路漫漫其修遠兮，吾將上下而求索
經驗淺薄，耐心積累；記性不好，記諸文字

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這個最接近之前提出的API轉換問題
這個需要掃描源代碼找到此類的方法調用處，然后在方法調用處的前后添加指令
即將代碼轉換成如下形式：

public class StringBuilder

{

public String buildString(int length) {

String result = "";

for (int i = 0; i < length; i++) {

result += (char)(i%26 + 'a');

}

return result;

}

public static void main(String[] argv) {

StringBuilder inst = new StringBuilder();

for (int i = 0; i < argv.length; i++) {

long start = System.currentTimeMillis();

            String result = inst.buildString(Integer.parseInt(argv[i]));
            System.out.println("Call to buildString$impl took " +
                    (System.currentTimeMillis()-start) + " ms.");

System.out.println("Constructed string of length " +

result.length());

}

轉換代碼如下：
先掃描這個類中的各個方法
我準備改變一下生成策略，不自己寫指令了，這個自己寫指令比較麻煩，但要加的代碼比較多時比較容易出錯，當所加的代碼有if,跳轉語句，自己根本就不會如何寫添哪些指令，這種寫類似匯編指令總是很麻煩的。

先要把加的代碼自己在某個類中事先用方法寫好，實例方法也好，靜態方法也好，方法帶有參數或者有返回值，
這些參數和返回值供調用方法中的局部變量來替換和使用。
再要添加代碼的方法的前后調用這些已經寫好的方法的字節碼的指令序列生成InstructionList，然后再添加到使用這個方法的指令序列中

如下

public class ToolUtil {

public static long printStart() {

System.out.println("start start start start");

long start = System.currentTimeMillis();

return start;

}

public static void printEnd(String methodname,long start){

System.out.println("Call to "+methodname+" took " +

(System.currentTimeMillis()-start) + " ms.");

System.out.println("end end end end end end");

}

原始的方法

public class StringBuilder {

/*

* 要在調用了此方法的方法的代碼的前后添加代碼

*/

public String buildString(int length) {

String result = "";

for (int i = 0; i < length; i++) {

result += (char) (i % 26 + 'a');

}

System.out.println(result);

return result;

}

/*

* 調用了buildString方法

*/

private String testInvokeMethod(){

String temp = null;

temp = buildString(10);

return temp;

}

/*

* 調用了buildString方法

*/

public static void main(String[] argv) {

StringBuilder inst = new StringBuilder();

for (int i = 0; i < argv.length; i++) {

String result = inst.buildString(Integer.parseInt(argv[i]));

System.out.println("Constructed string of length "

+ result.length());

}

生成的方法為

public class StringBuilder {

/*

* 要在調用了此方法的方法的代碼的前后添加代碼

*/

public String buildString(int length) {

String result = "";

for (int i = 0; i < length; i++) {

result += (char) (i % 26 + 'a');

}

System.out.println(result);

return result;

}

/*

* 調用了buildString方法

*/

private String testInvokeMethod(){

String temp = null;

//調用事先寫好的方法
long startTime = ToolUtil.printStart();

temp = buildString(10);

//調用事先寫好的方法
ToolUtil.printEnd("buildString", startTime);

System.out.println("我是測試方法,我是測試方法,我是測試方法,我是測試方法");

return temp;

}

/*

* 調用了buildString方法

*/

public static void main(String[] argv) {

StringBuilder inst = new StringBuilder();

for (int i = 0; i < argv.length; i++) {

//調用事先寫好的方法
long startTime = ToolUtil.printStart();

String result = inst.buildString(Integer.parseInt(argv[i]));

//調用事先寫好的方法
ToolUtil.printEnd("buildString", startTime);

System.out.println("Constructed string of length "

+ result.length());

}

main這個調用的代碼或者使用INVOKEXXXX指令實現，或者把這些調用方法的字節碼指令序列加入到main的指令序列當中來實現，直接加的話可能自己事先寫的方法的局部變量與main方法的局部變量會相同，而且涉及到所加的指令序列使用局部變量的問題,比如加的iload_0,istore_2就會引用現在方法的局部變量，但是現在的局部變量根本就不是這種指令所對應的類型
。所以還是使用方法調用比較方便

import java.io.FileOutputStream;

import org.apache.bcel.Constants;

import org.apache.bcel.classfile.ClassParser;

import org.apache.bcel.classfile.ConstantClass;

import org.apache.bcel.classfile.ConstantMethodref;

import org.apache.bcel.classfile.ConstantNameAndType;

import org.apache.bcel.classfile.ConstantPool;

import org.apache.bcel.classfile.JavaClass;

import org.apache.bcel.classfile.Method;

import org.apache.bcel.generic.ClassGen;

import org.apache.bcel.generic.ConstantPoolGen;

import org.apache.bcel.generic.INVOKEVIRTUAL;

import org.apache.bcel.generic.Instruction;

import org.apache.bcel.generic.InstructionFactory;

import org.apache.bcel.generic.InstructionHandle;

import org.apache.bcel.generic.InstructionList;

import org.apache.bcel.generic.LocalVariableGen;

import org.apache.bcel.generic.MethodGen;

import org.apache.bcel.generic.Type;

public class BCELTiming3 {

/*

* 掃描StringBuilder的各個方法的指令序列,在其中找Invokexxxx指令,

* 看此指令在常量池中引用的方法引用是否是要其前后加代碼的方法

* 方法所在的類要一致，方法的名稱要一致，方法的簽名要一致

*

*/

/**

*

* @param cgen 要被解析的類class文件

* @param classname 要被修改的方法所在的類名稱,若有包名,則為java/lang/Object類似的

* @param methodname 要被修改的方法的名稱

* @param methodSignature 要被修改的方法的簽名

*/

private static void modifyWrapper(ClassGen cgen,String classname,String methodname,String methodSignature){

