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.DataOutputStream; 021import java.io.IOException; 022 023import org.apache.bcel.Const; 024 025/** 026 * This class is derived from <em>Attribute</em> and represents a constant value, i.e., a default value for initializing 027 * a class field. This class is instantiated by the <em>Attribute.readAttribute()</em> method. 028 * 029 * @see Attribute 030 */ 031public final class ConstantValue extends Attribute { 032 033 private int constantValueIndex; 034 035 /** 036 * Initialize from another object. Note that both objects use the same references (shallow copy). Use clone() for a 037 * physical copy. 038 */ 039 public ConstantValue(final ConstantValue c) { 040 this(c.getNameIndex(), c.getLength(), c.getConstantValueIndex(), c.getConstantPool()); 041 } 042 043 /** 044 * Construct object from input stream. 045 * 046 * @param nameIndex Name index in constant pool 047 * @param length Content length in bytes 048 * @param input Input stream 049 * @param constantPool Array of constants 050 * @throws IOException if an I/O error occurs. 051 */ 052 ConstantValue(final int nameIndex, final int length, final DataInput input, final ConstantPool constantPool) throws IOException { 053 this(nameIndex, length, input.readUnsignedShort(), constantPool); 054 } 055 056 /** 057 * @param nameIndex Name index in constant pool 058 * @param length Content length in bytes 059 * @param constantValueIndex Index in constant pool 060 * @param constantPool Array of constants 061 */ 062 public ConstantValue(final int nameIndex, final int length, final int constantValueIndex, final ConstantPool constantPool) { 063 super(Const.ATTR_CONSTANT_VALUE, nameIndex, length, constantPool); 064 this.constantValueIndex = constantValueIndex; 065 } 066 067 /** 068 * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class. 069 * I.e., the hierarchy of methods, fields, attributes, etc. spawns a tree of objects. 070 * 071 * @param v Visitor object 072 */ 073 @Override 074 public void accept(final Visitor v) { 075 v.visitConstantValue(this); 076 } 077 078 /** 079 * @return deep copy of this attribute 080 */ 081 @Override 082 public Attribute copy(final ConstantPool constantPool) { 083 final ConstantValue c = (ConstantValue) clone(); 084 c.setConstantPool(constantPool); 085 return c; 086 } 087 088 /** 089 * Dump constant value attribute to file stream on binary format. 090 * 091 * @param file Output file stream 092 * @throws IOException if an I/O error occurs. 093 */ 094 @Override 095 public void dump(final DataOutputStream file) throws IOException { 096 super.dump(file); 097 file.writeShort(constantValueIndex); 098 } 099 100 /** 101 * @return Index in constant pool of constant value. 102 */ 103 public int getConstantValueIndex() { 104 return constantValueIndex; 105 } 106 107 /** 108 * @param constantValueIndex the index info the constant pool of this constant value 109 */ 110 public void setConstantValueIndex(final int constantValueIndex) { 111 this.constantValueIndex = constantValueIndex; 112 } 113 114 /** 115 * @return String representation of constant value. 116 */ 117 @Override 118 public String toString() { 119 Constant c = super.getConstantPool().getConstant(constantValueIndex); 120 String buf; 121 int i; 122 // Print constant to string depending on its type 123 switch (c.getTag()) { 124 case Const.CONSTANT_Long: 125 buf = String.valueOf(((ConstantLong) c).getBytes()); 126 break; 127 case Const.CONSTANT_Float: 128 buf = String.valueOf(((ConstantFloat) c).getBytes()); 129 break; 130 case Const.CONSTANT_Double: 131 buf = String.valueOf(((ConstantDouble) c).getBytes()); 132 break; 133 case Const.CONSTANT_Integer: 134 buf = String.valueOf(((ConstantInteger) c).getBytes()); 135 break; 136 case Const.CONSTANT_String: 137 i = ((ConstantString) c).getStringIndex(); 138 c = super.getConstantPool().getConstantUtf8(i); 139 buf = "\"" + Utility.convertString(((ConstantUtf8) c).getBytes()) + "\""; 140 break; 141 default: 142 throw new IllegalStateException("Type of ConstValue invalid: " + c); 143 } 144 return buf; 145 } 146}