536 lines
19 KiB
Java
536 lines
19 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package javax.servlet.jsp;
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import java.io.IOException;
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import javax.servlet.RequestDispatcher;
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import javax.servlet.Servlet;
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import javax.servlet.ServletConfig;
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import javax.servlet.ServletContext;
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import javax.servlet.ServletException;
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import javax.servlet.ServletRequest;
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import javax.servlet.ServletResponse;
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import javax.servlet.http.HttpSession;
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import javax.servlet.jsp.tagext.BodyContent;
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/**
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* <p>
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* PageContext extends JspContext to provide useful context information for
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* when JSP technology is used in a Servlet environment.
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* <p>
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* A PageContext instance provides access to all the namespaces associated
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* with a JSP page, provides access to several page attributes, as well as
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* a layer above the implementation details. Implicit objects are added
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* to the pageContext automatically.
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*
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* <p> The <code> PageContext </code> class is an abstract class, designed to be
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* extended to provide implementation dependent implementations thereof, by
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* conformant JSP engine runtime environments. A PageContext instance is
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* obtained by a JSP implementation class by calling the
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* JspFactory.getPageContext() method, and is released by calling
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* JspFactory.releasePageContext().
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*
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* <p> An example of how PageContext, JspFactory, and other classes can be
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* used within a JSP Page Implementation object is given elsewhere.
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*
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* <p>
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* The PageContext provides a number of facilities to the page/component
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* author and page implementor, including:
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* <ul>
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* <li>a single API to manage the various scoped namespaces
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* <li>a number of convenience API's to access various public objects
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* <li>a mechanism to obtain the JspWriter for output
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* <li>a mechanism to manage session usage by the page
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* <li>a mechanism to expose page directive attributes to the scripting
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* environment
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* <li>mechanisms to forward or include the current request to other active
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* components in the application
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* <li>a mechanism to handle errorpage exception processing
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* </ul>
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*
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* <p><B>Methods Intended for Container Generated Code</B>
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* <p>Some methods are intended to be used by the code generated by the
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* container, not by code written by JSP page authors, or JSP tag library
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* authors.
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* <p>The methods supporting <B>lifecycle</B> are <code>initialize()</code>
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* and <code>release()</code>
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*
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* <p>
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* The following methods enable the <B>management of nested</B> JspWriter
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* streams to implement Tag Extensions: <code>pushBody()</code>
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*
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* <p><B>Methods Intended for JSP authors</B>
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* <p>
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* The following methods provide <B>convenient access</B> to implicit objects:
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* <code>getException()</code>, <code>getPage()</code>
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* <code>getRequest()</code>, <code>getResponse()</code>,
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* <code>getSession()</code>, <code>getServletConfig()</code>
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* and <code>getServletContext()</code>.
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*
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* <p>
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* The following methods provide support for <B>forwarding, inclusion
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* and error handling</B>:
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* <code>forward()</code>, <code>include()</code>,
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* and <code>handlePageException()</code>.
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*/
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public abstract class PageContext
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extends JspContext
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{
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/**
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* Sole constructor. (For invocation by subclass constructors,
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* typically implicit.)
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*/
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public PageContext() {
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// NOOP by default
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}
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/**
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* Page scope: (this is the default) the named reference remains available
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* in this PageContext until the return from the current Servlet.service()
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* invocation.
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*/
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public static final int PAGE_SCOPE = 1;
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/**
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* Request scope: the named reference remains available from the
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* ServletRequest associated with the Servlet until the current request
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* is completed.
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*/
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public static final int REQUEST_SCOPE = 2;
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/**
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* Session scope (only valid if this page participates in a session):
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* the named reference remains available from the HttpSession (if any)
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* associated with the Servlet until the HttpSession is invalidated.
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*/
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public static final int SESSION_SCOPE = 3;
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/**
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* Application scope: named reference remains available in the
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* ServletContext until it is reclaimed.
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*/
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public static final int APPLICATION_SCOPE = 4;
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/**
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* Name used to store the Servlet in this PageContext's nametables.
