JSP/Servlet Core Concept

JSP/Servlet
Core Concepts
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Web Application
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Web Server
JVM
JSP/Servlet Container
JSP/Servlet
Request
Response
HTML/ JSON/XML
HTTP
Browser

Web Servers
Tomcat
JBoss
Jonas
Jetty
Weblogic
Web Sphere
Glass Fish
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My First html – Hello.html
<HTML>
<HEAD></HEAD>
<BODY>
<center>
<b><u>Hello Java</u></b>
</center>
</BODY>
</HTML>

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Write code inside HTML – Hello.jsp
 Print ‘Hello Java’ 5 times
<HTML>
<BODY>
<%
for (int i=0; i< 5; i++ ){
%>
<H1>Hello Java</H1>
<%
}
%>
</BODY>
</HTML>
Scriptlet –
<% code fragment %>
Contains :
1. Statements
2. Variables declarations
3. Expressions

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Display a value - Expression
Print ‘Hello Java’ 5 times with sequence numbers
<HTML>
<BODY>
<%
for (int i=0; i< 5; i++ ){
%>
<H1><%=i+1%> Hello Java</H1>
<%
}
%>
</BODY>
</HTML>
Expression –
<%= expression %>
Contains :
1. Expressions or RHS values

User Entry Form in HTML
 <FORM METHOD=GET ACTION=“HelloName.jsp">
 Text Field<INPUT TYPE="text" NAME="userId">
 Password Field<INPUT TYPE="password" NAME ="pwd">
 Checkbox <INPUT TYPE="checkbox" NAME=“kid" VALUE="1">
 Radio Button
 <INPUT TYPE="radio" NAME="degree" VALUE="MCA">
 <INPUT TYPE="radio" NAME="degree" VALUE="BE">
 Button <INPUT TYPE="button" NAME="action" VALUE="Go">
 Submit Button<INPUT TYPE="Submit" VALUE="Submit">
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More Form Fields
 Reset Button<INPUT TYPE="reset" VALUE="Clear"><BR>
 TextArea<TEXTAREA NAME="tArea" ROWS="2"
COLS="20"></TEXTAREA><BR>
 List <SELECT NAME="list">
o <OPTION VALUE="1">ONE</OPTION>
o <OPTION VALUE="2">TWO</OPTION>
 </SELECT><BR>
 Hidden Value <INPUT TYPE="hidden" NAME="id" VALUE="123">
 </FORM>
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Submit Data to JSP
<HTML>
<HEAD></HEAD>
<BODY>
<FORM METHOD=“GET” ACTION="HelloName.jsp">
Enter Name
<INPUT TYPE="text" NAME=“name">
<INPUT VALUE="GO" TYPE="submit">
</FORM>
</BODY>
</HTML>
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GET
POST
On Submit - http://localhost:8080/myapp/HelloName.jsp?name=Ram

Receive data in the JSP
Read parameter from request object and display.
<HTML>
<BODY>
<%
String name = request.getParameter(“name");
String lastName = request.getParameter(“surname");
for (int i=0; i< 5; i++ ){
%>
<H1><%=i+1%> Hello <%=name%></H1>
<%
}
%>
</BODY>
</HTML>
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http://localhost:8080/myapp/HelloName.jsp?name=Ram&surname=Sharma
GET
Method

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JSP is a Servlet
Hello.JSP Hello.Java Hello.class
JSP Servlet Class
Precompiler Compiler
•A JSP is converted into servlet on its first client call.

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How to write a Servlet
1. Extend your servlet by javax.servlet.http.HttpServlet class
2. Override doGet() method to handle GET request or override
doPost() method to handle POST request
3. Both methods receive two parameters HttpServletRequest and
HttpServletResponse
1. HttpServletRequest contains request parameters
2. HttpServletResponse is used to send data back to the client
4. Map servlet with a URL using @WebServlet() annotation. This
URL is used by client to access the servlet from browser.

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HelloWorld.java
package com.sunilos.servlet;
@WebServlet(“/HelloWorld”)
public class HelloWorld extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response) throws IOException,ServletException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<body>");
out.println("<h1>Hello World!</h1>");
out.println("</body>");
out.println("</html>");
out.close();
}
}
http://localhost:8080/demo/HelloWorld

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Navigate from one JSP to another JSP or Servlet
A.jsp
req
B.jsp
req
C.jsp
req
Req
Forward
Forward
Response
Browser

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Forward
JSP
 <jsp:forward page=“New.jsp” />
Servlet
 RequestDispatcher rd =request.getRequestDispatcher(“/New.jsp");
 rd.forward(request, response);

Disclaimer
This is an educational presentation to enhance the
skill of computer science students.
This presentation is available for free to computer
science students.
Some internet images from different URLs are
used in this presentation to simplify technical
examples and correlate examples with the real
world.
We are grateful to owners of these URLs and
pictures.
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Thank You!
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JSP/Servlet Core Concept

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