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pradeep 17Oct2005 21:49

JSP and Java Servlets
 
JSP

JSP stands for Java Server Pages. JSP is a server-side technology Java Server Pages are an extension to the Java Servlet technology that was developed by Sun.

JSPs have dynamic scripting capability that works in tandem with HTML code, separating the page logic from the static elements -- the actual design and display of the page -- to help make the HTML more functional (i.e. dynamic database queries).

JSPs are not restricted to any specific platform or server. It was originally created as an alternative to Microsoft's ASPs (Active Server Pages). Recently, however, Microsoft has countered JSP technology with its own ASP.NET, part of the .NET initiative.

Java Servlets

Servlets are Java technology's answer to CGI programming. A JSP is translated into Java servlet before being run and it processes HTTP requests and generates responses like any servlet. However, JSP technology provides a more convenient way to code a servlet. Translation occurs the first time the application is run. A JSP translator is triggered by the .jsp file name extension in a URL. JSPs are fully interoperable with servlets. You can include output from a servlet or forward the output to a servlet and a servlet can include output from a JSP or forward output to a JSP.

They are programs that run on a Web server and build Web pages. Building Web pages on the fly is useful (and commonly done) for a number of reasons:

The Web page is based on data submitted by the user. For example the results pages from search engines are generated this way and programs that process orders for e-commerce sites do this as well.

The data changes frequently. For example, a weather-report or news headlines page might build the page dynamically, perhaps returning a previously built page if it is still up to date.

The Web page uses information from corporate databases or other such sources. For example, you would use this for making a Web page at an on-line store that lists current prices and number of items in stock.

Advantage of Servlets Over CGI

Java servlets are more efficient, easier to use, more powerful, more portable, and cheaper than traditional CGI and than many alternative CGI-like technologies. More importantly, servlet developers get paid more than Perl programmers.

Efficient

With traditional CGI, a new process is started for each HTTP request. If the CGI program does a relatively fast operation, the overhead of starting the process can dominate the execution time. With servlets, the Java Virtual Machine stays up, and each request is handled by a lightweight Java thread, not a heavyweight operating system process. Similarly, in traditional CGI, if there are N simultaneous request to the same CGI program, then the code for the CGI program is loaded into memory N times. With servlets, however, there are N threads but only a single copy of the servlet class. Servlets also have more alternatives than do regular CGI programs for optimizations such as caching previous computations, keeping database connections open, and the like.

Convenient

Hey, you already know Java. Why learn Perl too? Besides the convenience of being able to use a familiar language, servlets have an extensive infrastructure for automatically parsing and decoding HTML form data, reading and setting HTTP headers, handling cookies, tracking sessions, and many other such utilities.

Powerful

Java servlets let you easily do several things that are difficult or impossible with regular CGI. For one thing, servlets can talk directly to the Web server (regular CGI programs can't). This simplifies operations that need to look up images and other data stored in standard places. Servlets can also share data among each other, making useful things like database connection pools easy to implement. They can also maintain information from request to request, simplifying things like session tracking and caching of previous computations.

Portable

Servlets are written in Java and follow a well-standardized API. Consequently, servlets written for, say I-Planet Enterprise Server can run virtually unchanged on Apache, Microsoft IIS, or WebStar. Servlets are supported directly or via a plugin on almost every major Web server.

Inexpensive

There are a number of free or very inexpensive Web servers available that are good for "personal" use or low-volume Web sites. However, with the major exception of Apache, which is free, most commercial-quality Web servers are relatively expensive. Nevertheless, once you have a Web server, no matter the cost of that server, adding servlet support to it (if it doesn't come preconfigured to support servlets) is generally free or cheap.

What is JSP?

