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a999888huang:
这个极难重现。。。虽然根据Java® Language Spe ...
<Java concurrency in practice>说这个代码不安全,记一下,慢慢理解 -
wjm251:
time.ctime(1387425025)+8时区时显示'T ...
python时间处理 -
wjm251:
datetime.strftime("%H:%M:% ...
python时间处理 -
wjm251:
今天在邮件列表里头看到有人问碰到这种怎么办s = u'\xbe ...
python的str,unicode对象的encode和decode方法 -
wjm251:
一定要有自己的鉴别啊
native2ascii用法说明
写出来贴在这留个纪念,没看过class规范看着是比较抽象,,也没写注释,sorry
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
public class ParseClassFile
{
static class CLASS_ACC{
public final static int ACC_PUBLIC = 0x0001;//class&interface
public final static int ACC_FINAL = 0x0010;//class
public final static int ACC_SUPER = 0x0020;//class&interface--->special
public final static int ACC_INTERFACE = 0x0200;//all interface
public final static int ACC_ABSTRACT = 0x0400;//all interface ,some class
public final static Object[][] ACC = new Object[][]{
{0x0001,"public"},
{0x0010,"final"},
{0x0020,"invokespecial"},
{0x0200,"interface"},
{0x0400,"abstract"},
};
}
static class FIELD_ACC{
//头3个标志public,private protected在类中只能有一个
//接口中必须设置为public static final
//final 和volatile不能同时出现
public final static int ACC_PUBLIC = 0x0001;
public final static int ACC_PRIVATE = 0x0002;
public final static int ACC_PROTECTED = 0x0004;
public final static int ACC_STATIC = 0x0008;
public final static int ACC_FINAL = 0x0010;
public final static int ACC_VOLATILE = 0x0040;
public final static int ACC_TRANSIENT = 0x0080;
public final static Object[][] ACC = new Object[][]{
{0x0001,"public"},
{0x0002,"private"},
{0x0004,"protected"},
{0x0008,"static"},
{0x0010,"final"},
{0x0040,"volatile"},
{0x0080,"transient"}
};
}
static class METHOD_ACC
{
/**
* 类(不含接口)中声明的方法只能有public private protected中的一个
* 如果一个方法设置了abstract,则private static final synchronized,native及strict都不能有
* 接口中方法必须使用public abstract不能有其他
*
* 构造方法<init>可以只使用public private和protected,<clinit>只会考虑ACC_STRICT标志
*/
public final static int ACC_PUBLIC = 0x0001;
public final static int ACC_PRIVATE = 0x0002;
public final static int ACC_PROTECTED = 0x0004;
public final static int ACC_STATIC = 0x0008;
public final static int ACC_FINAL = 0x0010;
public final static int ACC_SYNCHRONIZED = 0x0020;
public final static int ACC_NATIVE = 0x0100;
public final static int ACC_ABSTRACT = 0x0400;
public final static int ACC_STRICT = 0x0800;
public final static Object[][] ACC = new Object[][]{
{0x0001,"public"},
{0x0002,"private"},
{0x0004,"protected"},
{0x0008,"static"},
{0x0010,"final"},
{0x0020,"synchronized"},
{0x0100,"native"},
{0x0400,"abstract"},
{0x0800,"strict"}
};
}
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException
{
File f = new File("bin\\a.class");
FileInputStream in = new FileInputStream(f);
printMagicNumber(in);
printVersion(in);
int count = printConstantPoolEntryNumber(in);
printConstants(in, count);
System.out.println("access flag:"+parseACC(readInt(in,2), CLASS_ACC.ACC));
System.out.println("this class: class ref="+readInt(in,2));
System.out.println("super class: class ref="+readInt(in,2));
printInterfaces(in);
printFields(in);
printMethods(in);
parseAttrbute(in);
System.out.println();
System.out.println("remain bytes:" + in.available());
}
private static void printMethods(FileInputStream in)throws IOException
{
int methodCount = readInt(in,2);
System.out.println("method count: "+methodCount);
for(int i=0;i<methodCount;i++)
{
