The javax.servlet.Servlet interface defines the three methods known as life-cycle method.public void init(ServletConfig config) throws ServletExceptionpublic void service( ServletRequest req, ServletResponse res) throws ServletException, IOExceptionpublic void destroy()First the servlet is constructed, then initialized wih the init() method.Any request from client are handled initially by the service() method before delegating to the doXxx() methods in the case of HttpServlet.The servlet is removed from service, destroyed with the destroy() methid, then garbaged collected and finalized.
What is the difference between the getRequestDispatcher(String path) method of javax.servlet.ServletRequest interface and javax.servlet.ServletContext interface?
The getRequestDispatcher(String path) method of javax.servlet.ServletRequest interface accepts parameter the path to the resource to be included or forwarded to, which can be relative to the request of the calling servlet. If the path begins with a "/" it is interpreted as relative to the current context root.The getRequestDispatcher(String path) method of javax.servlet.ServletContext interface cannot accepts relative paths. All path must sart with a "/" and are interpreted as relative to curent context root.
Explain the directory structure of a web application?
The directory structure of a web application consists of two parts. A private directory called WEB-INFA public resource directory which contains public resource folder.WEB-INF folder consists of 1. web.xml2. classes directory3. lib directory
What are the common mechanisms used for session tracking?
Cookies
SSL sessions
URL- rewriting
Explain ServletContext?
ServletContext interface is a window for a servlet to view it's environment. A servlet can use this interface to get information such as initialization parameters for the web applicationor servlet container's version. Every web application has one and only one ServletContext and is accessible to all active resource of that application.
What is the difference between ServletContext and ServletConfig?
ServletContext: Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file.The ServletContext object is contained within the ServletConfig object, which the Web server provides the servlet when the servlet is initialized.
ServletConfig: The object created after a servlet is instantiated and its default constructor is read. It is created to pass initialization information to the servlet.
What is difference b/w doget() and dopost() methods?
- DoGet() method to get data will be attached URL.The DoPost()method will be HTTP request body.
- Doget() method to send the limited data and not secure.Dopost()method to send unlimited data and secure.
The getRequestDispatcher(String path) method of javax.servlet.ServletRequest interface accepts parameter the path to the resource to be included or forwarded to, which can be relative to the request of the calling servlet. If the path begins with a "/" it is interpreted as relative to the current context root.The getRequestDispatcher(String path) method of javax.servlet.ServletContext interface cannot accepts relative paths. All path must sart with a "/" and are interpreted as relative to curent context root.
What is a servlet?
Servlets are modules that extend request/response-oriented servers,such as Java-enabled web servers.
For example, a servlet might be responsible for taking data in an HTML order-entry form and applying the business logic used to update a company’s order database. Servlets are to servers what applets are to browsers. Unlike applets, however, servlets have no graphical user interface.
Whats the advantages using servlets over using CGI?
Servlets provide a way to generate dynamic documents that is both easier to write and faster to run. Servlets also address the problem of doing server-side programming with platform-specific APIs: they are developed with the Java Servlet API, a standard Java extension.
What are the general advantages and selling points of Servlets?
A servlet can handle multiple requests concurrently, and synchronize requests. This allows servlets to support systems such as onlinereal-time 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.
What’s the Servlet Interface?
The central abstraction in the Servlet API is the Servlet interface. All servlets implement this interface, either directly or, morecommonly, 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.
When a servlet accepts a call from a client, it receives two objects. What are they?ServletRequest (which encapsulates the communication from the client to the server) and ServletResponse (which encapsulates the communication from the servlet back to the client). ServletRequest and ServletResponse are interfaces defined inside javax.servlet package.
What information does ServletRequest allow access to?
Information such as the names of the parameters passed in by the client, the protocol (scheme) being used by the client, and the namesof the remote host that made the request and the server that received it. Also the input stream, as ServletInputStream.
Servlets use the input stream to get data from clients that use application protocols such as the HTTP POST and GET methods.
What type of constraints can ServletResponse interface set on the client?
It can set the content length and MIME type of the reply. It also provides an output stream, ServletOutputStream and a Writer throughwhich the servlet can send the reply data.
How does HTTP Servlet handle client requests?
An HTTP Servlet handles client requests through its service method. The service method supports standard HTTP client requests by dispatching each request to a method designed to handle that request.
What is the difference between JSP and Servlets ?
JSP is used mainly for presentation only. A JSP can only be HttpServlet that means the only supported protocol in JSP is HTTP. But a servlet can support any protocol like HTTP, FTP, SMTP etc.
What is difference between custom JSP tags and beans?
Custom JSP tag is a tag you defined. You define how a tag, its attributes and its body are interpreted, and then group your tags into collections called tag libraries that can be used in any number of JSP files. To use custom JSP tags, you need to define three separate components: the tag handler class that defines the tag's behavior ,the tag library descriptor file that maps the XML element names to the tag implementations and the JSP file that uses the tag library JavaBeans are Java utility classes you defined.
Beans have a standard format for Java classes. You use tags Custom tags and beans accomplish the same goals -- encapsulating complex behavior into simple and accessible forms. There are several differences:Custom tags can manipulate JSP content; beans cannot. Complex operations can be reduced to a significantly simpler form with custom tags than with beans. Custom tags require quite a bit more work to set up than do beans.
Custom tags usually define relatively self-contained behavior, whereas beans are often defined in one servlet and used in a different servlet or JSP page. Custom tags are available only in JSP 1.1 and later, but beans can be used in all JSP 1.x versions.
What are the different ways for session tracking?
Cookies, URL rewriting, HttpSession, Hidden form fields
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
Difference between GET and POST ?
In GET your entire form submission can be encapsulated in one URL, like a hyperlink. query length is limited to 255 characters, not secure, faster, quick and easy. The data is submitted as part of URL.In POST data is submitted inside body of the HTTP request. The data is not visible on the URL and it is more secure.
What is session?
The session is an object used by a servlet to track a user's interaction with a Web application across multiple HTTP requests. The session is stored on the server.
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.
What is a servlet ?
servlet is a java program that runs inside a web container.
Can we use the constructor, instead of init(), to initialize servlet?
Yes. But you will not get the servlet specific things from constructor. The original reason for init() was that ancient versions of Java couldn’t dynamically invoke constructors with arguments, so there was no way to give the constructor a ServletConfig. That no longer applies, but servlet containers still will only call your no-arg constructor. So you won’t have access to a ServletConfig or ServletContext.
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