Create A Jsp -based Web Application – Neha Vaidya is a technology enthusiast in Java, Image Processing, Cloud Computing, Hadoop. Passionate about Java, Image Processing, Cloud Computing, Hadoop technology.
In recent trends, billions of bytes of data are generated on a daily basis. Many of us believe in the misconception that all web applications are built on web frameworks like HTML, PHP, JavaScript etc. But did you know that web applications can be Java-based using services like servlets and JSPs? In this Servlet and JSP tutorial, let’s dive deeper into the technology and understand how it is useful for building a web application.
Create A Jsp -based Web Application
You can also go through this Servlet and JSP tutorial record where you can understand the topics in detail with examples.
Jsp Architecture And Lifecycle
Servlet and JSP Tutorial This tutorial will talk about Servlet and JSP, its life cycle and various steps to create Servlet and Java Server Pages.
The Web is an Internet server system that supports formatted documents. Documents are formatted using a markup language called HTML (Hypertext Markup Language) that supports links to other documents such as graphics, audio, video files, etc.
Now that we know what the web is, let us go further and understand what a website is. So a website is a collection of static files, such as web pages such as HTML pages, images, graphics, etc. And, web application is a web page with dynamic functionality on the server. Google, Facebook, Twitter are examples of web applications.
Clients and servers use HTTP to communicate over the web. It is considered a stateless protocol because it supports only one connection request. HTTP connects to the server to send a request to the client and then disconnects. And this process allows more users to connect to a given server in a given period of time. Here, the client sends an HTTP request and the server responds to the client with an HTML page using HTTP.
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That was all for HTTP and the web. Now let’s go deep into servlet and understand its working process.
A servlet is a server-side Java program module that handles client requests and implements the servlet interface. Servlets can respond to any type of request and are typically used to extend applications hosted by web servers.
As you can see in this diagram, a client sends a request to the server and the server generates the response, parses it and sends the response to the client.
The entire lifecycle of a servlet is managed by the servlet container, which uses the javax.servlet.Servlet interface to understand and manage servlet objects.
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Next, a servlet is started by calling the init() method.
Then, a servlet callsservice() method is called to inform the servlet about the client’s request to process the client’s request.
Finally, a servlet is terminated by calling thedestroy(). Thedestroy() method runs only once in the lifetime of a Servlet and signals the termination of the Servlet instance.
The init() and delete() methods are called only once. Finally, a servlet is garbage collected by the JVM garbage collector. So this completes the life cycle of a servlet. Now, let me walk you through the steps to create a Java server.
Solution: A Tutorial On Java Servlets And Java Server Pages Jsp Web
To create a servlet, we need to follow several steps in a row. They are as follows:
To run a servlet program, we need to install and configure the Apache Tomcat server. Eclipse for Java EE provides Apache Tomcat built-in. Once the server is configured, you can start with your program. One important thing to mention – you need 3 files for each servlet program – an index.html file, a java class file and a web.xml file. The first step is to create a dynamic web project and then proceed further.
Now, let’s take an example where I will create a simple login servlet and display the output in the browser.
In the above code, I have set a condition – if username and password are same then only it will be shown as successfully registered, otherwise login will be rejected. After writing the Java class file, the last step is to add the mapping to the web.xml file. Let’s see how to do it.
A Sample Java Web Application
The web.xml file will be present in the WEB-INF folder of your web content If it is not present then you can click on Generate Deployment Descriptor Stub by clicking on Deployment Descriptor. Once your web.xml file is ready, you need to add maps to it. Let’s see how mapping is done using the following example:
So this is how a servlet is created and configured. Let us now see what is generic servlet and how to create it.
It is a protocol-independent servlet that must override the service() method to handle client requests. The service() method accepts two arguments, the ServletRequest object and the ServletResponse object. The job of the Request object is to notify the servlet about the client’s request while the Response object returns a response to the client. GenericServlet is an abstract class and has only one abstract method, which is service(). The whole idea is that when we create a generic servlet by extending the GenericServlet class, we want to respond to the service() method.
Now, let’s see how to create and call a generic servlet. Again I will encode the 3 files as shown below:
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We are creating an HTML file that will call the servlet as soon as the web page link is clicked. Create this file in the WebContent folder. The path to this file should be: WebContent/index.html
Here we will create a generic servlet by extending the GenericServlet class. When creating a GenericServlet, you must override the service() method. Right click on the src folder and create a new class file and name the file generic. The file path should be like this: Java Resouces/src/default package/generic.java
This file can be found in the path WebContent/WEB-INF/web.xml. In this file, we will map the servlet to the specified URL. Since we are calling the welcome page as soon as we click the onindex.html link, this will set the welcome page in the servlet class we created above.
Next, start your Tomcat server and run the servlet. You will get desired results. So that was all for generic servlets. Now let’s go further and understand the concept of session tracking.
Jsp Word Document
A session means a specific time interval. Session tracking is a technique for maintaining user state (data) also known as evaluation management in servlets. Therefore, whenever the user queries the server, the server treats the request as a new request.
To identify specific users, we require session tracking. Now let’s go further and look at one of the session tracking techniques. Cookies
Acookies are small pieces of information that persist between multiple customer requests. A cookie consists of a name, a single value, and optional attributes such as a comment, path and domain qualifiers, a maximum age, and a version number.
Since this is a session tracking technique, by default each request is treated as a new request.
Java Server Pages
In it, we add a cookie with the response from the servlet. So cookies are stored in the browser cache. After that, when a request is sent by the user, a cookie will be automatically added to the request.
Now that you understand how cookies work, let’s look at a short example that demonstrates the use of cookies.
Let’s see an example of creating a cookie, adding a response and getting the results. Here I will write 2 java class files named MyServlet1 and MyServlet2.
Now you are ready to run. You can run the code and get the desired result. This is how a cookie works. So that was about Servlets. If you want to learn Java Advanced in depth, you can check out this Advanced Java Tutorial. Now that you have gained some knowledge about Servlets, let’s go ahead and understand what Java Server Pages are.
Jsp & Servlet In Java. When It Comes To Java Web Development…
JSP Server Pages Java is a technology used to create web applications such as servlet technology. It is an extension of servlet – as it provides more functionality than servlet like Expression Language, JSTL etc. A JSP page consists of HTML tags and JSP tags. JSP pages are easier to maintain than servlets because we can separate design and development.
Now that we know what JSP is, let’s compare JSP with Servlet and understand which is best suited for the web.
I hope you understand the difference between JSP and Servlets. Now, let’s go further and understand the elements of scripting.
The scripting component provides the ability to embed Java code within JSP. There are three types of script elements:
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In this example, we have created two files index.html and welcome.jsp. The index.html file gets the username from the user and the welcome.jsp file prints the username along with the welcome message. Now, look at the code.
Now let’s take a small example of displaying the current time. To display the current time, we use the getTime() method of the Calendar class. GetTime() is an instance method of the Calendar class, so we called it after getting an instance of the Calendar class with the getInstance() method.
In the following JSP statement tag example, we are defining the method that returns the cube
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