1⟩ What is Java 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.
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“Basic and Advanced Java Servlet Programming interview questions and answers...”
26 Java Servlet Programming Questions And Answers
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⟩ When a servlet accepts a call from a client, it receives two objects. What are they?
ServeltRequest: which encapsulates the communication from the client to the server.
ServletResponse: which encapsulates the communication from the servlet back to the client.
ServletRequest and ServletResponse are interfaces defined by the javax.servlet package.
4⟩ What’s the Servlet Interface?
The central abstraction in the Servlet API is the Servlet interface. All servlets implement this interface, either directly or, more commonly, by extending a class that implements it such as HttpServlet. Servlets–>Generic Servlet–>HttpServlet–>MyServlet. The Servlet interface declares, but does not implement, methods that manage the servlet and its communications with clients. Servlet writers provide some or all of these methods when developing a servlet.
5⟩ What’s the difference between servlets and applets?
Servlets are to servers;
applets are to browsers.
Unlike applets, however, servlets have no graphical user interface.
6⟩ What’s the advantages using servlets than using CGI?
Servlets provide a way to generate dynamic documents that is both easier to write and faster to run. It is efficient, convenient, powerful, portable, secure and inexpensive. Servlets also address the problem of doing server-side programming with platform-specific APIs: they are developed with Java Servlet API, a standard Java extension.
7⟩ What is the servlet?
Servlets are modules that extend request/response-oriented servers, such as Java-enabled web servers. For example, a servlet may be responsible for taking data in an HTML order-entry form and applying the business logic used to update a company’s order database.
8⟩ What are the uses of Servlets?
A servlet can handle multiple requests concurrently, and can synchronize requests. This allows servlets to support systems such as on-line conferencing. Servlets can forward requests to other servers and servlets. Thus servlets can be used to balance load among several servers that mirror the same content, and to partition a single logical service over several servers, according to task type or organizational boundaries.
9⟩ 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.
10⟩ 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
11⟩ 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.
12⟩ 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.
13⟩ Which interface must be implemented by all servlets?
Servlet interface.
14⟩ 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.
15⟩ What is servlet context ?
The servlet context is an object that contains a servlet's view of the Web application within which the servlet is running. Using the context, a servlet can log events, obtain URL references to resources, and set and store attributes that other servlets in the context can use. (answer supplied by Sun's tutorial).
16⟩ What is servlet mapping?
The servlet mapping defines an association between a URL pattern and a servlet. The mapping is used to map requests to servlets.
17⟩ What is Java Servlet session?
The session is an object used by a servlet to track a user's interaction with a Web application across multiple HTTP requests.
18⟩ Difference between GET and POST in Java Servlets?
In GET your entire form submission can be encapsulated in one URL, like a hyperlink. query length is limited to 260 characters, not secure, faster, quick and easy.
In POST Your name/value pairs inside the body of the HTTP request, which makes for a cleaner URL and imposes no size limitations on the form's output. It is used to send a chunk of data to the server to be processed, more versatile, most secure.
19⟩ What mechanisms are used by a Servlet Container to maintain session information?
Cookies, URL rewriting, and HTTPS protocol information are used to maintain session information
20⟩ The code in a finally clause will never fail to execute, right?
Using System.exit(1); in try block will not allow finally code to execute.
