    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 */
    017package org.apache.bcel.classfile;
    018
    019import java.io.DataInput;
    020import java.io.IOException;
    021import java.util.Objects;
    022
    023import org.apache.bcel.Const;
    024import org.apache.bcel.generic.Type;
    025import org.apache.bcel.util.BCELComparator;
    026
    027/**
    028 * This class represents the field info structure, i.e., the representation for a variable in the class. See JVM
    029 * specification for details.
    030 */
    031public final class Field extends FieldOrMethod {
    032
    033    /**
    034     * Empty array constant.
    035     *
    036     * @since 6.6.0
    037     */
    038    public static final Field[] EMPTY_ARRAY = {};
    039
    040    private static BCELComparator<Field> bcelComparator = new BCELComparator<Field>() {
    041
    042        @Override
    043        public boolean equals(final Field a, final Field b) {
    044            return a == b || a != null && b != null && Objects.equals(a.getName(), b.getName()) && Objects.equals(a.getSignature(), b.getSignature());
    045        }
    046
    047        @Override
    048        public int hashCode(final Field o) {
    049            return o != null ? Objects.hash(o.getSignature(), o.getName()) : 0;
    050        }
    051    };
    052
    053    /**
    054     * Empty array.
    055     */
    056    static final Field[] EMPTY_FIELD_ARRAY = {};
    057
    058    /**
    059     * @return Comparison strategy object.
    060     */
    061    public static BCELComparator<Field> getComparator() {
    062        return bcelComparator;
    063    }
    064
    065    /**
    066     * @param comparator Comparison strategy object.
    067     */
    068    public static void setComparator(final BCELComparator<Field> comparator) {
    069        bcelComparator = comparator;
    070    }
    071
    072    /**
    073     * Constructs object from file stream.
    074     *
    075     * @param file Input stream.
    076     */
    077    Field(final DataInput file, final ConstantPool constantPool) throws IOException, ClassFormatException {
    078        super(file, constantPool);
    079    }
    080
    081    /**
    082     * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
    083     * physical copy.
    084     *
    085     * @param c Source to copy.
    086     */
    087    public Field(final Field c) {
    088        super(c);
    089    }
    090
    091    /**
    092     * @param accessFlags Access rights of field
    093     * @param nameIndex Points to field name in constant pool
    094     * @param signatureIndex Points to encoded signature
    095     * @param attributes Collection of attributes
    096     * @param constantPool Array of constants
    097     */
    098    public Field(final int accessFlags, final int nameIndex, final int signatureIndex, final Attribute[] attributes, final ConstantPool constantPool) {
    099        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}