InstructionFactory ifact = new InstructionFactory(cgen);

ConstantPoolGen pgen = cgen.getConstantPool();

ConstantPool pool = pgen.getConstantPool();

String cname = cgen.getClassName();

Method[] methods = cgen.getMethods();

for(int i=0;i<methods.length;i++){

Method tempMethod = methods[i];

MethodGen tempMethodGen = new MethodGen(tempMethod,cname,pgen);

InstructionList tempList = tempMethodGen.getInstructionList();

tempList.iterator();

Instruction[] tempInstructions = tempList.getInstructions();

InstructionHandle[] tempInHandles = tempList.getInstructionHandles();

for(int j=0;j<tempInHandles.length;j++){

InstructionHandle ihandle = tempInHandles[j];

Instruction nowInstruction = ihandle.getInstruction();

if(nowInstruction.getOpcode()==Constants.INVOKEVIRTUAL){

INVOKEVIRTUAL invokeVirtual = (INVOKEVIRTUAL)nowInstruction;

ConstantMethodref cmr = (ConstantMethodref)pgen.getConstant(invokeVirtual.getIndex());

ConstantClass cc = (ConstantClass)pgen.getConstant(cmr.getClassIndex());

String nowClassName = cc.getBytes(pgen.getConstantPool());

ConstantNameAndType cnt = (ConstantNameAndType)pgen.getConstant(cmr.getNameAndTypeIndex());

String nowMethodName = cnt.getName(pgen.getConstantPool());

String nowMethodSignature = cnt.getSignature(pgen.getConstantPool());

//判斷此方法的所屬的類,方法的名稱,方法的簽名是否與所要加的一致(I)Ljava/lang/String;

if(nowClassName.equals(classname) && nowMethodName.equals(methodname) && nowMethodSignature.equals(methodSignature)){

cgen.removeMethod(tempMethodGen.getMethod());

//找到此方法在list的位置

InstructionList beforeList = new InstructionList();

//先加一個局部變量保存starttime的值

LocalVariableGen lvg = tempMethodGen.addLocalVariable("starttime", Type.LONG, null, null);

beforeList.append(ifact.createInvoke("ToolUtil", "printStart", Type.LONG, Type.NO_ARGS, Constants.INVOKESTATIC));

beforeList.append(InstructionFactory.createStore(Type.LONG, lvg.getIndex()));

tempList.insert(ihandle.getPrev().getPrev(), beforeList);

//加方法后的代碼

InstructionList afterList = new InstructionList();

afterList.append(ifact.createConstant(methodname));

afterList.append(ifact.createLoad(Type.LONG, lvg.getIndex()));

afterList.append(ifact.createInvoke("ToolUtil", "printEnd", Type.VOID, new Type[]{Type.STRING,Type.LONG}, Constants.INVOKESTATIC));

tempList.insert(ihandle.getNext().getNext(), afterList);

//finalize the construted method

tempMethodGen.stripAttributes(false);

tempMethodGen.setMaxStack();

tempMethodGen.setMaxLocals();

cgen.addMethod(tempMethodGen.getMethod());

System.out.println(tempMethodGen.getInstructionList());

System.out.println();

}

// tempList.setPositions();

// tempList.findHandle(pos);

}

/**

* @param args

*/

public static void main(String[] args) {

args[0]="D:\\java to eclipse\\javaeclipsestudy\\workspace\\BCELTest\\bin\\StringBuilder.class";

if(args.length==1 && args[0].endsWith(".class")){

try{

JavaClass jclas = new ClassParser(args[0]).parse();

ClassGen cgen = new ClassGen(jclas);

modifyWrapper(cgen,"StringBuilder","buildString","(I)Ljava/lang/String;");

cgen.getJavaClass().dump(args[0]);

}catch(Exception e){

e.printStackTrace();

}

}else{

System.out.println("usage: class-file");

}

posted on 2009-08-13 23:10 Frank_Fang 閱讀(1732) 評論(3) 編輯收藏所屬分類: bcel javassist

評論:

