class反编译还原
java class 利用jad 反编译之后，偶尔回碰到一些不正常的代码，例如：label0 :_L1 MISSING_BLOCK_LABEL_30、JVM INSTR ret 7 、JVM INSTR tableswitch 1 3: default 269、 JVM INSTR monitorexit、JVM INSTR monitorenter，这些一般是由特殊的for循环、try catch finally语句块、synchronized语句反编译后产生的。下面，就简单介绍一下，一些反编译后的特殊代码的还原规则。本文在Jdk 1.4.2_08+jad 1.58f下测试。jad 1.5.8f可以到这里http://download.csdn.net/source/470540 下载。
第一部分、for、while循环
1、普通的循环，原始
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反编译后的代码 view plaincopy to clipboardprint?
2、反编译后代码变的很古怪，这是java原代码 view plaincopy to clipboardprint?
Java反编译后的代码，部分逻辑丢失。 view plaincopy to clipboardprint?
3、就是比f2（）多了一行System.out.println("list[i]");，反编译后也挺怪的。源码如下： view plaincopy to clipboardprint?
反编译后的代码： view plaincopy to clipboardprint?
4、f2（）中的break语言，移动了位置。源码如下： view plaincopy to clipboardprint?
反编译后代码： view plaincopy to clipboardprint?
5、就是比f4（）多了一行System.out.println("list[i]");，反编译后相当怪的。源码如下： view plaincopy to clipboardprint?
反编译后比较晕的代码： view plaincopy to clipboardprint?
6、就是比f5()多了一行System.exit(0);代码，但是差异确很大。源码如下： view plaincopy to clipboardprint?
编译后代码，比f5()差异太大了。 view plaincopy to clipboardprint?
7、差异就是f6()中的System.exit(0);移动了位置，但是差异确很大。源码如下： view plaincopy to clipboardprint?
编译后代码，比f6()差异太大了。 view plaincopy to clipboardprint?
8、逻辑和f7比没有变，只是多了一些System.out.println()代码。 view plaincopy to clipboardprint?
反编译后的代码：和f7()比较一下，基本就可以确定反编译后的代码对应关系了。 view plaincopy to clipboardprint?
9、逻辑和f8比没有变，只是多了一行System.out.println()代码，导致了反编译后的/* Loop/switch isn't completed */。 view plaincopy to clipboardprint?
反编译后的代码： view plaincopy to clipboardprint?
java class 利用jad 反编译之后，偶尔回碰到一些不正常的代码，例如：label0 :_L1 MISSING_BLOCK_LABEL_30、JVM INSTR ret 7、JVM INSTR tableswitch 1 3: default 269、 JVM INSTR monitorexit、JVM INSTR monitorenter，这些一般是由特殊的for循环、try catch finally语句块、synchronized语句反编译后产生的。下面，就简单介绍一下，一些反编译后的特殊代码的还原规则。本文在Jdk 1.4.2_08+jad 1.58f下测试。jad 1.5.8f可以到这里http://download.csdn.net/source/470540 下载。
第二部分、异常
下面的代码前提是类中有如下属性， Calendar cal = Calendar.getInstance();。
1、Exceptioin的还原 反编译后的代码如下：
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public boolean f1()
{
return cal.getTime().after(new Date());
Exception e;
e;
e.printStackTrace();
return false;
}
public boolean f1()
{
return cal.getTime().after(new Date());
Exception e;
e;
e.printStackTrace();
return false;
}
还原后的Java代码 view plaincopy to clipboardprint?
public boolean f1()
{
try
{
return cal.getTime().after(new Date());
}
catch (Exception e)
{
e.printStackTrace();
return false;
}
}
public boolean f1()
{
try
{
return cal.getTime().after(new Date());
}
catch (Exception e)
{
e.printStackTrace();
return false;
}
}
2、finally代码的还原 反编译后的Java代码如下： view plaincopy to clipboardprint?
