Web Applications 2. Java EE Martin Klíma. WA2 Slide 1

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1 Web Applications 2 Java EE Martin Klíma Slide 1

2 Web Application Architecture App 1 request Thin client (HTML) HTTP response controller model (JavaBea n) view (HTML) HTML generator Data App 2 App 3 Data Web Server Application Server Thick client (non - HTML) Slide 2

3 Java Java ME = Java Micro Edition Mobile applications Java SE = Java Standard Edition Desktop applications Java EE = Java Enterprise Edition Web & application servers Slide 3

4 Java EE Application Client Web Client Client Tier Client Servlet Web Tier Java EE Server Enterprise Beans Enterprise Beans Bussiness Tier Database Database EIS Tier Database Server Slide 4

5 Deployment Each JEE application is packed into a standard format It contains Functional components like EJB, JSP, servlets, applets, static resources, Descriptor Once packed it can be deployed on any standard server Slide 5

6 Servlet Application Client Web Client Client Tier Client Servlets JSP Pages Web Tier Java EE Server Enterprise Beans Enterprise Beans Bussiness Tier Database Database EIS Tier Database Server Slide 6

7 Servlets Servlet is a class that augments the functionality of a server This is how we can influence the web pages generation. All servlets must implement javax.servlet.servlet interface, which defines the life cycle methods required by the servlet container. The most common way is to extend javax.servlet.http.httpservlet. A Servlet je mapped to particular URL (one or more) through web.xml file. Slide 7

8 Servlets API <<interface>> ServletRequest <<interface>> Servlet service() <<interface>> ServletResponse <<interface>> HTTPServlet service() Slide 8

9 Servlet lifecycle new destroyed ready init() destroy() service() Slide 9

10 Service method java.lang.object +--javax.servlet.genericservlet k +--javax.servlet.http.httpservlet A A GenericServlet has the service method. HTTPServlet overloads the service method by a set of methods corresponding to HTTP methods doget dopost doput dodelete dooptions dohead dotrace Slide 10

11 The servicing methods parameters Request is encapsulated ServletRequest resp. HttpServletRequest see and HttpServletRequest interesting methods Object getparameter(string name) void setparameter(string name, Object o) and many others Slide 11

12 The servicing methods parameters II To generate a response, write Into object of type ServletResponse resp. HttpServletResponse see and HttpServletResponse interesting methods addheader(string name, String value) PrintWriter getwriter() void addcookie(cookie cookie) and many others Slide 12

13 Form parameters nickname password protected void doget(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html;charset=utf-8"); PrintWriter out = response.getwriter(); try { out.println("<html>"); out.println("<head>"); out.println("<title>servlet FirstServlet</title>"); out.println("</head>"); out.println("<body>"); String jmeno = request.getparameter("nickname"); if (null!= jmeno) { out.println("jméno"); out.println("</body>"); out.println("</html>"); finally { out.close(); Slide 13

14 Usual technique how to generate a response Get the output stream For text output use PrintWriter For binary outpout use ServletOutputStream Modify headers, set output type, e.g. text/html, (MIME type) method setcontenttype(string type) Set buffering method setbuffersize(int size) Slide 14

15 package cz.cvut.fel; import java.io.*; import java.net.*; import javax.servlet.*; import javax.servlet.http.*; public class FirstServlet extends HttpServlet { Overloading the GET method protected void doget(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html;charset=utf-8"); PrintWriter out = response.getwriter(); try { out.println("<html>"); out.println("<head>"); out.println("<title>servlet FirstServlet</title>"); out.println("</head>"); out.println("<body>"); out.println("ahoj"); out.println("</body>"); out.println("</html>"); finally { out.close(); Write to output stream Slide 15

16 WEB XML Slide 16

17 Web.xml Configures the behavior of servlet container <?xml version="1.0" encoding="utf-8"?> <web-app version="2.5" xmlns=" xmlns:xsi=" xsi:schemalocation=" <servlet> <servlet-name>firstservlet</servlet-name> <servlet-class>cz.cvut.fel.firstservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>firstservlet</servlet-name> <url-pattern>/firstservlet</url-pattern> </servlet-mapping> <session-config> <session-timeout> 30 </session-timeout> </session-config> <welcome-file-list> <welcome-file>firstservlet</welcome-file> </welcome-file-list> </web-app> Servlet name i URL mapping Servlet may have multiple mappings Servlet implementing class The default mapping Slide 17

