JSP Directives IMPLICIT ACTIONS and HACKING.pptx
- 1. JSP Directives , Implicit Objects and Actions
- 2. JSP DIRECTIVES • jsp directives are messages that tells the web container how to translate a JSP page into the corresponding servlet. • There are three types of directives: 1. page directive 2. include directive 3. taglib directive • Syntax: <%@ directive attribute="value" %>
- 3. JSP page directive • The page directive defines attributes that apply to an entire JSP page. Syntax : <%@ page attribute="value" %> • Attributes of JSP page directive o import o contentType o extends o info o buffer o language o session o errorPage o isErrorPage
- 4. 1) import The import attribute is used to import class,interface or all the members of a package.It is similar to import keyword in java class or interface Example of import attribute <html> <body> <%@ page import="java.util.Date" %> Today is: <%= new Date() %> </body> </html>
- 5. 2) contentType • The contentType attribute defines the MIME(Multipurpose Internet Mail Extension) type of the HTTP response.The default value is "text/html;charset=ISO-8859-1". <html> <body> <%@ page contentType=application/msword %> Today is: <%= new java.util.Date() %> </body> </html>
- 6. 3)info • This attribute simply sets the information of the JSP page which is retrieved later by using getServletInfo() method of Servlet interface <html> <body> <%@ page info="current Date will displayed" %> Today is: <%= new java.util.Date() %> </body>
- 7. 4) errorPage • The errorPage attribute is used to define the error page, if exception occurs in the current page, it will be redirected to the error page. <html> <body> <%@ page errorPage="myerrorpage.jsp" %> <%= 100/0 %> </body> </html>
- 8. isErrorPage • The isErrorPage attribute is used to declare that the current page is the error page. • Note: The exception object can only be used in the error page. <html> <body> <%@ page isErrorPage="true" %> Sorry an exception occured!<br/> The exception is: <%= exception %> </body> </html>
- 9. JSP Include Directive • The include directive is used to include the contents of any resource it may be jsp file, html file or text file. The include directive includes the original content of the included resource at page translation time Advantage of Include directive • Code Reusability <%@ include file="resourceName" %>
- 10. JSP Include Directive… <html> <body> <%@ include file="header.html" %> Today is: <%= java.util.Calendar.getInstance().getTime() %> </body> </html>
- 11. JSP Implicit Objects • There are 9 jsp implicit objects. These objects are created by the web container that are available to all the jsp pages • Out • Request • Response • Session • Exception • Config • Appication • Page • PageContext
- 12. JSP request implicit object • The JSP request is an implicit object of type HttpServletRequest i.e. created for each jsp request by the web container. It can be used to get request information such as parameter index.html <form action="welcome.jsp"> <input type="text" name="uname"> <input type="submit" value="go"><br/> </form> welcome.jsp <% String name=request.getParameter("uname"); out.print("welcome "+name); %>
- 13. JSP response implicit object • In JSP, response is an implicit object of type HttpServletResponse. The instance of HttpServletResponse is created by the web container for each jsp request. index.html <form action="welcome.jsp"> <input type="text" name="uname"> <input type="submit" value="go"><br/> </form> welcome.jsp <% response.sendRedirect("http://www.google.com"); %>
- 14. session implicit object • In JSP, session is an implicit object of type HttpSession.The Java developer can use this object to set,get or remove attribute or to get session information. index.html <html> <body> <form action="welcome.jsp"> <input type="text" name="uname"> <input type="submit" value="go"><br/> </form> </body> </html>
- 15. welcome.jsp <html> <body> <% String name=request.getParameter("uname"); out.print("Welcome "+name); session.setAttribute("user",name); <a href="second.jsp">second jsp page</a> %> </body> </html>
- 17. exception implicit object • In JSP, exception is an implicit object of type java.lang.Throwable class. This object can be used to print the exception. But it can only be used in error pages.It is better to learn it after page error.jsp <%@ page isErrorPage="true" %> <html> <body> Sorry following exception occured:<%= exception %> </body> </html>
- 18. ACTIONS • There are many JSP action tags or elements. Each JSP action tag is used to perform some specific tasks. • The action tags are used to control the flow between pages and to use Java Bean. The Jsp action tags are given below. JSP Action Tags Description jsp:forward forwards the request and response to another resource. jsp:include includes another resource. jsp:useBean creates or locates bean object. jsp:setProperty sets the value of property in bean object. jsp:getProperty prints the value of property of the bean. jsp:plugin embeds another components such as applet. jsp:param sets the parameter value. It is used in forward and include mostly.
- 19. forward action tag • The jsp:forward action tag is used to forward the request to another resource it may be jsp, html or another resource. Syntax of jsp:forward action tag without parameter <jsp:forward page="relativeURL | <%= expression %>" /> Syntax of jsp:forward action tag with parameter <jsp:forward page="relativeURL | <%= expression %>"> <jsp:param name="parametername" value="parametervalue | <%=expression%>" /> </jsp:forward>
- 20. Example of jsp:forward action tag without parameter index.jsp <html> <body> <h2>This is first page</h2> <jsp:forward page="printdate.jsp" /> </body> </html> printdate.jsp <html> <body> <% out.print(“Anurag University”)%> </body> </html>
- 21. Example of jsp:forward action tag with parameter index.jsp <html> <body> <h2>this is index page</h2> <jsp:forward page=“welcome.jsp" > <jsp:param name="name" value=“CSE-C STUDENTS" /> </jsp:forward> </body> </html> welcome.jsp <html> <body> <% out.print("Today is:"+java.util.Calendar.getInstance().getTime()); %> <%= request.getParameter("name") %> </body> </html>
- 22. jsp:include action tag • The jsp:include action tag is used to include the content of another resource it may be jsp, html or servlet. • The jsp include action tag includes the resource at request time so it is better for dynamic pages because there might be changes in future. • The jsp:include tag can be used to include static as well as dynamic pages. Syntax of jsp:include action tag without parameter <jsp:include page="relativeURL | <%= expression %>" /> Syntax of jsp:include action tag with parameter <jsp:include page="relativeURL | <%= expression %>"> <jsp:param name="parametername" value="parametervalue | <%=expression%>" />
- 23. Example of jsp:include action tag without parameter File: index.jsp <h2>this is index page</h2> <jsp:include page="printdate.jsp" /> <h2>end section of index page</h2> File: printdate.jsp <% out.print("Today is:"+java.util.Calendar.getInstance().getTime()); %>
- 24. THANK YOU