    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     * @return Comparison strategy object.
    055     */
    056    public static BCELComparator<Field> getComparator() {
    057        return bcelComparator;
    058    }
    059
    060    /**
    061     * @param comparator Comparison strategy object.
    062     */
    063    public static void setComparator(final BCELComparator<Field> comparator) {
    064        bcelComparator = comparator;
    065    }
    066
    067    /**
    068     * Constructs object from file stream.
    069     *
    070     * @param file Input stream.
    071     */
    072    Field(final DataInput file, final ConstantPool constantPool) throws IOException, ClassFormatException {
    073        super(file, constantPool);
    074    }
    075
    076    /**
    077     * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
    078     * physical copy.
    079     *
    080     * @param c Source to copy.
    081     */
    082    public Field(final Field c) {
    083        super(c);
    084    }
    085
    086    /**
    087     * @param accessFlags Access rights of field
    088     * @param nameIndex Points to field name in constant pool
    089     * @param signatureIndex Points to encoded signature
    090     * @param attributes Collection of attributes
    091     * @param constantPool Array of constants
    092     */
    093    public Field(final int accessFlags, final int nameIndex, final int signatureIndex, final Attribute[] attributes, final ConstantPool constantPool) {
    094        super(accessFlags, nameIndex, signatureIndex, attributes, constantPool);
    095    }
    096
    097    /**
    098     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    099     * 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}