18 Web.xml - parameters <?xml version="1.0" encoding="utf-8"?> <web-app version="2.5" xmlns=" xmlns:xsi=" xsi:schemalocation=" <context-param> <param-name>author</param-name> <param-value>martin Klíma</param-value> </context-param> <context-param> <param-name>affiliation</param-name> <param-value>čvut</param-value> </context-param> <servlet> <servlet-name>firstservlet</servlet-name> <servlet-class>cz.cvut.fel.firstservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>firstservlet</servlet-name> <url-pattern>/firstservlet</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>firstservlet</servlet-name> <url-pattern>/prvniservlet</url-pattern> </servlet-mapping> <session-config> <session-timeout> 30 </session-timeout> </session-config> <welcome-file-list> <welcome-file>firstservlet</welcome-file> </welcome-file-list> </web-app> Slide 18 Parameters are accessible via Context object

19 JAVASERVER PAGES - JSP Slide 19

20 JSP JSP is a text document containing static data, usually (X)HTML JSP elements that generate dynamic content Suffix.jsp Two versions standard XML We will use the standard syntax further in the lecture. Slide 20

21 The simples jsp page <%-- Document : stranka1 Created on : , 11:44:52 Author : xklima --%> <%@page contenttype="text/html" pageencoding="utf-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" " <html> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"> <title>jsp Page</title> </head> <body> <h2>hello World!</h2> </body> </html> Slide 21

22 JSP life cycle Servlet Containere JSP comple Servlet generated from JSP HTTP request if JSP is newer than servlet then compile else execute servlet Slide 22

23 MVC Slide 23

24 MVC Bean, JSB, Servlet pocetkusu=7& produktid=22 pocetkusu produktid Bean (M) Browser Servlet (C) forward use JSP (V) Servlet (C) reads http parameters, calls the logic (M). Parameters reflect what the use wants (form data, etc.) Finally, when the logic is done, the control is handed over to JSP Slide 24

25 Java Bean can be used as application logic Servlet - Controller JavaBean - Model HTTP request StatementController Use, create StatementBean Forward JSP - view MVC StatementForm Slide 25

26 JavaBean can be used for information sharing public class StatementBean implements Serializable { protected ArrayList <String> statements; public StatementBean(){ super(); statements = new ArrayList <String>(); public synchronized String getstatement(int i) { return statements.get(i); public synchronized List <String> getallstatements(){ return statements; public synchronized void addstatement (String statement) { if (!statements.contains(statement)) { statements.add(statement); public synchronized int getstatementcount() { return statements.size(); Slide 26

27 Form for adding statements statementform.jsp contenttype="text/html" pageencoding="utf-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" " <html> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8"> <title>statements</title> </head> <body> <h2>list</h2> <jsp:usebean id="statements" scope="session" class="cz.cvut.fel.statementbean" /> <% for (String statement : statements.getallstatements()) { out.println(statement + "<br/>"); </html> %> <form action="statementcontroller" method="get"> <input type="text" name="statement"/> <input type="submit" value="submit" name="submit"/> </form> </body> Slide 27

28 Controller - servlet protected void processrequest(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html;charset=utf-8"); PrintWriter out = response.getwriter(); try { if (request.getparameter("statement")!= null) { StatementBean sb = (StatementBean) request.getsession().getattribute("statements"); if (sb == null) { sb = new StatementBean(); sb.addstatement((string)request.getparameter("statement")); request.getsession().setattribute("statements", sb); finally { RequestDispatcher dispatcher = getservletcontext().getrequestdispatcher("/statementform.jsp"); dispatcher.forward(request, response); Slide 28

29 Serialization in Java Value transfer and storage (marshal, unmarshal) java.io.serializable transient is excluded from serialization serialversionuid NotSerializableException MarshalException, UnmarshalException private void writeobject(objectoutputstream oos) throws IOException; private void readobject(objectinputstream oos) throws IOException, ClassNotFoundException; Slide 29

