/*
* 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
*
* 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.apache.shindig.gadgets.templates;
import java.beans.FeatureDescriptor;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import javax.el.ELContext;
import javax.el.ELResolver;
import javax.el.PropertyNotWritableException;
import javax.el.ValueExpression;
import com.google.common.collect.ImmutableSet;
/**
* ELResolver used to process OpenSocial templates. Provides three variables:
* <ul>
* <li>"Top": Global values </li>
* <li>"Cur": Current template variable</li>
* <li>"Context": Miscellaneous contextual information</li>
*/
public class TemplateELResolver extends ELResolver {
public static final String PROPERTY_TOP = "Top";
public static final String PROPERTY_CONTEXT = "Context";
public static final String PROPERTY_CUR = "Cur";
public static final String PROPERTY_MY = "My";
private static final Set<String> TOP_LEVEL_PROPERTIES =
ImmutableSet.of(PROPERTY_TOP, PROPERTY_CONTEXT, PROPERTY_CUR, PROPERTY_MY);
private final TemplateContext templateContext;
public TemplateELResolver(TemplateContext templateContext) {
this.templateContext = templateContext;
}
@Override
public Class<?> getCommonPropertyType(ELContext context, Object base) {
if (base == null) {
return String.class;
}
return null;
}
@Override
public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context,
Object base) {
return null;
}
@Override
public Class<?> getType(ELContext context, Object base, Object property) {
// TODO: implement
return null;
}
@Override
public Object getValue(ELContext context, Object base, Object property) {
if (base == null) {
if (TOP_LEVEL_PROPERTIES.contains(property)) {
context.setPropertyResolved(true);
if (PROPERTY_TOP.equals(property)) {
return templateContext.getTop();
} else if (PROPERTY_CONTEXT.equals(property)) {
return templateContext.getContext();
} else if (PROPERTY_MY.equals(property)) {
return templateContext.getMy();
} else {
return templateContext.getCur();
}
}
// Check variables.
if (property instanceof String) {
ValueExpression valueExp = context.getVariableMapper().resolveVariable((String) property);
if (valueExp != null) {
context.setPropertyResolved(true);
return valueExp.getValue(context);
}
}
// Check ${Cur} next.
Object cur = templateContext.getCur();
// Resolve through "cur" as if it were a value - if "isPropertyResolved()"
// is true, it was handled
if (cur != null) {
Object value = context.getELResolver().getValue(context, cur, property);
if (context.isPropertyResolved()) {
if (value != null) {
return value;
} else {
context.setPropertyResolved(false);
}
}
}
// Check ${My} next.
Map<String, ? extends Object> scope = templateContext.getMy();
if (scope != null && scope.containsKey(property)) {
context.setPropertyResolved(true);
return scope.get(property);
}
// Look at ${Top} context last.
scope = templateContext.getTop();
if (scope != null && scope.containsKey(property)) {
context.setPropertyResolved(true);
return scope.get(property);
}
}
return null;
}
@Override
public boolean isReadOnly(ELContext context, Object base, Object property) {
if (base == null && TOP_LEVEL_PROPERTIES.contains(property)) {
context.setPropertyResolved(true);
return true;
}
return false;
}
@Override
public void setValue(ELContext context, Object base, Object property, Object value) {
if (base == null && TOP_LEVEL_PROPERTIES.contains(property)) {
throw new PropertyNotWritableException();
}
}
}