    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, i.e., 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     * @return Comparison strategy object.
    057     */
    058    public static BCELComparator<Field> getComparator() {
    059        return bcelComparator;
    060    }
    061
    062    /**
    063     * @param comparator Comparison strategy object.
    064     */
    065    public static void setComparator(final BCELComparator<Field> comparator) {
    066        bcelComparator = comparator;
    067    }
    068
    069    /**
    070     * Constructs object from file stream.
    071     *
    072     * @param file Input stream.
    073     */
    074    Field(final DataInput file, final ConstantPool constantPool) throws IOException, ClassFormatException {
    075        super(file, constantPool);
    076    }
    077
    078    /**
    079     * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a
    080     * physical copy.
    081     *
    082     * @param c Source to copy.
    083     */
    084    public Field(final Field c) {
    085        super(c);
    086    }
    087
    088    /**
    089     * @param accessFlags Access rights of field
    090     * @param nameIndex Points to field name in constant pool
    091     * @param signatureIndex Points to encoded signature
    092     * @param attributes Collection of attributes
    093     * @param constantPool Array of constants
    094     */
    095    public Field(final int accessFlags, final int nameIndex, final int signatureIndex, final Attribute[] attributes, final ConstantPool constantPool) {
    096        super(accessFlags, nameIndex, signatureIndex, attributes, constantPool);
    097    }
    098
    099    /**
    100     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    101     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    102     *
    103     * @param v Visitor object
    104     */
    105    @Override
    106    public void accept(final Visitor v) {
    107        v.visitField(this);
    108    }
    109
    110    /**
    111     * @return deep copy of this field
    112     */
    113    public Field copy(final ConstantPool constantPool) {
    114        return (Field) copy_(constantPool);
    115    }
    116
    117    /**
    118     * Return value as defined by given BCELComparator strategy. By default two Field objects are said to be equal when
    119     * their names and signatures are equal.
    120     *
    121     * @see Object#equals(Object)
    122     */
    123    @Override
    124    public boolean equals(final Object obj) {
    125        return obj instanceof Field && bcelComparator.equals(this, (Field) obj);
    126    }
    127
    128    /**
    129     * @return constant value associated with this field (may be null)
    130     */
    131    public ConstantValue getConstantValue() {
    132        for (final Attribute attribute : super.getAttributes()) {
    133            if (attribute.getTag() == Const.ATTR_CONSTANT_VALUE) {
    134                return (ConstantValue) attribute;
    135            }
    136        }
    137        return null;
    138    }
    139
    140    /**
    141     * See https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.2.2
    142     *
    143     * @return type of field
    144     */
    145    public Type getType() {
    146        return Type.getType(getSignature());
    147    }
    148
    149    /**
    150     * Return value as defined by given BCELComparator strategy. By default return the hash code of the field's name XOR
    151     * signature.
    152     *
    153     * @see Object#hashCode()
    154     */
    155    @Override
    156    public int hashCode() {
    157        return bcelComparator.hashCode(this);
    158    }
    159
    160    /**
    161     * Return string representation close to declaration format, for example: 'public static final short MAX = 100'.
    162     *
    163     * @return String representation of field, including the signature.
    164     */
    165    @Override
    166    public String toString() {
    167        // Get names from constant pool
    168        String access = Utility.accessToString(super.getAccessFlags());
    169        access = access.isEmpty() ? "" : access + " ";
    170        final String signature = Utility.signatureToString(getSignature());
    171        final String name = getName();
    172        final StringBuilder buf = new StringBuilder(64); // CHECKSTYLE IGNORE MagicNumber
    173        buf.append(access).append(signature).append(" ").append(name);
    174        final ConstantValue cv = getConstantValue();
    175        if (cv != null) {
    176            buf.append(" = ").append(cv);
    177        }
    178        for (final Attribute attribute : super.getAttributes()) {
    179            if (!(attribute instanceof ConstantValue)) {
    180                buf.append(" [").append(attribute).append("]");
    181            }
    182        }
    183        return buf.toString();
    184    }
    185}