String access = parseACC(readInt(in,2),METHOD_ACC.ACC);
System.out.print("method["+i+"]"+access+"name ref="+readInt(in,2)+",descriptor ref="+readInt(in,2));
parseAttrbute(in);
}
}
private static void printFields(FileInputStream in) throws IOException
{
int fieldCount = readInt(in,2);
System.out.println("field count: "+fieldCount);
for(int i=0;i<fieldCount;i++)
{
String access = parseACC(readInt(in,2),FIELD_ACC.ACC);
System.out.print("field["+i+"]"+access+"name ref="+readInt(in,2)+",descriptor ref="+readInt(in,2));
parseAttrbute(in);
}
}
public static String parseACC(int accessFlag,Object[][] accType) throws IOException
{
StringBuilder access = new StringBuilder("[");
for(Object[] o : accType)
{
if((accessFlag&(Integer)o[0])!=0)
{
access.append(o[1]+",");
}
}
access.append("]");
return access.toString();
}
public static void parseAttrbute(FileInputStream in) throws IOException
{
int attrcount = readInt(in,2);
System.out.print(",attr count="+attrcount);
for(int j=0;j<attrcount;j++)
{
System.out.print(",attrname ref="+readInt(in,2));
int attrLen = readInt(in,4);
System.out.println(",attrlen="+attrLen);
//TODO parse attribute
in.skip(attrLen);
}
}
private static void printInterfaces(FileInputStream in) throws IOException
{
int interfaceCount = readInt(in,2);
System.out.println("interface count: "+interfaceCount);
for(int i=0;i<interfaceCount;i++)
{
System.out.println("interface["+i+"] ref="+readInt(in,2));
}
}
private static void printVersion(FileInputStream in) throws IOException
{
System.out.println("minor_version:" + readInt(in, 2));
System.out.println("major_version:" + readInt(in, 2));
}
private static void printMagicNumber(FileInputStream in) throws IOException
{
System.out.print("magic number:");
for (int i = 1; i <= 4; i++)
{
System.out.print(Integer.toHexString(readInt(in, 1)));
}
System.out.println();
}
private static int printConstantPoolEntryNumber(FileInputStream in)
throws IOException
{
int counstNum = readInt(in, 2) - 1;
System.out.println("constant pool entrys number:" + counstNum);
return counstNum;
}
private static void printConstants(FileInputStream in, int length)
throws IOException
{
for (int i = 1; i <= length; i++)
{
int flagType = readInt(in, 1);
System.out.print("counstPool " + i + ":tag=" + flagType + ",");
switch (flagType)
{
case 1: // CONSTANT_Utf8
{
int len = readInt(in, 2);
byte[] str = new byte[len];
in.read(str);
System.out.println("String:"+new String(str,"UTF-8"));
break;
}
case 3://CONSTANT_Integer
System.out.println("int value="+readInt(in,4));
break;
case 4://CONSTANT_Float
//TODO
in.skip(1);
System.out.println();
break;
case 5://CONSTANT_Long
System.out.println("long value="+Long.toString(readLong(in,8)));
i++;
break;
case 6://CONSTANT_Double
//double型占两个常量池入口
//TODO
in.skip(8);
i++;
System.out.println();
break;
case 7: // CONSTANT_Class
{
int name_index_entry = readInt(in, 2);
System.out.println("ClassInfo,reference constPool "
+ name_index_entry);
break;
}
case 8:// CONSTANT_String
System.out.println("String,ref"
+ readInt(in, 2));
break;
case 9:// CONSTANT_Fieldref
{
System.out.println("field: classref="+readInt(in,2)+",method ref="+readInt(in,2));
break;
}
case 10:// CONSTANT_Methodref
{
System.out.println("method from class: classref="+readInt(in,2)+",method ref="+readInt(in,2));
break;
}
case 11:// CONSTANT_InterfaceMethodref
System.out.println("method from interface: classref="+readInt(in,2)+",method ref="+readInt(in,2));
