/*
* Based on JUEL 2.2.1 code, 2006-2009 Odysseus Software GmbH
*
* 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.activiti.engine.impl.javax.el;
import java.beans.FeatureDescriptor;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
/**
* Defines property resolution behavior on instances of java.util.ResourceBundle. This resolver
* handles base objects of type java.util.ResourceBundle. It accepts any object as a property and
* coerces it to a java.lang.String for invoking java.util.ResourceBundle.getObject(String). This
* resolver is read only and will throw a {@link PropertyNotWritableException} if setValue is
* called. ELResolvers are combined together using {@link CompositeELResolver}s, to define rich
* semantics for evaluating an expression. See the javadocs for {@link ELResolver} for details.
*/
public class ResourceBundleELResolver extends ELResolver {
/**
* If the base object is a ResourceBundle, returns the most general type that this resolver
* accepts for the property argument. Otherwise, returns null. Assuming the base is a
* ResourceBundle, this method will always return String.class.
*
* @param context
* The context of this evaluation.
* @param base
* The bundle to analyze. Only bases of type ResourceBundle are handled by this
* resolver.
* @return null if base is not a ResourceBundle; otherwise String.class.
*/
@Override
public Class<?> getCommonPropertyType(ELContext context, Object base) {
return isResolvable(base) ? String.class : null;
}
/**
* If the base object is a ResourceBundle, returns an Iterator containing the set of keys
* available in the ResourceBundle. Otherwise, returns null. The Iterator returned must contain
* zero or more instances of java.beans.FeatureDescriptor. Each info object contains information
* about a key in the ResourceBundle, and is initialized as follows:
* <ul>
* <li>displayName - The String key name</li>
* <li>name - Same as displayName property</li>
* <li>shortDescription - Empty string</li>
* <li>expert - false</li>
* <li>hidden - false</li>
* <li>preferred - true</li>
* </ul>
* In addition, the following named attributes must be set in the returned FeatureDescriptors:
* <ul>
* <li>{@link ELResolver#TYPE} - String.class.</li>
* <li>{@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - true</li>
* </ul>
*
* @param context
* The context of this evaluation.
* @param base
* The bundle to analyze. Only bases of type ResourceBundle are handled by this
* resolver.
* @return An Iterator containing zero or more (possibly infinitely more) FeatureDescriptor
* objects, each representing a key in this bundle, or null if the base object is not a
* ResourceBundle.
*/
@Override
public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {
if (isResolvable(base)) {
final Enumeration<String> keys = ((ResourceBundle) base).getKeys();
return new Iterator<FeatureDescriptor>() {
public boolean hasNext() {
return keys.hasMoreElements();
}
public FeatureDescriptor next() {
FeatureDescriptor feature = new FeatureDescriptor();
feature.setDisplayName(keys.nextElement());
feature.setName(feature.getDisplayName());
feature.setShortDescription("");
feature.setExpert(true);
feature.setHidden(false);
feature.setPreferred(true);
feature.setValue(TYPE, String.class);
feature.setValue(RESOLVABLE_AT_DESIGN_TIME, true);
return feature;
}
public void remove() {
throw new UnsupportedOperationException("Cannot remove");
}
};
}
return null;
}
/**
* If the base object is an instance of ResourceBundle, return null, since the resolver is read
* only. If the base is ResourceBundle, the propertyResolved property of the ELContext object
* must be set to true by this resolver, before returning. If this property is not true after
* this method is called, the caller should ignore the return value.
*
* @param context
* The context of this evaluation.
* @param base
* The bundle to analyze. Only bases of type ResourceBundle are handled by this
* resolver.
* @param property
* The name of the property to analyze.
* @return If the propertyResolved property of ELContext was set to true, then null; otherwise
* undefined.
* @throws NullPointerException
* if context is null
*/
@Override
public Class<?> getType(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException("context is null");
}
if (isResolvable(base)) {
context.setPropertyResolved(true);
}
return null;
}
/**
* If the base object is an instance of ResourceBundle, the provided property will first be
* coerced to a String. The Object returned by getObject on the base ResourceBundle will be
* returned. If the base is ResourceBundle, the propertyResolved property of the ELContext
* object must be set to true by this resolver, before returning. If this property is not true
* after this method is called, the caller should ignore the return value.
*
* @param context
* The context of this evaluation.
* @param base
* The bundle to analyze. Only bases of type ResourceBundle are handled by this
* resolver.
* @param property
* The name of the property to analyze. Will be coerced to a String.
* @return If the propertyResolved property of ELContext was set to true, then null if property
* is null; otherwise the Object for the given key (property coerced to String) from the
* ResourceBundle. If no object for the given key can be found, then the String "???" +
* key + "???".
* @throws NullPointerException
* if context is null.
* @throws ELException
* if an exception was thrown while performing the property or variable resolution.
* The thrown exception must be included as the cause property of this exception, if
* available.
*/
@Override
public Object getValue(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException("context is null");
}
Object result = null;
if (isResolvable(base)) {
if (property != null) {
try {
result = ((ResourceBundle) base).getObject(property.toString());
} catch (MissingResourceException e) {
result = "???" + property + "???";
}
}
context.setPropertyResolved(true);
}
return result;
}
/**
* If the base object is not null and an instanceof java.util.ResourceBundle, return true.
*
* @return If the propertyResolved property of ELContext was set to true, then true; otherwise
* undefined.
* @throws NullPointerException
* if context is null.
*/
@Override
public boolean isReadOnly(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException("context is null");
}
if (isResolvable(base)) {
context.setPropertyResolved(true);
}
return true;
}
/**
* If the base object is a ResourceBundle, throw a {@link PropertyNotWritableException}.
*
* @param context
* The context of this evaluation.
* @param base
* The bundle to analyze. Only bases of type ResourceBundle are handled by this
* resolver.
* @param property
* The name of the property to analyze. Will be coerced to a String.
* @param value
* The value to be set.
* @throws NullPointerException
* if context is null.
* @throws PropertyNotWritableException
* Always thrown if base is an instance of ResourceBundle.
*/
@Override
public void setValue(ELContext context, Object base, Object property, Object value) {
if (context == null) {
throw new NullPointerException("context is null");
}
if (isResolvable(base)) {
throw new PropertyNotWritableException("resolver is read-only");
}
}
/**
* Test whether the given base should be resolved by this ELResolver.
*
* @param base
* The bean to analyze.
* @param property
* The name of the property to analyze. Will be coerced to a String.
* @return base instanceof ResourceBundle
*/
private final boolean isResolvable(Object base) {
return base instanceof ResourceBundle;
}
}