org.apache.myfaces.trinidad.util.ListFromCollection Maven / Gradle / Ivy

/*
 * 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 org.apache.myfaces.trinidad.util;

import java.util.AbstractMap;
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.RandomAccess;
import java.util.Set;

/**
 * 
 * Bean that can dynamically produce Lists from Collections.
 * The Collections must implement size().  Create an instance
 * of this bean as a managed bean:
 * 
 * Example:
 *  *  <managed-bean>
 *    <managed-bean-name>makeList</managed-bean-name>
 *    <managed-bean-class>
 *       org.apache.myfaces.trinidad.util.ListFromCollection
 *    </managed-bean-class>
 *    <managed-bean-scope>
 *       request
 *    </managed-bean-scope>
 *    <!-- Let's buffer 25 rows at a time (the default is 50) -->
 *    <managed-property>
 *      <property-name>size</property-name>
 *      <value>25</value>
 *    <managed-property>
 *  </managed-bean>
 * 
 *  *   <h:dataTable value="#{makeList.list[someSet]}>
 *   </h:dataTable>
 * 
 * 
 * Note, though, that it is extremely expensive to use this bean for
 * the items of an tr:forEach (or c:forEach in JSF 1.2 or Facelets).
 * 
 */
public class ListFromCollection
{
  public ListFromCollection()
  {
    _map = new MakeList();
    _size = _DEFAULT_SIZE;
  }

  public Map, List> getList()
  {
    return _map;
  }

  public int getSize()
  {
    return _size;
  }
  
  public void setSize(int size)
  {
    _size = size;
  }

  private class MakeList extends AbstractMap, List>
  {
    @Override
    public List get(Object o)
    {
      if (!(o instanceof Collection))
        return null;
      
      // Just send RandomAccess lists out;  wrap any other Collection
      // into a List
      if ((o instanceof List) &&
          (o instanceof RandomAccess))
        return (List) o;

      Collection c = (Collection) o;
      if (c.isEmpty())
        return Collections.emptyList();

      return new ListImpl(c, getSize());
    }

    @Override
    public Set, List>> entrySet()
    {
      // Not worth implementing at the moment;  this Map is only
      // accessed from 
      return Collections.emptySet();
    }
  }

  private static class ListImpl extends AbstractList