com.sun.faces.context.flash.FlashELResolver Maven / Gradle / Ivy
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/*
* Copyright (c) 2023 Contributors to Eclipse Foundation.
* Copyright (c) 1997, 2020 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package com.sun.faces.context.flash;
import jakarta.el.ELContext;
import jakarta.el.ELResolver;
import jakarta.el.PropertyNotFoundException;
import jakarta.el.PropertyNotWritableException;
import jakarta.faces.FactoryFinder;
import jakarta.faces.context.ExternalContext;
import jakarta.faces.context.FacesContext;
import jakarta.faces.context.Flash;
import jakarta.faces.context.FlashFactory;
import java.util.Map;
/**
*
* Provide a feature semantically identical to the
* "flash" concept in Ruby on
* Rails.
*
*
*
* The feature is exposed to users via a custom ELResolver which introduces a new implicit object,
* flash. The flash functions as Map and can be used in getValue( ) or
* setValue(
* ) expressions.
*
*
*
* Usage
*
*
*
* Consider three Faces views: viewA, viewB, and viewC. The user first views viewA, then clicks a button and is shown
* viewB, where she clicks a button and is shown viewC. If values are stored into the flash during the rendering or
* postback phases of viewA, they are available to during the rendering phase of viewB, but are not available during the
* rendering or postback phases of viewC. In other words, values stored into the flash on "this" request are accessible
* for the "next" request, but not thereafter.
*
*
*
* There are three ways to access the flash.
*
*
*
* -
* Using an Expression Language Expression, such as using
#{flash.foo} as the value of an attribute in a page.
*
* -
* Using the EL API, such as:
*
*
*
* FacesContext context = FacesContext.getCurrentInstance();
* ValueExpression flashExpression = context.getApplication().
* createValueExpression(context.getELContext(), "#{flash.foo}",
* null, Object.class);
* flashExpression.setValue(context.getELContext(), "Foo's new value");
*
*
*
*
* -
*
* Using getting the {@link ELFlash} directly, such as:
*
*
*
*
* Map<String,Object> flash = ELFlash.getFlash();
* flash.put("foo", "Foo's new value");
*
*
*
*
*
*
* The main entry point to this feature is the first one. This library includes a simple custom tag, jsfExt:set, that evaluates an expression and sets its value into
* another expression. jsfExt:set can be used to store values into the flash from JSP pages, like this:
*
*
*
* <jsfExt:set var="#{flash.foo}" value="fooValue"
* />
*
*
*
* or this:
*
*
*
* <jsfExt:set var="#{flash.keep.bar}" value="#{user.name}"
* />
*
*
*
* or even this:
*
*
*
*
* <jsfExt:set var="#{flash.now.baz}" value="#{cookie.userCookie}" />
*
* <h:outputText value="#{flash.now.baz}" />
*
*
*
*
*
* Related Classes
*
*
*
* The complete list of classes that make up this feature is
*
*
*
* FlashELResolver{@link ELFlash}
*/
public class FlashELResolver extends ELResolver {
/**
*
* Not intended for manual invocation. Only called by the Faces Runtime.
*
*/
public FlashELResolver() {
}
// ------------------------------------------------------ Manifest Constants
private static final String FLASH_VARIABLE_NAME = "flash";
private static final String FLASH_NOW_VARIABLE_NAME = "now";
private static final String FLASH_KEEP_VARIABLE_NAME = "keep";
// ------------------------------------------------ VariableResolver Methods
/**
*
* Hook into the EL resolution process to introduce the flash implicit object. If property is
* null, take no action and return null. if base is null, return null. If
* base is an instance of ELFlash and property is the literal string "keep", set a ThreadLocal
* property that will be inspected by the flash on the next link in the resolution chain and return the
* ELFlash instance. If base is an instance of ELFlash and property
* is the literal string "now", return the result of calling getRequestMap( ) on the
* ExternalContext for the FacesContext for this request. Call
* setPropertyResolved(true) on the ELContext where appropriate.
