org.opencms.util.CmsNullIgnoringConcurrentMap Maven / Gradle / Ivy
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/*
* This library is part of OpenCms -
* the Open Source Content Management System
*
* Copyright (c) Alkacon Software GmbH & Co. KG (http://www.alkacon.com)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* For further information about Alkacon Software, please see the
* company website: http://www.alkacon.com
*
* For further information about OpenCms, please see the
* project website: http://www.opencms.org
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package org.opencms.util;
import org.opencms.main.CmsLog;
import java.util.Collection;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.commons.logging.Log;
/**
* Wrapper around ConcurrentHashMap which allows null values.
*
* The point of this is the following: Often, HashMaps in older code are accessed concurrently by multiple threads. When these threads modify the
* map concurrently, an infinite loop may occur due to the standard HashMap implementation. But sometimes we can't just replace the HashMap with a
* ConcurrentHashMap because that class doesn't allow null values and we don't always know for certain whether null values are used or not.
*
* But if we don't care about the distinction about null values and entries not being present, we can use this map class which will just log an error
* and remove the entry when trying to set a null value.
*
* NOTE: Currently this wrapper does *not* check value modifications made to entries returned by entrySet!
*
* @param the key type
* @param the value type
*/
public class CmsNullIgnoringConcurrentMap implements Map {
/** The logger for this class. */
private static final Log LOG = CmsLog.getLog(CmsNullIgnoringConcurrentMap.class);
/** The wrapped map. */
private Map m_internalMap = new ConcurrentHashMap();
/**
* Creates a new instance.
*/
public CmsNullIgnoringConcurrentMap() {
}
/**
* Creates a new instance from another map.
*
* @param otherMap the other map
*/
public CmsNullIgnoringConcurrentMap(Map otherMap) {
for (Map.Entry entry : otherMap.entrySet()) {
put(entry.getKey(), entry.getValue());
}
}
/**
*
* @see java.util.Map#clear()
*/
public void clear() {
m_internalMap.clear();
}
/**
* @see java.util.Map#containsKey(java.lang.Object)
*/
public boolean containsKey(Object key) {
return m_internalMap.containsKey(key);
}
/**
* @see java.util.Map#containsValue(java.lang.Object)
*/
public boolean containsValue(Object value) {
return m_internalMap.containsValue(value);
}
/**
* @see java.util.Map#entrySet()
*/
public Set> entrySet() {
return m_internalMap.entrySet();
}
/**
* @see java.util.Map#equals(java.lang.Object)
*/
@Override
public boolean equals(Object o) {
return m_internalMap.equals(o);
}
/**
* @see java.util.Map#get(java.lang.Object)
*/
public V get(Object key) {
return m_internalMap.get(key);
}
/**
* @see java.util.Map#hashCode()
*/
@Override
public int hashCode() {
return m_internalMap.hashCode();
}
/**
* @see java.util.Map#isEmpty()
*/
public boolean isEmpty() {
return m_internalMap.isEmpty();
}
/**
* @see java.util.Map#keySet()
*/
public Set keySet() {
return m_internalMap.keySet();
}
/**
* Sets the given map value for the given key, unless either of them is null.
*
* If the value is null,
*
* @param key the key
* @param value the value
*
* @return the old value
*
* @see java.util.Map#put(java.lang.Object, java.lang.Object)
*/
public V put(K key, V value) {
if ((key != null) && (value != null)) {
return m_internalMap.put(key, value);
}
Exception e = new Exception();
try {
// we want to print a stack trace when null is used as a key/value
throw e;
} catch (Exception e2) {
e = e2;
}
if (key == null) {
LOG.warn("Invalid null key in map", e);
return null;
}
if (value == null) {
LOG.warn("Invalid null value in map", e);
return m_internalMap.remove(key);
}
return null;
}
/**
* @see java.util.Map#putAll(java.util.Map)
*/
public void putAll(Map m) {
for (Map.Entry entry : m.entrySet()) {
put(entry.getKey(), entry.getValue());
}
}
/**
* @see java.util.Map#remove(java.lang.Object)
*/
public V remove(Object key) {
return m_internalMap.remove(key);
}
/**
* @see java.util.Map#size()
*/
public int size() {
return m_internalMap.size();
}
/**
* @see java.util.Map#values()
*/
public Collection values() {
return m_internalMap.values();
}
}