/*
* Copyright 2004-2012 the original author or authors.
*
* Licensed 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
*
* http://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.springframework.webflow.expression.el;
import java.beans.FeatureDescriptor;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import javax.el.BeanELResolver;
import javax.el.ELContext;
import javax.el.ELResolver;
import javax.el.PropertyNotWritableException;
import org.springframework.binding.expression.el.DefaultELContext;
import org.springframework.webflow.execution.RequestContext;
import org.springframework.webflow.execution.RequestContextHolder;
/**
* Resolves "implicit" or well-known flow variables; for example "flowScope" in an expression like #{flowScope.foo}. The
* list of implicit flow variables consists of:
*
* <pre>
* requestParameters
* requestScope
* flashScope
* viewScope
* flowScope
* conversationScope
* messageContext
* externalContext
* flowExecutionContext
* flowExecutionUrl
* currentUser
* currentEvent
* </pre>
*
* @author Keith Donald
* @author Jeremy Grelle
*/
public class ImplicitFlowVariableELResolver extends ELResolver {
private RequestContext requestContext;
public ImplicitFlowVariableELResolver() {
}
public ImplicitFlowVariableELResolver(RequestContext requestContext) {
this.requestContext = requestContext;
}
public Class<?> getCommonPropertyType(ELContext context, Object base) {
if (base == null) {
return Object.class;
} else {
return null;
}
}
public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {
return null;
}
public Class<?> getType(ELContext context, Object base, Object property) {
RequestContext requestContext = getRequestContext();
if (base != null || requestContext == null) {
return null;
}
if (ImplicitVariables.matches(property)) {
context.setPropertyResolved(true);
return ImplicitVariables.value(context, requestContext, property).getClass();
} else {
return null;
}
}
public Object getValue(ELContext context, Object base, Object property) {
RequestContext requestContext = getRequestContext();
if (base != null || requestContext == null) {
return null;
}
if (ImplicitVariables.matches(property)) {
context.setPropertyResolved(true);
return ImplicitVariables.value(context, requestContext, property);
} else {
return null;
}
}
public boolean isReadOnly(ELContext context, Object base, Object property) {
RequestContext requestContext = getRequestContext();
if (base != null || requestContext == null) {
return false;
}
if (ImplicitVariables.matches(property)) {
context.setPropertyResolved(true);
return true;
} else {
return false;
}
}
public void setValue(ELContext context, Object base, Object property, Object value) {
RequestContext requestContext = getRequestContext();
if (base != null || requestContext == null) {
return;
}
if (ImplicitVariables.matches(property)) {
context.setPropertyResolved(true);
throw new PropertyNotWritableException("The implicit flow variable " + property + " is not writable.");
}
}
protected RequestContext getRequestContext() {
return requestContext != null ? requestContext : RequestContextHolder.getRequestContext();
}
private static final class ImplicitVariables {
private static final Map<String, PropertyResolver> vars = new HashMap<String, PropertyResolver>();
private static final PropertyResolver requestContextResolver = new PropertyResolver() {
protected Object doResolve(ELContext elContext, RequestContext requestContext, Object property) {
return elContext.getELResolver().getValue(elContext, requestContext, property);
}
};
private static final PropertyResolver externalContextResolver = new PropertyResolver() {
protected Object doResolve(ELContext elContext, RequestContext requestContext, Object property) {
return elContext.getELResolver().getValue(elContext, requestContext.getExternalContext(), property);
}
};
private static final PropertyResolver currentEventResolver = new PropertyResolver() {
protected Object doResolve(ELContext elContext, RequestContext requestContext, Object property) {
return requestContext.getCurrentEvent();
}
};
static {
vars.put("requestParameters", requestContextResolver);
vars.put("requestScope", requestContextResolver);
vars.put("flashScope", requestContextResolver);
vars.put("viewScope", requestContextResolver);
vars.put("flowScope", requestContextResolver);
vars.put("conversationScope", requestContextResolver);
vars.put("messageContext", requestContextResolver);
vars.put("externalContext", requestContextResolver);
vars.put("flowExecutionContext", requestContextResolver);
vars.put("flowExecutionUrl", requestContextResolver);
vars.put("currentUser", externalContextResolver);
vars.put("currentEvent", currentEventResolver);
}
public static boolean matches(Object property) {
return vars.containsKey(property);
}
public static Object value(ELContext elContext, RequestContext requestContext, Object property) {
PropertyResolver resolver = vars.get(property);
return resolver.resolve(requestContext, property);
}
}
private static abstract class PropertyResolver {
private static final BeanELResolver elPropertyResolver = new BeanELResolver();
public Object resolve(RequestContext context, Object property) {
ELContext elContext = new DefaultELContext(elPropertyResolver, null, null);
return doResolve(elContext, context, property);
}
protected abstract Object doResolve(ELContext elContext, RequestContext requestContext, Object property);
}
}