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products/Sources/formale Sprachen/Java/Tomcat/java/jakarta/servlet/jsp/ (Apache Software Stiftung Version 11.0^©) Datei vom 10.10.2023 mit Größe 18 kB

Quelle PageContext.java Sprache: JAVA

/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jakarta.servlet.jsp;

import java.io.IOException;

import jakarta.servlet.RequestDispatcher;
import jakarta.servlet.Servlet;
import jakarta.servlet.ServletConfig;
import jakarta.servlet.ServletContext;
import jakarta.servlet.ServletException;
import jakarta.servlet.ServletRequest;
import jakarta.servlet.ServletResponse;
import jakarta.servlet.http.HttpSession;
import jakarta.servlet.jsp.tagext.BodyContent;

/**
* 
* PageContext extends JspContext to provide useful context information for when JSP technology is used in a Servlet
* environment.
* 
* A PageContext instance provides access to all the namespaces associated with a JSP page, provides access to several
* page attributes, as well as a layer above the implementation details. Implicit objects are added to the pageContext
* automatically.
* 
* The <code> PageContext </code> class is an abstract class, designed to be extended to provide implementation
* dependent implementations thereof, by conformant JSP engine runtime environments. A PageContext instance is obtained
* by a JSP implementation class by calling the JspFactory.getPageContext() method, and is released by calling
* JspFactory.releasePageContext().
* 
* An example of how PageContext, JspFactory, and other classes can be used within a JSP Page Implementation object is
* given elsewhere.
* 
* The PageContext provides a number of facilities to the page/component author and page implementor, including:
* <ul>
* <li>a single API to manage the various scoped namespaces
* <li>a number of convenience API's to access various public objects
* <li>a mechanism to obtain the JspWriter for output
* <li>a mechanism to manage session usage by the page
* <li>a mechanism to expose page directive attributes to the scripting environment
* <li>mechanisms to forward or include the current request to other active components in the application
* <li>a mechanism to handle errorpage exception processing
* </ul>
* 
* Methods Intended for Container Generated Code
* 
* Some methods are intended to be used by the code generated by the container, not by code written by JSP page authors,
* or JSP tag library authors.
* 
* The methods supporting lifecycle are <code>initialize()</code> and <code>release()</code>
* 
* The following methods enable the management of nested JspWriter streams to implement Tag Extensions:
* <code>pushBody()</code>
* 
* Methods Intended for JSP authors
* 
* The following methods provide convenient access to implicit objects: <code>getException()</code>,
* <code>getPage()</code> <code>getRequest()</code>, <code>getResponse()</code>, <code>getSession()</code>,
* <code>getServletConfig()</code> and <code>getServletContext()</code>.
* 
* The following methods provide support for forwarding, inclusion and error handling: <code>forward()</code>,
* <code>include()</code>, and <code>handlePageException()</code>.
*/
public abstract class PageContext extends JspContext {

 /**
 * Sole constructor. (For invocation by subclass constructors, typically implicit.)
 */
 public PageContext() {
 // NOOP by default
 }

 /**
 * Page scope: (this is the default) the named reference remains available in this PageContext until the return from
 * the current Servlet.service() invocation.
 */

 public static final int PAGE_SCOPE = 1;

 /**
 * Request scope: the named reference remains available from the ServletRequest associated with the Servlet until
 * the current request is completed.
 */

 public static final int REQUEST_SCOPE = 2;

 /**
 * Session scope (only valid if this page participates in a session): the named reference remains available from the
 * HttpSession (if any) associated with the Servlet until the HttpSession is invalidated.
 */

 public static final int SESSION_SCOPE = 3;

 /**
 * Application scope: named reference remains available in the ServletContext until it is reclaimed.
 */

 public static final int APPLICATION_SCOPE = 4;

 /**
 * Name used to store the Servlet in this PageContext's nametables.
 */

 public static final String PAGE = "jakarta.servlet.jsp.jspPage";

 /**
 * Name used to store this PageContext in it's own name table.
 */

 public static final String PAGECONTEXT = "jakarta.servlet.jsp.jspPageContext";

 /**
 * Name used to store ServletRequest in PageContext name table.
 */

 public static final String REQUEST = "jakarta.servlet.jsp.jspRequest";

 /**
 * Name used to store ServletResponse in PageContext name table.
 */

 public static final String RESPONSE = "jakarta.servlet.jsp.jspResponse";

 /**
 * Name used to store ServletConfig in PageContext name table.
 */

 public static final String CONFIG = "jakarta.servlet.jsp.jspConfig";

 /**
 * Name used to store HttpSession in PageContext name table.
 */

 public static final String SESSION = "jakarta.servlet.jsp.jspSession";
 /**
 * Name used to store current JspWriter in PageContext name table.
 */

 public static final String OUT = "jakarta.servlet.jsp.jspOut";

 /**
 * Name used to store ServletContext in PageContext name table.
 */

 public static final String APPLICATION = "jakarta.servlet.jsp.jspApplication";

