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Both programs are designed to illustrate the concept of URL rewriting and are not intended to have any practical value in their own right.

I will explain both programs in fragments. A complete listing of the servlet named Java4560.java is provided in Listing 16 . A complete listing of the JSP program named Java4560b.jsp is provided in Listing 17 .

The servlet program

The servlet named Java4560a.java illustrates session tracking using URL rewriting. In this servlet, parameters containing the historical data are added to the servlet's URLeach time the servlet generates a new HTML page. The updated URL is included as a hyperlink in the new web page.

The servlet output

Each time the servlet is called, it creates and displays an HTML page on the client screen similar to that shown in Figure 2 .

Figure 2 - Servlet output screen.

Missing Figure

The page displays:

  • A hyperlink to the servlet URL labeled Click Here
  • A list of the dates and times on which the user previously called the servlet by clicking on the hyperlink.

A get request

Each time the user clicks the hyperlink, the client sends a GET request to the server. The GET request calls the servlet, which determines the current dateand time in milliseconds relative to January 1, 1970. An HTML page is created and sent back to the client.

Update the parameter string

The current date and time in milliseconds is added as a parameter named item to the servlet URL referenced by the hyperlink in the newly-created HTML page. In addition to the current date and time, the values ofthe previous dates and times on which the user called the servlet are retrieved from the incoming URL parameter string and appended to the new URL parameter string.

In other words, the parameter string values for each successive URL that is generated match those of the previous URL. In addition, a new parameter value isadded that represents the current date and time.

Embed historical data in the web page

In a manner similar to session tracking using hidden fields, the historical data is saved by embedding it in the new HTML page that is returned to the client. There is no requirement to save the historical data in adatabase or in the server's file system.

Figure 3 shows the HTML source code that corresponds to the web page shown in Figure 2 .

Figure 3 - HTML code created by servlet.

Missing Figure

The URL parameter string

The most interesting thing in Figure 3 is the content of Line 4. (Note that Line 4 is wrapped and appears as three physical lines in Figure 3 .) Each large numeric value that you see in Line 4 is the number of milliseconds sinceJanuary 1, 1970 for a particular date and time. These values in milliseconds are translated into actual dates and times and shown in Lines 6 through 9.

No special software requirements

This approach places no special requirements on the server software other than the ability to support Java servlets. The approach should be compatible with all browsers that support hyperlinks.

Interesting code fragments

Beginning of the doGet method

As mentioned earlier, I will explain this program in fragments. Listing 1 shows the beginning of the controlling class and the beginning of the doGet method. You have seen code like this before, so I won't discuss it further.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
Nasa has use it in the 60's, copper as water purification in the moon travel.
nanocopper obvius
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
analytical skills graphene is prepared to kill any type viruses .
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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