break;
case 12:// CONSTANT_NameAndType
{
System.out.println("fieldName ref="+readInt(in,2)+",fieldDescriptor ref="+readInt(in,2));
break;
}
default:
throw new RuntimeException();
}
}
}
public static byte[] int2Bytes(int val)
{
byte bs[] = new byte[4];
bs[0] = (byte) (val >> 24);
bs[1] = (byte) (val >> 16);
bs[2] = (byte) (val >>8);
bs[3] = (byte) val;
return bs;
}
public static int readInt(InputStream in, int byteNum) throws IOException
{
byte[] x = new byte[byteNum];
in.read(x);
return bytes2Int(x);
}
public static long readLong(InputStream in, int byteNum) throws IOException
{
byte[] x = new byte[byteNum];
in.read(x);
return bytes2Long(x);
}
private static int bytes2Int(byte bs[])
{
int var = 0;
for (int i = 1; i <= bs.length; i++)
{
var += (bs[i - 1] & 255) << 8 * (bs.length - i);
}
return var;
}
private static long bytes2Long(byte bs[])
{
long var = 0;
for (int i = 1; i <= bs.length; i++)
{
var += (bs[i - 1] & 255) << 8 * (bs.length - i);
}
return var;
}
}
参考
《深入java虚拟机》
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
public class ParseClassFile
{
static class CLASS_ACC{
public final static int ACC_PUBLIC = 0x0001;//class&interface
public final static int ACC_FINAL = 0x0010;//class
public final static int ACC_SUPER = 0x0020;//class&interface--->special
public final static int ACC_INTERFACE = 0x0200;//all interface
public final static int ACC_ABSTRACT = 0x0400;//all interface ,some class
public final static Object[][] ACC = new Object[][]{
{0x0001,"public"},
{0x0010,"final"},
{0x0020,"invokespecial"},
{0x0200,"interface"},
{0x0400,"abstract"},
};
}
static class FIELD_ACC{
//头3个标志public,private protected在类中只能有一个
//接口中必须设置为public static final
//final 和volatile不能同时出现
public final static int ACC_PUBLIC = 0x0001;
public final static int ACC_PRIVATE = 0x0002;
public final static int ACC_PROTECTED = 0x0004;
public final static int ACC_STATIC = 0x0008;
public final static int ACC_FINAL = 0x0010;
public final static int ACC_VOLATILE = 0x0040;
public final static int ACC_TRANSIENT = 0x0080;
public final static Object[][] ACC = new Object[][]{
{0x0001,"public"},
{0x0002,"private"},
{0x0004,"protected"},
{0x0008,"static"},
{0x0010,"final"},
{0x0040,"volatile"},
{0x0080,"transient"}
};
}
static class METHOD_ACC
{
/**
* 类(不含接口)中声明的方法只能有public private protected中的一个
* 如果一个方法设置了abstract,则private static final synchronized,native及strict都不能有
* 接口中方法必须使用public abstract不能有其他
*
* 构造方法<init>可以只使用public private和protected,<clinit>只会考虑ACC_STRICT标志
*/
public final static int ACC_PUBLIC = 0x0001;
public final static int ACC_PRIVATE = 0x0002;
public final static int ACC_PROTECTED = 0x0004;
public final static int ACC_STATIC = 0x0008;
public final static int ACC_FINAL = 0x0010;
public final static int ACC_SYNCHRONIZED = 0x0020;
public final static int ACC_NATIVE = 0x0100;
public final static int ACC_ABSTRACT = 0x0400;
public final static int ACC_STRICT = 0x0800;
public final static Object[][] ACC = new Object[][]{
{0x0001,"public"},
{0x0002,"private"},
{0x0004,"protected"},
{0x0008,"static"},
{0x0010,"final"},
{0x0020,"synchronized"},
{0x0100,"native"},
{0x0400,"abstract"},
{0x0800,"strict"}
};
}
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException
{
File f = new File("bin\\a.class");
FileInputStream in = new FileInputStream(f);
printMagicNumber(in);
printVersion(in);
int count = printConstantPoolEntryNumber(in);
