Jordan Anastasiade. All rights reserved.

Copyright @ 2000 Jordan Anastasiade. All rights reserved.
JavaServer Pages In this lesson you will be learning about: What JSP Technology is and how you can use it. How to define and write JSP Page. Syntax of JSP Page. How do JSP pages work. How is a JSP page invoked and compiled. Use of Beans in a JSP Page. How one could create XML pages using JSP technology. JavaServer Pages v1.2 Jordan Anastasiade. All rights reserved.

JavaServer Pages Technology
JavaServer Pages (JSP) technology provides a simplified, fast way to create web pages that display dynamically-generated content. The JSP 1.2specification is an important part of the Java 2 Platform, Enterprise Edition. Using JSP and Enterprise JavaBeans technologies together is a great way to implement distributed enterprise applications with web-based front ends. The first place to check for information on JSP technology is Jordan Anastasiade. All rights reserved.

JSP Page A JSP page is a page created by the web developer that includes JSP technology-specific tags, declarations, and possibly scriptlets, in combination with other static HTML or XML tags. A JSP page has the extension .jsp; this signals to the web server that the JSP engine will process elements on this page. Pages built using JSP technology are typically implemented using a translation phase that is performed once, the first time the page is called. The page is compiled into a Java Servlet class and remains in server memory, so subsequent calls to the page have very fast response times. Put .jsp pages into a WAR file (see Web ARchive) Deploy (upload) the WAR file as a Web Application to your Sun Java System Application Server Platform. Jordan Anastasiade. All rights reserved.

Overview JavaServer Pages (JSP) lets you separate the dynamic part of your pages from the static HTML. HTML tags and text <% some JSP code here %> <I> <%= request.getParameter("title") %> </I> You normally give your file a .jsp extension, and typically install it in any place you could place a normal Web page Jordan Anastasiade. All rights reserved.

Client and Server with JSP
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Translation Time A JSP application is usually a collection of JSP files, HTML files, graphics and other resources. A JSP page is compiled when your user loads it into a Web browser When the user loads the page for the first time, the files that make up the application are all translated together, without any dynamic data, into one Java source file (a .java file) The .java file is compiled to a .class file. In most implementations, the .java file is a Java servlet that complies with the Java Servlet API. Jordan Anastasiade. All rights reserved.

How JSP Works? User Request – JSP File Requested Server File Changed
Create Source from JSP Compile Execute Servlet Jordan Anastasiade. All rights reserved.

JSP Elements Declarations <%! code %> <jsp:declaration> </jsp:declaration > Expressions <%= expression %> <jsp:expression> </jsp:expression> Scriplets <% code %> <jsp:scriplet> </jsp:scriplet > Jordan Anastasiade. All rights reserved.

HTML Comment Generates a comment that is sent to the client. Syntax  Example:  Jordan Anastasiade. All rights reserved.

Declaration Declares a variable or method valid in the scripting language used in the JSP page. Syntax <%! declaration; [ declaration; ] %> Examples <%! String destin; %> <%! Public String getDestination() {return destin;}%> <%! Circle a = new Circle(2.0); %> You can declare any number of variables or methods within one declaration element, as long as you end each declaration with a semicolon. The declaration must be valid in the Java programming language. Jordan Anastasiade. All rights reserved.

Declaration Example <HTML> <HEAD><TITLE>JSP Declarations</TITLE></HEAD> <BODY><H1>JSP Declarations</H1> <%! private int keepCount = 0; %> <H2> Page accessed: <%= ++keepCount %> times </H2> </BODY> </HTML> Jordan Anastasiade. All rights reserved.

Predefined Variable – Implicit Objects
request – Object of HttpServletRequest (request parameters, HTTP headers, cookies response – Object of HttpServletResponse out - Object of PrintWriter buffered version JspWriter session - Object of HttpSession associated with the request application - Object of ServletContext shared by all servlets in the engine config - Object of ServletConfig pageContext - Object of PageContext in JSP for a single point of access page – variable synonym for this object Jordan Anastasiade. All rights reserved.

Expression Contains an expression valid in the scripting language used in the JSP page. Syntax <%= expression %> <%! String name = new String(“JSP World”); %> <%! public String getName() { return name; } %> <B><%= getName() %></B> Description: An expression element contains a scripting language expression that is evaluated, converted to a String, and inserted where the expression appears in the JSP file. Because the value of an expression is converted to a String, you can use an expression within a line of text, whether or not it is tagged with HTML, in a JSPfile. Expressions are evaluated from left to right. Jordan Anastasiade. All rights reserved.

