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Central module for Tapestry, containing interfaces to the Java
Servlet API and all core services and components.
// Copyright 2007, 2009, 2010 The Apache Software Foundation
//
// Licensed 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.tapestry5.util;
import java.io.Serializable;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.apache.tapestry5.PrimaryKeyEncoder;
import org.apache.tapestry5.ioc.internal.util.CollectionFactory;
/**
* A default, extensible version of {@link org.apache.tapestry5.PrimaryKeyEncoder} that is based on loading known values
* into an internal map. When there's a reasonable number (hundreds, perhaps thousands) of items to choose from, and
* those items are fast and cheap to read and instantiate, this implementation is a good bet. For very large result
* sets, you'll need to create your own implementation of {@link PrimaryKeyEncoder}.
*
* @param the key type (which must be serializable)
* @param the value type
* @deprecated See deprecation notes for {@link org.apache.tapestry5.PrimaryKeyEncoder}.
*/
public class DefaultPrimaryKeyEncoder implements PrimaryKeyEncoder
{
private final Map keyToValue = new LinkedHashMap();
private final Map valueToKey = CollectionFactory.newMap();
private Set deletedKeys;
private K currentKey;
private final Class keyType;
/**
* Compatibility with 5.0: new encoder, key type unknown. You will want to use the other constructor and
* specify the key type.
*/
public DefaultPrimaryKeyEncoder()
{
this(null);
}
/**
* @since 5.1.0.0
*/
public DefaultPrimaryKeyEncoder(Class keyType)
{
this.keyType = keyType;
}
public Class getKeyType()
{
return keyType;
}
/**
* Adds a new key/value pair to the encoder.
*/
public final void add(K key, V value)
{
assert key != null;
assert value != null;
V existing = keyToValue.get(key);
if (existing != null) throw new IllegalArgumentException(PublicUtilMessages.duplicateKey(key, value, existing));
keyToValue.put(key, value);
// TODO: Ensure that the value is unique?
valueToKey.put(value, key);
}
/**
* Returns the values previously {@link #add(Serializable, Object) added to the encoder}, in the order in which
* they were added. Values that are deleted are not returned.
*
* @return ordered list of values
*/
public final List getValues()
{
return valuesNotInKeySet(deletedKeys);
}
/**
* Returns a list of all the values except those values whose keys are in the provided set. The set may be
* null, in which case all values are returned.
*
* @param keySet set of keys identifying values to exclude, or null to exclude no values
* @return values (not in the set) in order origionally added
*/
protected final List valuesNotInKeySet(Set keySet)
{
if (keySet == null || keySet.isEmpty()) return getAllValues();
List result = CollectionFactory.newList();
for (Map.Entry entry : keyToValue.entrySet())
{
if (keySet.contains(entry.getKey())) continue;
result.add(entry.getValue());
}
return result;
}
public final List getAllValues()
{
List result = CollectionFactory.newList();
for (Map.Entry entry : keyToValue.entrySet())
{
result.add(entry.getValue());
}
return result;
}
/**
* For a previously {@link #add(Serializable, Object) added key/value pair}, returns the key corresponding to the
* given value.
*/
public final K toKey(V value)
{
assert value != null;
currentKey = valueToKey.get(value);
if (currentKey == null) throw new IllegalArgumentException(PublicUtilMessages.missingValue(value, valueToKey
.keySet()));
return currentKey;
}
public final V toValue(K key)
{
V result = keyToValue.get(key);
if (result == null)
{
result = provideMissingObject(key);
currentKey = key;
}
else
{
currentKey = key;
}
return result;
}
/**
* Invoked by {@link #toValue(Serializable)} whenever a key can not be converted to a value using the internal
* cache. This is an opportunity to record the fact that an error occured (they key was not valuable, possibly
* because it points to a deleted entity object) and provide a temporary object. This method may return null, but in
* a typical application, that will likely case NullPointerExceptions further down the processing chain.
*
* This implementation returns null, and is intended to be overriden in subclasses.
*
* @param key key for which a value is required
* @return a substitute value, or null
*/
protected V provideMissingObject(K key)
{
return null;
}
public final boolean isDeleted()
{
return inKeySet(deletedKeys);
}
public final void setDeleted(boolean value)
{
deletedKeys = modifyKeySet(deletedKeys, value);
}
/**
* Returns true if the current key is in the provided set.
*
* @param keySet the set of keys to check, or null
* @return true if the key is in the set, false if it is missing (or if keySet is null)
*/
protected final boolean inKeySet(Set keySet)
{
return keySet != null && keySet.contains(currentKey);
}
/**
* Modifies a keySet to add or remove the current key. If necessary, a new Set is created.
*
* Useage: private Set myFlagKeys;
*
* public boolean void setMyFlag(boolean value) { myFlagKeys = modifySet(myFlagKeys, value); }
*
* @param keySet the set of keys, or null
* @param value true to add the current key, false to remove
* @return the provided key set, or a new one
*/
protected final Set modifyKeySet(Set keySet, boolean value)
{
if (keySet == null)
{
if (!value) return null;
keySet = CollectionFactory.newSet();
}
if (value) keySet.add(currentKey);
else keySet.remove(currentKey);
return keySet;
}
/**
* Does nothing. Subclasses may override as necessary.
*/
public void prepareForKeys(List keys)
{
}
}