1 / 24

JSP

JSP. Web Technology Week 4. J2EE = Java 2 Enterprise Edition. Servlet Server-side Java-programs Process incoming requests from clients Supported through servlet engine(s) Example: Tomcat (Apache) JSP = Java Server Pages Mixes HTML and Java code Extension of servlet model

slone
Download Presentation

JSP

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. JSP Web Technology Week 4

  2. J2EE = Java 2 Enterprise Edition • Servlet • Server-side Java-programs • Process incoming requests from clients • Supported through servlet engine(s) • Example: Tomcat (Apache) • JSP = Java Server Pages • Mixes HTML and Java code • Extension of servlet model • JSP page is compiled into servlet • EJB = Enterprise Java Beans • See next section (part 2 course)

  3. Market shares….. • JSP continues fast growth, on a surprisingly diverse set of operating systems Last December we reported that the number of JSP sites had grown quickly during 2002, albeit from a small starting point. Reviewing the growth over the past year since July 2002, JSP continues to enjoy fast growth with a 94% increase in ip addresses running JSP based sites to over 44,000 ip addresses running some 105,000 active sites. More surprising is the composition of these sites choice of operating systems. One might expect that by far the most common operating system amongst JSP based sites would be Solaris, given JSP's links with application servers such as Weblogic, IBM Websphere, Oracle, and Apache Tomcat. However, Solaris is only placed 3rd with 17% behind Linux with 40% and Windows with 26%.

  4. Introduction to JSP • What is JavaServer Pages(JSP)? • A technology developed by Sun Microsystems that is used to create dynamic web sites based on Java and Java Servlet technologies • Java, Servlet, and JSP • Both Servlet and JSP are based on Java technology. Servlet is one component of a suit of Java products. JSP technology is an extension of the servlet technology. One JSP will be interpreted as one class of Java/Servlet. • Java Server Pages (JSPs) provide a way to separate the generation of dynamic content (java) from its presentation (html) • JSP specification builds on the functionality provided by the servlet specification.

  5. Getting Started with JSP • A JSP is a HTML page with scripting elements embedded in it. • A JSP is • first translated into a servlet and • then executed in the Servlet engine

  6. How do JSP’s Work index.jsp Servlet/JSP Server (e.g. Tomcat ) checks Browser (e.g., IE) converts Forwards to index.java Generated Servlet compiles DBMS (e.g. MySQL)

  7. Your First JSP <HTML> <BODY> Hello!  The time is now <%= new java.util.Date() %> </BODY> </HTML> Save it as hello.jsp

  8. Another example <HTML> <BODY> <%-- the comments go here --%> <% //The following code is used to demonstrate how java code works String myClassName = "inls259"; out.println("<B> demon of "+myClassName+"</B></br>"); java.util.Date date = new java.util.Date(); %> Hello! The time is now <%= date %> <% out.println("</br>Host: "+request.getRemoteHost()); %> </BODY> </HTML> out is the javax.servlet.jsp.JspWriter while request is javax.servlet.http.HttpServletRequest

  9. Scriptlets • Java statements can be enclosed in <% … %> inside a jsp <%     System.out.println( "Evaluating date now" );     java.util.Date date = new java.util.Date(); %>

  10. Mixing Scriptlets and HTML <HTML> <HEAD> <TITLE>Greetings</TITLE> </HEAD> <BODY> <H2>Greetings</H2> <% if (Math.random() < 0.5) { %> Have a <B>nice</B> day! <% } else { %> Have a <B>lousy</B> day! <% } %> </BODY> </HTML>

  11. Mixing Scriptlets and HTML • Everything that you want to be executed has to be in <% … %> • Everything that you want to be displayed as is in the browser has to be outside any <% … %> <TABLE BORDER=2> <%     for ( int i = 0; i < n; i++ ) {   %> <TR> <TD>Number</TD> <TD> <%= i+1 %> </TD> /TR> <%   } %> </TABLE>

