Sending and receiving XML in a Java application

Sending and receiving XMLin a Java application Sean C. Sullivan sean <at> seansullivan <dot> com September 2003

Agenda • XML • XML via HTTP • XML via JMS • XML via JavaMail • XML via FTP

XML <?xml version=“1.0”> <company> <name>Sun Microsystems</name> <stocksymbol>SUNW</stocksymbol> </company> XML is a syntax for describing and structuring data

Application integration “[If you look at] where XML is really, truly being used right now, it's [for] lightweight, quick and dirty enterprise application integration. […] you could achieve remarkably acceptable results in enterprise application integration simply by binding a set of XML messages to ship back and forth.” Tim Bray, 9/23/2003, news.com interview

Data exchange Application A Application B

XML request <?xml version=“1.0”> <raterequest> <origin>97210</origin> <destination>12208</destination> <weight>35</weight> <service>OVERNIGHT</service> </raterequest>

XML response <?xml version=“1.0”> <rateresponse> <rate>68.00</rate> </rateresponse>

HTTP protocol request HTTP client HTTP server

HTTP protocol request HTTP client HTTP server response

HTTP protocol methods • GET • POST • HEAD • …

HTTP headers • Content-Type • Accept

MIME types for XML • text/xml • application/xml • text/xml-external-parsed-entity • application/xml-external-parsed-entity • application/xml-dtd • application/soap+xml

Jakarta Commons HTTPClient

Example: HTTP POST import org.apache.commons.httpclient.*; import org.apache.commons.httpclient.methods*; PostMethod post = new PostMethod( “http://www.foo.com/bar”); post.setRequestBody(strXML); post.setRequestHeader( “Content-type”, “application/xml”);

Example: HTTP POST post.setRequestHeader( “Accept”, “application/xml”); HttpClient client = new HttpClient(); int result = client.executeMethod(post); // … String strXMLResponse = post.getResponseBodyAsString(); post.releaseConnection();

Receiving XML using a Servlet public class XMLServlet extends javax.servlet.http.HttpServlet { protected void doPost( HttpServletRequest req, HttpServletResponse resp) { // … method implementation … } }

doPost method // … String type = req.getContentType(); int contentLength = req.getContentLength(); char[] xmlData = new char[contentLength]; BufferedReader reader = httpRequest.getReader(); // …

doPost (continued) do { n = reader.read(xmlData, bytesRead, xmlData.length - bytesRead); if (n > 0) { bytesRead += n; } } while ( (n != -1) && (bytesRead < contentLength) )

Java Message Service • messaging API for J2EE platform • Point-to-point • JMS Queue • Publish-Subscribe • JMS Topic • “at most once” delivery mode • transactional

3 2 1 JMS message queue Message Producer Message Queue Message Consumer

Sending XML using JMS import javax.jms.*; import javax.naming.*; Queue queue; ConnectionFactory cf; queue = /* lookup via JNDI */; cf = /* lookup via JNDI */; Connection conn = cf.createConnection(); Session session = conn.createSession(…);

Sending XML using JMS MessageProducer producer; producer = session.createProducer(queue); TextMessage msg; msg = session.createTextMessage(); msg.setText(strXML); producer.send(msg); session.commit();

Receiving XML via JMS Choose one: • javax.jms.MessageConsumer • Message Driven Bean (MDB)

Example: Message Driven Bean public void onMessage(Message msg) { // … if (msg instanceof TextMessage) { TextMessage tm = (Message) msg; String strXML = tm.getText(); } // … }

JavaMail

Example: XML via JavaMail import javax.mail.*; import javax.mail.internet.*; Session sess = /* JNDI lookup */; MimeMessage msg = new MimeMessage(sess); msg.setFrom(from); // …

Example: XML via JavaMail // … msg.setRecipients( Message.RecipientType.TO, recipients); msg.setSubject(“Hello XML”); // …

Example: XML via JavaMail // … MimeBodyPart mbp = new MimeBodyPart(); mbp.setContent(strXML, “application/xml”); Multipart mp = new MimeMultipart(); mp.addBodyPart(mbp); msg.setContent(mp); Transport.send(msg); // …

FTP with Jakarta Commons Net

Example: XML via FTP import org.apache.commons.net.ftp.*; FTPClient ftp = new FTPClient(); ftp.connect(“ftp.example.com”); ftp.login(username, password);

Example: XML via FTP ftp.setFileType(FTP.BINARY_FILE_TYPE); ftp.enterLocalPassiveMode(); ftp.storeFile(“foo.xml”, xmlInputStream); ftp.logout(); ftp.disconnect();

Additional topics… • Sockets • SOAP • XML-RPC • Binary encodings for XML

Additional resources • http://www.w3.org/XML/ • http://www.xml.com/ • http://java.sun.com/xml/ • http://xml.apache.org/ • http://ws.apache.org/axis/ • http://jakarta.apache.org/

Summary Use XML for data exchange between heterogeneous applications. Sending and receiving XML is easy.

Sending and receiving XML in a Java application