scopedattributeelresolver.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.servlet.jsp.el;

import java.beans.FeatureDescriptor;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;

import javax.el.ELContext;
import javax.el.ELException;
import javax.el.ELResolver;
import javax.el.PropertyNotFoundException;
import javax.el.PropertyNotWritableException;
import javax.servlet.jsp.JspContext;
import javax.servlet.jsp.PageContext;

public class ScopedAttributeELResolver extends ELResolver {

	public ScopedAttributeELResolver() {
		super();
	}

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

		if (base == null) {
			context.setPropertyResolved(true);
			if (property != null) {
				String key = property.toString();
				PageContext page = (PageContext) context
						.getContext(JspContext.class);
				return page.findAttribute(key);
			}
		}

		return null;
	}

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

		if (base == null) {
			context.setPropertyResolved(true);
			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 == null) {
			context.setPropertyResolved(true);
			if (property != null) {
				String key = property.toString();
				PageContext page = (PageContext) context
						.getContext(JspContext.class);
				int scope = page.getAttributesScope(key);
				if (scope != 0) {
					page.setAttribute(key, value, scope);
				} else {
					page.setAttribute(key, value);
				}
			}
		}
	}

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

		if (base == null) {
			context.setPropertyResolved(true);
		}

		return false;
	}

	public Iterator<FeatureDescriptor> getFeatureDescriptors(ELContext context, Object base) {

		PageContext ctxt = (PageContext) context.getContext(JspContext.class);
		List<FeatureDescriptor> list = new ArrayList<FeatureDescriptor>();
		Enumeration e;
		Object value;
		String name;

		e = ctxt.getAttributeNamesInScope(PageContext.PAGE_SCOPE);
		while (e.hasMoreElements()) {
			name = (String) e.nextElement();
			value = ctxt.getAttribute(name, PageContext.PAGE_SCOPE);
			FeatureDescriptor descriptor = new FeatureDescriptor();
			descriptor.setName(name);
			descriptor.setDisplayName(name);
			descriptor.setExpert(false);
			descriptor.setHidden(false);
			descriptor.setPreferred(true);
			descriptor.setShortDescription("page scoped attribute");
			descriptor.setValue("type", value.getClass());
			descriptor.setValue("resolvableAtDesignTime", Boolean.FALSE);
			list.add(descriptor);
		}

		e = ctxt.getAttributeNamesInScope(PageContext.REQUEST_SCOPE);
		while (e.hasMoreElements()) {
			name = (String) e.nextElement();
			value = ctxt.getAttribute(name, PageContext.REQUEST_SCOPE);
			FeatureDescriptor descriptor = new FeatureDescriptor();
			descriptor.setName(name);
			descriptor.setDisplayName(name);
			descriptor.setExpert(false);
			descriptor.setHidden(false);
			descriptor.setPreferred(true);
			descriptor.setShortDescription("request scope attribute");
			descriptor.setValue("type", value.getClass());
			descriptor.setValue("resolvableAtDesignTime", Boolean.FALSE);
			list.add(descriptor);
		}

		if (ctxt.getSession() != null) {
			e = ctxt.getAttributeNamesInScope(PageContext.SESSION_SCOPE);
			while (e.hasMoreElements()) {
				name = (String) e.nextElement();
				value = ctxt.getAttribute(name, PageContext.SESSION_SCOPE);
				FeatureDescriptor descriptor = new FeatureDescriptor();
				descriptor.setName(name);
				descriptor.setDisplayName(name);
				descriptor.setExpert(false);
				descriptor.setHidden(false);
				descriptor.setPreferred(true);
				descriptor.setShortDescription("session scoped attribute");
				descriptor.setValue("type", value.getClass());
				descriptor.setValue("resolvableAtDesignTime", Boolean.FALSE);
				list.add(descriptor);
			}
		}

		e = ctxt.getAttributeNamesInScope(PageContext.APPLICATION_SCOPE);
		while (e.hasMoreElements()) {
			name = (String) e.nextElement();
			value = ctxt.getAttribute(name, PageContext.APPLICATION_SCOPE);
			FeatureDescriptor descriptor = new FeatureDescriptor();
			descriptor.setName(name);
			descriptor.setDisplayName(name);
			descriptor.setExpert(false);
			descriptor.setHidden(false);
			descriptor.setPreferred(true);
			descriptor.setShortDescription("application scoped attribute");
			descriptor.setValue("type", value.getClass());
			descriptor.setValue("resolvableAtDesignTime", Boolean.FALSE);
			list.add(descriptor);
		}
		return list.iterator();
	}

	private static void appendEnumeration(Collection c, Enumeration e) {
		while (e.hasMoreElements()) {
			c.add(e.nextElement());
		}
	}

	public Class<String> getCommonPropertyType(ELContext context, Object base) {
		if (base == null) {
			return String.class;
		}
		return null;
	}
}