printConstants(in, count);
System.out.println("access flag:"+parseACC(readInt(in,2), CLASS_ACC.ACC));
System.out.println("this class: class ref="+readInt(in,2));
System.out.println("super class: class ref="+readInt(in,2));
printInterfaces(in);
printFields(in);
printMethods(in);
parseAttrbute(in);
System.out.println();
System.out.println("remain bytes:" + in.available());
}
private static void printMethods(FileInputStream in)throws IOException
{
int methodCount = readInt(in,2);
System.out.println("method count: "+methodCount);
for(int i=0;i<methodCount;i++)
{
String access = parseACC(readInt(in,2),METHOD_ACC.ACC);
System.out.print("method["+i+"]"+access+"name ref="+readInt(in,2)+",descriptor ref="+readInt(in,2));
parseAttrbute(in);
}
}
private static void printFields(FileInputStream in) throws IOException
{
int fieldCount = readInt(in,2);
System.out.println("field count: "+fieldCount);
for(int i=0;i<fieldCount;i++)
{
String access = parseACC(readInt(in,2),FIELD_ACC.ACC);
System.out.print("field["+i+"]"+access+"name ref="+readInt(in,2)+",descriptor ref="+readInt(in,2));
parseAttrbute(in);
}
}
public static String parseACC(int accessFlag,Object[][] accType) throws IOException
{
StringBuilder access = new StringBuilder("[");
for(Object[] o : accType)
{
if((accessFlag&(Integer)o[0])!=0)
{
access.append(o[1]+",");
}
}
access.append("]");
return access.toString();
}
public static void parseAttrbute(FileInputStream in) throws IOException
{
int attrcount = readInt(in,2);
System.out.print(",attr count="+attrcount);
for(int j=0;j<attrcount;j++)
{
System.out.print(",attrname ref="+readInt(in,2));
int attrLen = readInt(in,4);
System.out.println(",attrlen="+attrLen);
//TODO parse attribute
in.skip(attrLen);
}
}
private static void printInterfaces(FileInputStream in) throws IOException
{
int interfaceCount = readInt(in,2);
System.out.println("interface count: "+interfaceCount);
for(int i=0;i<interfaceCount;i++)
{
System.out.println("interface["+i+"] ref="+readInt(in,2));
}
}
private static void printVersion(FileInputStream in) throws IOException
{
System.out.println("minor_version:" + readInt(in, 2));
System.out.println("major_version:" + readInt(in, 2));
}
private static void printMagicNumber(FileInputStream in) throws IOException
{
System.out.print("magic number:");
for (int i = 1; i <= 4; i++)
{
System.out.print(Integer.toHexString(readInt(in, 1)));
}
System.out.println();
}
private static int printConstantPoolEntryNumber(FileInputStream in)
throws IOException
{
int counstNum = readInt(in, 2) - 1;
System.out.println("constant pool entrys number:" + counstNum);
return counstNum;
}
private static void printConstants(FileInputStream in, int length)
throws IOException
{
for (int i = 1; i <= length; i++)
{
int flagType = readInt(in, 1);
System.out.print("counstPool " + i + ":tag=" + flagType + ",");
switch (flagType)
{
case 1: // CONSTANT_Utf8
{
int len = readInt(in, 2);
byte[] str = new byte[len];
in.read(str);
System.out.println("String:"+new String(str,"UTF-8"));
break;
}
case 3://CONSTANT_Integer
System.out.println("int value="+readInt(in,4));
break;
case 4://CONSTANT_Float
//TODO
in.skip(1);
System.out.println();
break;
case 5://CONSTANT_Long
System.out.println("long value="+Long.toString(readLong(in,8)));
i++;
break;
case 6://CONSTANT_Double
//double型占两个常量池入口
//TODO
in.skip(8);
i++;
System.out.println();
break;