# re: 用 BCEL 設計字節碼（三）直接在方法的調用處添加方法 2009-08-16 18:37 | Frank_Fang

原來方法的字節碼
--------------------------------33
--------------------------------33
0
2
CONSTANT_Utf8[1]("SourceFile")
true
CONSTANT_Utf8[1]("StringBuilder.java")
1
StringBuilder.java
StringBuilder.java
---------------------------------------------------------------------------
1:CONSTANT_Class[7](name_index = 2)
2:CONSTANT_Utf8[1]("StringBuilder")
3:CONSTANT_Class[7](name_index = 4)
4:CONSTANT_Utf8[1]("java/lang/Object")
5:CONSTANT_Utf8[1]("<init>")
6:CONSTANT_Utf8[1]("()V")
7:CONSTANT_Utf8[1]("Code")
8:CONSTANT_Methodref[10](class_index = 3, name_and_type_index = 9)
9:CONSTANT_NameAndType[12](name_index = 5, signature_index = 6)
10:CONSTANT_Utf8[1]("LineNumberTable")
11:CONSTANT_Utf8[1]("LocalVariableTable")
12:CONSTANT_Utf8[1]("this")
13:CONSTANT_Utf8[1]("LStringBuilder;")
14:CONSTANT_Utf8[1]("buildString")
15:CONSTANT_Utf8[1]("(I)Ljava/lang/String;")
16:CONSTANT_String[8](string_index = 17)
17:CONSTANT_Utf8[1]("")
18:CONSTANT_Class[7](name_index = 19)
19:CONSTANT_Utf8[1]("java/lang/StringBuilder")
20:CONSTANT_Methodref[10](class_index = 21, name_and_type_index = 23)
21:CONSTANT_Class[7](name_index = 22)
22:CONSTANT_Utf8[1]("java/lang/String")
23:CONSTANT_NameAndType[12](name_index = 24, signature_index = 25)
24:CONSTANT_Utf8[1]("valueOf")
25:CONSTANT_Utf8[1]("(Ljava/lang/Object;)Ljava/lang/String;")
26:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 27)
27:CONSTANT_NameAndType[12](name_index = 5, signature_index = 28)
28:CONSTANT_Utf8[1]("(Ljava/lang/String;)V")
29:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 30)
30:CONSTANT_NameAndType[12](name_index = 31, signature_index = 32)
31:CONSTANT_Utf8[1]("append")
32:CONSTANT_Utf8[1]("(C)Ljava/lang/StringBuilder;")
33:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 34)
34:CONSTANT_NameAndType[12](name_index = 35, signature_index = 36)
35:CONSTANT_Utf8[1]("toString")
36:CONSTANT_Utf8[1]("()Ljava/lang/String;")
37:CONSTANT_Fieldref[9](class_index = 38, name_and_type_index = 40)
*********************ConstantFieldref start**********************
cc.toString : CONSTANT_Class[7](name_index = 39)
java/lang/System
cnat.toString : CONSTANT_NameAndType[12](name_index = 41, signature_index = 42)
out
Ljava/io/PrintStream;
**********************ConstantFieldref end*******************************
38:CONSTANT_Class[7](name_index = 39)
39:CONSTANT_Utf8[1]("java/lang/System")
40:CONSTANT_NameAndType[12](name_index = 41, signature_index = 42)
41:CONSTANT_Utf8[1]("out")
42:CONSTANT_Utf8[1]("Ljava/io/PrintStream;")
43:CONSTANT_Methodref[10](class_index = 44, name_and_type_index = 46)
44:CONSTANT_Class[7](name_index = 45)
45:CONSTANT_Utf8[1]("java/io/PrintStream")
46:CONSTANT_NameAndType[12](name_index = 47, signature_index = 28)
47:CONSTANT_Utf8[1]("println")
48:CONSTANT_Utf8[1]("length")
49:CONSTANT_Utf8[1]("I")
50:CONSTANT_Utf8[1]("result")
51:CONSTANT_Utf8[1]("Ljava/lang/String;")
52:CONSTANT_Utf8[1]("i")
53:CONSTANT_Utf8[1]("testInvokeMethod")
54:CONSTANT_Methodref[10](class_index = 1, name_and_type_index = 55)
55:CONSTANT_NameAndType[12](name_index = 14, signature_index = 15)
56:CONSTANT_String[8](string_index = 57)
57:CONSTANT_Utf8[1]("我是測試方法,我是測試方法,我是測試方法,我是測試方法")
58:CONSTANT_Utf8[1]("temp")
59:CONSTANT_Utf8[1]("main")
60:CONSTANT_Utf8[1]("([Ljava/lang/String;)V")
61:CONSTANT_Methodref[10](class_index = 1, name_and_type_index = 9)
62:CONSTANT_Methodref[10](class_index = 63, name_and_type_index = 65)
63:CONSTANT_Class[7](name_index = 64)
64:CONSTANT_Utf8[1]("java/lang/Integer")
65:CONSTANT_NameAndType[12](name_index = 66, signature_index = 67)
66:CONSTANT_Utf8[1]("parseInt")
67:CONSTANT_Utf8[1]("(Ljava/lang/String;)I")
68:CONSTANT_String[8](string_index = 69)
69:CONSTANT_Utf8[1]("Constructed string of length ")
70:CONSTANT_Methodref[10](class_index = 21, name_and_type_index = 71)
71:CONSTANT_NameAndType[12](name_index = 48, signature_index = 72)
72:CONSTANT_Utf8[1]("()I")
73:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 74)
74:CONSTANT_NameAndType[12](name_index = 31, signature_index = 75)
75:CONSTANT_Utf8[1]("(I)Ljava/lang/StringBuilder;")
76:CONSTANT_Utf8[1]("argv")
77:CONSTANT_Utf8[1]("[Ljava/lang/String;")
78:CONSTANT_Utf8[1]("inst")
79:CONSTANT_Utf8[1]("SourceFile")
80:CONSTANT_Utf8[1]("StringBuilder.java")
--------------------------域----------------------------
-----------域的長度,此類定義的成員變量的個數-------------0

start method method method-----------------------------------
方法訪問標志
1
方法訪問名稱
<init>
CONSTANT_Utf8[1]("<init>")
方法簽名
()V
CONSTANT_Utf8[1]("()V")
方法的參數類型
方法的返回類型
void
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 47
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 5
給出該方法在執行中任何點操作數棧上字的最大個數 1
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 1
code的字節信息調用code.getCode()返回byte[] [B@1571886
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======1
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=5| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
完整的code.toString的信息
public void <init>()
Code(max_stack = 1, max_locals = 1, code_length = 5)
0: aload_0
1: invokespecial java.lang.Object.<init> ()V (8)
4: return

