Servlets introduction for beginners with explanation, examples and screenshots
For easy understanding, the Servlets Tutorial Architecture is given in Question/Answer format. 1. What is Component? A Component is a reusable software unit. 2. What is server-side component? In client/server communication, a server-side component is that one which is automatically invoked against client request, executed and responses to client fulfilling the requirement. 3. What is …
Servlets Tomcat: Install Tomcat server of your choice version by downloading from Apache site. Many versions of Tomcat can be found in the following link. http://tomcat.apache.org/download-60.cgi Check with the documentation of what JDK or JRE version is compatible to the specific Tomcat version. For example I loaded Tomcat 5.0 and is compatible with JDK 6.0. …
1. What is Deployment? Copying the .class file of the Servlet from the current directory to the classes folder of Tomcat (or any Web server) is known as deployment. When deployed, Tomcat is ready to load and execute the Servlet, at anytime, at the client request. 2. What is Deployment Descriptor? As the name indicates, …
About HTTP Protocol What is HTTP (HyperText Transfer Protocol) Protocol? A protocol sets standards for communication between systems, client to server or among servers. HTTP is specially meant to communicate between Client and Server using Web (or Internet). It was developed by W3C (World Wide Web Consortium) around in the year 1995. HTTP is an …
After going through the introduction and architecture of servlets, let us write a simple Login Validation program. As you have seen in the architecture, there will be two programs – one running on client machine and the other on server. Servlet Example explained in 10 steps First let us write the client-side program. I. Client …
In the first simple program Login Screen Validation, the data sent by the client is extracted from HttpServletRequest object req, using getParameter(String) method. The getParameter(String) method works to read a single text box (or any FORM field) only. The HttpServletRequest interface comes with another method getParameterNames() (inherited from ServletRequest interface) to read all the FORM …
Read Client HTML Form data with getParameterNames() Read More »
A Servlet may have some values needed for it’s execution or a Programmer may require some values to be fed to Servlet needed in the coding for execution. These values are specific to a particular Servlet and not required for all Servlets. For this, the deployment descriptor web.xml, comes with <init-param> tag and an example …
ServletConfig Example init-param read getInitParameter() Read More »
In this example, a dynamically created HTML form is sent to the client on-the-fly. Start reading. his is the modified code of the Login Screen Validation. In the first program, the user name and password are read by the Servlet, validated and sent back the result of validation (valid or invalid) as response. The modification …
Send Dynamically created HTML form to client in Servlets Read More »
It is the modification of the first program Login Validation. The modification is instead of sending INVALID message, a new HTML form is sent to the user wherein the user can fill up again and send. This HTML form is existing already on the server. It is not created on the fly. That is why, …
sendRedirect() Example Servlets – Send HTML form to Client Read More »
All the time we are accustomed to read client data with getParameter() method, most probably from HTML text fields. But, HTML FORM tag includes many GUI components like radio buttons, SELECT drop down lists, text areas etc. This Client HTML comes with rarely used FORM fields. To do with, a Student Feedback Form is designed …
One of the activities of a Servlet Developer is to read HTML form data sent by the client by clicking over Submit button. The data sent by the client lands finally in ServletRequest/HttpServletRequest object passed as parameter to service() method. To retrieve the data from ServletRequest object, the ServletRequest interface comes with three methods mostly …
All the HTML forms so far used contains only one submit button. But yet many times, it will be necessary to have multiple submit buttons in a single HTML form. User is at choice to click any one submit button. Now the question is how the Servlet knows from which submit button the request came …
This Servlet Life Cycle Tutorial gives the meaning of life cycle, the methods involved, their importance and how and where to use in coding 1. What is Servlet Life Cycle? Definition: Different states in which a Servlet exists between its object creation and object garbage collection is known as life cycle of Servlet. 2. Who …
After learning what Servlet life cycle is and the methods involved, let us go for an example involving the life cycle methods. I take the opportunity to connect to database and read table records using life cycle methods. Or to say, illustration of life cycle methods and learning JDBC through Servlet goes in a single …
So far all the earlier examples, we used to send text or HTML messages (text/html) to client. Now-a-days, images are also playing important role in client/server communication. For example, you go to Bank and give a self cheque to draw some money. Immediately, the Bank clerk checks your face to know exactly you are withdrawing …
Sometimes, the client may ask the Servlet to send the file contents of a file existing on the server. It is not file download. Here, the Servlet reads manually line-by-line and send each line separately to client. Read Servlet Read text file. Example on Servlet Read text file Client HTML Program: TextFileReadAndSend.html Getting File contents …
Servlet Read text file and Return contents Example Read More »
Earlier we did a program where client requested for a text file; but the case now is with HTML file. Now it is HTML file with Servlet read html file. If the user sends a request for HTML file, when it comes to the browser, it is interpreted and output of the HTML file is …
Before going ServletContext Example, see the difference between <init-param> and <context-param>, both written in web.xml file. What is <init-param>? portnumber 8888 We have seen the above code in Servlet web xml init param Example using ServletConfig where the "portnumber" and "8888" are accessible for the particular servlet "ReadInitParamValues". Other servlets in the container cannot access …
Communication is very needed between Servlets and Container. Towards this goal Servlet API comes with three interfaces. Following table gives the list and their functionality. Interface Functionality Example with explanation and screenshots available at ServletConfig Used to communicate with Container to read web.xml (meant for one servlet only) init-param Example using ServletConfig ServletContext Used to …
Communication (passing data in between) is an important concept in computers and for this Servlets is no exception. Towards this goal, we studied reading private data of a servlet and reading global data by all servlets. Now let us see how to pass data between two servlets (one-to-one) and for this Servlet API comes with …