Expression Example <HTML> <HEAD> <TITLE>JSP Expressions</TITLE> </HEAD> <BODY> <H2>JSP Expressions</H2> <UL> <LI>Current time: <%= new java.util.Date() %> <LI>Your hostname: <%= request.getRemoteHost() %> <LI>Your session ID: <%= session.getId() %> </UL> </BODY> </HTML> Jordan Anastasiade. All rights reserved.

Scriptlet Contains a code fragment valid in the page scripting language. Syntax <% code fragment %> <% String var1 = request.getParameter("name"); out.println(var1); %> This code will be placed in the generated servlet method: _jspService() Jordan Anastasiade. All rights reserved.

Scriplet Example <HTML> <HEAD><TITLE>Weather</TITLE></HEAD> <BODY> <H2>Today's weather</H2> <% if (Math.random() < 0.5) { %> Today will be a <B>suny</B> day! <% } else { %> Today will be a <B>windy</B> day! <% } %> </BODY> </HTML> Jordan Anastasiade. All rights reserved.

JSP Page Directive Directives are messages to the JSP container and do not produce output into the current output stream Syntax: directive attribute=“value” %> directive attribute1=“value1” attribute1 =“value2” … %> There are three types of directives: page include taglib XML form: <jsp:directive.directiveType attribute=“value” /> Jordan Anastasiade. All rights reserved.

Page Directive Defines attributes that apply to an entire JSP page. page [ language="java" ] [ extends="package.class" ] [ import="{package.class | package.*}, ..." ] [ session="true|false" ] [ buffer="none|8kb|sizekb" ] [ autoFlush="true|false" ] [ isThreadSafe="true|false" ] [ info="text" ] [ errorPage="relativeURL" ] [ contentType="mimeType [ ;charset=characterSet ]" [ isErrorPage="true|false" ] %> Jordan Anastasiade. All rights reserved.

Include Directive Includes a static file in a JSP file, parsing the file's JSP elements. Syntax include file="relativeURL" %> The include %> directive inserts a file of text or code in a JSP file at translation time, when the JSP file is compiled. include %> process is static. A static include means that the text of the included file is added to the JSP file. The included file can be: JSP file, HTML file, text file. Jordan Anastasiade. All rights reserved.

Taglib Directive Defines a tag library and prefix for the custom tags used in the JSP page. Syntax taglib uri="URIToTagLibrary" prefix="tagPrefix" %> taglib uri=" prefix="public" %> <public:loop> </public:loop> The taglib %> directive declares that the JSP file uses custom tags, names the tag library that defines them, and specifies their tag prefix. Jordan Anastasiade. All rights reserved.

Server Redirection One can forward to a text file (HTML), a CGI script, a servlet or another JSP page. One can only forward to a new page, provided no output of the original page has been sent to the browser. One may pass as many parameters as one needs with this method by using the param tag. The forward action ends execution of the current JSP page and removes any existing buffered output. The new page has access to application, request, and session objects as the starting file. A new pageContext object is generated for the page. To the browser, it will appear you have the originally requested page, not the page to which you are transferred. Example: <jsp:forward page="home/Default.jsp" > <jsp:param name="source" value="entry"/> </jsp:forward> Jordan Anastasiade. All rights reserved.

<jsp:forward> Forwards a client request to an HTML file, JSP file, or servlet for processing. Syntax <jsp:forward page="{relativeURL | <%= expression %>}" /> <jsp:forward page="{relativeURL | <%= expression %>}" > <jsp:param name="parameterName" value="{parameterValue | <%= expression %>}" />+ </jsp:forward> Jordan Anastasiade. All rights reserved.

<jsp:useBean> Locates or instantiates a bean with a specific name and scope. <jsp:useBean id="beanInstanceName" scope="page|request|session|application" { class="package.class" | type="package.class" | class="package.class" type="package.class" | beanName="{package.class | <%= expression %>}“ } { /> | > other elements </jsp:useBean> Jordan Anastasiade. All rights reserved.

