J2EE jsp_03


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J2EE jsp_03

  1. 1. Let’s Move on: JSP Objects An overview Biswabrata Banerjee
  2. 2. JSP Objects Built-in JSP Objects and Their Implementation Classes: JSP Object Implementation Class Request HttpServletRequest response HttpServletResponse out JspWriter session HttpSession application ServletContext pageContext PageContext config ServletConfig page Object exception Throwable Biswabrata Banerjee
  3. 3. Cont ‘d … JSP Objects These objects are implicitly created at the beginning of a page when your JSP is invoked, and they directly reference objects in the underlying servlet. They are always available to scriptlets and expressions. Biswabrata Banerjee
  4. 4. a brief description The request Object The request object represents the current request from the browser and is a subclass of the ServletRequest class. For most current implementations of JSP, the request object is an instance of HttpServletRequest. The response Object Like the request object, the response object is usually a subclass of the HTTP-specific version of ServletResponse. In other words, it is usually an instance of HttpServletResponse. The out Object The out object is responsible for writing responses back to the browser and is an instance of the JspWriter class. The session Object The session object is an instance of HttpSession. Because there is an obvious dependence on HTTP, this object is available only if your JSPs use HTTP. The application Object The application object is an instance of the ServletContext object. The names "application" and "ServletContext" don't seem very similar, but if you recall what the ServletContext class does, you'll see that it manages data at the application level. Biswabrata Banerjee
  5. 5. Cont ‘d… a brief description The pageContext Object The pageContext object is an instance of the PageContext class. Many of the items available through built-in variables are also available through the pageContext object. The config Object The config object gives you access to configuration information for your JSP and is an instance of the ServletConfig class. The page Object The page object is rather peculiar because it is a reference to the current JSP. In other words, it's like an alias for the this keyword in Java. The exception Object When you create an error page to deal with exceptions that occur during normal JSP processing, you might need access to the exception that caused the error page to be invoked. You can access that exception through the exception object. Biswabrata Banerjee
  6. 6. Request Object JSP Request Object Request Object in JSP is used to get the values that the client passes to the web server during an HTTP request. The request object is used to take the value from the client’s web browser and pass it to the server. This is performed using an HTTP request such as: headers, cookies or arguments. The class or the interface name of the object request is http.httpservletrequest. The object request is written: Javax.servlet.http.httpservletrequest.
  7. 7. Request Object Methods of request Object: There are numerous methods available for request Object. Some of them are: getCookies() getHeader(String name) getHeaderNames() getAttribute(String name) getAttributeNames() getMethod() getParameter(String name) getParameterNames() getParameterValues(String name) getQueryString() getRequestURI() getServletPath() setAttribute(String,Object) removeAttribute(String)
  8. 8. Response Object JSP Response Object The response object denotes the HTTP Response data. The result or the information of a request is denoted with this object. The response object handles the output of the client. This contrasts with the request object. The class or the interface name of the response object is http.HttpServletResponse. The response object is written as : Javax.servlet.http.httpservletresponse. The response object is generally used by cookies. The response object is also used with HTTP Headers.
  9. 9. Response Object Methods of response Object: There are numerous methods available for response object. Some of them are: setContentType() addCookie(Cookie cookie) addHeader(String name, String value) containsHeader(String name) setHeader(String name, String value) sendRedirect(String) sendError(int status_code)
  10. 10. Session Object JSP Session Object Session Object denotes the data associated with a specific session of user. The class or the interface name of the object session is http.HttpSession. The object session is written as: Javax.servlet.http.httpsession. The previous two objects, request and response, are used to pass information from web browser to server and from server to web browser respectively.The Session object provides the connection or association between the client and the server. The main use of Session Objects is to maintain states when there are multiple page requests. The main feature of session object is to navigate between multiple pages in a application where variables are stored for the entire user session. The session objects do not lose the variables and the value remains for the user’ session. The concept of maintenance of sessions can be performed by cookies or URL rewriting. A detailed approach of session handling will be discusses in coming sections.
  11. 11. Session Object Methods of session Object: There are numerous methods available for session object. Some of them are: getAttribute(String name) getAttributeNames isNew() getCreationTime getId invalidate() getLastAccessedTime getMaxInactiveInterval removeAttribute(String name) setAttribute(String, object)
  12. 12. Out Object JSP out object JSP out object denotes the Output stream in the context of page. The class or the interface name of the object out is jsp.JspWriter. The out object is written as: Javax.servlet.jsp.JspWriter The object that write to the JSP's output stream is defined by the out object. Methods of out Object: There are numerous methods available for out Object,some of them are : clear clearBuffer flush isAutoFlush getBufferSize getRemaining newLine print println