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*/
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public static final String PAGE = "javax.servlet.jsp.jspPage";
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/**
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* Name used to store this PageContext in it's own name table.
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*/
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public static final String PAGECONTEXT = "javax.servlet.jsp.jspPageContext";
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/**
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* Name used to store ServletRequest in PageContext name table.
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*/
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public static final String REQUEST = "javax.servlet.jsp.jspRequest";
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/**
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* Name used to store ServletResponse in PageContext name table.
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*/
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public static final String RESPONSE = "javax.servlet.jsp.jspResponse";
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/**
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* Name used to store ServletConfig in PageContext name table.
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*/
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public static final String CONFIG = "javax.servlet.jsp.jspConfig";
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/**
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* Name used to store HttpSession in PageContext name table.
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*/
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public static final String SESSION = "javax.servlet.jsp.jspSession";
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/**
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* Name used to store current JspWriter in PageContext name table.
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*/
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public static final String OUT = "javax.servlet.jsp.jspOut";
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/**
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* Name used to store ServletContext in PageContext name table.
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*/
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public static final String APPLICATION = "javax.servlet.jsp.jspApplication";
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/**
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* Name used to store uncaught exception in ServletRequest attribute
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* list and PageContext name table.
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*/
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public static final String EXCEPTION = "javax.servlet.jsp.jspException";
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/**
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* <p>
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* The initialize method is called to initialize an uninitialized PageContext
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* so that it may be used by a JSP Implementation class to service an
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* incoming request and response within it's _jspService() method.
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*
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* <p>
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* This method is typically called from JspFactory.getPageContext() in
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* order to initialize state.
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*
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* <p>
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* This method is required to create an initial JspWriter, and associate
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* the "out" name in page scope with this newly created object.
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*
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* <p>
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* This method should not be used by page or tag library authors.
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*
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* @param servlet The Servlet that is associated with this PageContext
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* @param request The currently pending request for this Servlet
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* @param response The currently pending response for this Servlet
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* @param errorPageURL The value of the errorpage attribute from the page
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* directive or null
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* @param needsSession The value of the session attribute from the
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* page directive
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* @param bufferSize The value of the buffer attribute from the page
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* directive
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* @param autoFlush The value of the autoflush attribute from the page
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* directive
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*
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* @throws IOException during creation of JspWriter
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* @throws IllegalStateException if out not correctly initialized
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* @throws IllegalArgumentException If one of the given parameters
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* is invalid
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*/
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public abstract void initialize(Servlet servlet, ServletRequest request,
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ServletResponse response, String errorPageURL, boolean needsSession,
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int bufferSize, boolean autoFlush)
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throws IOException, IllegalStateException, IllegalArgumentException;
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/**
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* <p>
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* This method shall "reset" the internal state of a PageContext, releasing
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* all internal references, and preparing the PageContext for potential
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* reuse by a later invocation of initialize(). This method is typically
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* called from JspFactory.releasePageContext().
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*
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* <p>
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* Subclasses shall envelope this method.
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*
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* <p>
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* This method should not be used by page or tag library authors.
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*
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*/
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public abstract void release();
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/**
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* The current value of the session object (an HttpSession).
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*
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* @return the HttpSession for this PageContext or null
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*/
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public abstract HttpSession getSession();
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/**
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* The current value of the page object (In a Servlet environment,
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* this is an instance of javax.servlet.Servlet).
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*
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* @return the Page implementation class instance associated
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* with this PageContext
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*/
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public abstract Object getPage();
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/**
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* The current value of the request object (a ServletRequest).
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*
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* @return The ServletRequest for this PageContext
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*/
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public abstract ServletRequest getRequest();
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/**
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* The current value of the response object (a ServletResponse).
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*
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* @return the ServletResponse for this PageContext
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*/
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public abstract ServletResponse getResponse();
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/**
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* The current value of the exception object (an Exception).
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*
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* @return any exception passed to this as an errorpage
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*/
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public abstract Exception getException();
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/**
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* The ServletConfig instance.
