package org.apache.velocity.tools.generic;
/*
* 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.
*/
import java.util.Set;
/**
* Tool for working with Sets in Velocity templates.
* Also provides methods to perform the following actions to Sets:
* <ul>
* <li>Check if it is empty.</li>
* <li>Check if it contains a certain element.</li>
* </ul>
*
* <p><pre>
* Example uses:
* $set.size($primes) -> 4
* set.isEmpty($primes) -> false
* $set.contains($primes, 7) -> true
*
* Example toolbox.xml config (if you want to use this with VelocityView):
* <tool>
* <key>set</key>
* <scope>application</scope>
* <class>org.apache.velocity.tools.generic.SetTool</class>
* </tool>
* </pre></p>
*
* <p>This tool is entirely threadsafe, and has no instance members.
* It may be used in any scope (request, session, or application).
* </p>
*
* @author <a href="mailto:shinobu@ieee.org">Shinobu Kawai</a>
* @version $Id: $
* @since VelocityTools 1.2
*/
public class SetTool
{
/**
* Default constructor.
*/
public SetTool() {
// DO NOTHING
}
/**
* Gets the size of a Set
* It will return null under the following conditions:
* <ul>
* <li><code>set</code> is null.</li>
* <li><code>set</code> is not a set</li>
* </ul>
* @param set the Set object.
* @return the size of the Set.
*/
public Integer size(Object set)
{
if (!isSet(set))
{
return null;
}
return Integer.valueOf(((Set) set).size());
}
/**
* Checks if an object is a Set.
* @param object the object to check.
* @return <code>true</code> if the object is a Set.
*/
public boolean isSet(Object object)
{
return object instanceof Set;
}
/**
* Checks if a Set is empty.
* @param set the Set to check.
* @return <code>true</code> if the Set is empty.
*/
public Boolean isEmpty(Object set)
{
Integer size = size(set);
if (size == null)
{
return null;
}
return Boolean.valueOf(size.intValue() == 0);
}
/**
* Checks if a Set contains a certain element.
* @param set the Set to check.
* @param element the element to check.
* @return <code>true</code> if the Set contains the element.
*/
public Boolean contains(Object set, Object element)
{
if (!isSet(set))
{
return null;
}
return Boolean.valueOf(((Set) set).contains(element));
}
}