ListELResolver.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 javax.el;

import java.beans.FeatureDescriptor;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

public class ListELResolver extends ELResolver {

	private final boolean readOnly;

	private final static Class UNMODIFIABLE = Collections.unmodifiableList(
			new ArrayList()).getClass();

	public ListELResolver() {
		this.readOnly = false;
	}

	public ListELResolver(boolean readOnly) {
		this.readOnly = readOnly;
	}

	public Object getValue(ELContext context, Object base, Object property)
			throws NullPointerException, PropertyNotFoundException, ELException {
		if (context == null) {
			throw new NullPointerException();
		}

		if (base instanceof List) {
			context.setPropertyResolved(true);
			List list = (List) base;
			int idx = coerce(property);
			if (idx < 0 || idx >= list.size()) {
				return null;
			}
			return list.get(idx);
		}

		return null;
	}

	public Class<?> getType(ELContext context, Object base, Object property)
			throws NullPointerException, PropertyNotFoundException, ELException {
		if (context == null) {
			throw new NullPointerException();
		}

		if (base instanceof List) {
			context.setPropertyResolved(true);
			List list = (List) base;
			int idx = coerce(property);
			if (idx < 0 || idx >= list.size()) {
                throw new PropertyNotFoundException(
                        new ArrayIndexOutOfBoundsException(idx).getMessage());
			}
			return Object.class;
		}

		return null;
	}

	public void setValue(ELContext context, Object base, Object property,
			Object value) throws NullPointerException,
			PropertyNotFoundException, PropertyNotWritableException,
			ELException {
		if (context == null) {
			throw new NullPointerException();
		}

		if (base instanceof List) {
			context.setPropertyResolved(true);
			List list = (List) base;

			if (this.readOnly) {
				throw new PropertyNotWritableException(message(context,
						"resolverNotWriteable", new Object[] { base.getClass()
								.getName() }));
			}

			int idx = coerce(property);
			try {
				list.set(idx, value);
			} catch (UnsupportedOperationException e) {
				throw new PropertyNotWritableException(e);
			} catch (IndexOutOfBoundsException e) {
				throw new PropertyNotFoundException(e);
			}
		}
	}

	public boolean isReadOnly(ELContext context, Object base, Object property)
			throws NullPointerException, PropertyNotFoundException, ELException {
		if (context == null) {
			throw new NullPointerException();
		}

		if (base instanceof List) {
			context.setPropertyResolved(true);
			List list = (List) base;
			int idx = coerce(property);
			if (idx < 0 || idx >= list.size()) {
				throw new PropertyNotFoundException(
						new ArrayIndexOutOfBoundsException(idx).getMessage());
			}
			return this.readOnly || UNMODIFIABLE.equals(list.getClass());
		}

		return this.readOnly;
	}

	public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {
		if (base instanceof List) {
			FeatureDescriptor[] descs = new FeatureDescriptor[((List) base).size()];
			for (int i = 0; i < descs.length; i++) {
				descs[i] = new FeatureDescriptor();
				descs[i].setDisplayName("["+i+"]");
				descs[i].setExpert(false);
				descs[i].setHidden(false);
				descs[i].setName(""+i);
				descs[i].setPreferred(true);
				descs[i].setValue(RESOLVABLE_AT_DESIGN_TIME, Boolean.FALSE);
				descs[i].setValue(TYPE, Integer.class);
			}
			return Arrays.asList(descs).iterator();
		}
		return null;
	}

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

	private final 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");
	}
}