 /**
 * Name used to store uncaught exception in ServletRequest attribute list and PageContext name table.
 */

 public static final String EXCEPTION = "jakarta.servlet.jsp.jspException";

 /**
 * 
 * The initialize method is called to initialize an uninitialized PageContext so that it may be used by a JSP
 * Implementation class to service an incoming request and response within it's _jspService() method.
 * 
 * This method is typically called from JspFactory.getPageContext() in order to initialize state.
 * 
 * This method is required to create an initial JspWriter, and associate the "out" name in page scope with this
 * newly created object.
 * 
 * This method should not be used by page or tag library authors.
 *
 * @param servlet The Servlet that is associated with this PageContext
 * @param request The currently pending request for this Servlet
 * @param response The currently pending response for this Servlet
 * @param errorPageURL The value of the errorpage attribute from the page directive or null
 * @param needsSession The value of the session attribute from the page directive
 * @param bufferSize The value of the buffer attribute from the page directive
 * @param autoFlush The value of the autoflush attribute from the page directive
 *
 * @throws IOException during creation of JspWriter
 * @throws IllegalStateException if out not correctly initialized
 * @throws IllegalArgumentException If one of the given parameters is invalid
 */

 public abstract void initialize(Servlet servlet, ServletRequest request, ServletResponse response,
 String errorPageURL, boolean needsSession, int bufferSize, boolean autoFlush)
 throws IOException, IllegalStateException, IllegalArgumentException;

 /**
 * 
 * This method shall "reset" the internal state of a PageContext, releasing all internal references, and preparing
 * the PageContext for potential reuse by a later invocation of initialize(). This method is typically called from
 * JspFactory.releasePageContext().
 * 
 * Subclasses shall envelope this method.
 * 
 * This method should not be used by page or tag library authors.
 */

 public abstract void release();

 /**
 * The current value of the session object (an HttpSession).
 *
 * @return the HttpSession for this PageContext or null
 */

 public abstract HttpSession getSession();

 /**
 * The current value of the page object (In a Servlet environment, this is an instance of jakarta.servlet.Servlet).
 *
 * @return the Page implementation class instance associated with this PageContext
 */

 public abstract Object getPage();

 /**
 * The current value of the request object (a ServletRequest).
 *
 * @return The ServletRequest for this PageContext
 */

 public abstract ServletRequest getRequest();

 /**
 * The current value of the response object (a ServletResponse).
 *
 * @return the ServletResponse for this PageContext
 */

 public abstract ServletResponse getResponse();

 /**
 * The current value of the exception object (an Exception).
 *
 * @return any exception passed to this as an errorpage
 */

 public abstract Exception getException();

 /**
 * The ServletConfig instance.
 *
 * @return the ServletConfig for this PageContext
 */

 public abstract ServletConfig getServletConfig();

 /**
 * The ServletContext instance.
 *
 * @return the ServletContext for this PageContext
 */

 public abstract ServletContext getServletContext();

 /**
 * 
 * This method is used to re-direct, or "forward" the current ServletRequest and ServletResponse to another active
 * component in the application.
 * 
 * 
 * If the relativeUrlPath begins with a "/" then the URL specified is calculated relative to the DOCROOT of
 * the <code> ServletContext </code> for this JSP. If the path does not begin with a "/" then the URL specified is
 * calculated relative to the URL of the request that was mapped to the calling JSP.
 * 
 * 
 * It is only valid to call this method from a <code> Thread </code> executing within a
 * <code> _jspService(...) </code> method of a JSP.
 * 
 * 
 * Once this method has been called successfully, it is illegal for the calling <code> Thread </code> to attempt to
 * modify the <code>
 * ServletResponse </code> object. Any such attempt to do so, shall result in undefined behavior. Typically, callers
 * immediately return from <code> _jspService(...) </code> after calling this method.
 * 
 *
 * @param relativeUrlPath specifies the relative URL path to the target resource as described above
 *
 * @throws IllegalStateException if <code> ServletResponse </code> is not in a state where a forward can be
 * performed
 * @throws ServletException if the page that was forwarded to throws a ServletException
 * @throws IOException if an I/O error occurred while forwarding
 */

 public abstract void forward(String relativeUrlPath) throws ServletException, IOException;

 /**
 * 
 * Causes the resource specified to be processed as part of the current ServletRequest and ServletResponse being
 * processed by the calling Thread. The output of the target resources processing of the request is written directly
 * to the ServletResponse output stream.
 * 
 * 
 * The current JspWriter "out" for this JSP is flushed as a side-effect of this call, prior to processing the
 * include.
 * 
 * 
 * If the relativeUrlPath begins with a "/" then the URL specified is calculated relative to the DOCROOT of
 * the <code>ServletContext</code> for this JSP. If the path does not begin with a "/" then the URL specified is
 * calculated relative to the URL of the request that was mapped to the calling JSP.
 * 
 * 
 * It is only valid to call this method from a <code> Thread </code> executing within a
 * <code> _jspService(...) </code> method of a JSP.
 * 
 *
 * @param relativeUrlPath specifies the relative URL path to the target resource to be included
 *
 * @throws ServletException if the page that was forwarded to throws a ServletException
 * @throws IOException if an I/O error occurred while forwarding
 */
 public abstract void include(String relativeUrlPath) throws ServletException, IOException;

