    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.DataOutputStream;
    022import java.io.IOException;
    023import java.util.Arrays;
    024
    025import org.apache.bcel.Const;
    026import org.apache.bcel.util.Args;
    027import org.apache.commons.lang3.ArrayUtils;
    028
    029/**
    030 * This class represents the table of exceptions that are thrown by a method. This attribute may be used once per
    031 * method. The name of this class is <em>ExceptionTable</em> for historical reasons; The Java Virtual Machine
    032 * Specification, Second Edition defines this attribute using the name <em>Exceptions</em> (which is inconsistent with
    033 * the other classes).
    034 *
    035 * <pre>
    036 * Exceptions_attribute {
    037 *   u2 attribute_name_index;
    038 *   u4 attribute_length;
    039 *   u2 number_of_exceptions;
    040 *   u2 exception_index_table[number_of_exceptions];
    041 * }
    042 * </pre>
    043 * @see Code
    044 */
    045public final class ExceptionTable extends Attribute {
    046
    047    private int[] exceptionIndexTable; // constant pool
    048
    049    /**
    050     * Initialize from another object. Note that both objects use the same references (shallow copy). Use copy() for a
    051     * physical copy.
    052     *
    053     * @param c Source to copy.
    054     */
    055    public ExceptionTable(final ExceptionTable c) {
    056        this(c.getNameIndex(), c.getLength(), c.getExceptionIndexTable(), c.getConstantPool());
    057    }
    058
    059    /**
    060     * Constructs object from input stream.
    061     *
    062     * @param nameIndex Index in constant pool
    063     * @param length Content length in bytes
    064     * @param input Input stream
    065     * @param constantPool Array of constants
    066     * @throws IOException if an I/O error occurs.
    067     */
    068    ExceptionTable(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException {
    069        this(nameIndex, length, (int[]) null, constantPool);
    070        final int exceptionCount = input.readUnsignedShort();
    071        exceptionIndexTable = new int[exceptionCount];
    072        for (int i = 0; i < exceptionCount; i++) {
    073            exceptionIndexTable[i] = input.readUnsignedShort();
    074        }
    075    }
    076
    077    /**
    078     * @param nameIndex Index in constant pool
    079     * @param length Content length in bytes
    080     * @param exceptionIndexTable Table of indices in constant pool
    081     * @param constantPool Array of constants
    082     */
    083    public ExceptionTable(final int nameIndex, final int length, final int[] exceptionIndexTable, final ConstantPool constantPool) {
    084        super(Const.ATTR_EXCEPTIONS, nameIndex, length, constantPool);
    085        this.exceptionIndexTable = ArrayUtils.nullToEmpty(exceptionIndexTable);
    086        Args.requireU2(this.exceptionIndexTable.length, "exceptionIndexTable.length");
    087    }
    088
    089    /**
    090     * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
    091     * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
    092     *
    093     * @param v Visitor object
    094     */
    095    @Override
    096    public void accept(final Visitor v) {
    097        v.visitExceptionTable(this);
    098    }
    099
    100    /**
    101     * @return deep copy of this attribute
    102     */
    103    @Override
    104    public Attribute copy(final ConstantPool constantPool) {
    105        final ExceptionTable c = (ExceptionTable) clone();
    106        if (exceptionIndexTable != null) {
    107            c.exceptionIndexTable = exceptionIndexTable.clone();
    108        }
    109        c.setConstantPool(constantPool);
    110        return c;
    111    }
    112
    113    /**
    114     * Dump exceptions attribute to file stream in binary format.
    115     *
    116     * @param file Output file stream
    117     * @throws IOException if an I/O error occurs.
    118     */
    119    @Override
    120    public void dump(final DataOutputStream file) throws IOException {
    121        super.dump(file);
    122        file.writeShort(exceptionIndexTable.length);
    123        for (final int index : exceptionIndexTable) {
    124            file.writeShort(index);
    125        }
    126    }
    127
    128    /**
    129     * @return Array of indices into constant pool of thrown exceptions.
    130     */
    131    public int[] getExceptionIndexTable() {
    132        return exceptionIndexTable;
    133    }
    134
    135    /**
    136     * @return class names of thrown exceptions
    137     */
    138    public String[] getExceptionNames() {
    139        final String[] names = new String[exceptionIndexTable.length];
    140        Arrays.setAll(names, i -> Utility.pathToPackage(super.getConstantPool().getConstantString(exceptionIndexTable[i], Const.CONSTANT_Class)));
    141        return names;
    142    }
    143
    144    /**
    145     * @return Length of exception table.
    146     */
    147    public int getNumberOfExceptions() {
    148        return exceptionIndexTable == null ? 0 : exceptionIndexTable.length;
    149    }
    150
    151    /**
    152     * @param exceptionIndexTable the list of exception indexes Also redefines number_of_exceptions according to table
    153     *        length.
    154     */
    155    public void setExceptionIndexTable(final int[] exceptionIndexTable) {
    156        this.exceptionIndexTable = ArrayUtils.nullToEmpty(exceptionIndexTable);
    157    }
    158
    159    /**
    160     * @return String representation, i.e., a list of thrown exceptions.
    161     */
    162    @Override
    163    public String toString() {
    164        final StringBuilder buf = new StringBuilder();
    165        String str;
    166        buf.append("Exceptions: ");
    167        for (int i = 0; i < exceptionIndexTable.length; i++) {
    168            str = super.getConstantPool().getConstantString(exceptionIndexTable[i], Const.CONSTANT_Class);
    169            buf.append(Utility.compactClassName(str, false));
    170            if (i < exceptionIndexTable.length - 1) {
    171                buf.append(", ");
    172            }
    173        }
    174        return buf.toString();
    175    }
    176}