case 7: // CONSTANT_Class
{
int name_index_entry = readInt(in, 2);
System.out.println("ClassInfo,reference constPool "
+ name_index_entry);
break;
}
case 8:// CONSTANT_String
System.out.println("String,ref"
+ readInt(in, 2));
break;
case 9:// CONSTANT_Fieldref
{
System.out.println("field: classref="+readInt(in,2)+",method ref="+readInt(in,2));
break;
}
case 10:// CONSTANT_Methodref
{
System.out.println("method from class: classref="+readInt(in,2)+",method ref="+readInt(in,2));
break;
}
case 11:// CONSTANT_InterfaceMethodref
System.out.println("method from interface: classref="+readInt(in,2)+",method ref="+readInt(in,2));
break;
case 12:// CONSTANT_NameAndType
{
System.out.println("fieldName ref="+readInt(in,2)+",fieldDescriptor ref="+readInt(in,2));
break;
}
default:
throw new RuntimeException();
}
}
}
public static byte[] int2Bytes(int val)
{
byte bs[] = new byte[4];
bs[0] = (byte) (val >> 24);
bs[1] = (byte) (val >> 16);
bs[2] = (byte) (val >>8);
bs[3] = (byte) val;
return bs;
}
public static int readInt(InputStream in, int byteNum) throws IOException
{
byte[] x = new byte[byteNum];
in.read(x);
return bytes2Int(x);
}
public static long readLong(InputStream in, int byteNum) throws IOException
{
byte[] x = new byte[byteNum];
in.read(x);
return bytes2Long(x);
}
private static int bytes2Int(byte bs[])
{
int var = 0;
for (int i = 1; i <= bs.length; i++)
{
var += (bs[i - 1] & 255) << 8 * (bs.length - i);
}
return var;
}
private static long bytes2Long(byte bs[])
{
long var = 0;
for (int i = 1; i <= bs.length; i++)
{
var += (bs[i - 1] & 255) << 8 * (bs.length - i);
}
return var;
}
}
参考
《深入java虚拟机》
发表评论
-
<Java Concurrency in Practice>笔记2——关于几种新并发容器或类的通俗理解
2011-03-25 10:05 1064关于几种新并发容器或类的通俗理解 SynchronousQue ... -
<Java Concurrency in Practice>笔记1
2011-03-25 10:04 1034之前的部分都没有记录了,从这里开始,所看过的自己意识中并非理所 ... -
阿拉伯数字转换为拼音读法
2011-03-19 23:56 2499今天同学让看下这个题目,折腾了两个多小时,设计了个巨复杂的算法 ... -
<Java concurrency in practice>说这个代码不安全,记一下,慢慢理解
2011-03-12 23:02 1240class Holder { private int ... -
eclipse远程调试java
2011-02-24 10:29 1621有了远程调试,调试java代码就方便多了,不用在eclipse ... -
native2ascii用法说明
2011-01-11 22:00 3169native2ascii用法 这个实 ... -
万能的toString
2010-07-21 22:28 865在http://leon-a.iteye.com/blog/4 ... -
beanshell运行
2009-12-26 19:47 1258beanshell运行 就一个jar文件下载后放到jdk的ex ... -
jvm下的脚本们-beanshell,groovy,,,
2009-11-17 22:42 4316jvm下的脚本们 项目中用 ... -
show一下java中的volatile的作用
2009-09-06 09:20 1774具体作用就不多讲了,大概就是保证可见性和防止重排序。 其实很早 ...
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2. **反编译原理**:反编译工具通过解析Class文件的字节码,将其转化为人类可读的源代码。这个过程涉及到对Java字节码的逆向工程,包括理解操作码、常量池引用、控制流结构等。 3. **JD-GUI特点**: - **直观界面*...
总之,代码反编译是软件开发中的一个重要辅助工具,jd-gui.exe作为一款便捷的反编译工具,为开发者提供了查看和理解.class文件源代码的能力。然而,正确使用和理解反编译的法律边界是每个开发者都应重视的。
Java反编译是编程领域中一个重要的技术环节,它允许开发者查看和理解已经编译成字节码(.class文件)的Java程序的原始源代码。这种能力在多种情况下非常有用,例如,当我们需要分析开源软件的实现细节,或者当我们...
需要注意的是,虽然反编译工具可以提供源码级别的信息,但它们并不能保证完全恢复原始的代码结构和变量名,因为这些信息在编译后并不保留。此外,使用反编译工具应尊重知识产权,仅用于合法的学习和研究目的,避免...
这些工具能够解析JAR文件中的.class文件,并将其转换为接近原始的Java源代码。虽然反编译的代码可能无法与原始源代码完全相同,但通常足以理解大部分逻辑。 JD-GUI 是一款图形用户界面的反编译工具,它允许用户直接...
然而,字节码并不是人类可以直接阅读的代码,因此反编译工具就显得尤为必要。 JD-GUI,作为压缩包中的主要文件,是一个图形用户界面的Java反编译器。它能够将.class文件转换回可读的Java源代码,帮助开发者分析或...
Java反编译工具是开发人员在处理Java字节码时不可或缺的辅助工具,它们能够将已编译的`.class`文件转换回接近原始的Java源代码形式。这在某些情况下非常有用,例如当源代码丢失或者需要查看第三方库的内部实现时。...
2. **高效反编译**:XJad具备强大的反编译引擎,能够准确地将Java字节码转换为源代码,尽管不如现代的反编译工具如JD-GUI、Procyon等那么完善,但在处理早期版本的Java Class文件时,XJad的表现依然出色。...