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Which method must to override in Servlet?
There are 3 main types of requests that get processed by a Servlet. They are: • Get • Post • Put Each of them have a corresponding doXXX() method in the Servlet class which would be: • doGet • doPost • doPut You must override either of these methods based on the type of requests that would be processed by your servlet
What is doGet method in servlet?
The doGet() method is the method inside a servlet that gets called every time a request from a jsp page is submitted. The control first reaches the doGet() method of the servlet and then the servlet decides what functionality to invoke based on the submit request. The get method called when the type of page submission is "GET" There is another way of submitting requests from a jsp page is "POST" and when that happens it calls the doPost() method inside the servlet.
What is doPost in servlet?
doPost() is the method in the servlet that is used to service the Http requests submitted using the Post option. HTML forms can be submitted in two ways using the Get method and the Post method. You can specify the method while declaring the form itself. So you will have two methods in the servlet doGet() and doPost() each for one of them
What is difference between GET and POST in servlets in java?
The difference between a GET and a POST is the way data is transferred to a servlet. With a GET, the URL will show each name/value pair on the query string in the URL. For example, if you had a form with a field named 'foo,' and when submitted had a value of 'bar,' the URL might be something like this: http://www.example.com/servlet?foo=bar With a POST, this information is not visible in the URL. Instead, it is transferred in the HTTP headers. As far as the actual servlet is concerned, there is not a great deal of difference when it comes to getting the parameters. Whether you use a GET or a POST, you still use request.getParameter("foo"); to get the value. The method used in the Servlet for processing either a GET or a POST is different too. If you use a GET, the method that is called is doGet(HttpServletRequest, HttpServletResponse). The doGet method is also called if there is no GET or POST data. If you use a POST, the method called is doPost(HttpServletRequest, HttpServletResponse).
Why do you use superclass init method inside your init method in a servlet?
Because, that is how all Java classes work. When a class is initialized/created all the classes it extends from (its super classes) need to be initialized as well.
Why no need of main in servlet?
I think you mean: why isn't there a function required in a servlet like the following? public static void main(String[] args) { } Because the main() method is what the Java VM 'boots up' into...it's the first thing the JVM executes. A servlet, however, is running inside a servlet container (e.g., Tomcat), which is running inside a JVM. *That* JVM gets started with a main() method, but unless you intend to run your servlet from the commandline, there's no explicit need for a main() method.
Which method must to override in Servlet?
There are 3 main types of requests that get processed by a Servlet. They are: • Get • Post • Put Each of them have a corresponding doXXX() method in the Servlet class which would be: • doGet • doPost • doPut You must override either of these methods based on the type of requests that would be processed by your servlet
What is doGet method in servlet?
The doGet() method is the method inside a servlet that gets called every time a request from a jsp page is submitted. The control first reaches the doGet() method of the servlet and then the servlet decides what functionality to invoke based on the submit request. The get method called when the type of page submission is "GET" There is another way of submitting requests from a jsp page is "POST" and when that happens it calls the doPost() method inside the servlet.
How does Apache httpd work?
Tomcat is a servlet container, and the following is how a servlet container works The init, service, and destroy methods are the servlet's lifecycle methods. The init method is called once by the servlet container after the servlet class has been instantiated to indicate to the servlet that it being placed into service. The init method must complete successfully before the servlet can receive any requests. A servlet programmer can override this method to write initialization code that needs to run only once, such as loading a database driver, initializing values, and so on. In other cases, this method is normally left blank. The service method is then called by the servlet container to allow the servlet to respond to a request. The servlet container passes a javax.servlet.ServletRequest object and a javax.servlet.ServletResponse object. The ServletRequest object contains the client's HTTP request information and the ServletResponse encapsulates the servlet's response. These two objects enable you to write custom code that determines how the servlet services the client request. The servlet container calls the destroy method before removing a servlet instance from service. This normally happens when the servlet container is shut down or when the servlet container needs some free memory. This method is called only after all threads within the servlet's service method have exited or after a timeout period has passed. After the servlet container calls destroy, it will not call the service method again on this servlet. The destroy method gives the servlet an opportunity to clean up any resources that are being held (for example, memory, file handles, and threads) and make sure that any persistent state is synchronized with the servlet's current state in memory. For Better Picture, Visit below article full of images to clear the concept : http://shivasoft.in/blog/java/servlet/how-container-handles-the-servlet-request/
Describe the life cycle of servelet?
Each servlet has the same life cycle: * A server loads and initializes the servlet * The servlet handles zero or more client requests * The server removes the servlet (some servers do this step only when they shut down) == When a server loads a servlet, the server runs the servlet's init method. Initialization completes before client requests are handled and before the servlet is destroyed. Even though most servlets are run in multi-threaded servers, servlets have no concurrency issues during servlet initialization. The server calls the init method once, when the server loads the servlet, and will not call the init method again unless the server is reloading the servlet. The server can not reload a servlet until after the server has destroyed the servlet by calling the destroy method. == After initialization, the servlet is able to handle client requests. This part of the servlet life cycle was handled in the previous lesson. == Servlets run until the server are destroys them, for example, at the request of a system administrator. When a server destroys a servlet, the server runs the servlet's destroy method. The method is run once; the server will not run that servlet again until after the server reloads and reinitializes the servlet. When the destroy method runs, another thread might be running a service request. The Handling Service Threads at Servlet Termination lesson shows you how to provide a clean shutdown when there could be long-running threads still running service requests.
How do you get servlet context instance to servlet?
You can get the ServletContext instance in a servlet by using the getServletContext() method provided by the HttpServlet class, which is the base class for servlets. This method returns the ServletContext object associated with the servlet. For example: ServletContext context = getServletContext();
What is doPost in servlet?
doPost() is the method in the servlet that is used to service the Http requests submitted using the Post option. HTML forms can be submitted in two ways using the Get method and the Post method. You can specify the method while declaring the form itself. So you will have two methods in the servlet doGet() and doPost() each for one of them
Is it possible to synchronize a service method in Servlet?
Yes, by implementing SingleThreadModel interface
What are types of servlet?
Http servlet and Generic servlet
How many times init method called if more then one instence are in servlet?
I have two questions how many times a method, modules or subroutines can be called? in most languages, how a variable is passed to a method?
Which method is used to retrive an initialitation parameters from a servlet context?
ServletContext sc=getServletContext(); String s=sc.getInitParameter();
What is java servlet chaining?
Servlet Chaining means the output of one servlet act as a input to another servlet. Servlet Aliasing allows us to invoke more than one servlet in sequence when the URL is opened with a common servlet alias. The output from first Servlet is sent as input to other Servlet and so on. The Output from the last Servlet is sent back to the browser. The entire process is called Servlet Chaining.