Java Server Pages (JSP) is a technology that lets you mix regular, static HTML with dynamically-generated HTML. Many Web pages that are built by CGI programs are mostly static, with the dynamic part limited to a few small locations. But most CGI variations, including servlets, make you generate the entire page via your program, even though most of it is always the same. JSP lets you create the two parts separately. Here's an example:
Code:

<html>
 Welcome to Our Store<head>
 <body>
 <h1>Welcome to Our Store
 <small>Welcome,
 <!-- User name is "New User" for first-time visitors -->
 <% out.println(Utils.getUserNameFromCookie(request)); %>
 To access your account settings, click
 <a href="account-settings.html">here.
 <p>Regular HTML for all the rest of the on-line store's Web page.
 </body>

Advantages of JSP

Over Active Server Pages (ASP)


ASP is a similar technology from Microsoft. The advantages of JSP are twofold. First, the dynamic part is written in Java, not Visual Basic or other MS-specific language, so it is more powerful and easier to use. Second, it is portable to other operating systems and non-Microsoft Web servers.

Over Pure Servlets

JSP doesn't give you anything that you couldn't in principle do with a servlet. But it is more convenient to write and to modify regular HTML than to have a zillion println statements that generate the HTML. Plus, by separating the look from the content you can put different people on different tasks: your Web page design experts can build the HTML, leaving places for your servlet programmers to insert the dynamic content.

Over Server-Side Includes (SSI)

SSI is a widely-supported technology for including externally-defined pieces into a static Web page. JSP is better because it lets you use servlets instead of a separate program to generate that dynamic part. Besides, SSI is really only intended for simple inclusions, not for "real" programs that use form data, make database connections, and the like.

Over JavaScript

JavaScript can generate HTML dynamically on the client. This is a useful capability, but only handles situations where the dynamic information is based on the client's environment. With the exception of cookies, HTTP and form submission data is not available to JavaScript. And, since it runs on the client, JavaScript can't access server-side resources like databases, catalogs, pricing information, and the like.

Over Static HTML

Regular HTML, of course, cannot contain dynamic information. JSP is so easy and convenient that it is quite feasible to augment HTML pages that only benefit marginally by the insertion of small amounts of dynamic data. Previously, the cost of using dynamic data would preclude its use in all but the most valuable instances.

hasmukh 31Jul2006 10:06

Re: JSP and Java Servlets
 
Bandhu i used to develop web page using ASP and ASP.net , then i decided to dirty my hands with JSP and believe me ..... Its just toughest thing to do . May be i selected wrong book to start with .

Suggest a good book for JSP

I am using java server pages in 24 hours---sams series

Thanks in Advance

:) HASMUKH :)

shabbir 1Aug2006 16:41

Re: JSP and Java Servlets
 
JSP resources have good list of books as well.

ali hasnain 13Jun2007 10:38

Re: JSP and Java Servlets
 
I have post my query from long time. nobuddy reply my query. It is request you to please give me the solution.

Dear All,

I need your help on below problems.

Hereís in my use two computers one is in my home use and second in my office use. On both computers I found some problems. Hereís I am mentioning the problem of my Computers

At home use: I am using windows me on my home computer. And I have Avg antivirus on my computer. The folder option not display on my control panel and tool menu and I found the folder.exe file on my computer and I delete this file with my pc but it comes again. Please advise and If you have any tips to improve the speed of my pc please advise.

At Office Use: I am using windows 2000 on my office computer and I have Norton antivirus on my computer. When my PC boot completely an error comes on my window screen RHVOST.EXE and another problem is that I canít load my Ms Office Excel file directly. First I run the Office Excel and then browse the required file. Please advise.

I hope you will entertain my quires. Thanks in advance.


Regards,

Ali hasnain

parvez.yu 6Mar2008 16:59

Re: JSP and Java Servlets
 
jsp is tough ,but i like it more than asp

prabhat1 23Mar2008 02:28

Re: JSP and Java Servlets
 
Quote:

Originally Posted by hasmukh
Bandhu i used to develop web page using ASP and ASP.net , then i decided to dirty my hands with JSP and believe me ..... Its just toughest thing to do . May be i selected wrong book to start with .