 /**
 * 
 * Causes the resource specified to be processed as part of the current ServletRequest and ServletResponse being
 * processed by the calling Thread. The output of the target resources processing of the request is written directly
 * to the current JspWriter returned by a call to getOut().
 * 
 * 
 * If flush is true, The current JspWriter "out" for this JSP is flushed as a side-effect of this call, prior to
 * processing the include. Otherwise, the JspWriter "out" is not flushed.
 * 
 * 
 * If the relativeUrlPath begins with a "/" then the URL specified is calculated relative to the DOCROOT of
 * the <code>ServletContext</code> for this JSP. If the path does not begin with a "/" then the URL specified is
 * calculated relative to the URL of the request that was mapped to the calling JSP.
 * 
 * 
 * It is only valid to call this method from a <code> Thread </code> executing within a
 * <code> _jspService(...) </code> method of a JSP.
 * 
 *
 * @param relativeUrlPath specifies the relative URL path to the target resource to be included
 * @param flush True if the JspWriter is to be flushed before the include, or false if not.
 *
 * @throws ServletException if the page that was forwarded to throws a ServletException
 * @throws IOException if an I/O error occurred while forwarding
 *
 * @since JSP 2.0
 */
 public abstract void include(String relativeUrlPath, boolean flush) throws ServletException, IOException;

 /**
 * 
 * This method is intended to process an unhandled 'page' level exception by forwarding the exception to the
 * specified error page for this JSP. If forwarding is not possible (for example because the response has already
 * been committed), an implementation dependent mechanism should be used to invoke the error page (e.g. "including"
 * the error page instead).
 * 
 * If no error page is defined in the page, the exception should be rethrown so that the standard servlet error
 * handling takes over.
 * 
 * A JSP implementation class shall typically clean up any local state prior to invoking this and will return
 * immediately thereafter. It is illegal to generate any output to the client, or to modify any ServletResponse
 * state after invoking this call.
 * 
 * This method is kept for backwards compatibility reasons. Newly generated code should use
 * PageContext.handlePageException(Throwable).
 *
 * @param e the exception to be handled
 *
 * @throws ServletException if an error occurs while invoking the error page
 * @throws IOException if an I/O error occurred while invoking the error page
 * @throws NullPointerException if the exception is null
 *
 * @see #handlePageException(Throwable)
 */

 public abstract void handlePageException(Exception e) throws ServletException, IOException;

 /**
 * 
 * This method is intended to process an unhandled 'page' level exception by forwarding the exception to the
 * specified error page for this JSP. If forwarding is not possible (for example because the response has already
 * been committed), an implementation dependent mechanism should be used to invoke the error page (e.g. "including"
 * the error page instead).
 * 
 * If no error page is defined in the page, the exception should be rethrown so that the standard servlet error
 * handling takes over.
 * 
 * This method is intended to process an unhandled "page" level exception by redirecting the exception to either the
 * specified error page for this JSP, or if none was specified, to perform some implementation dependent action.
 * 
 * A JSP implementation class shall typically clean up any local state prior to invoking this and will return
 * immediately thereafter. It is illegal to generate any output to the client, or to modify any ServletResponse
 * state after invoking this call.
 *
 * @param t the throwable to be handled
 *
 * @throws ServletException if an error occurs while invoking the error page
 * @throws IOException if an I/O error occurred while invoking the error page
 * @throws NullPointerException if the exception is null
 *
 * @see #handlePageException(Exception)
 */

 public abstract void handlePageException(Throwable t) throws ServletException, IOException;

 /**
 * Return a new BodyContent object, save the current "out" JspWriter, and update the value of the "out" attribute in
 * the page scope attribute namespace of the PageContext.
 *
 * @return the new BodyContent
 */

 public BodyContent pushBody() {
 return null; // XXX to implement
 }

 /**
 * Provides convenient access to error information.
 *
 * @return an ErrorData instance containing information about the error, as obtained from the request attributes, as
 * per the Servlet specification. If this is not an error page (that is, if the isErrorPage attribute of
 * the page directive is not set to "true"), the information is meaningless.
 *
 * @since JSP 2.0
 */
 public ErrorData getErrorData() {
 int status = 0;

 Integer status_code = (Integer) getRequest().getAttribute(RequestDispatcher.ERROR_STATUS_CODE);
 // Avoid NPE if attribute is not set
 if (status_code != null) {
 status = status_code.intValue();
 }

 return new ErrorData((Throwable) getRequest().getAttribute(RequestDispatcher.ERROR_EXCEPTION), status,
 (String) getRequest().getAttribute(RequestDispatcher.ERROR_REQUEST_URI),
 (String) getRequest().getAttribute(RequestDispatcher.ERROR_SERVLET_NAME));
 }

}

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