  12. JSP Declarations • JSP scriptlets are considered as one method in one class • Variables and Methods can also be added in declarations • add a declaration, you must use the <%! and %> <%@ page import="java.util.*" %> <HTML> <BODY> <%!     Date theDate = new Date();     Date getDate() {         return theDate;     } %> Hello!  The time is now <%= getDate() %> </BODY> </HTML>

  13. JSP Directive • Directives provide global information to the JSP engine • For example, a directive can be used to import java classes. • Directive elements have a syntax of the form<%@ directive … %> • Directives are JSP constructs that affect the jsp pages, but they are not Java constructs • Example: • page directive: • <%@ page import="java.util.*, java.text.*" %> • include directive: physically includes content or a page • <%@ include file="hello1.jsp" %>

  14. Scripting Elements • Allow java code – variable or method declarations, scriptlet, and expressions. • Declaration tag <%! … %> • Scriptlet tag <% … %> • Expression tag <%= … %>

  15. Declaration Tag • <%! … %> • Allows you to declare page wide variables and methods. <%! int counter = 0; %> <%! Vector beanList = new Vector(); %> • Methods and variables have class scope • Note, code must end with ; like any java code

  16. Scriptlet Tag • <% … %> • Used to include small pieces of Java code <% for(Enumeration e = beanList.elements(); e.hasMoreElements(); ) { UserBean uBean = (UserBean) e.nextElement(); out.println( uBean.getUserName() ); } %>

  17. Expression Tag • <%= … %> • Accepts any Java expression, evaluates the expression, converts to a String, and displays. <%= counter %> <%= uBean.getUserName() %> Short hand for: <% out.println( uBean.getUserName() ); %>

  18. Page Directives • The page directive defines a number of page dependent attributes <%@ page language=“Java” [ extends=“className” ] [ import=“importList” ] [ session= “true|false” ] [ buffer=“none|sizekb” ] [ autoFlush=“true|false” ] [ isThreadSafe=“true|false” ] … %>

  19. Page Directive • If language attribute is set, must be = “Java” • Default import list is java.lang.*, javax.servlet.*, javax.servlet.jsp.* and javax.servlet.http.*. • If session = “true” then default session variable of type javax.servlet.http.HttpSession references the current/new session for the page.

  20. JSP Sessions • Form page • Sent to otherpage • Starts session • Next • Continues session <HTML> <BODY> <FORM METHOD=POST ACTION="SaveName.jsp"> What's your name? <INPUT TYPE=TEXT NAME=username SIZE=20> <P><INPUT TYPE=SUBMIT> </FORM> </BODY> </HTML> <% String name = request.getParameter( "username" ); session.setAttribute( "theName", name ); %> <HTML> <BODY> <A HREF="NextPage.jsp">Continue</A> </BODY> </HTML> <HTML> <BODY> Hello, <%= session.getAttribute( "theName" ) %> </BODY> </HTML>

  21. Include Directive • The include directive is used to inline text and/or code at JSP page translation-time. <%@ page include file=“relativeURL” %> <%@ page include=“/navbar.html”%>

  22. Implicit objects • out, request, response, application, config, exception, page, pageContext, and session • Out—send output to client web browser • Request—store inf1112ormation supplied by a client, including form data • Response—store information generated by web server • Session—store information associated with a session • Application—store information about an application related to a specific directory • Config—store information about configuration of the environment • Exception—handle errors • Page—typically not accessed from JSP • pageContext—access characteristics of a JSP page

  23. Examples • application • application.setAttribute(“siteName”,”inls259” • application.getAttribute(“siteName”) • Request • String name =request.getParameter(“userName”) • String[] names =request.getParameterValues(“friends”); • Out • out.flush() • Response • Response.addCookie(myCookie)

  24. Jbuilder and running JSP/Servlets • Tomcat server delivered with Jbuilder • Tomcat automatically • Started when <run program> • Stopped when program is stopped • Simple web-app • New project • New • web – JavaServerPage – (web module – new – empty web module) – whatever (first page – submit form?) – finish • Add other JSP-pages • One .jsp-page is started as default • Run application • Application and classes copied to right location • While running: Tomcat server can be addressed from other machines • http://Ip-adres:8080

More Related