30 APPLICATION SERVER Slide 30

31 Web application architecture application server request App 1 Thin client (HTML) HTTP response controller model (JavaBean) view (HTML) HTML generator Web Server Data App 2 App 3 Application Server Data Thick client (non - HTML) Slide 31

32 Enterprise Beans A component running on application server Managed by EJB container Accessible from a stand-alone application (RMI) Accessible from web application (Servlet container RMI) Architecture ready to use session management transaction management db connection management use authentication, authorization asynchronous messaging Slide 32

33 Enterprise beans Several types of EJB Session bean Stateless Singleton (since EJB 3.1) Statefull Entity bean EJB 3.0 ->Entity Message driven bean Slide 33

34 Session beans Represent application logic Two types: Bound to a particular client (statefull)!!!not a HTTP session Client independent (stateless) Slide 34

35 Entity Objects representing a persistent element (ORM) Bound to database Transactions, search Object OP approach to data persistency Relations to other entities Slide 35

36 Message driven bean Event driven application logic Events generated by other applications B2B Asynchronous Typically very short lifetime Not bound to persistant data Stateless Slide 36

37 EJB 3.x POJO = Plain Old Java Object Container is driven by annotations provided Container controls their livecycle Local and remote interface Registered in JNDI (registry) Serach by name Remote access Slide 37

Example @Stateless (mappedname = "Repeater") public class RepeaterSessionBean implements RepeaterSessionBeanRemote, RepeaterSessionBeanLocal { public String repeatnormallocal(final String text) {

38 (mappedname = "Repeater") public class RepeaterSessionBean implements RepeaterSessionBeanRemote, RepeaterSessionBeanLocal { public String repeatnormallocal(final String text) { return text; public String repeatnormalremote(final String text) { return text; public String repeatreverseremote(final String text) { return getreversestring(text); public String repeatreverselocal(final String text) { return getreversestring(text); Stateless EJB JNDI publicinterface RepeaterSessionBeanRemote { String repeatnormalremote(final String text); String repeatreverseremote(final String publicinterface RepeaterSessionBeanLocal { String repeatnormallocal(final String text); String repeatreverselocal(final String text); private String getreversestring(string text) { StringBuffer b = new StringBuffer(text.length()); for (int i = text.length(); i > 0; i--) { b.append(text.charat(i - 1)); return b.tostring(); Slide 38

39 Example cont. public class FormBean1 RepeaterSessionBeanLocal repeaterbean; private String text; private String reverse; Injection public FormBean1() { public String gettext() { return text; public void settext(string text) { this.text = text; public String translate() { setreverse(repeaterbean.repeatreverselocal(text)); return null; Použití public String getreverse() { return reverse; public void setreverse(string reverse) { this.reverse = reverse; Slide 39

40 Stateless { String name() default ""; String mappedname() default ""; String description() Stateful { String name() default ""; String mappedname() default ""; String description() default ""; Slide 40

41 Stateless EJB livecycle stateless = no memory Slide 41

42 Stateful EJB Livecycle Slide 42

43 The same image without transactions Slide 43

44 Lookup and use 1. Dependency Injection Container takes care of the DI Annotation helps to do the job public class FormBean1 RepeaterSessionBeanLocal repeaterbean; 2. JNDI lookup static RepeaterSessionBeanRemote repeatersessionbean; Context context; try { context = new InitialContext(); repeatersessionbean = (RepeaterSessionBeanRemote) context.lookup("jndi_name"); catch (NamingException e) { e.printstacktrace(); throw new RuntimeException(e); Slide 44

45 Calling Stateless EJB from a web application Same as from stand-alone application Usong a Stateful EJB is not recommended from a stateless context (HTTPServlet) Use Stateless EJB whenever possible Slide 45

46 Local & Remote interface RMI is complicated and resource concuming In same cases the EJB is located in the same VM can be called locally Therefore there is a Local Interface Slide 46

47 Stateless vs Statefull EJB Use stateless whenever possible Stateless are easy to scale Stateless do not need persistency Statefull must be stored in memory Demanding for the server Do not scale well Good for big tada processing - transactional We do not have to care of multithreading Slide 47