Attribute(s) =
LineNumber(0, 1)
LocalVariable(start_pc = 0, length = 5, index = 0:StringBuilder this)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
1
方法訪問名稱
buildString
CONSTANT_Utf8[1]("buildString")
方法簽名
(I)Ljava/lang/String;
CONSTANT_Utf8[1]("(I)Ljava/lang/String;")
方法的參數類型
int方法的返回類型
java.lang.String
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 143
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 51
給出該方法在執行中任何點操作數棧上字的最大個數 3
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 4
code的字節信息調用code.getCode()返回byte[] [B@1c184f4
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======4
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=51| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=0| lv.getLength=51| lv.getNameIndex()=48 | lv.getName()=length| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=1
--------------------第 2 個局部變量的信息
lv.getStartPC()=3| lv.getLength=48| lv.getNameIndex()=50 | lv.getName()=result| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=2
--------------------第 3 個局部變量的信息
lv.getStartPC()=5| lv.getLength=37| lv.getNameIndex()=52 | lv.getName()=i| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=3
完整的code.toString的信息
public String buildString(int length)
Code(max_stack = 3, max_locals = 4, code_length = 51)
0: ldc "" (16)
2: astore_2
3: iconst_0
4: istore_3
5: goto #37
8: new <java.lang.StringBuilder> (18)
11: dup
12: aload_2
13: invokestatic java.lang.String.valueOf (Ljava/lang/Object;)Ljava/lang/String; (20)
16: invokespecial java.lang.StringBuilder.<init> (Ljava/lang/String;)V (26)
19: iload_3
20: bipush 26
22: irem
23: bipush 97
25: iadd
26: i2c
27: invokevirtual java.lang.StringBuilder.append (C)Ljava/lang/StringBuilder; (29)
30: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
33: astore_2
34: iinc %3 1
37: iload_3
38: iload_1
39: if_icmplt #8
42: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
45: aload_2
46: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
49: aload_2
50: areturn

Attribute(s) =
LineNumber(0, 9), LineNumber(3, 10), LineNumber(8, 11), LineNumber(34, 10),
LineNumber(42, 13), LineNumber(49, 15)
LocalVariable(start_pc = 0, length = 51, index = 0:StringBuilder this)
LocalVariable(start_pc = 0, length = 51, index = 1:int length)
LocalVariable(start_pc = 3, length = 48, index = 2:String result)
LocalVariable(start_pc = 5, length = 37, index = 3:int i)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
2
方法訪問名稱
testInvokeMethod
CONSTANT_Utf8[1]("testInvokeMethod")
方法簽名
()Ljava/lang/String;
CONSTANT_Utf8[1]("()Ljava/lang/String;")
方法的參數類型
方法的返回類型
java.lang.String
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 83
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 19
給出該方法在執行中任何點操作數棧上字的最大個數 2
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 2
code的字節信息調用code.getCode()返回byte[] [B@1ffbd68
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======2
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=19| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=2| lv.getLength=17| lv.getNameIndex()=58 | lv.getName()=temp| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=1
完整的code.toString的信息
private String testInvokeMethod()
Code(max_stack = 2, max_locals = 2, code_length = 19)
0: aconst_null
1: astore_1
2: aload_0
3: bipush 10
5: invokevirtual StringBuilder.buildString (I)Ljava/lang/String; (54)
8: astore_1
9: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
12: ldc "我是測試方法,我是測試方法,我是測試方法,我是測試方法" (56)
14: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
17: aload_1
18: areturn

Attribute(s) =
LineNumber(0, 27), LineNumber(2, 31), LineNumber(9, 35), LineNumber(17, 37)

LocalVariable(start_pc = 0, length = 19, index = 0:StringBuilder this)
LocalVariable(start_pc = 2, length = 17, index = 1:String temp)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
9
方法訪問名稱
main
CONSTANT_Utf8[1]("main")
方法簽名
([Ljava/lang/String;)V
CONSTANT_Utf8[1]("([Ljava/lang/String;)V")
方法的參數類型
java.lang.String[]方法的返回類型
void
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 159
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 59
給出該方法在執行中任何點操作數棧上字的最大個數 4
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 4
code的字節信息調用code.getCode()返回byte[] [B@ec16a4
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======4
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=59| lv.getNameIndex()=76 | lv.getName()=argv| lv.getSignatureIndex()=77 | lv.getSignature()=[Ljava/lang/String; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=8| lv.getLength=51| lv.getNameIndex()=78 | lv.getName()=inst| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=1
--------------------第 2 個局部變量的信息
lv.getStartPC()=10| lv.getLength=48| lv.getNameIndex()=52 | lv.getName()=i| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=2
--------------------第 3 個局部變量的信息
lv.getStartPC()=24| lv.getLength=25| lv.getNameIndex()=50 | lv.getName()=result| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=3
完整的code.toString的信息
public static void main(String[] argv)
Code(max_stack = 4, max_locals = 4, code_length = 59)
0: new <StringBuilder> (1)
3: dup
4: invokespecial StringBuilder.<init> ()V (61)
7: astore_1
8: iconst_0
9: istore_2
10: goto #52
13: aload_1
14: aload_0
15: iload_2
16: aaload
17: invokestatic java.lang.Integer.parseInt (Ljava/lang/String;)I (62)
20: invokevirtual StringBuilder.buildString (I)Ljava/lang/String; (54)
23: astore_3
24: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
27: new <java.lang.StringBuilder> (18)
30: dup
31: ldc "Constructed string of length " (68)
33: invokespecial java.lang.StringBuilder.<init> (Ljava/lang/String;)V (26)
36: aload_3
37: invokevirtual java.lang.String.length ()I (70)
40: invokevirtual java.lang.StringBuilder.append (I)Ljava/lang/StringBuilder; (73)
43: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
46: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
49: iinc %2 1
52: iload_2
53: aload_0
54: arraylength
55: if_icmplt #13
58: return