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*
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* @return the ServletConfig for this PageContext
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*/
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public abstract ServletConfig getServletConfig();
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/**
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* The ServletContext instance.
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*
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* @return the ServletContext for this PageContext
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*/
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public abstract ServletContext getServletContext();
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/**
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* <p>
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* This method is used to re-direct, or "forward" the current
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* ServletRequest and ServletResponse to another active component in
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* the application.
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* </p>
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* <p>
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* If the <I> relativeUrlPath </I> begins with a "/" then the URL specified
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* is calculated relative to the DOCROOT of the <code> ServletContext </code>
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* for this JSP. If the path does not begin with a "/" then the URL
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* specified is calculated relative to the URL of the request that was
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* mapped to the calling JSP.
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* </p>
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* <p>
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* It is only valid to call this method from a <code> Thread </code>
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* executing within a <code> _jspService(...) </code> method of a JSP.
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* </p>
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* <p>
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* Once this method has been called successfully, it is illegal for the
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* calling <code> Thread </code> to attempt to modify the <code>
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* ServletResponse </code> object. Any such attempt to do so, shall result
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* in undefined behavior. Typically, callers immediately return from
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* <code> _jspService(...) </code> after calling this method.
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* </p>
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*
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* @param relativeUrlPath specifies the relative URL path to the target
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* resource as described above
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*
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* @throws IllegalStateException if <code> ServletResponse </code> is not
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* in a state where a forward can be performed
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* @throws ServletException if the page that was forwarded to throws
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* a ServletException
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* @throws IOException if an I/O error occurred while forwarding
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*/
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public abstract void forward(String relativeUrlPath)
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throws ServletException, IOException;
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/**
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* <p>
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* Causes the resource specified to be processed as part of the current
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* ServletRequest and ServletResponse being processed by the calling Thread.
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* The output of the target resources processing of the request is written
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* directly to the ServletResponse output stream.
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* </p>
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* <p>
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* The current JspWriter "out" for this JSP is flushed as a side-effect
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* of this call, prior to processing the include.
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* </p>
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* <p>
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* If the <I> relativeUrlPath </I> begins with a "/" then the URL specified
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* is calculated relative to the DOCROOT of the <code>ServletContext</code>
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* for this JSP. If the path does not begin with a "/" then the URL
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* specified is calculated relative to the URL of the request that was
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* mapped to the calling JSP.
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* </p>
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* <p>
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* It is only valid to call this method from a <code> Thread </code>
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* executing within a <code> _jspService(...) </code> method of a JSP.
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* </p>
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*
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* @param relativeUrlPath specifies the relative URL path to the target
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* resource to be included
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*
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* @throws ServletException if the page that was forwarded to throws
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* a ServletException
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* @throws IOException if an I/O error occurred while forwarding
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*/
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public abstract void include(String relativeUrlPath)
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throws ServletException, IOException;
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/**
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* <p>
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* Causes the resource specified to be processed as part of the current
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* ServletRequest and ServletResponse being processed by the calling Thread.
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* The output of the target resources processing of the request is written
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* directly to the current JspWriter returned by a call to getOut().
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* </p>
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* <p>
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* If flush is true, The current JspWriter "out" for this JSP
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* is flushed as a side-effect of this call, prior to processing
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* the include. Otherwise, the JspWriter "out" is not flushed.
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* </p>
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* <p>
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* If the <i>relativeUrlPath</i> begins with a "/" then the URL specified
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* is calculated relative to the DOCROOT of the <code>ServletContext</code>
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* for this JSP. If the path does not begin with a "/" then the URL
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* specified is calculated relative to the URL of the request that was
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* mapped to the calling JSP.
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* </p>
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* <p>
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* It is only valid to call this method from a <code> Thread </code>
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* executing within a <code> _jspService(...) </code> method of a JSP.
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* </p>
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*
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* @param relativeUrlPath specifies the relative URL path to the
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* target resource to be included
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* @param flush True if the JspWriter is to be flushed before the include,
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* or false if not.
