java/jakarta/el/ResourceBundleELResolver.java

/*
 * 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 jakarta.el;

import java.util.MissingResourceException;
import java.util.Objects;
import java.util.ResourceBundle;

/**
 * EL resolver for resource bundle properties.
 * <p>
 * This resolver handles base objects of type {@link ResourceBundle}. It accepts
 * any non-null object as a property, coerces it to a String, and uses it to
 * look up the corresponding message in the resource bundle. If the key is not
 * found, the resolver returns a placeholder string of the form {@code ???key???}.
 * Resource bundles are always read-only.
 * <p>
 * {@code ELResolver}s are combined using {@link CompositeELResolver}s to define
 * rich semantics for evaluating an expression. See the javadocs for
 * {@link ELResolver} for details.
 *
 * @since EL 2.1
 */
public class ResourceBundleELResolver extends ELResolver {

    /**
     * Constructs a new instance of the resolver.
     */
    public ResourceBundleELResolver() {
        super();
    }

    @Override
    public Object getValue(ELContext context, Object base, Object property) {
        Objects.requireNonNull(context);

        if (base instanceof ResourceBundle) {
            context.setPropertyResolved(base, property);

            if (property != null) {
                try {
                    return ((ResourceBundle) base).getObject(property.toString());
                } catch (MissingResourceException mre) {
                    return "???" + property.toString() + "???";
                }
            }
        }

        return null;
    }

    @Override
    public Class<?> getType(ELContext context, Object base, Object property) {
        Objects.requireNonNull(context);

        if (base instanceof ResourceBundle) {
            context.setPropertyResolved(base, property);
            /*
             * ResourceBundles are always read-only so fall-through to return null
             */
        }

        return null;
    }

    @Override
    public void setValue(ELContext context, Object base, Object property, Object value) {
        Objects.requireNonNull(context);

        if (base instanceof ResourceBundle) {
            context.setPropertyResolved(base, property);
            throw new PropertyNotWritableException(
                    Util.message(context, "resolverNotWritable", base.getClass().getName()));
        }
    }

    @Override
    public boolean isReadOnly(ELContext context, Object base, Object property) {
        Objects.requireNonNull(context);

        if (base instanceof ResourceBundle) {
            context.setPropertyResolved(base, property);
            return true;
        }

        return false;
    }

    @Override
    public Class<?> getCommonPropertyType(ELContext context, Object base) {
        if (base instanceof ResourceBundle) {
            return String.class;
        }
        return null;
    }

}