Attribute(s) =
LineNumber(0, 47), LineNumber(8, 48), LineNumber(13, 52), LineNumber(24, 56),
LineNumber(36, 57), LineNumber(46, 56), LineNumber(49, 48), LineNumber(58, 59)

LocalVariable(start_pc = 0, length = 59, index = 0:String[] argv)
LocalVariable(start_pc = 8, length = 51, index = 1:StringBuilder inst)
LocalVariable(start_pc = 10, length = 48, index = 2:int i)
LocalVariable(start_pc = 24, length = 25, index = 3:String result)

end method method method-----------------------------------

回復更多評論

# re: 用 BCEL 設計字節碼（三）直接在方法的調用處添加方法 2009-08-16 18:39 | Frank_Fang

自己在程序加調用語句用編譯器生成的字節碼
--------------------------------33
--------------------------------33
0
2
CONSTANT_Utf8[1]("SourceFile")
true
CONSTANT_Utf8[1]("StringBuilder.java")
1
StringBuilder.java
StringBuilder.java
---------------------------------------------------------------------------
1:CONSTANT_Class[7](name_index = 2)
2:CONSTANT_Utf8[1]("StringBuilder")
3:CONSTANT_Class[7](name_index = 4)
4:CONSTANT_Utf8[1]("java/lang/Object")
5:CONSTANT_Utf8[1]("<init>")
6:CONSTANT_Utf8[1]("()V")
7:CONSTANT_Utf8[1]("Code")
8:CONSTANT_Methodref[10](class_index = 3, name_and_type_index = 9)
9:CONSTANT_NameAndType[12](name_index = 5, signature_index = 6)
10:CONSTANT_Utf8[1]("LineNumberTable")
11:CONSTANT_Utf8[1]("LocalVariableTable")
12:CONSTANT_Utf8[1]("this")
13:CONSTANT_Utf8[1]("LStringBuilder;")
14:CONSTANT_Utf8[1]("buildString")
15:CONSTANT_Utf8[1]("(I)Ljava/lang/String;")
16:CONSTANT_String[8](string_index = 17)
17:CONSTANT_Utf8[1]("")
18:CONSTANT_Class[7](name_index = 19)
19:CONSTANT_Utf8[1]("java/lang/StringBuilder")
20:CONSTANT_Methodref[10](class_index = 21, name_and_type_index = 23)
21:CONSTANT_Class[7](name_index = 22)
22:CONSTANT_Utf8[1]("java/lang/String")
23:CONSTANT_NameAndType[12](name_index = 24, signature_index = 25)
24:CONSTANT_Utf8[1]("valueOf")
25:CONSTANT_Utf8[1]("(Ljava/lang/Object;)Ljava/lang/String;")
26:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 27)
27:CONSTANT_NameAndType[12](name_index = 5, signature_index = 28)
28:CONSTANT_Utf8[1]("(Ljava/lang/String;)V")
29:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 30)
30:CONSTANT_NameAndType[12](name_index = 31, signature_index = 32)
31:CONSTANT_Utf8[1]("append")
32:CONSTANT_Utf8[1]("(C)Ljava/lang/StringBuilder;")
33:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 34)
34:CONSTANT_NameAndType[12](name_index = 35, signature_index = 36)
35:CONSTANT_Utf8[1]("toString")
36:CONSTANT_Utf8[1]("()Ljava/lang/String;")
37:CONSTANT_Fieldref[9](class_index = 38, name_and_type_index = 40)
*********************ConstantFieldref start**********************
cc.toString : CONSTANT_Class[7](name_index = 39)
java/lang/System
cnat.toString : CONSTANT_NameAndType[12](name_index = 41, signature_index = 42)
out
Ljava/io/PrintStream;
**********************ConstantFieldref end*******************************
38:CONSTANT_Class[7](name_index = 39)
39:CONSTANT_Utf8[1]("java/lang/System")
40:CONSTANT_NameAndType[12](name_index = 41, signature_index = 42)
41:CONSTANT_Utf8[1]("out")
42:CONSTANT_Utf8[1]("Ljava/io/PrintStream;")
43:CONSTANT_Methodref[10](class_index = 44, name_and_type_index = 46)
44:CONSTANT_Class[7](name_index = 45)
45:CONSTANT_Utf8[1]("java/io/PrintStream")
46:CONSTANT_NameAndType[12](name_index = 47, signature_index = 28)
47:CONSTANT_Utf8[1]("println")
48:CONSTANT_Utf8[1]("length")
49:CONSTANT_Utf8[1]("I")
50:CONSTANT_Utf8[1]("result")
51:CONSTANT_Utf8[1]("Ljava/lang/String;")
52:CONSTANT_Utf8[1]("i")
53:CONSTANT_Utf8[1]("testInvokeMethod")
54:CONSTANT_Methodref[10](class_index = 55, name_and_type_index = 57)
55:CONSTANT_Class[7](name_index = 56)
56:CONSTANT_Utf8[1]("ToolUtil")
57:CONSTANT_NameAndType[12](name_index = 58, signature_index = 59)
58:CONSTANT_Utf8[1]("printStart")
59:CONSTANT_Utf8[1]("()J")
60:CONSTANT_Methodref[10](class_index = 1, name_and_type_index = 61)
61:CONSTANT_NameAndType[12](name_index = 14, signature_index = 15)
62:CONSTANT_String[8](string_index = 14)
63:CONSTANT_Methodref[10](class_index = 55, name_and_type_index = 64)
64:CONSTANT_NameAndType[12](name_index = 65, signature_index = 66)
65:CONSTANT_Utf8[1]("printEnd")
66:CONSTANT_Utf8[1]("(Ljava/lang/String;J)V")
67:CONSTANT_String[8](string_index = 68)
68:CONSTANT_Utf8[1]("我是測試方法,我是測試方法,我是測試方法,我是測試方法")
69:CONSTANT_Utf8[1]("temp")
70:CONSTANT_Utf8[1]("startTime")
71:CONSTANT_Utf8[1]("J")
72:CONSTANT_Utf8[1]("main")
73:CONSTANT_Utf8[1]("([Ljava/lang/String;)V")
74:CONSTANT_Methodref[10](class_index = 1, name_and_type_index = 9)
75:CONSTANT_Methodref[10](class_index = 76, name_and_type_index = 78)
76:CONSTANT_Class[7](name_index = 77)
77:CONSTANT_Utf8[1]("java/lang/Integer")
78:CONSTANT_NameAndType[12](name_index = 79, signature_index = 80)
79:CONSTANT_Utf8[1]("parseInt")
80:CONSTANT_Utf8[1]("(Ljava/lang/String;)I")
81:CONSTANT_String[8](string_index = 82)
82:CONSTANT_Utf8[1]("Constructed string of length ")
83:CONSTANT_Methodref[10](class_index = 21, name_and_type_index = 84)
84:CONSTANT_NameAndType[12](name_index = 48, signature_index = 85)
85:CONSTANT_Utf8[1]("()I")
86:CONSTANT_Methodref[10](class_index = 18, name_and_type_index = 87)
87:CONSTANT_NameAndType[12](name_index = 31, signature_index = 88)
88:CONSTANT_Utf8[1]("(I)Ljava/lang/StringBuilder;")
89:CONSTANT_Utf8[1]("argv")
90:CONSTANT_Utf8[1]("[Ljava/lang/String;")
91:CONSTANT_Utf8[1]("inst")
92:CONSTANT_Utf8[1]("SourceFile")
93:CONSTANT_Utf8[1]("StringBuilder.java")
--------------------------域----------------------------
-----------域的長度,此類定義的成員變量的個數-------------0

