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The javax.servlet.Servlet
interface defines the three methods known as life-cycle method.
public void init(ServletConfig config) throws ServletException public void service( ServletRequest req, ServletResponse res) throws ServletException, IOException public 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 thedoXxx() methods in the case of HttpServlet.
The servlet is removed from service, destroyed with the destroy() methid,
then garbaged collected and finalized.
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2:
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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.
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3:
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The directory structure of a web
application consists of two parts.
A private directory called WEB-INF A public resource directory which contains public resource folder. WEB-INF folder consists of 1. web.xml 2. classes directory 3. lib directory |
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4:
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A:
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Cookies
SSL sessions URL- rewriting |
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5:
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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.
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6:
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A container doesnot initialize the
servlets ass soon as it starts up, it initializes a servlet when it receives
a request for that servlet first time. This is called lazy loading. The
servlet specification defines the <load-on-startup> element, which can
be specified in the deployment descriptor to make the servlet container load
and initialize the servlet as soon as it starts up. The process of loading a
servlet before any request comes in is called preloading or preinitializing a
servlet.
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7:
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A doGet() method is limited with
2k of data to be sent, and doPost() method doesn't have this limitation. A
request string for doGet() looks like the following:
http://www.allapplabs.com/svt1?p1=v1&p2=v2&...&pN=vN doPost() method call doesn't need a long text tail after a servlet name in a request. All parameters are stored in a request itself, not in a request string, and it's impossible to guess the data transmitted to a servlet only looking at a request string. |
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8:
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A GenericServlet has a service()
method aimed to handle requests. HttpServlet extends GenericServlet and adds
support for doGet(), doPost(), doHead() methods (HTTP 1.0) plus doPut(),
doOptions(), doDelete(), doTrace() methods (HTTP 1.1). Both these classes are abstract.
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9:
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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. |
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