/*
* Copyright (C) 2007 Sun Microsystems, Inc. All rights reserved. Use is
* subject to license terms.
*/
package org.jdesktop.el;
import java.beans.FeatureDescriptor;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.MissingResourceException;
import java.util.ResourceBundle;
/**
* Defines property resolution behavior on instances of
* {@link java.util.ResourceBundle}.
*
* <p>
* This resolver handles base objects of type
* <code>java.util.ResourceBundle</code>. It accepts any object as a property
* and coerces it to a <code>java.lang.String</code> for invoking
* {@link java.util.ResourceBundle#getObject(java.lang.String)}.
* </p>
*
* <p>
* This resolver is read only and will throw a
* {@link PropertyNotWritableException} if <code>setValue</code> is called.
* </p>
*
* <p>
* <code>ELResolver</code>s are combined together using
* {@link CompositeELResolver}s, to define rich semantics for evaluating an
* expression. See the javadocs for {@link ELResolver} for details.
* </p>
*
* @see CompositeELResolver
* @see ELResolver
* @see java.util.ResourceBundle
* @since JSP 2.1
*/
public class ResourceBundleELResolver extends ELResolver {
/**
* If the base object is an instance of <code>ResourceBundle</code>,
* the provided property will first be coerced to a <code>String</code>.
* The <code>Object</code> returned by <code>getObject</code> on
* the base <code>ResourceBundle</code> will be returned.
* </p>
* If the base is <code>ResourceBundle</code>, the
* <code>propertyResolved</code> property of the <code>ELContext</code>
* object must be set to <code>true</code> by this resolver, before
* returning. If this property is not <code>true</code> after this method
* is called, the caller should ignore the return value.
* </p>
* @param context
* The context of this evaluation.
* @param base
* The ResourceBundle to analyze.
* @param property
* The name of the property to analyze. Will be coerced to a
* <code>String</code>.
* @return If the <code>propertyResolved</code> property of
* <code>ELContext</code> was set to <code>true</code>, then
* <code>null</code> if property is <code>null</code>;
* otherwise the <code>Object</code> for the given key
* (property coerced to <code>String</code>) from the
* <code>ResourceBundle</code>.
* If no object for the given key can be found, then the
* <code>String</code> "???" + key + "???".
* @throws NullPointerException
* if context is <code>null</code>
* @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.
*/
public Object getValue(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base instanceof ResourceBundle) {
context.setPropertyResolved(true);
if (property != null) {
try {
return ((ResourceBundle) base).getObject(property
.toString());
} catch (MissingResourceException e) {
return "???" + property + "???";
}
}
}
return null;
}
/**
* If the base object is an instance of <code>ResourceBundle</code>,
* return <code>null</code>, since the resolver is read only.
*
* <p>
* If the base is <code>ResourceBundle</code>, the
* <code>propertyResolved</code> property of the <code>ELContext</code>
* object must be set to <code>true</code> by this resolver, before
* returning. If this property is not <code>true</code> after this method
* is called, the caller should ignore the return value.
* </p>
*
* @param context
* The context of this evaluation.
* @param base
* The ResourceBundle to analyze.
* @param property
* The name of the property to analyze.
* @return If the <code>propertyResolved</code> property of
* <code>ELContext</code> was set to <code>true</code>, then
* <code>null</code>; otherwise undefined.
* @throws NullPointerException
* if context is <code>null</code>
*/
public Class<?> getType(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base instanceof ResourceBundle) {
context.setPropertyResolved(true);
}
return null;
}
/**
* If the base object is a ResourceBundle, throw a
* {@link PropertyNotWritableException}.
*
* @param context
* The context of this evaluation.
* @param base
* The ResourceBundle to be modified. Only bases that are of type
* ResourceBundle are handled.
* @param property
* The String property to use.
* @param value
* The value to be set.
* @throws NullPointerException
* if context is <code>null</code>.
* @throws PropertyNotWritableException
* Always thrown if base is an instance of ReasourceBundle.