public boolean f2()
{
boolean flag = cal.getTime().after(new Date());
System.out.println("finally");
return flag;
Exception e;
e;
e.printStackTrace();
System.out.println("finally");
return false;
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
public boolean f2()
{
boolean flag = cal.getTime().after(new Date());
System.out.println("finally");
return flag;
Exception e;
e;
e.printStackTrace();
System.out.println("finally");
return false;
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
还原后的代码如下： view plaincopy to clipboardprint?
public boolean f2()
{
try
{
return cal.getTime().after(new Date());
}
catch (Exception e)
{
e.printStackTrace();
return false;
}
finally
{
System.out.println("finally");
}
}
public boolean f2()
{
try
{
return cal.getTime().after(new Date());
}
catch (Exception e)
{
e.printStackTrace();
return false;
}
finally
{
System.out.println("finally");
}
}
3、MISSING_BLOCK_LABEL_的还原反编译后的代码 view plaincopy to clipboardprint?
public Object f22()
{
Date date = cal.getTime();
System.out.println("finally");
return date;
Exception e;
e;
e.printStackTrace();
System.out.println("finally");
break MISSING_BLOCK_LABEL_45;
Exception exception;
exception;
System.out.println("finally");
throw exception;
return null;
}
public Object f22()
{
Date date = cal.getTime();
System.out.println("finally");
return date;
Exception e;
e;
e.printStackTrace();
System.out.println("finally");
break MISSING_BLOCK_LABEL_45;
Exception exception;
exception;
System.out.println("finally");
throw exception;
return null;
}
还原后的Java代码 view plaincopy to clipboardprint?
public Object f22()
{
try
{
return cal.getTime();
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
System.out.println("finally");
}
return null;
}
public Object f22()
{
try
{
return cal.getTime();
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
System.out.println("finally");
}
return null;
}
4、异常中:label的还原反编译后的代码 view plaincopy to clipboardprint?
public String f4()
throws Exception
{
l0:
{
try
{
Integer i = new Integer(1);
if(i.intValue() > 0)
{
System.out.println(i);
break label0;
}
System.err.println(i);
}
catch(Exception dae)
{
System.err.println(dae);
throw new RuntimeException(dae);
}
return null;
}
return "Hello";
}
public String f4()
throws Exception
{
label0:
{
try
{
Integer i = new Integer(1);
if(i.intValue() > 0)
{
System.out.println(i);
break label0;
}
System.err.println(i);
}
catch(Exception dae)
{
System.err.println(dae);
throw new RuntimeException(dae);
}
return null;
}
return "Hello";
}
注意，这个代码有点诡异，实际代码如下： view plaincopy to clipboardprint?
public String f4() throws Exception
{
try
{
Integer i = new Integer(1);
if (i.intValue() > 0)
{
System.out.println(i);
}
else
{
System.err.println(i);
return null;
}
return "Hello";
}
catch (Exception dae)
{
System.err.println(dae);
throw new RuntimeException(dae);
}
}
public String f4() throws Exception
{
try
{
Integer i = new Integer(1);
if (i.intValue() > 0)
{
System.out.println(i);
}
else
{
System.err.println(i);
return null;
}
return "Hello";
}
catch (Exception dae)
{
System.err.println(dae);
throw new RuntimeException(dae);
}
}
5、典型数据库操作代码还原反编译后代码 view plaincopy to clipboardprint?
public HashMap f5()
{
Connection conn = null;
HashMap hashmap;
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
String columnVallue;
for(ResultSet rs = pstmt.executeQuery(); rs.next(); map.put(columnVallue, ""))
columnVallue = rs.getString("column");
hashmap = map;
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
return hashmap;
ClassNotFoundException cnfe;
cnfe;
cnfe.printStackTrace();
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
SQLException sqle;
sqle;
sqle.printStackTrace();
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
Exception exception;
exception;
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
throw exception;
return null;
}
public HashMap f5()
{
Connection conn = null;
HashMap hashmap;
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
String columnVallue;
for(ResultSet rs = pstmt.executeQuery(); rs.next(); map.put(columnVallue, ""))
columnVallue = rs.getString("column");
hashmap = map;
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
return hashmap;
ClassNotFoundException cnfe;
cnfe;
cnfe.printStackTrace();
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
SQLException sqle;
sqle;
sqle.printStackTrace();
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
Exception exception;
exception;
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
throw exception;
return null;
}
实际代码如下： view plaincopy to clipboardprint?
