javax.servlet.jsp.PageContext Maven / Gradle / Ivy
/*
* 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 javax.servlet.jsp;
import java.io.IOException;
import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpSession;
import javax.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 PageContext 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:
*
* - a single API to manage the various scoped namespaces
*
- a number of convenience API's to access various public objects
*
- a mechanism to obtain the JspWriter for output
*
- a mechanism to manage session usage by the page
*
- a mechanism to expose page directive attributes to the scripting
* environment
*
- mechanisms to forward or include the current request to other active
* components in the application
*
- a mechanism to handle errorpage exception processing
*
*
* 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 initialize()
* and release()
*
*
* The following methods enable the management of nested JspWriter
* streams to implement Tag Extensions: pushBody()
*
*
Methods Intended for JSP authors
*
* The following methods provide convenient access to implicit objects:
* getException(), getPage()
* getRequest(), getResponse(),
* getSession(), getServletConfig()
* and getServletContext().
*
*
* The following methods provide support for forwarding, inclusion
* and error handling:
* forward(), include(),
* and handlePageException().
*/
abstract public 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 = "javax.servlet.jsp.jspPage";
/**
* Name used to store this PageContext in it's own name table.
*/
public static final String PAGECONTEXT = "javax.servlet.jsp.jspPageContext";
/**
* Name used to store ServletRequest in PageContext name table.
*/
public static final String REQUEST = "javax.servlet.jsp.jspRequest";
/**
* Name used to store ServletResponse in PageContext name table.
*/
public static final String RESPONSE = "javax.servlet.jsp.jspResponse";
/**
* Name used to store ServletConfig in PageContext name table.
*/
public static final String CONFIG = "javax.servlet.jsp.jspConfig";
/**
* Name used to store HttpSession in PageContext name table.
*/
public static final String SESSION = "javax.servlet.jsp.jspSession";
/**
* Name used to store current JspWriter in PageContext name table.
*/
public static final String OUT = "javax.servlet.jsp.jspOut";
/**
* Name used to store ServletContext in PageContext name table.
*/
public static final String APPLICATION = "javax.servlet.jsp.jspApplication";
/**
* Name used to store uncaught exception in ServletRequest attribute
* list and PageContext name table.
*/
public static final String EXCEPTION = "javax.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
*/
abstract public 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.
*
*/
abstract public void release();
/**
* The current value of the session object (an HttpSession).
*
* @return the HttpSession for this PageContext or null
*/
abstract public HttpSession getSession();
/**
* The current value of the page object (In a Servlet environment,
* this is an instance of javax.servlet.Servlet).
*
* @return the Page implementation class instance associated
* with this PageContext
*/
abstract public Object getPage();
/**
* The current value of the request object (a ServletRequest).
*
* @return The ServletRequest for this PageContext
*/
abstract public ServletRequest getRequest();
/**
* The current value of the response object (a ServletResponse).
*
* @return the ServletResponse for this PageContext
*/
abstract public ServletResponse getResponse();
/**
* The current value of the exception object (an Exception).
*
* @return any exception passed to this as an errorpage
*/
abstract public Exception getException();
/**
* The ServletConfig instance.
*
* @return the ServletConfig for this PageContext
*/
abstract public ServletConfig getServletConfig();
/**
* The ServletContext instance.
*
* @return the ServletContext for this PageContext
*/
abstract public 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 ServletContext
* 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 Thread
* executing within a _jspService(...) method of a JSP.
*
*
* Once this method has been called successfully, it is illegal for the
* calling Thread to attempt to modify the
* ServletResponse object. Any such attempt to do so, shall result
* in undefined behavior. Typically, callers immediately return from
* _jspService(...) after calling this method.
*
*
* @param relativeUrlPath specifies the relative URL path to the target
* resource as described above
*
* @throws IllegalStateException if ServletResponse 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
*/
abstract public 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 ServletContext
* 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 Thread
* executing within a _jspService(...) 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
*/
abstract public 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 ServletContext
* 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 Thread
* executing within a _jspService(...) 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 2.0
*/
abstract public 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)
*/
abstract public 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)
*/
abstract public 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 2.0
*/
public ErrorData getErrorData() {
int status = 0;
Integer status_code = (Integer)getRequest().getAttribute(
"javax.servlet.error.status_code");
// Avoid NPE if attribute is not set
if (status_code != null) {
status = status_code.intValue();
}
return new ErrorData(
(Throwable)getRequest().getAttribute( "javax.servlet.error.exception" ),
status,
(String)getRequest().getAttribute( "javax.servlet.error.request_uri" ),
(String)getRequest().getAttribute( "javax.servlet.error.servlet_name" ) );
}
}