Servlet Interview Questions and Answers
Question - 71 : - How do you configure a centralized error handler in servlets?
Answer - 71 : -
If we wish to include a central Error Handler for all the exceptions then we can define following error-page instead of defining separate error-page elements for an individual exception
- java.lang.Throwable
- /ErrorHandler
Answer - 72 : -
The Packages are used to separate the servlets under a directory to eradicate confusion among programmers working simultaneously on creating servlets on the same server. This can be done through the following steps:
- Sorting of files into different subdirectories by matching the package name to the subdirectory name to organize the packages.
- After sorting the packages into subdirectories insert the package statement in the class file.
Let us understand through this an example as follows:
- import java.io.*;
- import javax.servlet.*;
- import javax.servlet.http.*;
- public class servlet1 extends HttpServlet{
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException {
- response.setContentType("text/html");
- PrintWriter out = response.getWriter();
- String docType = "n";
- out.println(docType + "n" + "Edurekan" + "n" + "");
- }
- }
How can you use a servlet to generate a plain text instead of HTML?
Answer - 73 : -
A servlet basically generates HTML. We can set the content-type response header by any of the methods. The example for producing text message EDUREKA using the HTML code inside the servlets.
- import java.io.*;
- import javax.servlet.*;
- import javax.servlet.http.*;
- public class EDUREKA extends HttpServlet{
- public void doGet(HttpServletRequest request, HttpServletResponse response)
- throws ServletException, IOException{
- response.setContentType("text/html");
- PrintWriter out = response.getWriter();
- out.println("n" +"n" +"EDUREKAn" + "n" + "
HAPPY LEARNING
n" + ""); - }
- }
Answer - 74 : -
Only one object at the time of first request by servlet or web container.
Question - 75 : - What is the life-cycle of a servlet?
Answer - 75 : -
- Servlet is loaded
- servlet is instantiated
- servlet is initialized
- service the request
- servlet is destroyed
Question - 76 : - What are the life-cycle methods for a servlet?
Answer - 76 : -
| Method | Description |
| public void init(ServletConfig config) | It is invoked only once when first request comes for the servlet. It is used to initialize the servlet. |
| public void service(ServletRequest request,ServletResponse)throws ServletException,IOException | It is invoked at each request.The service() method is used to service the request. |
| public void destroy() | It is invoked only once when servlet is unloaded. |
Question - 77 : - Who is responsible to create the object of servlet?
Answer - 77 : -
The web container or servlet container.
Question - 78 : - What is difference between PrintWriter and ServletOutputStream?
Answer - 78 : -
PrintWriter is a character-stream class where as ServletOutputStream is a byte-stream class. The PrintWriter class can be used to write only character-based information whereas ServletOutputStream class can be used to write primitive values as well as character-based information.
Question - 79 : - What is difference between GenericServlet and HttpServlet?
Answer - 79 : -
The GenericServlet is protocol independent whereas HttpServlet is HTTP protocol specific. HttpServlet provides additional functionalities such as state management etc.
Question - 80 : - What is servlet collaboration?
Answer - 80 : -
When one servlet communicates to another servlet, it is known as servlet collaboration. There are many ways of servlet collaboration:
- RequestDispacher interface
- sendRedirect() method etc.