public HashMap f5()
{
Connection conn = null;
try
{
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
ResultSet rs = pstmt.executeQuery();
while (rs.next())
{
String columnVallue = rs.getString("column");
map.put(columnVallue, "");
}
return map;
}
catch (ClassNotFoundException cnfe)
{
cnfe.printStackTrace();
}
catch (SQLException sqle)
{
sqle.printStackTrace();
}
finally
{
if (conn != null)
{
try
{
conn.close();
}
catch (SQLException sqlce)
{
sqlce.printStackTrace();
}
}
}
return null;
}
public HashMap f5()
{
Connection conn = null;
try
{
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
ResultSet rs = pstmt.executeQuery();
while (rs.next())
{
String columnVallue = rs.getString("column");
map.put(columnVallue, "");
}
return map;
}
catch (ClassNotFoundException cnfe)
{
cnfe.printStackTrace();
}
catch (SQLException sqle)
{
sqle.printStackTrace();
}
finally
{
if (conn != null)
{
try
{
conn.close();
}
catch (SQLException sqlce)
{
sqlce.printStackTrace();
}
}
}
return null;
}
6、两层异常嵌套代码还原反编译后的代码 view plaincopy to clipboardprint?
public int f6()
{
int i = cal.getTime().compareTo(new Date());
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
System.out.println("finally");
return -2;
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
public int f6()
{
int i = cal.getTime().compareTo(new Date());
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
System.out.println("finally");
return -2;
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
实际代码 view plaincopy to clipboardprint?
public int f6()
{
try
{
try
{
return cal.getTime().compareTo(new Date());
}
catch (Exception e1)
{
e1.printStackTrace();
return -1;
}
}
catch (Exception e2)
{
e2.printStackTrace();
return -2;
}
finally
{
System.out.println("finally");
}
}
public int f6()
{
try
{
try
{
return cal.getTime().compareTo(new Date());
}
catch (Exception e1)
{
e1.printStackTrace();
return -1;
}
}
catch (Exception e2)
{
e2.printStackTrace();
return -2;
}
finally
{
System.out.println("finally");
}
}
7、非常诡异的代码反编译后的代码 view plaincopy to clipboardprint?
public int f7()
{
int i = cal.getTime().compareTo(new Date());
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
_L2:
System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
if(true) goto _L2; else goto _L1
_L1:
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
public int f7()
{
int i = cal.getTime().compareTo(new Date());
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
_L2:
System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
if(true) goto _L2; else goto _L1
_L1:
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
原始代码 view plaincopy to clipboardprint?
public int f7()
{
try
{
try
{
return cal.getTime().compareTo(new Date());
}
catch (Exception e1)
{
e1.printStackTrace();
return -1;
}
}
catch (Exception e2)
{
e2.printStackTrace();
return -1;
}
finally
{
System.out.println("finally");
}
}
第一部分、for、while循环
1、普通的循环，原始
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public void f1() {
boolean flag = false;
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
for (int i = 0; i < 10; i++) {
flag = Boolean.getBoolean("sys");
if (flag) {
System.exit(0);
}
}
}
}
public void f1() {
boolean flag = false;
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
for (int i = 0; i < 10; i++) {
flag = Boolean.getBoolean("sys");
if (flag) {
System.exit(0);
}
}
}
}
反编译后的代码 view plaincopy to clipboardprint?