*
*
* @throws PropertyNotFoundException if property is null.
*/
@Override
public Object getValue(ELContext elContext, Object base, Object property) {
if (null == property) {
// take no action.
return null;
}
Object result = null;
if (null == base) {
return null;
}
// If the base argument is the flash itself...
else if (base instanceof Flash) {
FacesContext facesContext = (FacesContext) elContext.getContext(FacesContext.class);
ExternalContext extCtx = facesContext.getExternalContext();
// and the property argument is "keep"...
switch (property.toString()) {
// Otherwise, if base is the flash, and property is "now"...
case FLASH_KEEP_VARIABLE_NAME:
elContext.setPropertyResolved(true);
// then this is a request to promote the value
// "property", which is assumed to have been previously
// stored in request scope via the "flash.now"
// expression, to flash scope.
result = base;
// Set a flag so the flash itself can look in the request
// and promote the value to the next request
FlashFactory ff = (FlashFactory) FactoryFinder.getFactory(FactoryFinder.FLASH_FACTORY);
ff.getFlash(true);
ELFlash.setKeepFlag(facesContext);
break;
case FLASH_NOW_VARIABLE_NAME:
// PENDING(edburns): use FacesContext.getAttributes() instead of
// request scope.
Map requestMap = extCtx.getRequestMap();
requestMap.put(ELFlash.FLASH_NOW_REQUEST_KEY, property);
elContext.setPropertyResolved(true);
result = requestMap;
break;
default:
result = null;
break;
}
}
return result;
}
/**
*
* Return the valid Class for a future set operation, which will always be null because sets
* happen via the MapELResolver operating on the {@link ELFlash} instance as a Map.
*
*
* @throws PropertyNotFoundException if property is null.
*/
@Override
public Class getType(ELContext elContext, Object base, Object property) {
if (null != base) {
return null;
}
if (null == property) {
String message = " base " + base + " property " + property;
throw new PropertyNotFoundException(message);
}
if (property.toString().equals(FLASH_VARIABLE_NAME)) {
elContext.setPropertyResolved(true);
}
return null;
}
/**
*
* This method will throw PropertyNotWritableException if called with a null base
* and a property value equal to the literal string "flash". This is because set operations normally go
* through the MapELResolver via the ELFlash Map.
*
*
*
* In other words, do not call this method directly to set a value into the flash! The only way to access the flash is
* via the EL API.
*
*
* @throws PropertyNotFoundException if base is null and property is
* null.
* @throws PropertyNotWritableException if base is null and property is the
* literal string "flash".
*/
@Override
public void setValue(ELContext elContext, Object base, Object property, Object value) {
if (base != null) {
return;
}
if (property == null) {
String message = " base " + base + " property " + property;
throw new PropertyNotFoundException(message);
}
if (property.toString().equals(FLASH_VARIABLE_NAME)) {
elContext.setPropertyResolved(true);
throw new PropertyNotWritableException(property.toString());
}
}
/**
*
* Returns true because write operations take place via the MapELResolver on the actual
* {@link ELFlash} instance.
*
*
* @throws PropertyNotFoundException if base is null and property is
* null.
*/
@Override
public boolean isReadOnly(ELContext elContext, Object base, Object property) {
if (base != null) {
return false;
}
if (property == null) {
String message = " base " + base + " property " + property;
throw new PropertyNotFoundException(message);
}
if (property.toString().equals(FLASH_VARIABLE_NAME)) {
elContext.setPropertyResolved(true);
return true;
}
return false;
}
/**
*
* If base is non-null and is the literal string "flash", return Object.class.
*
*/
@Override
public Class getCommonPropertyType(ELContext context, Object base) {
Class result = null;
if (null != base) {
if (FLASH_VARIABLE_NAME.equals(base.toString())) {
result = Object.class;
}
}
return result;
}
}