Attributes and Usage id="beanInstanceName" A variable that identifies the bean in the scope you specify. The name is case sensitive and must conform to the naming conventions of the scripting language used in the JSP page scope="page|request|session|application“ page One can use the bean within the JSP page with the <jsp:useBean> element or any of the page's static include files, until the page sends a response back to the client or forwards a request to another resource request One can use the bean from any JSP page processing the same request, until a JSP page sends a response to the client or forwards the request to another resource. One can use the request object to access the bean, for example, request.getAttribute(beanInstanceName). session One can use the bean from any JSP page in the same session as the JSP page that created the bean. The bean exists across the entire session, and any page that participates in the session can use it. The page in which you create the bean must have a page directive with session="true". application One can use the bean from any JSP page in the same application as the JSP page that created the bean. The bean exists across an entire JSP application, and any page in the application can use the Jordan Anastasiade. All rights reserved.

Different Scope Most visible Objects accessible from pages Belong to the same application. Application Session Objects accessible from pages Belonging to the same session. Request Objects accessible from pages processing the request. Page Objects accessible only within pages where they were created. Least visible Jordan Anastasiade. All rights reserved.

<jsp:setProperty>
Sets a property value or values in a bean. Syntax <jsp:setProperty name="beanInstanceName" { property="*" | property="propertyName" [ param="parameterName" ] | property="propertyName" value="{string | <%= expression %>}" } /> Examples <jsp:setProperty name="mybean" property="*" /> <jsp:setProperty name="mybean" property="username" /> <jsp:setProperty name="mybean" property="username" value="Steve" /> The <jsp:setProperty> element sets the value of one or more properties in a bean, using the bean's setter methods. You must declare the bean with<jsp:useBean> before you set a property value with <jsp:setProperty>. Jordan Anastasiade. All rights reserved.

<jsp:getProperty>
Gets the value of a bean property so that you can display it in a result page. Syntax <jsp:getProperty name="beanInstanceName“ property="propertyName" /> Example: <jsp:useBean id="calendar" scope="page" class="employee.Calendar" /> <h2> Calendar of <jsp:getProperty name="calendar" property="username" /> </h2> The <jsp:getProperty> element gets a bean property value using the property's getter methods and displays the property value in a JSP page. You must create or locate a bean with <jsp:useBean> before you use <jsp:getProperty>. Jordan Anastasiade. All rights reserved.

Jsp with Beans public class MessageBean { private String message = "No Message"; public String getMessage() { return message; } public void setMessage(String message) { this.message = message; Jordan Anastasiade. All rights reserved.

JavaBeans with JSP Page
<jsp:useBean id="firstBean" scope="session" class="packBeans.MessageBean"/> <jsp:setProperty name="firstBean" property="message" value="This is a message from a bean" /> <H1>Message: <I><font color="#0000FF" size=+3> <jsp:getProperty name="firstBean" property="message" /> </I></font> </H1> Jordan Anastasiade. All rights reserved.

Handling Forms with JSP
package packBeans; public class NameBean { private String name; public NameBean() { name = null; } public String getName() { return name; public void setName(String aName) { name = aName; Jordan Anastasiade. All rights reserved.

JSP Form <jsp:useBean id='nb' scope='session' class=‘packBeans.NameBean'/> <jsp:setProperty name='nb' property="*"/> <HTML> <BODY> <H1>Please enter your name to be registered to JSP Course?</H1> <FORM method="get"> <INPUT type="text" name="name" size="25"> <INPUT type="submit" value="Submit"> </FORM> <% if ( request.getParameter("name") != null ) } %> <%= "Click<a href=GetName.jsp> here</a> to confirm your registration" %> <% } %> </BODY> </HTML> Jordan Anastasiade. All rights reserved.

JSP Results <jsp:useBean id='nb' scope="session“class=“packBeans.NameBean"/> <HTML> <HEAD> <TITLE>Registered Name</TITLE> </HEAD> <BODY> <jsp:getProperty name="nb" property="name"/> </BODY> </HTML> Jordan Anastasiade. All rights reserved.

Conclusion JavaServer Pages (JSP) lets you separate the dynamic part of your pages from the static HTML. 1. One can simply write the regular HTML in the normal manner, using whatever Web-page-building tools you normally use. One can enclose then the code for the dynamic parts in special tags, most of which start with "<%" and end with "%>" Jordan Anastasiade. All rights reserved.

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