start method method method-----------------------------------
方法訪問標志
1
方法訪問名稱
<init>
CONSTANT_Utf8[1]("<init>")
方法簽名
()V
CONSTANT_Utf8[1]("()V")
方法的參數類型
方法的返回類型
void
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 47
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 5
給出該方法在執行中任何點操作數棧上字的最大個數 1
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 1
code的字節信息調用code.getCode()返回byte[] [B@1571886
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======1
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=5| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
完整的code.toString的信息
public void <init>()
Code(max_stack = 1, max_locals = 1, code_length = 5)
0: aload_0
1: invokespecial java.lang.Object.<init> ()V (8)
4: return

Attribute(s) =
LineNumber(0, 1)
LocalVariable(start_pc = 0, length = 5, index = 0:StringBuilder this)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
1
方法訪問名稱
buildString
CONSTANT_Utf8[1]("buildString")
方法簽名
(I)Ljava/lang/String;
CONSTANT_Utf8[1]("(I)Ljava/lang/String;")
方法的參數類型
int方法的返回類型
java.lang.String
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 143
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 51
給出該方法在執行中任何點操作數棧上字的最大個數 3
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 4
code的字節信息調用code.getCode()返回byte[] [B@1c184f4
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======4
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=51| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=0| lv.getLength=51| lv.getNameIndex()=48 | lv.getName()=length| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=1
--------------------第 2 個局部變量的信息
lv.getStartPC()=3| lv.getLength=48| lv.getNameIndex()=50 | lv.getName()=result| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=2
--------------------第 3 個局部變量的信息
lv.getStartPC()=5| lv.getLength=37| lv.getNameIndex()=52 | lv.getName()=i| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=3
完整的code.toString的信息
public String buildString(int length)
Code(max_stack = 3, max_locals = 4, code_length = 51)
0: ldc "" (16)
2: astore_2
3: iconst_0
4: istore_3
5: goto #37
8: new <java.lang.StringBuilder> (18)
11: dup
12: aload_2
13: invokestatic java.lang.String.valueOf (Ljava/lang/Object;)Ljava/lang/String; (20)
16: invokespecial java.lang.StringBuilder.<init> (Ljava/lang/String;)V (26)
19: iload_3
20: bipush 26
22: irem
23: bipush 97
25: iadd
26: i2c
27: invokevirtual java.lang.StringBuilder.append (C)Ljava/lang/StringBuilder; (29)
30: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
33: astore_2
34: iinc %3 1
37: iload_3
38: iload_1
39: if_icmplt #8
42: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
45: aload_2
46: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
49: aload_2
50: areturn