Suggest a good book for JSP

I am using java server pages in 24 hours---sams series

Thanks in Advance

:) HASMUKH :)


hiiiiiiii Mr. pradeep i m new to JSP kindly help me in updating database(SQL server 05) thru JSP but always getting unexpected results like insertion of null values,persistence of previous values into the string........looking forward for your help.......thanks

pradeep 23Mar2008 09:58

Re: JSP and Java Servlets
 
We'll need to have a look at your code to debug what's wrong, please your DB insertion code.

prabhat1 23Mar2008 13:21

Re: JSP and Java Servlets
 
******** post by prabhat*********for database updation
the relation table is" test(roll(int),sub_code(int),stud_name(varchar),su b_name(varchar),fees(money),status(bit)
*********
basic prob is that when updation is done the form keeps the prevoius values of updation and that leads to incosistent results..........

HTML Code:

<%@ page import="java.sql.*"%>
<html>

<head><title>table update test</title></head>
<body>
<form name="f1">

<%
       

int id=0;


Connection con = null;
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver") ;
con=DriverManager.getConnection("jdbc:odbc:SQL_SERVER;user=sa;password=password@123");
       
        Statement stmt=con.createStatement();

// for test table update         

    int id1=0;
    float id2=0;
        String st=request.getParameter("cmbroll");
        String st1=request.getParameter("txtsub_code");
        String st2=request.getParameter("txtstud_name");
        String st3=request.getParameter("txtsub_name");
        String st4=request.getParameter("txtfees");
        boolean st5=Boolean.parseBoolean(request.getParameter("txtstatus"));

        if(st!=null)
        {
                  id=Integer.parseInt(st);
        }
       
        if(st1!=null)
        {
          id1=Integer.parseInt(st1);
        }
       
        if(st4!=null)
        {
                id2=Float.parseFloat(st4);
        }
       
       
         
       
%>


<h2>roll<sup>*</sup><select name="cmbroll" onChange="document.f1.submit()"></h2>
<option>select</option>
 <%
 ResultSet rs=stmt.executeQuery("select roll from test ");
        while(rs.next())
        {
       
                int x=rs.getInt("roll");
       
       
  %>

<option
<% if(id!=0 && id==x)
out.println("selected");
 %>


>


<%= x %></option>

<%

}

%>
 
</select>

 <%
 
 
       
        if(id!=0)
        {
       
                ResultSet rs1=stmt.executeQuery("select * from test where roll="+id);
                while(rs1.next())
                {
                          int code=rs1.getInt("
sub_code");
                          String sname=rs1.getString("stud_name");
                          String sbname=rs1.getString("sub_name");
                          float fss=rs1.getFloat("fees");
                          boolean sts=rs1.getBoolean("status");



                         
       
       
  %>

 
 
  <h2>Subject Code<input type="text" name="txtsub_code" value="<%=code%>"></h2>
  <h2>Student Name<input type="text" name="txtstud_name" value="<%=sname%>"></h2>
  <h2>Subject Name<input type="text" name="txtsub_name" value="<%=sbname%>"></h2>
  <h2>Fees<input type="text" name="txtfees" value="<%=fss%>"></h2>
  <h2>Status<input type="text" name="txtstatus" value="<%=sts%>"></h2>
  <input type="submit" value="update">
 
  <%
            }
                  if(st1!=null && id1!=0 && st3!=null && id2!=0)
                  stmt.executeUpdate("update test set sub_code="+id1+",stud_name='"+st2+"',sub_name='"+st3+"',fees="+id2+",status='"+st5+"' where roll="+id);

  }
 
 
 
 %>

 
 </form>
 </body>
 </html>

looking forard for your response......
thanks .........
prabhat....

prabhat1 23Mar2008 14:00

Re: JSP and Java Servlets
 
hiiiiiiiii.. pradeep .......i hope there is no changes in the code.........thn where was d problem is .......

pradeep 23Mar2008 22:42

Re: JSP and Java Servlets
 
You should make an update only when the second form is posted, here you are running the update while displaying the form...make a flowchart of your program then you'll understand!


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