Different operating systems use different line terminators, and println( ) uses whatever terminator is expected on the local system. The standard line terminator for network services, however, is the two-character sequence “\r\n”. We use it explicitly here, so that this client program works correctly regardless of the platform-specific line terminator.

Example 5-3. SendMail.java

1. Example 5-3. SendMail.java
   
2. package je3.net;
   
3. import java.io.*;
   
4. import java.net.*;
   
5. 
   
6. /**
   
7. * This program sends e-mail using a mailto: URL
   
8. **/
   
9. public class SendMail {
   
10.     public static void main(String[  ] args) {
    
11.         try {
    
12.             // If the user specified a mailhost, tell the system about it.
    
13.             if (args.length >= 1)
    
14.                 System.getProperties( ).put("mail.host", args[0]);
    
15.             
    
16.             // A Reader stream to read from the console
    
17.             BufferedReader in =
    
18.                 new BufferedReader(new InputStreamReader(System.in));
    
19.             
    
20.             // Ask the user for the from, to, and subject lines
    
21.             System.out.print("From: ");
    
22.             String from = in.readLine( );
    
23.             System.out.print("To: ");
    
24.             String to = in.readLine( );
    
25.             System.out.print("Subject: ");
    
26.             String subject = in.readLine( );
    
27.             
    
28.             // Establish a network connection for sending mail
    
29.             URL u = new URL("mailto:" + to);      // Create a mailto: URL
    
30.             URLConnection c = u.openConnection( ); // Create its URLConnection
    
31.             c.setDoInput(false);                  // Specify no input from it
    
32.             c.setDoOutput(true);                  // Specify we'll do output
    
33.             System.out.println("Connecting...");  // Tell the user
    
34.             System.out.flush( );                   // Tell them right now
    
35.             c.connect( );                          // Connect to mail host
    
36.             PrintWriter out =                     // Get output stream to host
    
37.                 new PrintWriter(new OutputStreamWriter(c.getOutputStream( )));
    
38. 
    
39.             // We're talking to the SMTP server now.
    
40.             // Write out mail headers.  Don't let users fake the From address
    
41.             out.print("From: \"" + from + "\" <" +
    
42.                       System.getProperty("user.name") + "@" +
    
43.                       InetAddress.getLocalHost( ).getHostName( ) + ">\r\n");
    
44.             out.print("To: " + to + "\r\n");
    
45.             out.print("Subject: " + subject + "\r\n");
    
46.             out.print("\r\n");  // blank line to end the list of headers
    
47. 
    
48.             // Now ask the user to enter the body of the message
    
49.             System.out.println("Enter the message. " +
    
50.                                "End with a '.' on a line by itself.");
    
51.             // Read message line by line and send it out.
    
52.             String line;
    
53.             for(;;) {
    
54.                 line = in.readLine( );
    
55.                 if ((line == null) || line.equals(".")) break;
    
56.                 out.print(line + "\r\n");
    
57.             }
    
58.             
    
59.             // Close (and flush) the stream to terminate the message
    
60.             out.close( );
    
61.             // Tell the user it was successfully sent.
    
62.             System.out.println("Message sent.");
    
63.         }
    
64.         catch (Exception e) {  // Handle any exceptions, print error message.
    
65.             System.err.println(e);
    
66.             System.err.println("Usage: java SendMail [<mailhost>]");
    
67.         }
    
68.     }
    
69. }

复制代码

扫码加我 拉你入群

请注明：姓名-公司-职位

以便审核进群资格，未注明则拒绝

分享0 收藏0 回帖

关键词：connection Connect Through ending Using Email different includes protocol message