我正在尝试将rdf模型中的电子邮件存储到apche tdb中。这是我的代码：
/*Program to download the mails from mail servers and then to store
them in tdb store using rdf model*/
//import all the classes needed
import java.io.*;
import java.util.*;
import javax.mail.*;
import javax.mail.Flags.Flag;
import javax.mail.internet.*;
import com.sun.mail.imap.IMAPFolder;
import com.sun.mail.imap.IMAPMessage;
import static com.hp.hpl.jena.query.ReadWrite.READ ;
import static com.hp.hpl.jena.query.ReadWrite.WRITE ;
import com.hp.hpl.jena.query.ReadWrite ;
import com.hp.hpl.jena.query.Dataset ;
import com.hp.hpl.jena.query.Query ;
import com.hp.hpl.jena.query.QueryExecution ;
import com.hp.hpl.jena.query.QueryExecutionFactory ;
import com.hp.hpl.jena.query.QueryFactory ;
import com.hp.hpl.jena.query.QuerySolution ;
import com.hp.hpl.jena.query.ResultSet ;
import com.hp.hpl.jena.tdb.TDBFactory ;
import email.*; // import this to add properties as entities of email
import com.hp.hpl.jena.rdf.model.Model;
import com.hp.hpl.jena.rdf.model.*;
import com.hp.hpl.jena.vocabulary.*;
public class test2 {
public static void main(String[] args) throws MessagingException, IOException {
IMAPFolder folder = null;
Store store = null;
String subjec = null;
Flag flag = null;
//String too;
//Directory where the tdb files will be stored
String directory = "MYDATABASES/DATA2" ;
//create the dataset for the tdb store
Dataset ds = TDBFactory.createDataset(directory) ;
//create default rdf model
Model model = ds.getDefaultModel() ;
//write to the tdb dataset
ds.begin(ReadWrite.WRITE);
try
{ //connecting to the server to download the emails
Properties props = System.getProperties();
props.setProperty("mail.store.protocol", "imaps");
Session session = Session.getDefaultInstance(props, null);
store = session.getStore("imaps");
store.connect("imap.gmail.com","hjcooljohny75@gmail.com", "ferry@786");
//folder = (IMAPFolder) store.getFolder("[Gmail]/Spam"); // This doesn't work for enter code here`other email account
//to select the paticular types of mails
folder = (IMAPFolder) store.getFolder("inbox");// This works for both email account
if(!folder.isOpen())
folder.open(Folder.READ_WRITE);
Message[] messages = folder.getMessages();
System.out.println("No of Messages : " + folder.getMessageCount());
System.out.println("No of Unread Messages : " + folder.getUnreadMessageCount());
System.out.println(messages.length);
//Displaying the info. of the messages
for (int i=messages.length-1; i > messages.length-10;i--)
{
System.out.println("*****************************************************************************");
System.out.println("MESSAGE " + (i + 1) + ":");
MimeMessage msg = (MimeMessage) messages[i];
//creating rdf model of the message
//too=toString(msg.getAllRecipients()[0]);
Resource mail= model.createResource(msg.getMessageID())
.addProperty(EMAILRDF.SUBJECT, msg.getSubject())
.addProperty(EMAILRDF.TO,msg.getAllRecipients()[0])
.addLiteral(EMAILRDF.FROM,msg.getFrom()[0])
.addLiteral(EMAILRDF.ENCODING,msg.getEncoding())
.addLiteral(EMAILRDF.CONTENT,msg.getContent())
.addLiteral(EMAILRDF.DATE,msg.getReceivedDate())
.addLiteral(EMAILRDF.CONTENT_TYPE,msg.getContentType());
// list the statements in the graph
StmtIterator iter = model.listStatements();
// print out the predicate, subject and object of each statement
while (iter.hasNext()) {
Statement stmt = iter.nextStatement(); // get next statement
Resource subject = stmt.getSubject(); // get the subject
Property predicate = stmt.getPredicate(); // get the predicate
RDFNode object = stmt.getObject(); // get the object
System.out.print(subject.toString());
System.out.print(" "+ predicate.toString() + " ");
if (object instanceof Resource) {
System.out.print(object.toString());
} else {
// object is a literal
System.out.print(" \"" + object.toString() + "\"");
}
System.out.println(" .");
}
//System.out.println(msg.getMessageNumber());
//Object String;
//System.out.println(folder.getUID(msg)
//subject = msg.getSubject();
//System.out.println("Subject: " + subject);
//System.out.println("From: " + msg.getFrom()[0]);
//System.out.println("To: "+msg.getAllRecipients()[0]);
//System.out.println("Date: "+msg.getReceivedDate());
//System.out.println("Size: "+msg.getSize());
//System.out.println("Id: "+msg.getMessageID());
//System.out.println(msg.getFlags());
//System.out.println("Body: \n"+ msg.getContent());
//System.out.println(msg.getContentType());
}
}
finally
{ //closing the connection
if (folder != null && folder.isOpen()) { folder.close(true); }
if (store != null) { store.close(); }
}
//closing the dataset
ds.commit();
ds.end();
}
}
但是这会在addLteral（）方法中出错。我尝试使用AddProperty（）但是也会出错。
error: WARN [main] (LiteralLabelImpl.java:141) - inventing a datatype for class com.sun.mail.imap.protocol.IMAPAddress
Exception in thread "main" java.lang.NullPointerException
at com.hp.hpl.jena.datatypes.TypeMapper.getTypeByValue(TypeMapper.java:156)
at com.hp.hpl.jena.graph.impl.LiteralLabelImpl.<init>(LiteralLabelImpl.java:131)
at com.hp.hpl.jena.graph.impl.LiteralLabelFactory.create(LiteralLabelFactory.java:77)
at com.hp.hpl.jena.rdf.model.impl.ModelCom.createTypedLiteral(ModelCom.java:781)
at com.hp.hpl.jena.rdf.model.impl.ResourceImpl.addLiteral(ResourceImpl.java:263)
at test2.main(test2.java:80)
我认为这可能是由于我在addproperty()或addLiteral()函数中输入的类的数据类型。
任何想法???
答案 0 :(得分：1)
JavaDoc可能已经充分回答了这个问题。 Resource定义了许多addLiteral方法，每个方法都接受一个属性，第二个参数类型为boolean，char，double，float，Literal，long或Object。基于警告“WARN [main]（LiteralLabelImpl.java:141） - 为
class com.sun.mail.imap.protocol.IMAPAddress，“听起来你正在使用addLiteral（Property，Object）方法。
当你这样做时，正如JavaDoc所说，你正试图
将具有typed-literal值o的属性p添加到此资源，即 将（this，p，typed（o））添加到此模型中。 ...... typed literal等于使用构造的文字 this.getModel（）。createTypedLiteral（○）。
您可以从stacktrace中看到正在调用createTypedLiteral，并且没有为com.sun.mail.imap.protocol.IMAPAddress定义数据类型也就不足为奇了。无论哪个对addLiteral的调用都有一个IMAPAddress作为第二个参数，您需要将第二个参数替换为可以转换为类型文字的调用。最简单的方法可能是使用它的toString（）方法。