public abstract class PageContext extends JspContext
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:
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()
.
Modifier and Type | Field and Description |
---|---|
static java.lang.String |
APPLICATION
Name used to store ServletContext in PageContext name table.
|
static int |
APPLICATION_SCOPE
Application scope: named reference remains available in the ServletContext until it is reclaimed.
|
static java.lang.String |
CONFIG
Name used to store ServletConfig in PageContext name table.
|
static java.lang.String |
EXCEPTION
Name used to store uncaught exception in ServletRequest attribute list and PageContext name table.
|
static java.lang.String |
OUT
Name used to store current JspWriter in PageContext name table.
|
static java.lang.String |
PAGE
Name used to store the Servlet in this PageContext's nametables.
|
static int |
PAGE_SCOPE
Page scope: (this is the default) the named reference remains available in this PageContext until the return from
the current Servlet.service() invocation.
|
static java.lang.String |
PAGECONTEXT
Name used to store this PageContext in it's own name table.
|
static java.lang.String |
REQUEST
Name used to store ServletRequest in PageContext name table.
|
static int |
REQUEST_SCOPE
Request scope: the named reference remains available from the ServletRequest associated with the Servlet until
the current request is completed.
|
static java.lang.String |
RESPONSE
Name used to store ServletResponse in PageContext name table.
|
static java.lang.String |
SESSION
Name used to store HttpSession in PageContext name table.
|
static int |
SESSION_SCOPE
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.
|
Constructor and Description |
---|
PageContext()
Sole constructor.
|
Modifier and Type | Method and Description |
---|---|
abstract void |
forward(java.lang.String relativeUrlPath)
This method is used to re-direct, or "forward" the current ServletRequest and ServletResponse to another active
component in the application.
|
ErrorData |
getErrorData()
Provides convenient access to error information.
|
abstract java.lang.Exception |
getException()
The current value of the exception object (an Exception).
|
abstract java.lang.Object |
getPage()
The current value of the page object (In a Servlet environment, this is an instance of javax.servlet.Servlet).
|
abstract ServletRequest |
getRequest()
The current value of the request object (a ServletRequest).
|
abstract ServletResponse |
getResponse()
The current value of the response object (a ServletResponse).
|
abstract ServletConfig |
getServletConfig()
The ServletConfig instance.
|
abstract ServletContext |
getServletContext()
The ServletContext instance.
|
abstract HttpSession |
getSession()
The current value of the session object (an HttpSession).
|
abstract void |
handlePageException(java.lang.Exception e)
This method is intended to process an unhandled 'page' level exception by forwarding the exception to the
specified error page for this JSP.
|
abstract void |
handlePageException(java.lang.Throwable t)
This method is intended to process an unhandled 'page' level exception by forwarding the exception to the
specified error page for this JSP.
|
abstract void |
include(java.lang.String relativeUrlPath)
Causes the resource specified to be processed as part of the current ServletRequest and ServletResponse being
processed by the calling Thread.
|
abstract void |
include(java.lang.String relativeUrlPath,
boolean flush)
Causes the resource specified to be processed as part of the current ServletRequest and ServletResponse being
processed by the calling Thread.
|
abstract void |
initialize(Servlet servlet,
ServletRequest request,
ServletResponse response,
java.lang.String errorPageURL,
boolean needsSession,
int bufferSize,
boolean autoFlush)
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.
|
BodyContent |
pushBody()
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.
|
abstract void |
release()
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().
|
findAttribute, getAttribute, getAttribute, getAttributeNamesInScope, getAttributesScope, getELContext, getExpressionEvaluator, getOut, getVariableResolver, popBody, pushBody, removeAttribute, removeAttribute, setAttribute, setAttribute
public static final int PAGE_SCOPE
public static final int REQUEST_SCOPE
public static final int SESSION_SCOPE
public static final int APPLICATION_SCOPE
public static final java.lang.String PAGE
public static final java.lang.String PAGECONTEXT
public static final java.lang.String REQUEST
public static final java.lang.String RESPONSE
public static final java.lang.String CONFIG
public static final java.lang.String SESSION
public static final java.lang.String OUT
public static final java.lang.String APPLICATION
public static final java.lang.String EXCEPTION
public PageContext()
public abstract void initialize(Servlet servlet, ServletRequest request, ServletResponse response, java.lang.String errorPageURL, boolean needsSession, int bufferSize, boolean autoFlush) throws java.io.IOException, java.lang.IllegalStateException, java.lang.IllegalArgumentException
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.
servlet
- The Servlet that is associated with this PageContextrequest
- The currently pending request for this Servletresponse
- The currently pending response for this ServleterrorPageURL
- The value of the errorpage attribute from the page directive or nullneedsSession
- The value of the session attribute from the page directivebufferSize
- The value of the buffer attribute from the page directiveautoFlush
- The value of the autoflush attribute from the page directivejava.io.IOException
- during creation of JspWriterjava.lang.IllegalStateException
- if out not correctly initializedjava.lang.IllegalArgumentException
- If one of the given parameters is invalidpublic abstract void release()
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 HttpSession getSession()
public abstract java.lang.Object getPage()
public abstract ServletRequest getRequest()
public abstract ServletResponse getResponse()
public abstract java.lang.Exception getException()
public abstract ServletConfig getServletConfig()
public abstract ServletContext getServletContext()
public abstract void forward(java.lang.String relativeUrlPath) throws ServletException, java.io.IOException
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.
relativeUrlPath
- specifies the relative URL path to the target resource as described abovejava.lang.IllegalStateException
- if ServletResponse
is not in a state where a forward can be
performedServletException
- if the page that was forwarded to throws a ServletExceptionjava.io.IOException
- if an I/O error occurred while forwardingpublic abstract void include(java.lang.String relativeUrlPath) throws ServletException, java.io.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.
relativeUrlPath
- specifies the relative URL path to the target resource to be includedServletException
- if the page that was forwarded to throws a ServletExceptionjava.io.IOException
- if an I/O error occurred while forwardingpublic abstract void include(java.lang.String relativeUrlPath, boolean flush) throws ServletException, java.io.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.
relativeUrlPath
- specifies the relative URL path to the target resource to be includedflush
- True if the JspWriter is to be flushed before the include, or false if not.ServletException
- if the page that was forwarded to throws a ServletExceptionjava.io.IOException
- if an I/O error occurred while forwardingpublic abstract void handlePageException(java.lang.Exception e) throws ServletException, java.io.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 compatiblity reasons. Newly generated code should use PageContext.handlePageException(Throwable).
e
- the exception to be handledServletException
- if an error occurs while invoking the error pagejava.io.IOException
- if an I/O error occurred while invoking the error pagejava.lang.NullPointerException
- if the exception is nullhandlePageException(Throwable)
public abstract void handlePageException(java.lang.Throwable t) throws ServletException, java.io.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.
t
- the throwable to be handledServletException
- if an error occurs while invoking the error pagejava.io.IOException
- if an I/O error occurred while invoking the error pagejava.lang.NullPointerException
- if the exception is nullhandlePageException(Exception)
public BodyContent pushBody()
public ErrorData getErrorData()