JXPathServletContexts.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
*
* https://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 org.apache.commons.jxpath.servlet;
import javax.servlet.ServletContext;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.PageContext;
import org.apache.commons.jxpath.JXPathContext;
import org.apache.commons.jxpath.JXPathContextFactory;
import org.apache.commons.jxpath.JXPathIntrospector;
/**
* Static methods that allocate and cache JXPathContexts bound to {@link PageContext}, {@link ServletRequest}, {@link HttpSession} and {@link ServletContext}.
* <p>
* The {@link JXPathContext} returned by {@link #getPageContext 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.
* <p>
* 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".
* <p>
* 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.
* <p>
* 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.
* <p>
* 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.
* <p>
* Each of the four context declares exactly one variable, the value of which is the corresponding object: PageContext, etc.
* <p>
* The "session" variable will be undefined if there is no session for this servlet. JXPath does not automatically create sessions.
*/
public final class JXPathServletContexts {
private static JXPathContextFactory factory;
static {
JXPathIntrospector.registerDynamicClass(PageScopeContext.class, PageScopeContextHandler.class);
JXPathIntrospector.registerDynamicClass(PageContext.class, PageContextHandler.class);
JXPathIntrospector.registerDynamicClass(ServletContext.class, ServletContextHandler.class);
JXPathIntrospector.registerDynamicClass(ServletRequestAndContext.class, ServletRequestHandler.class);
JXPathIntrospector.registerDynamicClass(HttpSessionAndServletContext.class, HttpSessionHandler.class);
factory = JXPathContextFactory.newInstance();
}
/**
* Returns a JXPathContext bound to the "application" scope. Caches that context within the servlet context itself.
*
* @param servletContext operative
* @return JXPathContext
*/
public static JXPathContext getApplicationContext(final ServletContext servletContext) {
JXPathContext context = (JXPathContext) servletContext.getAttribute(Constants.JXPATH_CONTEXT);
if (context == null) {
context = factory.newContext(null, servletContext);
context.setVariables(new KeywordVariables(Constants.APPLICATION_SCOPE, servletContext));
servletContext.setAttribute(Constants.JXPATH_CONTEXT, context);
}
return context;
}
/**
* Returns a JXPathContext bound to the "page" scope. Caches that context within the PageContext itself.
*
* @param pageContext as described
* @return JXPathContext
*/
public static JXPathContext getPageContext(final PageContext pageContext) {
JXPathContext context = (JXPathContext) pageContext.getAttribute(Constants.JXPATH_CONTEXT);
if (context == null) {
final JXPathContext parentContext = getRequestContext(pageContext.getRequest(), pageContext.getServletContext());
context = factory.newContext(parentContext, pageContext);
context.setVariables(new KeywordVariables(Constants.PAGE_SCOPE, new PageScopeContext(pageContext)));
pageContext.setAttribute(Constants.JXPATH_CONTEXT, context);
}
return context;
}
/**
* Returns a JXPathContext bound to the "request" scope. Caches that context within the request itself.
*
* @param request as described
* @param servletContext operative
* @return JXPathContext
*/
public static JXPathContext getRequestContext(final ServletRequest request, final ServletContext servletContext) {
JXPathContext context = (JXPathContext) request.getAttribute(Constants.JXPATH_CONTEXT);
// If we are in an included JSP or Servlet, the request parameter
// will represent the included URL, but the JXPathContext we have
// just acquired will represent the outer request.
if (context != null) {
final ServletRequestAndContext handle = (ServletRequestAndContext) context.getContextBean();
if (handle.getServletRequest() == request) {
return context;
}
}
JXPathContext parentContext = null;
if (request instanceof HttpServletRequest) {
final HttpSession session = ((HttpServletRequest) request).getSession(false);
if (session != null) {
parentContext = getSessionContext(session, servletContext);
} else {
parentContext = getApplicationContext(servletContext);
}
}
final ServletRequestAndContext handle = new ServletRequestAndContext(request, servletContext);
context = factory.newContext(parentContext, handle);
context.setVariables(new KeywordVariables(Constants.REQUEST_SCOPE, handle));
request.setAttribute(Constants.JXPATH_CONTEXT, context);
return context;
}
/**
* Returns a JXPathContext bound to the "session" scope. Caches that context within the session itself.
*
* @param session as described
* @param servletContext operative
* @return JXPathContext
*/
public static JXPathContext getSessionContext(final HttpSession session, final ServletContext servletContext) {
JXPathContext context = (JXPathContext) session.getAttribute(Constants.JXPATH_CONTEXT);
if (context == null) {
final JXPathContext parentContext = getApplicationContext(servletContext);
final HttpSessionAndServletContext handle = new HttpSessionAndServletContext(session, servletContext);
context = factory.newContext(parentContext, handle);
context.setVariables(new KeywordVariables(Constants.SESSION_SCOPE, handle));
session.setAttribute(Constants.JXPATH_CONTEXT, context);
}
return context;
}
/**
* Constructs a new instance.
*
* @deprecated Will be private in the next major version.
*/
@Deprecated
public JXPathServletContexts() {
// empty
}
}