public void f1()
{
boolean flag = false;
if(Boolean.getBoolean("sys"))
{
System.out.println("sys");
} else
{
for(int i = 0; i < 10; i++)
{
flag = Boolean.getBoolean("sys");
if(flag)
System.exit(0);
}
}
}
public void f1()
{
boolean flag = false;
if(Boolean.getBoolean("sys"))
{
System.out.println("sys");
} else
{
for(int i = 0; i < 10; i++)
{
flag = Boolean.getBoolean("sys");
if(flag)
System.exit(0);
}
}
}
2、反编译后代码变的很古怪，这是java原代码 view plaincopy to clipboardprint?
public void f2() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
if (list[i] == 2) {
continue check;
} else {
break;
}
}
}
}
}
public void f2() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
if (list[i] == 2) {
continue check;
} else {
break;
}
}
}
}
}
Java反编译后的代码，部分逻辑丢失。 view plaincopy to clipboardprint?
public void f2()
{
int list[] = {
1, 2, 3, 4
};
if(Boolean.getBoolean("sys"))
System.out.println("sys");
else
do
{
int i = 0;
if(i >= list.length || list[i] != 2);
} while(true);
}
public void f2()
{
int list[] = {
1, 2, 3, 4
};
if(Boolean.getBoolean("sys"))
System.out.println("sys");
else
do
{
int i = 0;
if(i >= list.length || list[i] != 2);
} while(true);
}
3、就是比f2（）多了一行System.out.println("list[i]");，反编译后也挺怪的。源码如下： view plaincopy to clipboardprint?
public void f3() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
} else {
break;
}
}
}
}
}
public void f3() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
} else {
break;
}
}
}
}
}
反编译后的代码： view plaincopy to clipboardprint?
public void f3()
{
int list[] = {
1, 2, 3, 4
};
if(Boolean.getBoolean("sys"))
System.out.println("sys");
else
do
{
int i;
do
i = 0;
while(i >= list.length);
System.out.println("list[i]");
if(list[i] != 2);
} while(true);
}
public void f3()
{
int list[] = {
1, 2, 3, 4
};
if(Boolean.getBoolean("sys"))
System.out.println("sys");
else
do
{
int i;
do
i = 0;
while(i >= list.length);
System.out.println("list[i]");
if(list[i] != 2);
} while(true);
}
4、f2（）中的break语言，移动了位置。源码如下： view plaincopy to clipboardprint?
public void f4() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
if (list[i] == 2) {
continue check;
}
}
break;
}
}
}
public void f4() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
if (list[i] == 2) {
continue check;
}
}
break;
}
}
}
反编译后代码： view plaincopy to clipboardprint?
public void f4()
{
int list[] = {
1, 2, 3, 4
};
int i;
if(Boolean.getBoolean("sys"))
System.out.println("sys");
else
label0:
do
{
for(i = 0; i < list.length; i++)
if(list[i] == 2)
continue label0;
break;
} while(true);
}
public void f4()
{
int list[] = {
1, 2, 3, 4
};
int i;
if(Boolean.getBoolean("sys"))
System.out.println("sys");
else
label0:
do
{
for(i = 0; i < list.length; i++)
if(list[i] == 2)
continue label0;
break;
} while(true);
}
5、就是比f4（）多了一行System.out.println("list[i]");，反编译后相当怪的。源码如下： view plaincopy to clipboardprint?
public void f5() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
}
}
break;
}
}
}
public void f5() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
}
}
break;
}
}
}
反编译后比较晕的代码： view plaincopy to clipboardprint?
