compositeelresolver.java

梅花雪树的经典制作

/*
 * 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.Iterator;

public class CompositeELResolver extends ELResolver {

	private int size;

	private ELResolver[] resolvers;

	public CompositeELResolver() {
		this.size = 0;
		this.resolvers = new ELResolver[2];
	}

	public void add(ELResolver elResolver) {
		if (elResolver == null) {
			throw new NullPointerException();
		}

		if (this.size >= this.resolvers.length) {
			ELResolver[] nr = new ELResolver[this.size * 2];
			System.arraycopy(this.resolvers, 0, nr, 0, this.size);
			this.resolvers = nr;
		}
		this.resolvers[this.size++] = elResolver;
	}

	public Object getValue(ELContext context, Object base, Object property)
			throws NullPointerException, PropertyNotFoundException, ELException {
		context.setPropertyResolved(false);
		int sz = this.size;
		Object result = null;
		for (int i = 0; i < sz; i++) {
			result = this.resolvers[i].getValue(context, base, property);
			if (context.isPropertyResolved()) {
				return result;
			}
		}
		return null;
	}

	public void setValue(ELContext context, Object base, Object property,
			Object value) throws NullPointerException,
			PropertyNotFoundException, PropertyNotWritableException,
			ELException {
		context.setPropertyResolved(false);
		int sz = this.size;
		for (int i = 0; i < sz; i++) {
			this.resolvers[i].setValue(context, base, property, value);
			if (context.isPropertyResolved()) {
				return;
			}
		}
	}

	public boolean isReadOnly(ELContext context, Object base, Object property)
			throws NullPointerException, PropertyNotFoundException, ELException {
		context.setPropertyResolved(false);
		int sz = this.size;
		boolean readOnly = false;
		for (int i = 0; i < sz; i++) {
			readOnly = this.resolvers[i].isReadOnly(context, base, property);
			if (context.isPropertyResolved()) {
				return readOnly;
			}
		}
		return false;
	}

	public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {
		return new FeatureIterator(context, base, this.resolvers, this.size);
	}

	public Class<?> getCommonPropertyType(ELContext context, Object base) {
		int sz = this.size;
		Class<?> commonType = null, type = null;
		for (int i = 0; i < sz; i++) {
			type = this.resolvers[i].getCommonPropertyType(context, base);
			if (type != null
					&& (commonType == null || commonType.isAssignableFrom(type))) {
				commonType = type;
			}
		}
		return commonType;
	}

	public Class<?> getType(ELContext context, Object base, Object property)
			throws NullPointerException, PropertyNotFoundException, ELException {
		context.setPropertyResolved(false);
		int sz = this.size;
		Class<?> type;
		for (int i = 0; i < sz; i++) {
			type = this.resolvers[i].getType(context, base, property);
			if (context.isPropertyResolved()) {
				return type;
			}
		}
		return null;
	}

	private final static class FeatureIterator implements Iterator<FeatureDescriptor> {

		private final ELContext context;

		private final Object base;

		private final ELResolver[] resolvers;

		private final int size;

		private Iterator itr;

		private int idx;

		public FeatureIterator(ELContext context, Object base,
				ELResolver[] resolvers, int size) {
			this.context = context;
			this.base = base;
			this.resolvers = resolvers;
			this.size = size;

			this.idx = 0;
			this.guaranteeIterator();
		}
		
		private void guaranteeIterator() {
			while (this.itr == null && this.idx < this.size) {
				this.itr = this.resolvers[this.idx].getFeatureDescriptors(
						this.context, this.base);
				this.idx++;
			}
		}

		public boolean hasNext() {
			return this.itr != null;
		}

		public FeatureDescriptor next() {
			Object result = null;
			if (this.itr != null) {
				if (this.itr.hasNext()) {
					result = this.itr.next();
					if (!this.itr.hasNext()) {
						this.itr = null;
						this.guaranteeIterator();
					}
				}
			}
			return (FeatureDescriptor) result;
		}

		public void remove() {
			throw new UnsupportedOperationException();
		}
	}

}