001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 *
017 */
018package org.apache.bcel.classfile;
019
020import java.io.DataInput;
021import java.io.IOException;
022import java.util.Objects;
023
024import org.apache.bcel.Const;
025import org.apache.bcel.generic.Type;
026import org.apache.bcel.util.BCELComparator;
027
028/**
029 * This class represents the field info structure, i.e., the representation for a variable in the class. See JVM
030 * specification for details.
031 *
032 */
033public final class Field extends FieldOrMethod {
034
035    /**
036     * Empty array constant.
037     *
038     * @since 6.6.0
039     */
040    public static final Field[] EMPTY_ARRAY = {};
041
042    private static BCELComparator bcelComparator = new BCELComparator() {
043
044        @Override
045        public boolean equals(final Object o1, final Object o2) {
046            final Field THIS = (Field) o1;
047            final Field THAT = (Field) o2;
048            return Objects.equals(THIS.getName(), THAT.getName()) && Objects.equals(THIS.getSignature(), THAT.getSignature());
049        }
050
051        @Override
052        public int hashCode(final Object o) {
053            final Field THIS = (Field) o;
054            return THIS.getSignature().hashCode() ^ THIS.getName().hashCode();
055        }
056    };
057
058    /**
059     * Empty array.
060     */
061    static final Field[] EMPTY_FIELD_ARRAY = {};
062
063    /**
064     * @return Comparison strategy object
065     */
066    public static BCELComparator getComparator() {
067        return bcelComparator;
068    }
069
070    /**
071     * @param comparator Comparison strategy object
072     */
073    public static void setComparator(final BCELComparator comparator) {
074        bcelComparator = comparator;
075    }
076
077    /**
078     * Construct object from file stream.
079     *
080     * @param file Input stream
081     */
082    Field(final DataInput file, final ConstantPool constant_pool) throws IOException, ClassFormatException {
083        super(file, constant_pool);
084    }
085
086    /**
087     * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
088     * physical copy.
089     */
090    public Field(final Field c) {
091        super(c);
092    }
093
094    /**
095     * @param access_flags Access rights of field
096     * @param name_index Points to field name in constant pool
097     * @param signature_index Points to encoded signature
098     * @param attributes Collection of attributes
099     * @param constant_pool Array of constants
100     */
101    public Field(final int access_flags, final int name_index, final int signature_index, final Attribute[] attributes, final ConstantPool constant_pool) {
102        super(access_flags, name_index, signature_index, attributes, constant_pool);
103    }
104
105    /**
106     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
107     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
108     *
109     * @param v Visitor object
110     */
111    @Override
112    public void accept(final Visitor v) {
113        v.visitField(this);
114    }
115
116    /**
117     * @return deep copy of this field
118     */
119    public Field copy(final ConstantPool constantPool) {
120        return (Field) copy_(constantPool);
121    }
122
123    /**
124     * Return value as defined by given BCELComparator strategy. By default two Field objects are said to be equal when
125     * their names and signatures are equal.
126     *
127     * @see Object#equals(Object)
128     */
129    @Override
130    public boolean equals(final Object obj) {
131        return bcelComparator.equals(this, obj);
132    }
133
134    /**
135     * @return constant value associated with this field (may be null)
136     */
137    public ConstantValue getConstantValue() {
138        for (final Attribute attribute : super.getAttributes()) {
139            if (attribute.getTag() == Const.ATTR_CONSTANT_VALUE) {
140                return (ConstantValue) attribute;
141            }
142        }
143        return null;
144    }
145
146    /**
147     * @return type of field
148     */
149    public Type getType() {
150        return Type.getReturnType(getSignature());
151    }
152
153    /**
154     * Return value as defined by given BCELComparator strategy. By default return the hashcode of the field's name XOR
155     * signature.
156     *
157     * @see Object#hashCode()
158     */
159    @Override
160    public int hashCode() {
161        return bcelComparator.hashCode(this);
162    }
163
164    /**
165     * Return string representation close to declaration format, `public static final short MAX = 100', e.g..
166     *
167     * @return String representation of field, including the signature.
168     */
169    @Override
170    public String toString() {
171        String name;
172        String signature;
173        String access; // Short cuts to constant pool
174
175        // Get names from constant pool
176        access = Utility.accessToString(super.getAccessFlags());
177        access = access.isEmpty() ? "" : access + " ";
178        signature = Utility.signatureToString(getSignature());
179        name = getName();
180        final StringBuilder buf = new StringBuilder(64); // CHECKSTYLE IGNORE MagicNumber
181        buf.append(access).append(signature).append(" ").append(name);
182        final ConstantValue cv = getConstantValue();
183        if (cv != null) {
184            buf.append(" = ").append(cv);
185        }
186        for (final Attribute attribute : super.getAttributes()) {
187            if (!(attribute instanceof ConstantValue)) {
188                buf.append(" [").append(attribute).append("]");
189            }
190        }
191        return buf.toString();
192    }
193}