Java Server Pages

JavaServer Pages (JSP) Svetlin Nakov Borislava Spasova Creating Dynamic Web Pages

Contents ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Contents (2) ,[object Object],[object Object],[object Object],[object Object]

Introduction to JSP Technology

What is JSP? ,[object Object],[object Object],[object Object],[object Object],[object Object]

JSP Technology ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Date JSP Page – Example ,[object Object],<html> <head><title>Date JSP example </title></head> <body> The date is: <% out.println(new java.util.Date()); %> </body> </html> date.jsp

JSP Expressions ,[object Object],[object Object],[object Object],<%= Java e xpression %> The time is : <%= new java.util.Date() %> The square root of 2 is : <%= Math.sqrt(2) %> The value of PI is: <%= Math.PI %>

Predefined JSP Variables ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

JSP Expressions – More Examples ,[object Object],[object Object],[object Object],Your hostname: <%= request.getRemoteHost() %> Session timeout : <%= session.getMaxInactiveInterval() %> Browser: <%= request.getHeader("User-Agent") %>

JSP Scriptlets ,[object Object],[object Object],<% Java c ode %> <% String queryData = request.getQueryString(); out.println("Attached GET data: " + queryData); %>

JSP Scriptlets – Example ,[object Object],[object Object],<% if (Math.random() < 0.5) { %> Have a <B>nice</B> day! <% } else { %> Have an <B>interesting</B> day! <% } %> <% for (int i=0; i<10; i++) { %> <%= i %> * <%= i %> = <%= i*i %> <br> <% } %>

JSP Internals How JSP Pages Are Transformed to Servlets?

JSP Technology Internals ,[object Object],[object Object],[object Object],[object Object],JSP Page ( date .jsp ) Java servlet ( date .java ) Compiled Java servlet ( date . class ) JSP compiler javac

JSP Technology Internals ,[object Object],<html> <head><title>Date JSP example</title></head> <body> The date is: <% out.println(new java.util.Date()); %> </body> </html> date.jsp JSP compilation package org.apache.jsp; public final class date_jsp extends HttpJspBase implements JspSourceDependent { ... } date_jsp.java ebappsSP-Demosdate.jsp orkatalinaocalhostJSP-Demosrgpachesp

JSP Declarations and Directives

JSP Declarations ,[object Object],[object Object],[object Object],<%! Java c ode (fields and methods) %> <%! long counter = 0; public void getCounter() { return counter; } %>

JSP Declarations ,[object Object],[object Object],[object Object],[object Object],<%! private static int accessCount = 0; %> This page has been accessed <%= ++accessCount %> times.

JSP Directives ,[object Object],[object Object],[object Object],<%@ directive attribute="value" %> <%@ directive attribute1="value1" attribute2="value2" ... attributeN="valueN" %>

The JSP @ page Directive ,[object Object],[object Object],[object Object],[object Object],import="package.class " or import="package.class1, ..., package.classN" <%@ page import="java.util.*" %>

The JSP @ page Directive (2) ,[object Object],[object Object],[object Object],contentType="MIME-Type" or contentType="MIME-Type; charset=Character-Set" <%@ page contentType="text/plain" %> <% response.setContentType("text/plain"); %>

The JSP @ page Directive (3) ,[object Object],[object Object],[object Object],session="true|false" errorPage="url" isErrorPage="true|false"

The JSP @ include Directive ,[object Object],[object Object],[object Object],[object Object],<%@ include file="relative url" %> <%@ include file="/ include/ menu.jsp" %>

Using JSP @ include Directive ,[object Object],< html > < body > <%@ include file="/navbar.html" %>  </ body > </ html >

Dynamic Include ,[object Object],[object Object],[object Object],<jsp:include page="header.jsp" /> <% String headerPage = "header.jsp" ; %> <jsp:include page="<%= headerPage %>" />

JSP Predefined Variables request , response , session , application , config , …

More About The JSP Predefined Variables ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

More About The JSP Predefined Variables (2) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

More About The JSP Predefined Variables (3) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

More About The JSP Predefined Variables (4) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Using The application Object ,[object Object],[object Object],[object Object],synchronized (application) { Vector items = (Vector) application.getAttribute ("items"); if (sharedItems == null) { sharedItems = new Vector (); application.setAttribute ("items", items); } }

Using The application Object – Example <%@ page import="java.util.Vector" %> <%// Get the global list of shared items Vector<String> sharedItems; synchronized (application) { sharedItems = (Vector<String>) application.getAttribute ("items"); if (sharedItems == null) { sharedItems = new Vector<String>(); application.setAttribute ("items", sharedItems); } } // Append the new item (if exists) String newItem = request.getParameter("item"); if (newItem != null) sharedItems.addElement(newItem); %>

Using The application Object – Example (2) <html> <head><title>Global Shared List</title></head> <body> Available shared items: <ol> <% for (String item : sharedItems) { %> <li><%= item %></li> <% } %> </ol> <form method="POST" action="Global-Shared-List.jsp"> <input type="text" name="item"> <input type="submit" value="Add"> </form> </body> </html>

Client and Server Redirections

Client Redirection to Another URL ,[object Object],[object Object],[object Object],[object Object],[object Object],response.sendRedirect(<url>); response.sendRedirect("date.jsp");

Server Redirection to Another Resource ,[object Object],[object Object],[object Object],[object Object],request.getRequestDispatcher(<url>). forward(request, response) request.getRequestDispatcher("date.jsp"). forward(request, response);

<jsp:forward> ,[object Object],[object Object],[object Object],<jsp:forward page= {" relativeURL " | "<%= expression %>"} /> <jsp:forward page={" relativeURL " | "<%= expression %>"} > <jsp:param name=" parameterName " value="{ parameterValue | <%= expression %>}" /> </jsp:forward>

<jsp:forward> – Example ,[object Object],[object Object],[object Object],<jsp:forward page="Global-Shared-List.jsp"> <jsp:param name=" item " value= "This item is added by JSP-forward.jsp" /> </jsp:forward>

Escaping Problems And How to Avoid Them

Escaping Problems ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Escaping Problems – Example ,[object Object],[object Object],<html> You entered: <%= request.getParameter("something") %> <form> Enter something:<br> <input type="text" name="something"> <input type="submit"> </form> </html> <script language="JavaScript">alert('Bug!');</script>

What To Escape? ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Escape The HTML Special Characters ,[object Object],[object Object]," " Quotation Mark & & Ampersand > > Greater Than < < Less Than Character HTML Entity Character Name       Tab <br> New Line   Space Escaping Character Name

HTML Escaping ,[object Object],[object Object],public static String htmlEscape(String text) { if (text == null) { return ""; } StringBuilder escapedText = new StringBuilder(); for (int i=0; i<text.length(); i++) { char ch = text.charAt(i);

HTML Escaping (2) if (ch == '<') escapedText.append("<"); else if (ch == '>') escapedText.append(">"); else if (ch == '&') escapedText.append("&"); else if (ch == 'amp;quot;') escapedText.append("""); else escapedText.append(ch); } String result = escapedText.toString(); return result; }

Problems ,[object Object],[object Object],[object Object]

Problems (2) ,[object Object],[object Object],[object Object]

Homework ,[object Object],[object Object],[object Object]

Homework (2) ,[object Object],[object Object],[object Object]

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