public void f5()
{
int list[] = {
1, 2, 3, 4
};
if(!Boolean.getBoolean("sys")) goto _L2; else goto _L1
_L1:
System.out.println("sys");
goto _L3
_L2:
int i = 0;
goto _L4
_L6:
System.out.println("list[i]");
if(list[i] != 2) goto _L5; else goto _L2
_L5:
i++;
_L4:
if(i < list.length) goto _L6; else goto _L3
_L3:
}
public void f5()
{
int list[] = {
1, 2, 3, 4
};
if(!Boolean.getBoolean("sys")) goto _L2; else goto _L1
_L1:
System.out.println("sys");
goto _L3
_L2:
int i = 0;
goto _L4
_L6:
System.out.println("list[i]");
if(list[i] != 2) goto _L5; else goto _L2
_L5:
i++;
_L4:
if(i < list.length) goto _L6; else goto _L3
_L3:
}
6、就是比f5()多了一行System.exit(0);代码，但是差异确很大。源码如下： view plaincopy to clipboardprint?
public void f6() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
}
}
System.exit(0);
break;
}
}
}
public void f6() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
}
}
System.exit(0);
break;
}
}
}
编译后代码，比f5()差异太大了。 view plaincopy to clipboardprint?
public void f6()
{
int list[];
list = (new int[] {
1, 2, 3, 4
});
if(Boolean.getBoolean("sys"))
{
System.out.println("sys");
break MISSING_BLOCK_LABEL_75;
}
_L2:
int i = 0;
goto _L1
_L5:
System.out.println("list[i]");
if(list[i] != 2) goto _L3; else goto _L2
_L3:
i++;
_L1:
if(i < list.length) goto _L5; else goto _L4
_L4:
System.exit(0);
}
public void f6()
{
int list[];
list = (new int[] {
1, 2, 3, 4
});
if(Boolean.getBoolean("sys"))
{
System.out.println("sys");
break MISSING_BLOCK_LABEL_75;
}
_L2:
int i = 0;
goto _L1
_L5:
System.out.println("list[i]");
if(list[i] != 2) goto _L3; else goto _L2
_L3:
i++;
_L1:
if(i < list.length) goto _L5; else goto _L4
_L4:
System.exit(0);
}
7、差异就是f6()中的System.exit(0);移动了位置，但是差异确很大。源码如下： view plaincopy to clipboardprint?
public void f7() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
}
}
break;
}
System.exit(0);
}
}
public void f7() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
check: while (true) {
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
}
}
break;
}
System.exit(0);
}
}
编译后代码，比f6()差异太大了。 view plaincopy to clipboardprint?
public void f7()
{
int list[];
list = (new int[] {
1, 2, 3, 4
});
if(Boolean.getBoolean("sys"))
{
System.out.println("sys");
break MISSING_BLOCK_LABEL_75;
}
_L2:
int i = 0;
goto _L1
_L5:
System.out.println("list[i]");
if(list[i] != 2) goto _L3; else goto _L2
_L3:
i++;
_L1:
if(i < list.length) goto _L5; else goto _L4
_L4:
System.exit(0);
}
public void f7()
{
int list[];
list = (new int[] {
1, 2, 3, 4
});
if(Boolean.getBoolean("sys"))
{
System.out.println("sys");
break MISSING_BLOCK_LABEL_75;
}
_L2:
int i = 0;
goto _L1
_L5:
System.out.println("list[i]");
if(list[i] != 2) goto _L3; else goto _L2
_L3:
i++;
_L1:
if(i < list.length) goto _L5; else goto _L4
_L4:
System.exit(0);
}
8、逻辑和f7比没有变，只是多了一些System.out.println()代码。 view plaincopy to clipboardprint?
public void f8() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
System.out.println(":check while");
check: while (true) {
System.out.println("for");
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
}
}
System.out.println("break");
break;
}
System.out.println("exit(0)");
System.exit(0);
}
}
public void f8() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
System.out.println(":check while");
check: while (true) {
System.out.println("for");
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
continue check;
}
}
System.out.println("break");
break;
}
System.out.println("exit(0)");
System.exit(0);
}
}
反编译后的代码：和f7()比较一下，基本就可以确定反编译后的代码对应关系了。 view plaincopy to clipboardprint?
