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 * @return Comparison strategy object.
55 */
56 public static BCELComparator<Field> getComparator() {
57 return bcelComparator;
58 }
59
60 /**
61 * @param comparator Comparison strategy object.
62 */
63 public static void setComparator(final BCELComparator<Field> comparator) {
64 bcelComparator = comparator;
65 }
66
67 /**
68 * Constructs object from file stream.
69 *
70 * @param file Input stream.
71 */
72 Field(final DataInput file, final ConstantPool constantPool) throws IOException, ClassFormatException {
73 super(file, constantPool);
74 }
75
76 /**
77 * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
78 * physical copy.
79 *
80 * @param c Source to copy.
81 */
82 public Field(final Field c) {
83 super(c);
84 }
85
86 /**
87 * @param accessFlags Access rights of field
88 * @param nameIndex Points to field name in constant pool
89 * @param signatureIndex Points to encoded signature
90 * @param attributes Collection of attributes
91 * @param constantPool Array of constants
92 */
93 public Field(final int accessFlags, final int nameIndex, final int signatureIndex, final Attribute[] attributes, final ConstantPool constantPool) {
94 super(accessFlags, nameIndex, signatureIndex, attributes, constantPool);
95 }
96
97 /**
98 * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
99 * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
100 *
101 * @param v Visitor object
102 */
103 @Override
104 public void accept(final Visitor v) {
105 v.visitField(this);
106 }
107
108 /**
109 * @return deep copy of this field
110 */
111 public Field copy(final ConstantPool constantPool) {
112 return (Field) copy_(constantPool);
113 }
114
115 /**
116 * Return value as defined by given BCELComparator strategy. By default two Field objects are said to be equal when
117 * their names and signatures are equal.
118 *
119 * @see Object#equals(Object)
120 */
121 @Override
122 public boolean equals(final Object obj) {
123 return obj instanceof Field && bcelComparator.equals(this, (Field) obj);
124 }
125
126 /**
127 * @return constant value associated with this field (may be null)
128 */
129 public ConstantValue getConstantValue() {
130 for (final Attribute attribute : super.getAttributes()) {
131 if (attribute.getTag() == Const.ATTR_CONSTANT_VALUE) {
132 return (ConstantValue) attribute;
133 }
134 }
135 return null;
136 }
137
138 /**
139 * See https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.2.2
140 *
141 * @return type of field
142 */
143 public Type getType() {
144 return Type.getType(getSignature());
145 }
146
147 /**
148 * Return value as defined by given BCELComparator strategy. By default return the hash code of the field's name XOR
149 * signature.
150 *
151 * @see Object#hashCode()
152 */
153 @Override
154 public int hashCode() {
155 return bcelComparator.hashCode(this);
156 }
157
158 /**
159 * Return string representation close to declaration format, 'public static final short MAX = 100', e.g..
160 *
161 * @return String representation of field, including the signature.
162 */
163 @Override
164 public String toString() {
165 String name;
166 String signature;
167 String access; // Short cuts to constant pool
168
169 // Get names from constant pool
170 access = Utility.accessToString(super.getAccessFlags());
171 access = access.isEmpty() ? "" : access + " ";
172 signature = Utility.signatureToString(getSignature());
173 name = getName();
174 final StringBuilder buf = new StringBuilder(64); // CHECKSTYLE IGNORE MagicNumber
175 buf.append(access).append(signature).append(" ").append(name);
176 final ConstantValue cv = getConstantValue();
177 if (cv != null) {
178 buf.append(" = ").append(cv);
179 }
180 for (final Attribute attribute : super.getAttributes()) {
181 if (!(attribute instanceof ConstantValue)) {
182 buf.append(" [").append(attribute).append("]");
183 }
184 }
185 return buf.toString();
186 }
187 }