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| java.lang.Object
 javax.servlet.jsp.JspContext
javax.servlet.jsp.PageContext
| PageContext | | abstract public class PageContext extends JspContext (Code) | |
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().
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| Field Summary | |
| final public static String | APPLICATION
Name used to store ServletContext in PageContext name table. | | final public static int | APPLICATION_SCOPE
Application scope: named reference remains available in the
ServletContext until it is reclaimed. | | final public static String | CONFIG
Name used to store ServletConfig in PageContext name table. | | final public static String | EXCEPTION
Name used to store uncaught exception in ServletRequest attribute
list and PageContext name table. | | final public static String | OUT
Name used to store current JspWriter in PageContext name table. | | final public static String | PAGE
Name used to store the Servlet in this PageContext's nametables. | | final public static String | PAGECONTEXT
Name used to store this PageContext in it's own name table. | | final public 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. | | final public static String | REQUEST
Name used to store ServletRequest in PageContext name table. | | final public static int | REQUEST_SCOPE
Request scope: the named reference remains available from the
ServletRequest associated with the Servlet until the current request
is completed. | | final public static String | RESPONSE
Name used to store ServletResponse in PageContext name table. | | final public static String | SESSION
Name used to store HttpSession in PageContext name table. | | final public 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 Summary | |
| public | PageContext()
Sole constructor. |
| Method Summary | |
| abstract public void | forward(String relativeUrlPath)
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. | | public ErrorData | getErrorData()
Provides convenient access to error information.
an ErrorData instance containing information about the error, as obtained from the request attributes, as per the Servlet specification. | | abstract public Exception | getException()
The current value of the exception object (an Exception). | | abstract public Object | getPage()
The current value of the page object (In a Servlet environment,
this is an instance of javax.servlet.Servlet). | | abstract public ServletRequest | getRequest()
The current value of the request object (a ServletRequest). | | abstract public ServletResponse | getResponse()
The current value of the response object (a ServletResponse). | | abstract public ServletConfig | getServletConfig()
The ServletConfig instance. | | abstract public ServletContext | getServletContext()
The ServletContext instance. | | abstract public HttpSession | getSession()
The current value of the session object (an HttpSession). | | abstract public void | handlePageException(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 public void | handlePageException(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 public void | include(String relativeUrlPath)
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. | | abstract public void | include(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.
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. | | abstract public void | initialize(Servlet servlet, ServletRequest request, ServletResponse response, 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. | | public 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 public 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(). |
| APPLICATION | | final public static String APPLICATION(Code) | | Name used to store ServletContext in PageContext name table.
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| APPLICATION_SCOPE | | final public static int APPLICATION_SCOPE(Code) | | Application scope: named reference remains available in the
ServletContext until it is reclaimed.
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| CONFIG | | final public static String CONFIG(Code) | | Name used to store ServletConfig in PageContext name table.
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| EXCEPTION | | final public static String EXCEPTION(Code) | | Name used to store uncaught exception in ServletRequest attribute
list and PageContext name table.
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| OUT | | final public static String OUT(Code) | | Name used to store current JspWriter in PageContext name table.
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| PAGE | | final public static String PAGE(Code) | | Name used to store the Servlet in this PageContext's nametables.
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| PAGECONTEXT | | final public static String PAGECONTEXT(Code) | | Name used to store this PageContext in it's own name table.
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| PAGE_SCOPE | | final public static int PAGE_SCOPE(Code) | | Page scope: (this is the default) the named reference remains available
in this PageContext until the return from the current Servlet.service()
invocation.
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| REQUEST | | final public static String REQUEST(Code) | | Name used to store ServletRequest in PageContext name table.
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| REQUEST_SCOPE | | final public static int REQUEST_SCOPE(Code) | | Request scope: the named reference remains available from the
ServletRequest associated with the Servlet until the current request
is completed.
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| RESPONSE | | final public static String RESPONSE(Code) | | Name used to store ServletResponse in PageContext name table.
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| SESSION | | final public static String SESSION(Code) | | Name used to store HttpSession in PageContext name table.
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| SESSION_SCOPE | | final public static int SESSION_SCOPE(Code) | | 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.
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| PageContext | | public PageContext()(Code) | | Sole constructor. (For invocation by subclass constructors,
typically implicit.)
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| forward | | abstract public void forward(String relativeUrlPath) throws ServletException, IOException(Code) | |
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.
Parameters:
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 throwsa ServletException
throws:
IOException - if an I/O error occurred while forwarding |
| getErrorData | | public ErrorData getErrorData()(Code) | | Provides convenient access to error information.
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 setto "true"), the information is meaningless.
since:
2.0 |
| getException | | abstract public Exception getException()(Code) | | The current value of the exception object (an Exception).
any exception passed to this as an errorpage |
| getPage | | abstract public Object getPage()(Code) | | The current value of the page object (In a Servlet environment,
this is an instance of javax.servlet.Servlet).
the Page implementation class instance associated with this PageContext |
| getRequest | | abstract public ServletRequest getRequest()(Code) | | The current value of the request object (a ServletRequest).
The ServletRequest for this PageContext |
| getResponse | | abstract public ServletResponse getResponse()(Code) | | The current value of the response object (a ServletResponse).
the ServletResponse for this PageContext |
| getServletConfig | | abstract public ServletConfig getServletConfig()(Code) | | The ServletConfig instance.
the ServletConfig for this PageContext |
| getServletContext | | abstract public ServletContext getServletContext()(Code) | | The ServletContext instance.
the ServletContext for this PageContext |
| getSession | | abstract public HttpSession getSession()(Code) | | The current value of the session object (an HttpSession).
the HttpSession for this PageContext or null |
| handlePageException | | abstract public void handlePageException(Exception e) throws ServletException, IOException(Code) | |
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).
Parameters:
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 errorpage
throws:
NullPointerException - if the exception is null
See Also: PageContext.handlePageException(Throwable) |
| handlePageException | | abstract public void handlePageException(Throwable t) throws ServletException, IOException(Code) | |
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.
Parameters:
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 errorpage
throws:
NullPointerException - if the exception is null
See Also: PageContext.handlePageException(Exception) |
| include | | abstract public void include(String relativeUrlPath) throws ServletException, IOException(Code) | |
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.
Parameters:
relativeUrlPath - specifies the relative URL path to the target resource to be included
throws:
ServletException - if the page that was forwarded to throwsa ServletException
throws:
IOException - if an I/O error occurred while forwarding |
| include | | abstract public void include(String relativeUrlPath, boolean flush) throws ServletException, IOException(Code) | |
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.
Parameters:
relativeUrlPath - specifies the relative URL path to the target resource to be included
Parameters:
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 throwsa ServletException
throws:
IOException - if an I/O error occurred while forwarding
since:
2.0 |
| initialize | | abstract public void initialize(Servlet servlet, ServletRequest request, ServletResponse response, String errorPageURL, boolean needsSession, int bufferSize, boolean autoFlush) throws IOException, IllegalStateException, IllegalArgumentException(Code) | |
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.
Parameters:
servlet - The Servlet that is associated with this PageContext
Parameters:
request - The currently pending request for this Servlet
Parameters:
response - The currently pending response for this Servlet
Parameters:
errorPageURL - The value of the errorpage attribute from the page directive or null
Parameters:
needsSession - The value of the session attribute from the page directive
Parameters:
bufferSize - The value of the buffer attribute from the page directive
Parameters:
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 parametersis invalid |
| pushBody | | public BodyContent pushBody()(Code) | | 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.
the new BodyContent |
| release | | abstract public void release()(Code) | |
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.
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