Servlet Interview questions and Answers

Both WAR and JAR have the same file structure of a single file that is compressed and contains multiple files inside it. WAR files combine servlets, JSPs, Java and XML files, JAR libraries, javascript libraries, static web pages, and other resources that are needed to run the applications.

HTTP outlines a set of request methods that indicate the action to be performed for a resource. Each request method implements a different semantic, but they also share some common features. Here are the 7 HTTP request methods every web developer preparing for Servlet interview questions and answers should know:

• GET
• HEAD
• POST
• PUT
• DELETE
• OPTIONS
• PATCH

In order to create a WAR file, use JDK's JAR tool. Use -c switch of jar for creating the war file. Enter the project directory of your project and write this command: jar -cvf projectname.war * Here, -c is for creating file, -v for generating verbose output and -f for specifying name of the archive file.

The SingleThreadModel interface ensures that only one thread is executed at a given point of time in a given servlet service method. This is a marker interface and contains no methods. This interface also ensures thread-safe servlets.

URL Encoding process transforms user input to a Common Gateway Interface (CGI) form. It is fit to travel across the network through stripping spaces, punctuation and replacement with escape characters.

Here are 2 methods for getting client’s IP address in Servlet:

HttpServletRequest.getRemoteAddr method returns IP of the client that sends request.

HttpServletRequestgetRemoteHost method returns the hostname of the client that is sending the request. However, it may return an empty string if hostname is unknown.

Servlet 3.0 is an update of Servlet 2.5. Servlet 3.0 focuses on extensibility and pluggability. Key features in Servlet 3.0 can be categorized into the following areas:

• Easier development with annotations.
• Web application modularity.
• Asynchronous Servlet.
• Programmatic instantiation of Servlets/Filters.
• Security Enhancements.

There are ways of servlet authentication:

• HTTP basic authentication.
• HTTP digest authentication.
• HTTPS client authentication.
• Form-based authentication.

You can invoke a JSP web page from a servlet via the functionality of the popular javax.servlet.RequestDispatcher interface. Complete the following steps in your code to use this mechanism:

• Get a servlet context instance from the servlet instance:
  ServletContext sc = this.getServletContext();
• Get a request dispatcher from the servlet context instance, specifying the page-relative or application-relative course of the goal JSP page as enter to the getRequestDispatcher() method:
  RequestDispatcher rd = sc.getRequestDispatcher("/jsp/mypage.jsp");
  Prior to or in the course of this step, you can optionally make facts on hand to the JSP page thru attributes of the HTTP request object. See the next section, "Passing Data Between a JSP Page and a Servlet", for information.
• Invoke the include() or forward() approach of the request dispatcher, specifying the HTTP request and response objects as arguments. The performance of these techniques is similar to that of jsp:include and jsp:forward actions. The include() approach solely briefly transfers control; execution returns to the invoking servlet afterward.