在继续本章之前，有两个方面需要理解.它们是检查和获取.
检查在JavaMail中发送电子邮件是我们在邮箱中打开相应文件夹并获取每条消息的过程.这里我们只检查每条消息的标题，即 From，To，subject .内容未被阅读.
在JavaMail中获取电子邮件是我们打开邮箱中相应文件夹的过程每条消息.除了标题之外，我们还通过识别内容类型来阅读内容.
要使用JavaMail API检查或获取电子邮件，我们会需要POP或IMAP服务器.要检查和获取电子邮件，需要文件夹和商店类.这里我们使用了GMAIL的POP3服务器(pop.gmail.com).本章将学习如何使用JavaMail API检查电子邮件.后续章节将介绍提取.要查看电子邮件:
获取会话
创建pop3 Store对象并与pop服务器连接.
创建文件夹对象.打开邮箱中的相应文件夹.
收到邮件.
关闭存储和文件夹对象.
创建java类文件 CheckingMails ，其内容如下:
package com.it1352;
import java.util.Properties;
import javax.mail.Folder;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.NoSuchProviderException;
import javax.mail.Session;
import javax.mail.Store;
public class CheckingMails {
public static void check(String host, String storeType, String user,
String password)
{
try {
//create properties field
Properties properties = new Properties();
properties.put("mail.pop3.host", host);
properties.put("mail.pop3.port", "995");
properties.put("mail.pop3.starttls.enable", "true");
Session emailSession = Session.getDefaultInstance(properties);
//create the POP3 store object and connect with the pop server
Store store = emailSession.getStore("pop3s");
store.connect(host, user, password);
//create the folder object and open it
Folder emailFolder = store.getFolder("INBOX");
emailFolder.open(Folder.READ_ONLY);
// retrieve the messages from the folder in an array and print it
Message[] messages = emailFolder.getMessages();
System.out.println("messages.length---" + messages.length);
for (int i = 0, n = messages.length; i < n; i++) {
Message message = messages[i];
System.out.println("---------------------------------");
System.out.println("Email Number " + (i + 1));
System.out.println("Subject: " + message.getSubject());
System.out.println("From: " + message.getFrom()[0]);
System.out.println("Text: " + message.getContent().toString());
}
//close the store and folder objects
emailFolder.close(false);
store.close();
} catch (NoSuchProviderException e) {
e.printStackTrace();
} catch (MessagingException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String[] args) {
String host = "pop.gmail.com";// change accordingly
String mailStoreType = "pop3";
String username = "yourmail@gmail.com";// change accordingly
String password = "*****";// change accordingly
check(host, mailStoreType, username, password);
}
}现在我们的类已经准备好了，让我们编译上面的类.我已将类CheckingMails.java保存到目录:/home/manisha/JavaMailAPIExercise .我们需要类路径中的jar javax.mail.jar 和 activation.jar .执行以下命令从命令提示符编译类(两个jar放在/home/manisha/目录中):
javac -cp /home/manisha/activation.jar:/home/manisha/javax.mail.jar: CheckingMails.java
现在该类已编译，请执行下面的命令运行:
java -cp /home/manisha/activation.jar:/home/manisha/javax.mail.jar: CheckingMails
您应该在命令控制台上看到以下消息:
messages.length---4 --------------------------------- Email Number 1 Subject: Test Mail--Fetch From: <abcd@gmail.com> Text: javax.mail.internet.MimeMultipart@327a5b7f --------------------------------- Email Number 2 Subject: testing ----checking simple email From: <abcd@gmail.com> Text: javax.mail.internet.MimeMultipart@7f0d08bc --------------------------------- Email Number 3 Subject: Email with attachment From: <abcd@gmail.com> Text: javax.mail.internet.MimeMultipart@30b8afce --------------------------------- Email Number 4 Subject: Email with Inline image From: <abcd@gmail.com> Text: javax.mail.internet.MimeMultipart@2d1e165f
这里我们打印了INBOX中的消息数量，在这种情况下为4 .我们还为每封电子邮件打印了主题，发件人地址和文本.
