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documentation examples changes overview quick start installation command-line configuration admin amber clustering caching database deployment ejb 3.0 embedding filters hessian hmtp ioc jsp logging messaging performance quercus/php remoting scheduled tasks security server push servlets third-party troubleshooting virtual hosting watchdog webapp xml and xslt introduction compilation el jstl directives variables actions applications schema for jsp-2.0 .tld files velocity syntax jsp templates | directives
JSP Directives control the processing of an entire page. Directive examples include setting a scripting language, setting an error page, including other sections, and setting a character encoding. <%@ page language="lang" %>Sets the JSP script language to . Defaults to Java. All JSP 1.0 implementations must support Java. Some implementations, like Resin, may support other scripting languages, e.g. JavaScript.<%@ page import="package" %>Adds to the Java package import list for the generated Java file. Note Only relevant when using Java.<%@ page errorPage="path" %>Defines a page to display if an error occurs in the JSP page. Robust applications can return informative error pages when something goes wrong in a file, for example if a database is overloaded. exception containing the thrown exception. is returned as the response file. The error page can use the additional implicit variableis relative to the current page. Its root is relative to the application root. The error page itself can be a JSP page. If the error page is a
JSP page, it can use the implicit variable <%@ page isErrorPage="true" %>Gives an error page access to the errorpage.jsp <%@ page isErrorPage="true" %> <h1>Received error <%= exception.message %></h1> <%@ include file="path" %>Includes the raw file at translation time.The include directive is a replacement for an SSI include (or the C '#include'). It includes the contents of the file at into the JSP file. The included file is parsed as JSP, so it can have active elements like expressions, declarations and scriptlets.is relative to the current page, and its root is the application root. header.jsp <html><head> <title><%= title %></title> </head> <body color=white> page.jsp <% var title = "Hello, World"; %> <%@ include file='header.jsp' %> <h1><%= title %></h1> <%@ page buffer=sizekb %>Gives the JSP 1.0 gives page writers flexibility by buffering its output before sending the response to HTTP. The buffering allows error recovery and forwarding, even after generating some content. Once the buffer has filled, it will be flushed. So applications must still detect their errors early. The following example generates an XML section (for variety). If the form's query is missing the 'name' parameter, it will redirect the results. <?xml version='1.0'?> <form> <% if (request.form["name"] == null) pageContext.forward("redo-form.jsp"); for (var name in request.form) { out.print("<" + name + ">"); out.print(request.form[name]); out.println("</" + name + ">"); } %> </form> <%@ page autoFlush="true" %>Tells JSP to flush the page buffer when it fills. Default is true. If autoFlush is false, the JSP engine will throw an exception if the buffer overflows. <%@ page session="true" %>Tells JSP that the page participates in a session. Defaults to true. The session declaration makes the session implicit variable available to a JSP page. If the page doesn't use sessions, it should set <%@ page session="true" %> <% session.value.count++; %> <h1>Welcome, visitor <%= count %></h1;> <%@ page isThreadSafe="true" %>Tells the JSP that multiple pages can execute in parallel. Defaults to true. JSP pages are always responsible for synchronization of shared
variables, such as the Even with In the following example, a JSP engine might create 3 servlet instances of the page. So three calls to the same page may return counts of 17, 3 and 398. In addition, the JSP engine is free to destroy and recreate the servlet at any time, essentially resetting the counter to 0. <%@ page isThreadSafe="false" %> <%! var count = 0; %> <h1>Welcome, visitor <%= count++ %> <%@ page contentType="description" %>Sets the content type and character encoding of the page.
<%@ page contentType="text/plain; charset=utf-8" %> <%! var count = 0; %> <h1>Welcome, visitor <%= count++ %> <%@ page extends="Java class" %>Changes the generated servlet's class. In general, a filter is a better solution than using the extends directive. <%@ taglib prefix="x" uri="foo" %>Configures tags with prefix to use the tag library .<%@ taglib prefix='x' uri='http://www.caucho.com/mytag/test' %> <x:mytag/>
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