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Servlet Interview Questions and Answers Part 1

 

1.What is Servlet?

  • A servlet is a Java technology-based Web component, managed by a container called servlet container or servlet engine, that generates dynamic content and interacts with web clients via a request\/response paradigm.

 

2.Why is Servlet so popular?

  • Because servlets are platform-independent Java classes that are compiled to platform-neutral byte code that can be loaded dynamically into and run by a Java technology-enabled Web server.

 

3.What is servlet container?

  • The servlet container is a part of a Web server or application server that provides the network services over which requests and responses are sent, decodes MIME-based requests, and formats MIME-based responses.

  • A servlet container also contains and manages servlets through their lifecycle.

 

4.When a client request is sent to the servlet container, how does the container choose which servlet to invoke?

  • The servlet container determines which servlet to invoke based on the configuration of its servlets, and calls it with objects representing the request and response.

 

5.If a servlet is not properly initialized, what exception may be thrown?

  • During initialization or service of a request, the servlet instance can throw an UnavailableException or a ServletException.

 

6.Given the request path below, which are context path, servlet path and path info?

  • /bookstore/education/index.html

  • context path: /bookstore

  • servlet path: /education

  • path info: /index.html

 

7.What is filter? Can filter be used as request or response?

  • A filter is a reusable piece of code that can transform the content of HTTP requests,responses, and header information.

  • Filters do not generally create a response or respond to a request as servlets do, rather they modify or adapt the requests for a resource, and modify or adapt responses from a resource.

 

8.When using servlets to build the HTML, you build a DOCTYPE line, why do you do that?

  • I know all major browsers ignore it even though the HTML 3.2 and 4.0 specifications require it.

  • But building a DOCTYPE line tells HTML validators which version of HTML you are using so they know which specification to check your document against.

  • These validators are valuable debugging services, helping you catch HTML syntax errors.

 

9. What is new in ServletRequest interface ?

  • The following methods have been added to ServletRequest 2.4 version:

public int getRemotePort()

public java.lang.String getLocalName()

public java.lang.String getLocalAddr()

public int getLocalPort()

 

10. Request parameter How to find whether a parameter exists in the request object?

  • boolean hasFoo = !(request.getParameter("foo") == null || request.getParameter("foo").equals(""));
    boolean hasParameter = request.getParameterMap().contains(theParameter);
    (which works in Servlet 2.3+)


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