/
IdentityMap.java
86 lines (75 loc) · 2.57 KB
/
IdentityMap.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
//@formatter:off
/*
* Identity Map - demonstrates IDENTITY MAP
* Code-Beispiel zum Buch Patterns Kompakt, Verlag Springer Vieweg
* Copyright 2014 Karl Eilebrecht
*
* 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.
*/
//@formatter:on
package de.calamanari.pk.identitymap;
import java.util.HashMap;
import java.util.Map;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Identity Map - demonstrates IDENTITY MAP
*
* @author <a href="mailto:Karl.Eilebrecht(a/t)calamanari.de">Karl Eilebrecht</a>
* @param <K> type of the entity key
* @param <E> entity type
*/
public class IdentityMap<K, E extends Entity<K>> {
private static final Logger LOGGER = LoggerFactory.getLogger(IdentityMap.class);
/**
* internal map to maintain entities
*/
private final Map<K, E> instances = new HashMap<>();
/**
* we store a reference to the entity type class only for demonstration purposes, this is not required, but useful for debugging
*/
private final Class<E> entityType;
/**
* Creates identity map
*
* @param entityType class of entity to be maintained
*/
public IdentityMap(Class<E> entityType) {
this.entityType = entityType;
}
/**
* Adds an entity to the map
*
* @param entity (null will be silently ignored)
*/
public void add(E entity) {
if (entity != null) {
LOGGER.debug("{}(entityType={}).add() called", this.getClass().getSimpleName(), entityType.getSimpleName());
instances.put(entity.getId(), entity);
}
}
/**
* Returns the requested entity corresponding to the key
*
* @param id (primary key)
* @return entity or null if unknown
*/
public E get(K id) {
LOGGER.debug("{}(entityType={}).get('{}') called", this.getClass().getSimpleName(), entityType.getSimpleName(), id);
return instances.get(id);
}
@Override
public String toString() {
return this.getClass().getSimpleName() + "(entityType=" + entityType.getSimpleName() + ", currentSize=" + instances.size() + ")";
}
}