JSP Java Server Pages Softsmith Infotech 1 Java

Java Server Pages • JSP (Java Server Pages) is an alternate way of creating

JSP scripting elements • There is more than one type of JSP “tag, ”

Example JSP • <HTML> <BODY> Hello! The time is now <%= new java. util.

Variables • You can declare your own variables, as usual • JSP provides several

Scriptlets • • Scriptlets are enclosed in <%. . . %> tags – Scriptlets

Declarations • Use <%!. . . %> for declarations to be added to your

Directives • Directives affect the servlet class itself • A directive has the form:

JSP Comments • Different from HTML comments. • HTML comments are visible to client.

The include directive • The include directive inserts another file into the file being

Actions • Actions are XML-syntax tags used to control the servlet engine • <jsp:

JSP in XML • JSP can be embedded in XML as well as in

Action – use. Bean tag • The use. Bean action tag is the most

Session in jsp • In session management whenever a request comes for any resource,

Java. Script language • The Java. Script language is an interpreted, object oriented based

Where to use Java. Script • Verify the end user input data contains legitimate

How to run Java. Scripts • Java. Script statements are interpreted and run by

Java. Script programming example <HTML> 2 <HEAD><TITLE> Java. Script Example 1 </TITLE></HEAD> 3 <BODY>

Events An event is an identifiable occurrence or action that has taken place in

Binding Events In client side web programming, the web browser contains it's own event

Common web browser events Event Description click Used to indicate an entity (usually a

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JSP Java Server Pages Softsmith Infotech 1

Java Server Pages • JSP (Java Server Pages) is an alternate way of creating servlets – JSP is written as ordinary HTML, with a little Java mixed in – The Java is enclosed in special tags, such as <%. . . %> – The HTML is known as the template text • JSP files must have the extension. jsp – JSP is translated into a Java servlet, which is then compiled – Servlets are run in the usual way – The browser or other client sees only the resultant HTML, as usual • Tomcat knows how to handle servlets and JSP pages Softsmith Infotech 2

Jsp Execution Softsmith Infotech 3

JSP scripting elements • There is more than one type of JSP “tag, ” depending on what you want done with the Java • <%= expression %> – The expression is evaluated and the result is inserted into the HTML page • <% code %> – The code is inserted into the servlet's service method – This construction is called a scriptlet • <%! declarations %> – The declarations are inserted into the servlet class, not into a method Softsmith Infotech 4

Example JSP • <HTML> <BODY> Hello! The time is now <%= new java. util. Date() %> </BODY> </HTML> • Notes: – The <%=. . . %> tag is used, because we are computing a value and inserting it into the HTML – The fully qualified name (java. util. Date) is used, instead of the short name (Date), because we haven’t yet talked about how to do import declarations Softsmith Infotech 5

Variables • You can declare your own variables, as usual • JSP provides several predefined variables – request : The Http. Servlet. Request parameter – response : The Http. Servlet. Response parameter – session : The Http. Session associated with the request, or null if there is none – out : A Jsp. Writer (like a Print. Writer) used to send output to the client • Example: – Your hostname: <%= request. get. Remote. Host() %> Softsmith Infotech 6

Scriptlets • • Scriptlets are enclosed in <%. . . %> tags – Scriptlets do not produce a value that is inserted directly into the HTML (as is done with <%=. . . %>) – Scriptlets are Java code that may write into the HTML – Example: <% String query. Data = request. get. Query. String(); out. println("Attached GET data: " + query. Data); %> Scriptlets are inserted into the servlet exactly as written, and are not compiled until the entire servlet is compiled – Example: <% if (Math. random() < 0. 5) { %> Have a <B>nice</B> day! <% } else { %> Have a <B>lousy</B> day! <% } %> Softsmith Infotech 7

Declarations • Use <%!. . . %> for declarations to be added to your servlet class, not to any particular method – Caution: Servlets are multithreaded, so nonlocal variables must be handled with extreme care – If declared with <%. . . %>, variables are local and OK – Data can also safely be put in the request or session objects • Example: <%! private int access. Count = 0; %> Accesses to page since server reboot: <%= ++access. Count %> • You can use <%!. . . %> to declare methods as easily as to declare variables Softsmith Infotech 8

Directives • Directives affect the servlet class itself • A directive has the form: <%@ directive attribute="value" %> or <%@ directive attribute 1="value 1" attribute 2="value 2". . . attribute. N="value. N" %> • The most useful directive is page, which lets you import packages – Example: <%@ page import="java. util. *" %> Softsmith Infotech 9

JSP Comments • Different from HTML comments. • HTML comments are visible to client.  • JSP comments are used for documenting JSP code. • JSP comments are not visible client-side. <%-- a JSP comment --%> Softsmith Infotech 10

