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package javax.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}.
*
*
* 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
* {@link java.util.ResourceBundle#getObject(java.lang.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.
*
*
* @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 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 ResourceBundle to analyze.
* @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.
*/
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 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 ResourceBundle to analyze.
* @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
*/
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 null.
* @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 true.
*
* @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 propertyResolved property of
* ELContext was set to true, then
* true; otherwise undefined.
* @throws NullPointerException
* if context is null
*/
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 Iterator
* containing the set of keys available in the ResourceBundle.
* Otherwise, returns null.
*
*
* The Iterator 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:
*
*
displayName - The String key
* name - Same as displayName property.
* shortDescription - Empty string
* expert - false
* hidden - false
* preferred - true
*
* In addition, the following named attributes must be set in the returned
* FeatureDescriptors:
*
*
{@link ELResolver#TYPE} - String.class
* {@link ELResolver#RESOLVABLE_AT_DESIGN_TIME} - true
*
*
*
* @param context
* The context of this evaluation.
* @param base
* The bundle whose keys are to be iterated over. 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.
*/
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 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.
*/
public Class getCommonPropertyType(ELContext context, Object base) {
if (base instanceof ResourceBundle) {
return String.class;
}
return null;
}
}