1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.bcel.classfile;
18
19 import java.io.DataInput;
20 import java.io.IOException;
21 import java.util.Objects;
22
23 import org.apache.bcel.Const;
24 import org.apache.bcel.generic.Type;
25 import org.apache.bcel.util.BCELComparator;
26
27 /**
28 * This class represents the field info structure, i.e., the representation for a variable in the class. See JVM
29 * specification for details.
30 */
31 public final class Field extends FieldOrMethod {
32
33 /**
34 * Empty array constant.
35 *
36 * @since 6.6.0
37 */
38 public static final Field[] EMPTY_ARRAY = {};
39
40 private static BCELComparator<Field> bcelComparator = new BCELComparator<Field>() {
41
42 @Override
43 public boolean equals(final Field a, final Field b) {
44 return a == b || a != null && b != null && Objects.equals(a.getName(), b.getName()) && Objects.equals(a.getSignature(), b.getSignature());
45 }
46
47 @Override
48 public int hashCode(final Field o) {
49 return o != null ? Objects.hash(o.getSignature(), o.getName()) : 0;
50 }
51 };
52
53 /**
54 * Empty array.
55 */
56 static final Field[] EMPTY_FIELD_ARRAY = {};
57
58 /**
59 * @return Comparison strategy object.
60 */
61 public static BCELComparator<Field> getComparator() {
62 return bcelComparator;
63 }
64
65 /**
66 * @param comparator Comparison strategy object.
67 */
68 public static void setComparator(final BCELComparator<Field> comparator) {
69 bcelComparator = comparator;
70 }
71
72 /**
73 * Constructs object from file stream.
74 *
75 * @param file Input stream.
76 */
77 Field(final DataInput file, final ConstantPool constantPool) throws IOException, ClassFormatException {
78 super(file, constantPool);
79 }
80
81 /**
82 * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
83 * physical copy.
84 *
85 * @param c Source to copy.
86 */
87 public Field(final Field c) {
88 super(c);
89 }
90
91 /**
92 * @param accessFlags Access rights of field
93 * @param nameIndex Points to field name in constant pool
94 * @param signatureIndex Points to encoded signature
95 * @param attributes Collection of attributes
96 * @param constantPool Array of constants
97 */
98 public Field(final int accessFlags, final int nameIndex, final int signatureIndex, final Attribute[] attributes, final ConstantPool constantPool) {
99 super(accessFlags, nameIndex, signatureIndex, attributes, constantPool);
100 }
101
102 /**
103 * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
104 * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
105 *
106 * @param v Visitor object
107 */
108 @Override
109 public void accept(final Visitor v) {
110 v.visitField(this);
111 }
112
113 /**
114 * @return deep copy of this field
115 */
116 public Field copy(final ConstantPool constantPool) {
117 return (Field) copy_(constantPool);
118 }
119
120 /**
121 * Return value as defined by given BCELComparator strategy. By default two Field objects are said to be equal when
122 * their names and signatures are equal.
123 *
124 * @see Object#equals(Object)
125 */
126 @Override
127 public boolean equals(final Object obj) {
128 return obj instanceof Field && bcelComparator.equals(this, (Field) obj);
129 }
130
131 /**
132 * @return constant value associated with this field (may be null)
133 */
134 public ConstantValue getConstantValue() {
135 for (final Attribute attribute : super.getAttributes()) {
136 if (attribute.getTag() == Const.ATTR_CONSTANT_VALUE) {
137 return (ConstantValue) attribute;
138 }
139 }
140 return null;
141 }
142
143 /**
144 * See https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.2.2
145 *
146 * @return type of field
147 */
148 public Type getType() {
149 return Type.getType(getSignature());
150 }
151
152 /**
153 * Return value as defined by given BCELComparator strategy. By default return the hash code of the field's name XOR
154 * signature.
155 *
156 * @see Object#hashCode()
157 */
158 @Override
159 public int hashCode() {
160 return bcelComparator.hashCode(this);
161 }
162
163 /**
164 * Return string representation close to declaration format, 'public static final short MAX = 100', e.g..
165 *
166 * @return String representation of field, including the signature.
167 */
168 @Override
169 public String toString() {
170 String name;
171 String signature;
172 String access; // Short cuts to constant pool
173
174 // Get names from constant pool
175 access = Utility.accessToString(super.getAccessFlags());
176 access = access.isEmpty() ? "" : access + " ";
177 signature = Utility.signatureToString(getSignature());
178 name = getName();
179 final StringBuilder buf = new StringBuilder(64); // CHECKSTYLE IGNORE MagicNumber
180 buf.append(access).append(signature).append(" ").append(name);
181 final ConstantValue cv = getConstantValue();
182 if (cv != null) {
183 buf.append(" = ").append(cv);
184 }
185 for (final Attribute attribute : super.getAttributes()) {
186 if (!(attribute instanceof ConstantValue)) {
187 buf.append(" [").append(attribute).append("]");
188 }
189 }
190 return buf.toString();
191 }
192 }