General discussion on Servlets given indepth like differences, WAR file creation etc.
First let us know the earlier Web technologies, their drawbacks and how they are overcome in Servlets. Earlier to Servlets, the other Web technologies existed were CGI/PERL and ASP. Servlets vs CGI vs ASP I. CGI/PERL (Common Gateway Interface/Practical Extraction and Report Language) CGI/Perl is process based. For every request a separate process is started. …
I. Servlets Advantages over ASP are tabulated. Feature Servlet ASP Platform-independent Servelts are platform-independent being written in Java. Works on Windows, a Microsoft product, only. Java Benefits Servlets are written in Java and can take advantage of OOPs, robustness and most important garbage collection in code development. Written in VBScript (or JScript), a Microsoft product, …
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Earlier we have seen the ways of receiving data from client. Now let us do with response. The response object functionality is to send data to client of what client is interested. For this, response uses IO Streams. There are two streams involved depending on the nature of data like text data or binary data. …
1. What is SingleThreadModel? It is an interface from javax.servlet package used with Servlets. It is marker interface having no methods. Few servlets may require this to implement. 2. Are Servlets multithreaded? Yes, Servlets are multithreaded being Java supports multithreading. 3. Explain how Servlets are multithreaded? First time when a request comes to a Web …
ServletConfig interface is specific to a particular Servlet. It cannot read other Servlet <init-param> data because <init-param> is written within <servlet> tag. What is ServletContext? On the contrary, ServletContext is global. The ServletContext object can be used by all the Servlets under execution in an application. Application comprises of many programs bundled together to achieve …
What is Servlet vs GenericServlet vs HttpServlet? Servlets are platform-independent server-side components, being written in Java. Before going for differences, first let us see how the three Servlet, GenericServlet, HttpServlet are related, their signatures and also at the end similarities. See how to write a Servlet. public class Validation extends HttpServlet To write a servlet, …
When the client clicks the submit button and sends a request to the server to invoke some Servlet (by giving the alias name of Servlet), the Servlet container loads the servlet and calls the service() method. The container also creates objects of ServeltRequest and ServletResponse and passes them to service() method. The ServletRequest receives the …
When the client sends a request to the Web server, the server loads the concerned Servlet and executes the service() method. In the process of execution, the container creates objects of ServletRequest and ServletResponse and passes them to the service() method. This is discussed in First Example – Login Screen Validation. ServletResponse vs HttpServletResponse Observe, …
Both HttpServletRequest and HttpServletResponse are inevitable in each Servlet, the Programmer write. Both exist in Servlet code as parameters to service() method. Even a Novice should be acquainted of these two interfaces. List of Differences HttpServletRequest vs HttpServletResponse Both are interfaces from javax.servlet.http package. They are derived from ServletRequest and ServletResponse interfaces. Both objects are …
After knowing fully of ServletConfig and ServletContext with examples, explanation and screen outputs, it is time to compare them for still better understanding. ServletConfig vs ServletContext: Following table summarizes the differences between the two. S.No. ServletConfig ServletContext 1 Defined in javax.servlet package. Defined in the same javax.servlet package. 2 Values are placed in web.xml file. …
Before going into init-param vs context-param, let us know the meaning and purpose of init-param and context-param in Servlet coding. 1. 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 …
We have seen earlier include() and forward() methods of
We have seen two programs with include() and forward() methods of RequestDispatcher. In both the programs, getRequestDispatcher(String path) of ServletRequest is used to obtain an object of RequestDispatcher. Infact, RequestDispatcher object can be obtained in another way also – using javax.servlet.ServletContext. The same getRequestDispatcher(String path) method exist in ServletContext also. That is, the same method …
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Yes, you can have as per rule. It is executed even before init(). Then why generally we avoid constructor in Servlets. First let us write one simple example and see it is true or not; then we will go into details. Example on Servlet Constructor import javax.servlet.ServletException; import javax.servlet.http.*; import java.io.*; public class ConstructorServlet extends …
What is Page Refresh Servlets? Sometimes, user requires latest information on Cricket score or latest Share prices etc. where he is required to refresh the page, say by typing F5 key. To make user’s job easier, Servlet comes with setHeader("refresh", "5") method. With this method, the same Servlet is called for every 5 seconds once …
We know when a Servlet is loaded, the Servlet container creates an object of Servlet, calls service() method, creates an object of HttpServletRequest and also an object of HttpServletResponse and passes these objects to service() method. The job of HttpServletResponse (referred as response object in this discussion) is to pass data required by the client …
1. What is Status code in HTTP? 2. Why status codes? This gives introduction to status code. Here, I talk in my own style for a better understanding for a very beginner. Suppose, I develop a software product like School product and supplied to a School. Well, the software is working nice to the satisfaction …
After knowing clearly in a simple way "what a status code is?" and "why it is needed?", let us dig further in the subject. A status code is a numeric value with 3 digits. W3C divided all the status codes broadly into 5 categories starting with digit 1 (of type 1xx), with digit 2 (of …
Before going through, it is advised to read What is Status code in HTTP Servlets? and Classification of Web Status Codes in HTTP. Following table gives you the list of Web status codes. Only commonly occurring are given. Status code Value Description 100 Continue 101 Switching Protocols 102 Processing 200 OK 201 Created 202 Accepted …
What is 404 Not Found Errror? It is status code of the execution of a Servlet or Web application. More clear in the next explanation. User clicks over a hyperlink, some Servlet is called, executed and the response is sent to the user. Sometimes, the mouse click on the hyperlink calls such an attribute of …
What is 404 Not Found Error in Servlets? How to Fix it? Read More »
