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config generate, create qr code 2d barcode none in software projects Microsoft Office Official Website exception javax.servlet.jsp. JspWriter java.lang.Object javax.servlet.jsp. PageContext page pageContext request javax.servlet. ServletRequest response javax.servlet. ServletResponse session javax.servlet.http. HttpSession The following e xample JSP illustrates the use of several of the JSP implicit objects:. <%@ page lan Software QRCode guage="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.

org/TR/html4/loose.dtd"> <%@page import="java.util.

Enumeration"%> [ 87 ]. JavaServer Page s <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Implicit Objects Demo</title> </head> <body> <p>This page uses JSP Implicit objects to attach objects to the request, session, and application scopes.<br /> It also retrieves some initialization parameters sent in the web.xml configuration file.

<br /> The third thing it does is get the buffer size from the implicit response object.<br /> </p> <p> <% application.setAttribute("applicationAttribute", new String( "This string is accessible across sessions.

")); session.setAttribute("sessionAttribute", new String( "This string is accessible across requests")); request.setAttribute("requestAttribute", new String( "This string is accessible in a single request")); Enumeration initParameterNames = config.

getInitParameterNames(); out.print("Initialization parameters obtained "); out.print("from the implicit <br/>"); out.

println("config object:<br/><br/>"); while (initParameterNames.hasMoreElements()) { String parameterName = (String) initParameterNames.nextElement(); out.

print(parameterName + " = "); out.print(config.getInitParameter((String) parameterName)); out.

print("<br/>"); } out.println("<br/>"); out.println("Implicit object <b>page</b> is of type " + page.

getClass().getName() + "<br/><br/>"); out.println("Buffer size is: " + response.

getBufferSize() + " bytes"); %> [ 88 ]. 3 </p> <p> <a href="implicitobjects2.jsp"> Click here to continue. </a> </p> </body> </html> This JSP utiliz es most of the implicit objects available to JSP scriptlets. The first thing it does is attach objects to the application, session, and request implicit objects. It then gets all initialization parameters from the implicit config object and displays their names and values on the browser by using the implicit out object.

Next, it displays the fully qualified name of the implicit page object. Finally, it displays the buffer size by accessing the implicit response object..

web.xml file. F Software QR or this application, the web.

xml file looks as follows:. JSP (and optionally servlet) initialization parameters are declared in the application"s < xml versio QR for None n="1.0" encoding="UTF-8" > <web-app version="2.4" xmlns="http://java.

sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.

org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.

sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <servlet> <servlet-name>ImplicitObjectsJsp</servlet-name> <jsp-file>/implicitobjects.

jsp</jsp-file> <init-param> <param-name>webxmlparam</param-name> <param-value> This is set in the web.xml file </param-value> </init-param> </servlet> <servlet-mapping> <servlet-name>ImplicitObjectsJsp</servlet-name> <url-pattern>/implicitobjects.jsp</url-pattern> </servlet-mapping> </web-app>.

[ 89 ]. JavaServer Pages Remember that a JSP gets compiled into a servlet at runtime the first time it is accessed after deployment. As such, we can treat it as a servlet in the web.xml file.

In order to be able to pass initialization parameters to a JSP, we must treat it like a servlet, as initialization parameters are placed between the <init-param> and </init-param> XML tags. As shown in the previous web.xml file, the parameter name is placed between the <param-name> and </param-name> tags, and the parameter value is placed between the <param-value> and </param-value> tags.

A servlet (and a JSP) can have multiple initialization parameters. Each initialization parameter must be declared inside a separate <init-param> tag. Notice that in the previous web.

xml file, we declared a servlet mapping for our JSP. This was necessary to allow GlassFish"s web container to pass initialization parameters to the JSP. As we didn"t want the URL of the JSP to change, we used the JSP"s actual URL as the value for the <url-pattern> tag.

If we wanted to access the JSP via a different URL (not necessarily one ending in .jsp), we could have placed the desired URL inside the <url-pattern> tag. At the bottom of implicitobjects.

jsp, there is a hyperlink to a second JSP, called implicitobjects2.jsp. The markup and code for implicitobjects2.

jsp looks as follows:. <%@ page lan Software QRCode guage="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.

org/TR/html4/loose.dtd"> <%@page import="java.util.

Enumeration"%> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Sanity Check</title> </head> <body> <p>This page makes sure we can retrieve the application, session and request attributes set in the previous page. <br /> </p> <p>applicationAttribute value is: <%=application.getAttribute("applicationAttribute")%> <br /> sessionAttribute value is: <%=session.

getAttribute("sessionAttribute")%> <br /> requestAttribute value is: <%=request.getAttribute("requestAttribute")%> <br /> [ 90 ]. 3 </p> & lt;p> The following attributes were found at the application scope: <br/><br/> <% Enumeration applicationAttributeNames = pageContext .getAttributeNamesInScope(pageContext.APPLICATION_SCOPE); while (applicationAttributeNames.

hasMoreElements()) { out.println(applicationAttributeNames.nextElement() + "<br/>"); } %> </p> <p><a href="buggy.

jsp">This hyperlink points to a JSP that will throw an exception.</a></p> </body> </html>. In this second Software QR Code JSP, we retrieve the objects that were attached to the application, session, and request objects. The attached objects are obtained by calling the appropriate implicit object"s getAttribute() method. Notice how all calls to the getAttribute() method are nested between the <%= and %> delimiters.

Snippets of code between these delimiters are called JSP expressions. JSP expressions are evaluated and their return value is displayed in the browser without having to call the out.print() method.

This JSP also retrieves the names of all objects attached to the application scope and displays them in the browser window. At the bottom of the previous JSP, there is a hyperlink to a third JSP. This third JSP is called buggy.

jsp. Its only purpose is to demonstrate the errorPage attribute of the page directive, the error attribute of the page directive, and the exception implicit object. Therefore, it is not terribly complicated.

. <%@ page lan guage="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" errorPage="error.jsp" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.

w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Buggy JSP</title> </head> <body> [ 91 ].

JavaServer Page qr codes for None s <p> This text will never be seen in the browser since the exception will be thrown before the page renders. <% Object o = null; out.println(o.

toString()); //NullPointerException thrown here. %> </p> </body> </html>. The only thing this JSP does is force a NullPointerException, which will result in GlassFish"s servlet container directing the user to the page declared as an error page in the errorPage attribute of the page directive. This page is error.jsp; its markup and code is shown next:.

<%@ page lan Software qrcode guage="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" isErrorPage="true"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.

org/TR/html4/loose.dtd"> <%@page import="java.io.

StringWriter"%> <%@page import="java.io.PrintWriter"%> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>There was an error in the application</title> </head> <body> <h2>Exception caught</h2> <p>Stack trace for the exception is:<br /> <% StringWriter stringWriter = new StringWriter(); PrintWriter printWriter = new PrintWriter(stringWriter); exception.

printStackTrace(printWriter); out.write(stringWriter.toString()); %> </p> </body> </html>.

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