48 Interceptor Interceptor is kind of event handler Similar to event handlers elsewhere in Java (Swing) Depending on the EJB bean, for example: Slide 48

49 Two way to use interceptors 1. Directly in the Bean public Object profile(invocationcontext inv) throws Exception { long time = System.currentTimeMillis(); try { return inv.proceed(); finally { long endtime = time - System.currentTimeMillis(); System.out.println(inv.getMethod() + " took " + endtime + " milliseconds."); Slide 49

In a separate class linked by annotation EJB @Interceptors(cz.cvut.fel.ejb.interceptors.RepeaterInterceptor.

repeatnormallocal(final String text) { return text; Comma separated list public String repeatnormalremote(final String text) { return text; public class

50 In a separate class linked by = "Repeater") public class RepeaterSessionBean implements RepeaterSessionBeanRemote, RepeaterSessionBeanLocal { public String repeatnormallocal(final String text) { return text; Comma separated list public String repeatnormalremote(final String text) { return text; public class RepeaterInterceptor public Object profile(invocationcontext ctx) throws Exception { try { System.out.print("Zavolana metoda " + ctx.getmethod().getname()); finally { return ctx.proceed(); Slide 50

51 MESSAGE DRIVEN BEANS MDB Slide 51

52 What is MDB? Components that process messages Similar to Stateless EJB stateless interchangeable they have different purpose Messaging is a basic principle of distributed systems MDB is typically target for messages Slide 52

53 MDB JNDI assigned Container Client Destination or endpoint MDB MDB MDB Slide 53

54 MDB Two communication modes Point to point: queues, FIFO associated with one bean Publish / subscribe: topics, distribuce multiple receivers Implements interface javax.jms.messagelistener onmessage method Slide 54

55 MDB Lifecycle Slide 55

56 JMS Java Message Service JMS message Several types of message Header, properties and body Header: delivery mode, msg ID, timestamp, priority, ReplyTo, msg type Properties: key, value Body: Stream, Map, Text, Object, Bytes Slide 56

57 Example = "jms/school", activationconfig = = "acknowledgemode", propertyvalue = = "destinationtype", propertyvalue = "javax.jms.queue") ) public class SchoolMessageBean implements MessageListener { public SchoolMessageBean() { public void onmessage(message message) { TextMessage tm = (TextMessage) message; String teacher; try { teacher = tm.gettext(); System.out.println("Prijata informace o pridani ucitele: " + teacher); catch (JMSException ex) { Logger.getLogger(SchoolMessageBean.class.getName()).log(Level.SEVERE, null, ex); Slide 57

58 Client sending public class SchoolSessionBean implements SchoolSessionBeanRemote, SchoolSessionBeanLocal = "jms/school") private Queue = "jms/schoolfactory") private ConnectionFactory schoolfactory; public PartTimeTeacherEntity addparttimeteacher(final String firstname, final String lastname, final float parttime) { try { sendjmsmessagetoschool(firstname + teacher added ); catch (JMSException ex) { Logger.getLogger(SchoolSessionBean.class.getName()).log(Level.SEVERE, null, ex); return teacher; private Message createjmsmessageforjmsschool(session session, Object messagedata) throws JMSException { TextMessage tm = session.createtextmessage(); tm.settext(messagedata.tostring()); return tm; pokračování na dalším slide Slide 58

59 Client cont. private void sendjmsmessagetoschool(object messagedata) throws JMSException { Connection connection = null; Session session = null; try { connection = schoolfactory.createconnection(); session = connection.createsession(false, Session.AUTO_ACKNOWLEDGE); MessageProducer messageproducer = session.createproducer(school); messageproducer.send(createjmsmessageforjmsschool(session, messagedata)); finally { if (session!= null) { try { session.close(); catch (JMSException e) { Logger.getLogger(this.getClass().getName()).log(Level.WARNING, "Cannot close session", e); if (connection!= null) { connection.close(); Slide 59

60 References 30/ Slide 60

Stateless -Session Bean

Stateless -Session Bean Prepared by: A.Saleem Raja MCA.,M.Phil.,(M.Tech) Lecturer/MCA Chettinad College of Engineering and Technology-Karur E-Mail: asaleemrajasec@gmail.com Creating an Enterprise Application