Attribute(s) =
LineNumber(0, 9), LineNumber(3, 10), LineNumber(8, 11), LineNumber(34, 10),
LineNumber(42, 13), LineNumber(49, 15)
LocalVariable(start_pc = 0, length = 51, index = 0:StringBuilder this)
LocalVariable(start_pc = 0, length = 51, index = 1:int length)
LocalVariable(start_pc = 3, length = 48, index = 2:String result)
LocalVariable(start_pc = 5, length = 37, index = 3:int i)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
2
方法訪問名稱
testInvokeMethod
CONSTANT_Utf8[1]("testInvokeMethod")
方法簽名
()Ljava/lang/String;
CONSTANT_Utf8[1]("()Ljava/lang/String;")
方法的參數類型
方法的返回類型
java.lang.String
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 111
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 29
給出該方法在執行中任何點操作數棧上字的最大個數 3
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 4
code的字節信息調用code.getCode()返回byte[] [B@1ffbd68
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======3
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=29| lv.getNameIndex()=12 | lv.getName()=this| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=2| lv.getLength=27| lv.getNameIndex()=69 | lv.getName()=temp| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=1
--------------------第 2 個局部變量的信息
lv.getStartPC()=6| lv.getLength=23| lv.getNameIndex()=70 | lv.getName()=startTime| lv.getSignatureIndex()=71 | lv.getSignature()=J |lv.getIndex()=2
完整的code.toString的信息
private String testInvokeMethod()
Code(max_stack = 3, max_locals = 4, code_length = 29)
0: aconst_null
1: astore_1
2: invokestatic ToolUtil.printStart ()J (54)
5: lstore_2
6: aload_0
7: bipush 10
9: invokevirtual StringBuilder.buildString (I)Ljava/lang/String; (60)
12: astore_1
13: ldc "buildString" (62)
15: lload_2
16: invokestatic ToolUtil.printEnd (Ljava/lang/String;J)V (63)
19: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
22: ldc "我是測試方法,我是測試方法,我是測試方法,我是測試方法" (67)
24: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
27: aload_1
28: areturn

Attribute(s) =
LineNumber(0, 27), LineNumber(2, 29), LineNumber(6, 31), LineNumber(13, 33),
LineNumber(19, 35), LineNumber(27, 37)
LocalVariable(start_pc = 0, length = 29, index = 0:StringBuilder this)
LocalVariable(start_pc = 2, length = 27, index = 1:String temp)
LocalVariable(start_pc = 6, length = 23, index = 2:long startTime)

end method method method-----------------------------------

start method method method-----------------------------------
方法訪問標志
9
方法訪問名稱
main
CONSTANT_Utf8[1]("main")
方法簽名
([Ljava/lang/String;)V
CONSTANT_Utf8[1]("([Ljava/lang/String;)V")
方法的參數類型
java.lang.String[]方法的返回類型
void
方法的ExceptionTable屬性----------方法的throws聲明的異常信息------------------------
exceptionTable==null true
方法的Code---------------------------------------------
7
CONSTANT_Utf8[1]("Code")
code.getLength() 屬性結構中attribute length 的長度 189
code.getCode().length 屬性結構中的code數組的長度 code_length 的長度 71
給出該方法在執行中任何點操作數棧上字的最大個數 4
給出該方法使用的局部變量的個數，包括調用時傳遞給方法的參數 6
code的字節信息調用code.getCode()返回byte[] [B@ec16a4
ce.length===========0
code 內部結構中的各異常信息結構------------方法內部的try 塊catch的信息----------
方法的Code的LineNumberTable
方法的Code的LocalVariableTable
LocalVariableTable
localvariableTable==null false
lvs==null false
lvs.length======5
--------------------第 0 個局部變量的信息
lv.getStartPC()=0| lv.getLength=71| lv.getNameIndex()=89 | lv.getName()=argv| lv.getSignatureIndex()=90 | lv.getSignature()=[Ljava/lang/String; |lv.getIndex()=0
--------------------第 1 個局部變量的信息
lv.getStartPC()=8| lv.getLength=63| lv.getNameIndex()=91 | lv.getName()=inst| lv.getSignatureIndex()=13 | lv.getSignature()=LStringBuilder; |lv.getIndex()=1
--------------------第 2 個局部變量的信息
lv.getStartPC()=10| lv.getLength=60| lv.getNameIndex()=52 | lv.getName()=i| lv.getSignatureIndex()=49 | lv.getSignature()=I |lv.getIndex()=2
--------------------第 3 個局部變量的信息
lv.getStartPC()=17| lv.getLength=44| lv.getNameIndex()=70 | lv.getName()=startTime| lv.getSignatureIndex()=71 | lv.getSignature()=J |lv.getIndex()=3
--------------------第 4 個局部變量的信息
lv.getStartPC()=29| lv.getLength=32| lv.getNameIndex()=50 | lv.getName()=result| lv.getSignatureIndex()=51 | lv.getSignature()=Ljava/lang/String; |lv.getIndex()=5
完整的code.toString的信息
public static void main(String[] argv)
Code(max_stack = 4, max_locals = 6, code_length = 71)
0: new <StringBuilder> (1)
3: dup
4: invokespecial StringBuilder.<init> ()V (74)
7: astore_1
8: iconst_0
9: istore_2
10: goto #64
13: invokestatic ToolUtil.printStart ()J (54)
16: lstore_3
17: aload_1
18: aload_0
19: iload_2
20: aaload
21: invokestatic java.lang.Integer.parseInt (Ljava/lang/String;)I (75)
24: invokevirtual StringBuilder.buildString (I)Ljava/lang/String; (60)
27: astore %5
29: ldc "buildString" (62)
31: lload_3
32: invokestatic ToolUtil.printEnd (Ljava/lang/String;J)V (63)
35: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
38: new <java.lang.StringBuilder> (18)
41: dup
42: ldc "Constructed string of length " (81)
44: invokespecial java.lang.StringBuilder.<init> (Ljava/lang/String;)V (26)
47: aload %5
49: invokevirtual java.lang.String.length ()I (83)
52: invokevirtual java.lang.StringBuilder.append (I)Ljava/lang/StringBuilder; (86)
55: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
58: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
61: iinc %2 1
64: iload_2
65: aload_0
66: arraylength
67: if_icmplt #13
70: return

