org.apache.commons.jxpath.servlet
Class JXPathServletContexts

java.lang.Object
  org.apache.commons.jxpath.servlet.JXPathServletContexts

public final class JXPathServletContexts

extends java.lang.Object

Static methods that allocate and cache JXPathContexts bound to PageContext, ServletRequest, HttpSession and ServletContext.

The JXPathContext returned by getPageContext() provides access to all scopes via the PageContext.findAttribute() method. Thus, an expression like "foo" will first look for the attribute named "foo" in the "page" context, then the "request" context, then the "session" one and finally in the "application" context.

If you need to limit the attibute lookup to just one scope, you can use the pre-definded variables "page", "request", "session" and "application". For example, the expression "$session/foo" extracts the value of the session attribute named "foo".

Following are some implementation details. There is a separate JXPathContext for each of the four scopes. These contexts are chained according to the nesting of the scopes. So, the parent of the "page" JXPathContext is a "request" JXPathContext, whose parent is a "session" JXPathContext (that is if there is a session), whose parent is an "application" context.

The XPath context node for each context is the corresponding object: PageContext, ServletRequest, HttpSession or ServletContext. This feature can be used by servlets. A servlet can use one of the methods declared by this class and work with a specific JXPathContext for any scope.

Since JXPath chains lookups for variables and extension functions, variables and extension function declared in the outer scopes are also available in the inner scopes.

Each of the four context declares exactly one variable, the value of which is the corresponding object: PageContext, etc.

The "session" variable will be undefined if there is no session for this servlet. JXPath does not automatically create sessions.

Version:

$Revision: 1.6 $ $Date: 2004/05/08 15:10:49 $

Author:

Dmitri Plotnikov

Field Summary

private static JXPathContextFactory

factory

Constructor Summary

JXPathServletContexts()

Method Summary

static JXPathContext	getApplicationContext(javax.servlet.ServletContext servletContext) Returns a JXPathContext bound to the "application" scope.
static JXPathContext	getPageContext(javax.servlet.jsp.PageContext pageContext) Returns a JXPathContext bound to the "page" scope.
static JXPathContext	getRequestContext(javax.servlet.ServletRequest request, javax.servlet.ServletContext servletContext) Returns a JXPathContext bound to the "request" scope.
static JXPathContext	getSessionContext(javax.servlet.http.HttpSession session, javax.servlet.ServletContext servletContext) Returns a JXPathContext bound to the "session" scope.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

factory

private static JXPathContextFactory factory

Constructor Detail

JXPathServletContexts

public JXPathServletContexts()

Method Detail

getPageContext

public static JXPathContext getPageContext(javax.servlet.jsp.PageContext pageContext)

Returns a JXPathContext bound to the "page" scope. Caches that context within the PageContext itself.

getRequestContext

public static JXPathContext getRequestContext(javax.servlet.ServletRequest request,
                                              javax.servlet.ServletContext servletContext)

Returns a JXPathContext bound to the "request" scope. Caches that context within the request itself.

getSessionContext

public static JXPathContext getSessionContext(javax.servlet.http.HttpSession session,
                                              javax.servlet.ServletContext servletContext)

Returns a JXPathContext bound to the "session" scope. Caches that context within the session itself.

getApplicationContext

public static JXPathContext getApplicationContext(javax.servlet.ServletContext servletContext)

Returns a JXPathContext bound to the "application" scope. Caches that context within the servlet context itself.