The include directive • The include directive inserts another file into the file being parsed – The included file is treated as just more JSP, hence it can include static HTML, scripting elements, actions, and directives • Syntax: <%@ include file="URL " %> – The URL is treated as relative to the JSP page – If the URL begins with a slash, it is treated as relative to the home directory of the Web server • The include directive is especially useful for inserting things like navigation bars Softsmith Infotech 11

Actions • Actions are XML-syntax tags used to control the servlet engine • <jsp: include page="URL " /> – Inserts the indicated relative URL at execution time (not at compile time, like the include directive does) – This is great for rapidly changing data • <jsp: forward page="URL" /> <jsp: forward page="<%= Java. Expression %>" /> – Jump to the (static) URL or the (dynamically computed) Java. Expression resulting in a URL Softsmith Infotech 12

JSP in XML • JSP can be embedded in XML as well as in HTML • Due to XML’s syntax rules, the tags must be different (but they do the same things) • HTML: <%= expression %> XML: <jsp: expression>expression</jsp: expression> • HTML: <% code %> XML: <jsp: scriptlet>code</jsp: scriptlet> • HTML: <%! declarations %> XML: <jsp: declaration>declarations</jsp: declaration> • HTML: <%@ include file=URL %> XML: <jsp: directive. include file="URL"/> Softsmith Infotech 13

Action – use. Bean tag • The use. Bean action tag is the most commonly used tag because of its powerful features. • It allows a JSP to create an instance or receive an instance of a Java Bean. • It is used for creating or instantiating a bean with a specific name and scope. • Examples • <jsp: use. Bean id=“time" scope="session" class="com. time. Current. Time. Bean" /> Softsmith Infotech 14

Session in jsp • In session management whenever a request comes for any resource, a unique token is generated by the server and transmitted to the client by the response object and stored on the client machine as a cookie. Session management (i) Session Object (ii) Cookies (iii) Hidden Form Fields (iv) URL Rewriting Softsmith Infotech 15

Javascript Softsmith Infotech 16

Java. Script language • The Java. Script language is an interpreted, object oriented based scripting language. • Java. Script coding statements are commonly embedded inside a webpage using the HTML tags <SCRIPT> </SCRIPT>. • When the web browser is rendering the webpage, any Java. Script coding statements encountered are immediately interpreted and run before the rendering continues. Softsmith Infotech 17

Where to use Java. Script • Verify the end user input data contains legitimate data values. • Handle any arithmetic or logic processing that needs to be executed on the web browser. • Directly manipulate the web browser objects such as the status bar, address bar, and the web browser's rendered controls (such as textboxes, selection lists, etc. . . ). • Handle and process client-side events that have been generated. Softsmith Infotech 18

How to run Java. Scripts • Java. Script statements are interpreted and run by the web browser • Most common web browsers contain a Java. Script interpreter program – interpret and run the Java. Script commands that have been embedded inside a webpage. Question 1: In a web application, which entity executes JSPs? Question 2: In a web application, which entity executes Java. Script commands? Softsmith Infotech 19

Java. Script programming example <HTML> 2 <HEAD><TITLE> Java. Script Example 1 </TITLE></HEAD> 3 <BODY> 4 <H 1>Javascript Example 1</H 1> 5 An alert box will appear using the window object 6 7 <SCRIPT> 8 window. alert("hello world"); 9 </SCRIPT> 10 11 Goodbye! 12 13 </BODY> 14 </HTML> Softsmith Infotech 20

Events An event is an identifiable occurrence or action that has taken place in the system. Writing programs that generate and handle events is known as event programming. Events are typically generated in the following ways. • GUI programs can generate an event to indicate there has been some interaction between the widget and the end user. – when an end user presses a button, a click event is generated. • Input/output programs can generate an event to indicate an input/output event has occurred. – A mouse event is generated when the end user moves the mouse. Softsmith Infotech 21

Binding Events Softsmith Infotech 22

Binding Events In client side web programming, the web browser contains it's own event listener. Therefore you must do two things in order to process an event that has been generated. 1. Write the code that binds the event to the event handler. 2. Write the code for the event handler. Softsmith Infotech 23

Common web browser events Event Description click Used to indicate an entity (usually a control) has been clicked submit Used to indicate the submit button has been pushed mouseover Used to indicate the mouse cursor has been moved over the entity. Typically the entity is a control or an anchor. mouseout Used to indicate the mouse cursor has been moved away from the entity. Typically the entity is a control or an anchor. load Used to indicate the webpage has been completely parsed and loaded into the web browser. unload Used to indicate the webpage has been unloaded from the web browser. Unloading a webpage occurs when the web browser is about to load another webpage. The unload event is the last event that will be generated from the current webpage before the next webpage is loaded. When the web Softsmith 24 browser is closed or exited, the unload event. Infotech is not generated.