public void f8()
{
int list[];
list = (new int[] {
1, 2, 3, 4
});
if(Boolean.getBoolean("sys"))
{
System.out.println("sys");
break MISSING_BLOCK_LABEL_107;
}
System.out.println(":check while");
_L2:
int i;
System.out.println("for");
i = 0;
goto _L1
_L5:
System.out.println("list[i]");
if(list[i] != 2) goto _L3; else goto _L2
_L3:
i++;
_L1:
if(i < list.length) goto _L5; else goto _L4
_L4:
System.out.println("break");
System.out.println("exit(0)");
System.exit(0);
}
public void f8()
{
int list[];
list = (new int[] {
1, 2, 3, 4
});
if(Boolean.getBoolean("sys"))
{
System.out.println("sys");
break MISSING_BLOCK_LABEL_107;
}
System.out.println(":check while");
_L2:
int i;
System.out.println("for");
i = 0;
goto _L1
_L5:
System.out.println("list[i]");
if(list[i] != 2) goto _L3; else goto _L2
_L3:
i++;
_L1:
if(i < list.length) goto _L5; else goto _L4
_L4:
System.out.println("break");
System.out.println("exit(0)");
System.exit(0);
}
9、逻辑和f8比没有变，只是多了一行System.out.println()代码，导致了反编译后的/* Loop/switch isn't completed */。 view plaincopy to clipboardprint?
public void f9() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
System.out.println(":check while");
check: while (true) {
System.out.println("for");
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
System.out.println("continue check");
continue check;
}
}
System.out.println("break");
break;
}
System.out.println("exit(0)");
System.exit(0);
}
}
}
public void f9() {
int[] list = new int[] { 1, 2, 3, 4 };
if (Boolean.getBoolean("sys")) {
System.out.println("sys");
} else {
System.out.println(":check while");
check: while (true) {
System.out.println("for");
for (int i = 0; i < list.length; i++) {
System.out.println("list[i]");
if (list[i] == 2) {
System.out.println("continue check");
continue check;
}
}
System.out.println("break");
break;
}
System.out.println("exit(0)");
System.exit(0);
}
}
}
反编译后的代码： view plaincopy to clipboardprint?
public void f9()
{
int list[] = {
1, 2, 3, 4
};
if(!Boolean.getBoolean("sys")) goto _L2; else goto _L1
_L1:
System.out.println("sys");
goto _L3
_L2:
System.out.println(":check while");
_L5:
System.out.println("for");
for(int i = 0; i < list.length; i++)
{
System.out.println("list[i]");
if(list[i] != 2)
continue;
System.out.println("continue check");
continue; /* Loop/switch isn't completed */
}
System.out.println("break");
System.out.println("exit(0)");
System.exit(0);
_L3:
return;
if(true) goto _L5; else goto _L4
_L4:
}
}
java class 利用jad 反编译之后，偶尔回碰到一些不正常的代码，例如：label0 :_L1 MISSING_BLOCK_LABEL_30、JVM INSTR ret 7、JVM INSTR tableswitch 1 3: default 269、 JVM INSTR monitorexit、JVM INSTR monitorenter，这些一般是由特殊的for循环、try catch finally语句块、synchronized语句反编译后产生的。下面，就简单介绍一下，一些反编译后的特殊代码的还原规则。本文在Jdk 1.4.2_08+jad 1.58f下测试。jad 1.5.8f可以到这里http://download.csdn.net/source/470540 下载。
第二部分、异常
下面的代码前提是类中有如下属性， Calendar cal = Calendar.getInstance();。
1、Exceptioin的还原 反编译后的代码如下：
view plaincopy to clipboardprint?
public boolean f1()
{
return cal.getTime().after(new Date());
Exception e;
e;
e.printStackTrace();
return false;
}
public boolean f1()
{
return cal.getTime().after(new Date());
Exception e;
e;
e.printStackTrace();
return false;
}
还原后的Java代码 view plaincopy to clipboardprint?