*/
public void setValue(ELContext context, Object base, Object property,
Object value) {
if (context == null) {
throw new NullPointerException();
}
if (base instanceof ResourceBundle) {
context.setPropertyResolved(true);
throw new PropertyNotWritableException(
"ResourceBundles are immutable");
}
}
/**
* If the base object is not null and an instanceof {@link ResourceBundle},
* return <code>true</code>.
*
* @param context
* The context of this evaluation.
* @param base
* The ResourceBundle to be modified. Only bases that are of type
* ResourceBundle are handled.
* @param property
* The String property to use.
* @return If the <code>propertyResolved</code> property of
* <code>ELContext</code> was set to <code>true</code>, then
* <code>true</code>; otherwise undefined.
* @throws NullPointerException
* if context is <code>null</code>
*/
public boolean isReadOnly(ELContext context, Object base, Object property) {
if (context == null) {
throw new NullPointerException();
}
if (base instanceof ResourceBundle) {
context.setPropertyResolved(true);
return true;
}
return false;
}
/**
* If the base object is a ResourceBundle, returns an <code>Iterator</code>
* containing the set of keys available in the <code>ResourceBundle</code>.
* Otherwise, returns <code>null</code>.
*
* <p>
* The <code>Iterator</code> returned must contain zero or more instances
* of {@link java.beans.FeatureDescriptor}. Each info object contains
* information about a key in the ResourceBundle, and is initialized as
* follows:
* <dl>
* <li>displayName - The <code>String</code> key
* <li>name - Same as displayName property.</li>
* <li>shortDescription - Empty string</li>
* <li>expert - <code>false</code></li>
* <li>hidden - <code>false</code></li>
* <li>preferred - <code>true</code></li>
* </dl>
* In addition, the following named attributes must be set in the returned
* <code>FeatureDescriptor</code>s:
* <dl>
* <li>{@link ELResolver#TYPE} - <code>String.class</code></li>
* <li>{@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - <code>true</code></li>
* </dl>
* </p>
*
* @param context
* The context of this evaluation.
* @param base
* The bundle whose keys are to be iterated over. Only bases of
* type <code>ResourceBundle</code> are handled by this
* resolver.
* @return An <code>Iterator</code> containing zero or more (possibly
* infinitely more) <code>FeatureDescriptor</code> objects, each
* representing a key in this bundle, or <code>null</code> if the
* base object is not a ResourceBundle.
*/
public Iterator getFeatureDescriptors(ELContext context, Object base) {
if (base instanceof ResourceBundle) {
ResourceBundle bundle = (ResourceBundle) base;
List features = new ArrayList();
String key = null;
FeatureDescriptor desc = null;
for (Enumeration e = bundle.getKeys(); e.hasMoreElements();) {
key = (String) e.nextElement();
desc = new FeatureDescriptor();
desc.setDisplayName(key);
desc.setExpert(false);
desc.setHidden(false);
desc.setName(key);
desc.setPreferred(true);
desc.setValue(TYPE, String.class);
desc.setValue(RESOLVABLE_AT_DESIGN_TIME, Boolean.TRUE);
features.add(desc);
}
return features.iterator();
}
return null;
}
/**
* If the base object is a ResourceBundle, returns the most general type
* that this resolver accepts for the <code>property</code> argument.
* Otherwise, returns <code>null</code>.
*
* <p>
* Assuming the base is a <code>ResourceBundle</code>, this method will
* always return <code>String.class</code>.
*
* @param context
* The context of this evaluation.
* @param base
* The bundle to analyze. Only bases of type
* <code>ResourceBundle</code> are handled by this resolver.
* @return <code>null</code> if base is not a <code>ResourceBundle</code>;
* otherwise <code>String.class</code>.
*/
public Class<?> getCommonPropertyType(ELContext context, Object base) {
if (base instanceof ResourceBundle) {
return String.class;
}
return null;
}
}