    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one
    003 * or more contributor license agreements.  See the NOTICE file
    004 * distributed with this work for additional information
    005 * regarding copyright ownership.  The ASF licenses this file
    006 * to you under the Apache License, Version 2.0 (the
    007 * "License"); you may not use this file except in compliance
    008 * with the License.  You may obtain a copy of the License at
    009 *
    010 *   https://www.apache.org/licenses/LICENSE-2.0
    011 *
    012 * Unless required by applicable law or agreed to in writing,
    013 * software distributed under the License is distributed on an
    014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
    015 * KIND, either express or implied.  See the License for the
    016 * specific language governing permissions and limitations
    017 * under the License.
    018 */
    019package org.apache.bcel.classfile;
    020
    021import java.io.DataInput;
    022import java.io.IOException;
    023import java.util.Objects;
    024
    025import org.apache.bcel.Const;
    026import org.apache.bcel.generic.Type;
    027import org.apache.bcel.util.BCELComparator;
    028
    029/**
    030 * This class represents the field info structure, that is, the representation for a variable in the class. See JVM
    031 * specification for details.
    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<Field> bcelComparator = new BCELComparator<Field>() {
    043
    044        @Override
    045        public boolean equals(final Field a, final Field b) {
    046            return a == b || a != null && b != null && Objects.equals(a.getName(), b.getName()) && Objects.equals(a.getSignature(), b.getSignature());
    047        }
    048
    049        @Override
    050        public int hashCode(final Field o) {
    051            return o != null ? Objects.hash(o.getSignature(), o.getName()) : 0;
    052        }
    053    };
    054
    055    /**
    056     * Gets the comparison strategy object.
    057     *
    058     * @return Comparison strategy object.
    059     */
    060    public static BCELComparator<Field> getComparator() {
    061        return bcelComparator;
    062    }
    063
    064    /**
    065     * Sets the comparison strategy object.
    066     *
    067     * @param comparator Comparison strategy object.
    068     */
    069    public static void setComparator(final BCELComparator<Field> comparator) {
    070        bcelComparator = comparator;
    071    }
    072
    073    /**
    074     * Constructs object from file stream.
    075     *
    076     * @param file Input stream.
    077     * @param constantPool the constant pool.
    078     */
    079    Field(final DataInput file, final ConstantPool constantPool) throws IOException, ClassFormatException {
    080        super(file, constantPool);
    081    }
    082
    083    /**
    084     * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
    085     * physical copy.
    086     *
    087     * @param c Source to copy.
    088     */
    089    public Field(final Field c) {
    090        super(c);
    091    }
    092
    093    /**
    094     * Constructs a Field.
    095     *
    096     * @param accessFlags Access rights of field.
    097     * @param nameIndex Points to field name in constant pool.
    098     * @param signatureIndex Points to encoded signature.
    099     * @param attributes Collection of attributes.
    100     * @param constantPool Array of constants.
    101     */
    102    public Field(final int accessFlags, final int nameIndex, final int signatureIndex, final Attribute[] attributes, final ConstantPool constantPool) {
    103        super(accessFlags, nameIndex, signatureIndex, attributes, constantPool);
    104    }
    105
    106    /**
    107     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    108     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    109     *
    110     * @param v Visitor object.
    111     */
    112    @Override
    113    public void accept(final Visitor v) {
    114        v.visitField(this);
    115    }
    116
    117    /**
    118     * Creates a deep copy of this field.
    119     *
    120     * @param constantPool the constant pool.
    121     * @return deep copy of this field.
    122     */
    123    public Field copy(final ConstantPool constantPool) {
    124        return (Field) copy_(constantPool);
    125    }
    126
    127    /**
    128     * Return value as defined by given BCELComparator strategy. By default two Field objects are said to be equal when
    129     * their names and signatures are equal.
    130     *
    131     * @see Object#equals(Object)
    132     */
    133    @Override
    134    public boolean equals(final Object obj) {
    135        return obj instanceof Field && bcelComparator.equals(this, (Field) obj);
    136    }
    137
    138    /**
    139     * Gets the constant value associated with this field.
    140     *
    141     * @return constant value associated with this field (may be null).
    142     */
    143    public ConstantValue getConstantValue() {
    144        for (final Attribute attribute : super.getAttributes()) {
    145            if (attribute.getTag() == Const.ATTR_CONSTANT_VALUE) {
    146                return (ConstantValue) attribute;
    147            }
    148        }
    149        return null;
    150    }
    151
    152    /**
    153     * See https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.2.2
    154     *
    155     * @return type of field.
    156     */
    157    public Type getType() {
    158        return Type.getType(getSignature());
    159    }
    160
    161    /**
    162     * Return value as defined by given BCELComparator strategy. By default return the hash code of the field's name XOR
    163     * signature.
    164     *
    165     * @see Object#hashCode()
    166     */
    167    @Override
    168    public int hashCode() {
    169        return bcelComparator.hashCode(this);
    170    }
    171
    172    /**
    173     * Return string representation close to declaration format, for example: 'public static final short MAX = 100'.
    174     *
    175     * @return String representation of field, including the signature.
    176     */
    177    @Override
    178    public String toString() {
    179        // Get names from constant pool
    180        String access = Utility.accessToString(super.getAccessFlags());
    181        access = access.isEmpty() ? "" : access + " ";
    182        final String signature = Utility.signatureToString(getSignature());
    183        final String name = getName();
    184        final StringBuilder buf = new StringBuilder(64); // CHECKSTYLE IGNORE MagicNumber
    185        buf.append(access).append(signature).append(" ").append(name);
    186        final ConstantValue cv = getConstantValue();
    187        if (cv != null) {
    188            buf.append(" = ").append(cv);
    189        }
    190        for (final Attribute attribute : super.getAttributes()) {
    191            if (!(attribute instanceof ConstantValue)) {
    192                buf.append(" [").append(attribute).append("]");
    193            }
    194        }
    195        return buf.toString();
    196    }
    197}