public boolean f1()
{
try
{
return cal.getTime().after(new Date());
}
catch (Exception e)
{
e.printStackTrace();
return false;
}
}
public boolean f1()
{
try
{
return cal.getTime().after(new Date());
}
catch (Exception e)
{
e.printStackTrace();
return false;
}
}
2、finally代码的还原 反编译后的Java代码如下： view plaincopy to clipboardprint?
public boolean f2()
{
boolean flag = cal.getTime().after(new Date());
System.out.println("finally");
return flag;
Exception e;
e;
e.printStackTrace();
System.out.println("finally");
return false;
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
public boolean f2()
{
boolean flag = cal.getTime().after(new Date());
System.out.println("finally");
return flag;
Exception e;
e;
e.printStackTrace();
System.out.println("finally");
return false;
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
还原后的代码如下： view plaincopy to clipboardprint?
public boolean f2()
{
try
{
return cal.getTime().after(new Date());
}
catch (Exception e)
{
e.printStackTrace();
return false;
}
finally
{
System.out.println("finally");
}
}
public boolean f2()
{
try
{
return cal.getTime().after(new Date());
}
catch (Exception e)
{
e.printStackTrace();
return false;
}
finally
{
System.out.println("finally");
}
}
3、MISSING_BLOCK_LABEL_的还原反编译后的代码 view plaincopy to clipboardprint?
public Object f22()
{
Date date = cal.getTime();
System.out.println("finally");
return date;
Exception e;
e;
e.printStackTrace();
System.out.println("finally");
break MISSING_BLOCK_LABEL_45;
Exception exception;
exception;
System.out.println("finally");
throw exception;
return null;
}
public Object f22()
{
Date date = cal.getTime();
System.out.println("finally");
return date;
Exception e;
e;
e.printStackTrace();
System.out.println("finally");
break MISSING_BLOCK_LABEL_45;
Exception exception;
exception;
System.out.println("finally");
throw exception;
return null;
}
还原后的Java代码 view plaincopy to clipboardprint?
public Object f22()
{
try
{
return cal.getTime();
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
System.out.println("finally");
}
return null;
}
public Object f22()
{
try
{
return cal.getTime();
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
System.out.println("finally");
}
return null;
}
4、异常中:label的还原反编译后的代码 view plaincopy to clipboardprint?
public String f4()
throws Exception
{
l0:
{
try
{
Integer i = new Integer(1);
if(i.intValue() > 0)
{
System.out.println(i);
break label0;
}
System.err.println(i);
}
catch(Exception dae)
{
System.err.println(dae);
throw new RuntimeException(dae);
}
return null;
}
return "Hello";
}
public String f4()
throws Exception
{
label0:
{
try
{
Integer i = new Integer(1);
if(i.intValue() > 0)
{
System.out.println(i);
break label0;
}
System.err.println(i);
}
catch(Exception dae)
{
System.err.println(dae);
throw new RuntimeException(dae);
}
return null;
}
return "Hello";
}
注意，这个代码有点诡异，实际代码如下： view plaincopy to clipboardprint?
public String f4() throws Exception
{
try
{
Integer i = new Integer(1);
if (i.intValue() > 0)
{
System.out.println(i);
}
else
{
System.err.println(i);
return null;
}
return "Hello";
}
catch (Exception dae)
{
System.err.println(dae);
throw new RuntimeException(dae);
}
}
public String f4() throws Exception
{
try
{
Integer i = new Integer(1);
if (i.intValue() > 0)
{
System.out.println(i);
}
else
{
System.err.println(i);
return null;
}
return "Hello";
}
catch (Exception dae)
{
System.err.println(dae);
throw new RuntimeException(dae);
}
}
5、典型数据库操作代码还原反编译后代码 view plaincopy to clipboardprint?
