-
Notifications
You must be signed in to change notification settings - Fork 2
/
ObjectGraphTraverser.java
130 lines (111 loc) · 4.31 KB
/
ObjectGraphTraverser.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
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
/**
* Copyright (C) 2017 Czech Technical University in Prague
* <p>
* This program is free software: you can redistribute it and/or modify it under
* the terms of the GNU General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any
* later version.
* <p>
* This program 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 General Public License for more
* details. You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package cz.cvut.kbss.jsonld.serialization.traversal;
import cz.cvut.kbss.jsonld.common.BeanAnnotationProcessor;
import cz.cvut.kbss.jsonld.common.BeanClassProcessor;
import cz.cvut.kbss.jsonld.exception.JsonLdSerializationException;
import java.lang.reflect.Field;
import java.util.*;
public class ObjectGraphTraverser implements InstanceVisitor {
private static final Object EMPTY_OBJECT = new Object();
private final Set<InstanceVisitor> visitors = new HashSet<>(4);
private Map<Object, Object> knownInstances;
public void addVisitor(InstanceVisitor visitor) {
Objects.requireNonNull(visitor);
visitors.add(visitor);
}
public void removeVisitor(InstanceVisitor visitor) {
visitors.remove(visitor);
}
private void resetKnownInstances() {
this.knownInstances = new IdentityHashMap<>();
}
public void traverse(Object instance) {
Objects.requireNonNull(instance);
resetKnownInstances();
try {
if (instance instanceof Collection) {
traverseCollection((Collection<?>) instance);
} else {
traverseImpl(instance);
}
} catch (IllegalAccessException e) {
throw new JsonLdSerializationException("Unable to extract field value.", e);
}
}
private void traverseCollection(Collection<?> col) throws IllegalAccessException {
openCollection(col);
for (Object item : col) {
traverseImpl(item);
}
closeCollection(col);
}
private void traverseImpl(Object instance) throws IllegalAccessException {
if (knownInstances.containsKey(instance)) {
visitKnownInstance(instance);
return;
}
openInstance(instance);
for (Field f : BeanAnnotationProcessor.getSerializableFields(instance)) {
final Object value = BeanClassProcessor.getFieldValue(f, instance);
visitField(f, value);
if (value != null && BeanAnnotationProcessor.isObjectProperty(f)) {
traverseObjectPropertyValue(value);
}
}
closeInstance(instance);
}
private void traverseObjectPropertyValue(Object value) throws IllegalAccessException {
if (value instanceof Collection) {
final Collection<?> col = (Collection<?>) value;
openCollection(col);
for (Object elem : col) {
traverseImpl(elem);
}
closeCollection(col);
} else if (value.getClass().isArray()) {
throw new JsonLdSerializationException("Arrays are not supported, yet.");
} else {
traverseImpl(value);
}
}
@Override
public void openInstance(Object instance) {
if (!BeanClassProcessor.isIdentifierType(instance.getClass())) {
knownInstances.put(instance, EMPTY_OBJECT);
}
visitors.forEach(v -> v.openInstance(instance));
}
@Override
public void closeInstance(Object instance) {
visitors.forEach(v -> v.closeInstance(instance));
}
@Override
public void visitKnownInstance(Object instance) {
visitors.forEach(v -> v.visitKnownInstance((instance)));
}
@Override
public void visitField(Field field, Object value) {
visitors.forEach(v -> v.visitField(field, value));
}
@Override
public void openCollection(Collection<?> collection) {
visitors.forEach(v -> v.openCollection(collection));
}
@Override
public void closeCollection(Collection<?> collection) {
visitors.forEach(v -> v.closeCollection(collection));
}
}