org.apache.river.lookup.util.ConsistentMap 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.river.lookup.util;
import java.io.IOException;
import java.io.Serializable;
import java.util.AbstractMap;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import org.apache.river.api.io.AtomicSerial;
import org.apache.river.api.io.AtomicSerial.GetArg;
/**
* An implementation of the java.util.Map interface that has
* a serialized form consistent in all virtual machines. ConsistentMap
* instances are unmodifiable. All mutator methods, such as add and
* remove, throw UnsupportedOperationException.
* This class permits null values and the null key.
*
*
* Although instances of this class are unmodifiable, they are not necessarily
* immutable. If a client retrieves a mutable object (either a key or value) contained in a
* ConsistentMap and mutates that object, the client in effect
* mutates the state of the ConsistentMap. In this case, the
* serialized form of the ConsistentMap will most likely also
* have been mutated. A ConsistentMap that contains only immutable
* objects will maintain a consistent serialized form indefinitely. But a
* ConsistentMap that contains mutable objects will maintain a
* consistent serialized form only so long as the mutable objects are not
* mutated.
*
* @author Bill Venners
*/
@AtomicSerial
public class ConsistentMap extends AbstractMap implements Serializable {
private static final long serialVersionUID = -5223157327307155247L;
/**
* @serial A Set of java.util.Map.Entry objects,
* the key-value pairs contained in this ConsistentMap.
*/
private final Set> entrySet;
/**
* Constructs a new, empty ConsistentMap. All instances
* of ConsistentMap are unmodifiable.
*/
public ConsistentMap() {
entrySet = new ConsistentSet>(new HashSet>());
}
/**
* Constructs a new ConsistentMap containing the elements
* in the passed collection. All instances of ConsistentMap
* are unmodifiable.
*
* @param init the map whose elements are to be placed into this map.
* @throws NullPointerException if the passed init reference
* is null
*/
public ConsistentMap(Map init) {
this(entrySet(init));
}
public ConsistentMap(GetArg arg) throws IOException {
this(entrySet((Map) arg.get("entrySet", null)));
}
private static Set> entrySet(Map init){
if (init == null) {
throw new NullPointerException();
}
// Must put the key-value pairs into ConsistentMapEntry objects,
// so they'll behave correctly when setValue() is invoked on them.
Set> unmodEntries = new HashSet>(init.size());
Set> entries = init.entrySet();
Iterator> it = entries.iterator();
while (it.hasNext()) {
Map.Entry entry = it.next();
Map.Entry unmodEntry = new ConsistentMapEntry(entry.getKey(), entry.getValue());
unmodEntries.add(unmodEntry);
}
return new ConsistentSet>(unmodEntries);
}
private ConsistentMap(Set> set){
entrySet = set;
}
/**
* Returns a set view of the mappings contained in this
* ConsistentMap. Each element in the returned
* set is a Map.Entry
*
* @return a set view of the mappings contained in this
* ConsistentMap.
*/
@Override
public Set> entrySet() {
return Collections.unmodifiableSet(entrySet);
}
}