java/jakarta/el/ArrayELResolver.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.lang.reflect.Array;
import java.util.Objects;

/**
 * Standard ELResolver for working with arrays.
 */
public class ArrayELResolver extends ELResolver {

    private static final String LENGTH_PROPERTY_NAME = "length";

    private final boolean readOnly;

    /**
     * Creates a writable instance of the standard array resolver.
     */
    public ArrayELResolver() {
        this.readOnly = false;
    }

    /**
     * Creates an instance of the standard array resolver.
     *
     * @param readOnly {@code true} if the created instance should be read-only otherwise false.
     */
    public ArrayELResolver(boolean readOnly) {
        this.readOnly = readOnly;
    }

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

        if (base != null && base.getClass().isArray()) {
            context.setPropertyResolved(base, property);

            if (LENGTH_PROPERTY_NAME.equals(property)) {
                // Always read-only
                return null;
            }

            try {
                int idx = coerce(property);
                checkBounds(base, idx);
            } catch (IllegalArgumentException e) {
                // ignore
            }
            /*
             * The resolver may have been created in read-only mode but the array and its elements will always be
             * read-write.
             */
            if (readOnly) {
                return null;
            }
            return base.getClass().getComponentType();
        }

        return null;
    }

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

        if (base != null && base.getClass().isArray()) {
            context.setPropertyResolved(base, property);
            if (LENGTH_PROPERTY_NAME.equals(property)) {
                return Integer.valueOf(Array.getLength(base));
            }
            int idx = coerce(property);
            if (idx < 0 || idx >= Array.getLength(base)) {
                return null;
            }
            return Array.get(base, idx);
        }

        return null;
    }

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

        if (base != null && base.getClass().isArray()) {
            context.setPropertyResolved(base, property);

            if (LENGTH_PROPERTY_NAME.equals(property)) {
                throw new PropertyNotWritableException(
                        Util.message(context, "propertyNotWritable", base.getClass().getName(), property));
            }

            if (this.readOnly) {
                throw new PropertyNotWritableException(
                        Util.message(context, "resolverNotWritable", base.getClass().getName()));
            }

            int idx = coerce(property);
            checkBounds(base, idx);
            if (value != null && !Util.isAssignableFrom(value.getClass(), base.getClass().getComponentType())) {
                throw new ClassCastException(Util.message(context, "objectNotAssignable", value.getClass().getName(),
                        base.getClass().getComponentType().getName()));
            }
            Array.set(base, idx, value);
        }
    }

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

        if (base != null && base.getClass().isArray()) {
            context.setPropertyResolved(base, property);
            if (LENGTH_PROPERTY_NAME.equals(property)) {
                // Always read-only
                return true;
            }
            try {
                int idx = coerce(property);
                checkBounds(base, idx);
            } catch (IllegalArgumentException e) {
                // ignore
            }
        }

        return this.readOnly;
    }

    @Override
    public Class<?> getCommonPropertyType(ELContext context, Object base) {
        if (base != null && base.getClass().isArray()) {
            return Integer.class;
        }
        return null;
    }

    private static void checkBounds(Object base, int idx) {
        if (idx < 0 || idx >= Array.getLength(base)) {
            throw new PropertyNotFoundException(new ArrayIndexOutOfBoundsException(idx).getMessage());
        }
    }

    private static int coerce(Object property) {
        if (property instanceof Number) {
            return ((Number) property).intValue();
        }
        if (property instanceof Character) {
            return ((Character) property).charValue();
        }
        if (property instanceof Boolean) {
            return ((Boolean) property).booleanValue() ? 1 : 0;
        }
        if (property instanceof String) {
            return Integer.parseInt((String) property);
        }
        throw new IllegalArgumentException(property != null ? property.toString() : "null");
    }

}