Attribute(s) =
LineNumber(0, 47), LineNumber(8, 48), LineNumber(13, 51), LineNumber(17, 52),
LineNumber(29, 54), LineNumber(35, 56), LineNumber(47, 57), LineNumber(58, 56),
LineNumber(61, 48), LineNumber(70, 59)
LocalVariable(start_pc = 0, length = 71, index = 0:String[] argv)
LocalVariable(start_pc = 8, length = 63, index = 1:StringBuilder inst)
LocalVariable(start_pc = 10, length = 60, index = 2:int i)
LocalVariable(start_pc = 17, length = 44, index = 3:long startTime)
LocalVariable(start_pc = 29, length = 32, index = 5:String result)

end method method method-----------------------------------

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# re: 用 BCEL 設計字節碼（三）直接在方法的調用處添加方法 2009-08-16 18:46 | Frank_Fang

自己生成的字節碼，注意看與上一個main中的區別
因為main中調用buildString(Integer.parseInt(argv[i]))時，方法的參數是使用語句產生的，而我在自己生成字節碼時，是在buildString的invokevirtual的上兩個指令加的我自己的指令,與編譯器產生的有的區別

完整的code.toString的信息
public String buildString(int length)
Code(max_stack = 3, max_locals = 4, code_length = 51)
0: ldc "" (16)
2: astore_2
3: iconst_0
4: istore_3
5: goto #37
8: new <java.lang.StringBuilder> (18)
11: dup
12: aload_2
13: invokestatic java.lang.String.valueOf (Ljava/lang/Object;)Ljava/lang/String; (20)
16: invokespecial java.lang.StringBuilder.<init> (Ljava/lang/String;)V (26)
19: iload_3
20: bipush 26
22: irem
23: bipush 97
25: iadd
26: i2c
27: invokevirtual java.lang.StringBuilder.append (C)Ljava/lang/StringBuilder; (29)
30: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
33: astore_2
34: iinc %3 1
37: iload_3
38: iload_1
39: if_icmplt #8
42: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
45: aload_2
46: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
49: aload_2
50: areturn

Attribute(s) =
LineNumber(0, 9), LineNumber(3, 10), LineNumber(8, 11), LineNumber(34, 10),
LineNumber(42, 13), LineNumber(49, 15)
LocalVariable(start_pc = 0, length = 51, index = 0:StringBuilder this)
LocalVariable(start_pc = 0, length = 51, index = 1:int length)
LocalVariable(start_pc = 3, length = 48, index = 2:String result)
LocalVariable(start_pc = 5, length = 37, index = 3:int i)

end method method method-----------------------------------

完整的code.toString的信息
private String testInvokeMethod()
Code(max_stack = 3, max_locals = 4, code_length = 29)
0: aconst_null
1: astore_1
2: invokestatic ToolUtil.printStart ()J (86)
5: lstore_2
6: aload_0
7: bipush 10
9: invokevirtual StringBuilder.buildString (I)Ljava/lang/String; (54)
12: astore_1
13: ldc "buildString" (87)
15: lload_2
16: invokestatic ToolUtil.printEnd (Ljava/lang/String;J)V (91)
19: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
22: ldc "我是測試方法,我是測試方法,我是測試方法,我是測試方法" (56)
24: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
27: aload_1
28: areturn

Attribute(s) =
LocalVariable(start_pc = 0, length = 29, index = 0:StringBuilder this)
LocalVariable(start_pc = 6, length = 23, index = 1:String temp)
LocalVariable(start_pc = 0, length = 29, index = 2:long starttime)
LineNumber(0, 27), LineNumber(6, 31), LineNumber(19, 35), LineNumber(27, 37)

end method method method-----------------------------------

完整的code.toString的信息
public static void main(String[] argv)
Code(max_stack = 5, max_locals = 6, code_length = 71)
0: new <StringBuilder> (1)
3: dup
4: invokespecial StringBuilder.<init> ()V (61)
7: astore_1
8: iconst_0
9: istore_2
10: goto #64
13: aload_1
14: aload_0
15: iload_2
16: invokestatic ToolUtil.printStart ()J (86)
19: lstore %4
21: aaload
22: invokestatic java.lang.Integer.parseInt (Ljava/lang/String;)I (62)
25: invokevirtual StringBuilder.buildString (I)Ljava/lang/String; (54)
28: astore_3
29: ldc "buildString" (87)
31: lload %4
33: invokestatic ToolUtil.printEnd (Ljava/lang/String;J)V (91)
36: getstatic java.lang.System.out Ljava/io/PrintStream; (37)
39: new <java.lang.StringBuilder> (18)
42: dup
43: ldc "Constructed string of length " (68)
45: invokespecial java.lang.StringBuilder.<init> (Ljava/lang/String;)V (26)
48: aload_3
49: invokevirtual java.lang.String.length ()I (70)
52: invokevirtual java.lang.StringBuilder.append (I)Ljava/lang/StringBuilder; (73)
55: invokevirtual java.lang.StringBuilder.toString ()Ljava/lang/String; (33)
58: invokevirtual java.io.PrintStream.println (Ljava/lang/String;)V (43)
61: iinc %2 1
64: iload_2
65: aload_0
66: arraylength
67: if_icmplt #13
70: return

Attribute(s) =
LocalVariable(start_pc = 0, length = 71, index = 0:String[] argv)
LocalVariable(start_pc = 8, length = 63, index = 1:StringBuilder inst)
LocalVariable(start_pc = 10, length = 61, index = 2:int i)
LocalVariable(start_pc = 36, length = 28, index = 3:String result)
LocalVariable(start_pc = 0, length = 71, index = 4:long starttime)
LineNumber(0, 47), LineNumber(8, 48), LineNumber(13, 52), LineNumber(36, 56),
LineNumber(48, 57), LineNumber(58, 56), LineNumber(61, 48), LineNumber(70, 59)

end method method method-----------------------------------

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