public HashMap f5()
{
Connection conn = null;
HashMap hashmap;
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
String columnVallue;
for(ResultSet rs = pstmt.executeQuery(); rs.next(); map.put(columnVallue, ""))
columnVallue = rs.getString("column");
hashmap = map;
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
return hashmap;
ClassNotFoundException cnfe;
cnfe;
cnfe.printStackTrace();
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
SQLException sqle;
sqle;
sqle.printStackTrace();
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
Exception exception;
exception;
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
throw exception;
return null;
}
public HashMap f5()
{
Connection conn = null;
HashMap hashmap;
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
String columnVallue;
for(ResultSet rs = pstmt.executeQuery(); rs.next(); map.put(columnVallue, ""))
columnVallue = rs.getString("column");
hashmap = map;
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
return hashmap;
ClassNotFoundException cnfe;
cnfe;
cnfe.printStackTrace();
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
SQLException sqle;
sqle;
sqle.printStackTrace();
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
Exception exception;
exception;
if(conn != null)
try
{
conn.close();
}
catch(SQLException sqlce)
{
sqlce.printStackTrace();
}
throw exception;
return null;
}
实际代码如下： view plaincopy to clipboardprint?
public HashMap f5()
{
Connection conn = null;
try
{
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
ResultSet rs = pstmt.executeQuery();
while (rs.next())
{
String columnVallue = rs.getString("column");
map.put(columnVallue, "");
}
return map;
}
catch (ClassNotFoundException cnfe)
{
cnfe.printStackTrace();
}
catch (SQLException sqle)
{
sqle.printStackTrace();
}
finally
{
if (conn != null)
{
try
{
conn.close();
}
catch (SQLException sqlce)
{
sqlce.printStackTrace();
}
}
}
return null;
}
public HashMap f5()
{
Connection conn = null;
try
{
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
ResultSet rs = pstmt.executeQuery();
while (rs.next())
{
String columnVallue = rs.getString("column");
map.put(columnVallue, "");
}
return map;
}
catch (ClassNotFoundException cnfe)
{
cnfe.printStackTrace();
}
catch (SQLException sqle)
{
sqle.printStackTrace();
}
finally
{
if (conn != null)
{
try
{
conn.close();
}
catch (SQLException sqlce)
{
sqlce.printStackTrace();
}
}
}
return null;
}
6、两层异常嵌套代码还原反编译后的代码 view plaincopy to clipboardprint?
public int f6()
{
int i = cal.getTime().compareTo(new Date());
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
System.out.println("finally");
return -2;
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
public int f6()
{
int i = cal.getTime().compareTo(new Date());
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
System.out.println("finally");
return -2;
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
实际代码 view plaincopy to clipboardprint?
public int f6()
{
try
{
try
{
return cal.getTime().compareTo(new Date());
}
catch (Exception e1)
{
e1.printStackTrace();
return -1;
}
}
catch (Exception e2)
{
e2.printStackTrace();
return -2;
}
finally
{
System.out.println("finally");
}
}
public int f6()
{
try
{
try
{
return cal.getTime().compareTo(new Date());
}
catch (Exception e1)
{
e1.printStackTrace();
return -1;
}
}
catch (Exception e2)
{
e2.printStackTrace();
return -2;
}
finally
{
System.out.println("finally");
}
}
7、非常诡异的代码反编译后的代码 view plaincopy to clipboardprint?
public int f7()
{
int i = cal.getTime().compareTo(new Date());
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
_L2:
System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
if(true) goto _L2; else goto _L1
_L1:
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
public int f7()
{
int i = cal.getTime().compareTo(new Date());
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
_L2:
System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
if(true) goto _L2; else goto _L1
_L1:
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
原始代码 view plaincopy to clipboardprint?
public int f7()
{
try
{
try
{
return cal.getTime().compareTo(new Date());
}
catch (Exception e1)
{
e1.printStackTrace();
return -1;
}
}
catch (Exception e2)
{
e2.printStackTrace();
return -1;
}
finally
{
System.out.println("finally");
}
}