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*
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* @throws ServletException if the page that was forwarded to throws
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* a ServletException
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* @throws IOException if an I/O error occurred while forwarding
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* @since 2.0
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*/
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public abstract void include(String relativeUrlPath, boolean flush)
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throws ServletException, IOException;
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/**
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* <p>
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* This method is intended to process an unhandled 'page' level
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* exception by forwarding the exception to the specified
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* error page for this JSP. If forwarding is not possible (for
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* example because the response has already been committed), an
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* implementation dependent mechanism should be used to invoke
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* the error page (e.g. "including" the error page instead).
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*
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* <p>
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* If no error page is defined in the page, the exception should
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* be rethrown so that the standard servlet error handling
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* takes over.
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*
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* <p>
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* A JSP implementation class shall typically clean up any local state
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* prior to invoking this and will return immediately thereafter. It is
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* illegal to generate any output to the client, or to modify any
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* ServletResponse state after invoking this call.
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*
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* <p>
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* This method is kept for backwards compatibility reasons. Newly
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* generated code should use PageContext.handlePageException(Throwable).
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*
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* @param e the exception to be handled
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*
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* @throws ServletException if an error occurs while invoking the error page
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* @throws IOException if an I/O error occurred while invoking the error
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* page
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* @throws NullPointerException if the exception is null
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*
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* @see #handlePageException(Throwable)
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*/
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public abstract void handlePageException(Exception e)
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throws ServletException, IOException;
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/**
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* <p>
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* This method is intended to process an unhandled 'page' level
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* exception by forwarding the exception to the specified
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* error page for this JSP. If forwarding is not possible (for
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* example because the response has already been committed), an
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* implementation dependent mechanism should be used to invoke
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* the error page (e.g. "including" the error page instead).
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*
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* <p>
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* If no error page is defined in the page, the exception should
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* be rethrown so that the standard servlet error handling
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* takes over.
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*
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* <p>
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* This method is intended to process an unhandled "page" level exception
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* by redirecting the exception to either the specified error page for this
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* JSP, or if none was specified, to perform some implementation dependent
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* action.
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*
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* <p>
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* A JSP implementation class shall typically clean up any local state
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* prior to invoking this and will return immediately thereafter. It is
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* illegal to generate any output to the client, or to modify any
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* ServletResponse state after invoking this call.
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*
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* @param t the throwable to be handled
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*
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* @throws ServletException if an error occurs while invoking the error page
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* @throws IOException if an I/O error occurred while invoking the error
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* page
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* @throws NullPointerException if the exception is null
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*
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* @see #handlePageException(Exception)
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*/
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public abstract void handlePageException(Throwable t)
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throws ServletException, IOException;
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/**
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* Return a new BodyContent object, save the current "out" JspWriter,
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* and update the value of the "out" attribute in the page scope
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* attribute namespace of the PageContext.
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*
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* @return the new BodyContent
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*/
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public BodyContent pushBody() {
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return null; // XXX to implement
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}
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/**
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* Provides convenient access to error information.
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*
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* @return an ErrorData instance containing information about the
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* error, as obtained from the request attributes, as per the
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* Servlet specification. If this is not an error page (that is,
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* if the isErrorPage attribute of the page directive is not set
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* to "true"), the information is meaningless.
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*
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* @since 2.0
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*/
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public ErrorData getErrorData() {
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int status = 0;
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Integer status_code = (Integer)getRequest().getAttribute(
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RequestDispatcher.ERROR_STATUS_CODE);
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// Avoid NPE if attribute is not set
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if (status_code != null) {
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status = status_code.intValue();
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}
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return new ErrorData(
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(Throwable)getRequest().getAttribute(
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RequestDispatcher.ERROR_EXCEPTION),
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status,
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(String)getRequest().getAttribute(
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RequestDispatcher.ERROR_REQUEST_URI),
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(String)getRequest().getAttribute(
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RequestDispatcher.ERROR_SERVLET_NAME)
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);
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}
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}
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