android 反编译心得

工程文件反编译后,首先查看资源文件与配置文件格式是否对的,将src下的R文件放入gen下,修正src下源文件的编码错误.

R.styleable:R下文件的编码错误通常是由资源文件引起的,修改资源文件

<declare-styleable name="TileView">
<attr name="tileSize" format="integer" />
</declare-styleable>

通常反编译后类型为Object的,修改其编译类型,如int的则修改为int类型.

null值错误,可以看其类型改为0或""

去掉:import dalvik.annotation.Signature;

去掉: @Signature({"Ljava/util/ArrayList", "<", "Lcom/example/android/snake/SnakeView$Coordinate;", ">;"})

这是反编译时dalvik虚拟机自动生成的.

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。

异常

下面的代码前提是类中有如下属性，

显示代码打印1 Calendar cal = Calendar.getInstance();

1、Exceptioin的还原

反编译后的代码如下：

显示代码打印1 public boolean f1() { return cal.getTime().after(new Date());

2 Exception e;

3 e;

4 e.printStackTrace();

5 return false;

6 }

还原后的Java代码

显示代码打印1 public boolean f1() { try { return cal.getTime().after(new Date());

2 } catch (Exception e) { e.printStackTrace();

3 return false;

4 } }

2、finally代码的还原反编译后的Java代码如下：

显示代码打印01 public boolean f2() { boolean flag = cal.getTime().after(new Date());

02 System.out.println("finally");

03 return flag;

04 Exception e;

05 e;

06 e.printStackTrace();

07 System.out.println("finally");

08 return false;

09 Exception exception;

10 exception;

11 System.out.println("finally");

12 throw exception;

13 }

还原后的代码如下：

显示代码打印1 public boolean f2() { try { return cal.getTime().after(new Date());

2 } catch (Exception e) { e.printStackTrace();

3 return false;

4 } finally { System.out.println("finally");

5 } }

3、MISSING_BLOCK_LABEL_的还原反编译后的代码

显示代码打印01 public Object f22() { Date date = cal.getTime();

02 System.out.println("finally");

03 return date;

04 Exception e;

05 e;

06 e.printStackTrace();

07 System.out.println("finally");

08 break MISSING_BLOCK_LABEL_45;

09 Exception exception;

10 exception;

11 System.out.println("finally");

12 throw exception;

13 return null;

14 }

还原后的Java代码

显示代码打印1 public Object f22() { try { return cal.getTime();

2 } catch (Exception e) { e.printStackTrace();

3 } finally { System.out.println("finally");

4 } return null;

5 }

4、异常中:label的还原反编译后的代码

显示代码打印01 public String f4() throws Exception { label0: { try { Integer i = new Integer(1);

02 if(i.intValue() >

03 0) { System.out.println(i);

04 break label0;

05 } System.err.println(i);

06 } catch(Exception dae) { System.err.println(dae);

07 throw new RuntimeException(dae);

08 } return null;

09 } return "Hello";

10 }

注意，这个代码有点诡异，实际代码如下：

显示代码打印1 public String f4() throws Exception { try { Integer i = new Integer(1);

2 if (i.intValue() >

3 0) { System.out.println(i);

4 } else { System.err.println(i);

5 return null;

6 } return "Hello";

7 } catch (Exception dae) { System.err.println(dae);

8 throw new RuntimeException(dae);

9 } }

5、典型数据库操作代码还原反编译后代码

显示代码打印01 public HashMap f5() { Connection conn = null;

02 HashMap hashmap;

03 HashMap map = new HashMap();

04 Class.forName("");

05 conn = DriverManager.getConnection("jdbc:odbc:");

06 PreparedStatement pstmt = conn.prepareStatement("select * from table");

07 pstmt.setString(1, "param");

08 String columnVallue;

09 for(ResultSet rs = pstmt.executeQuery();

10 rs.next();

11 map.put(columnVallue, "")) columnVallue = rs.getString("column");

12 hashmap = map;

13 if(conn != null) try { conn.close();

14 } catch(SQLException sqlce) { sqlce.printStackTrace();

15 } return hashmap;

16 ClassNotFoundException cnfe;

17 cnfe;

18 cnfe.printStackTrace();

19 if(conn != null) try { conn.close();

20 } catch(SQLException sqlce) { sqlce.printStackTrace();

21 } break MISSING_BLOCK_LABEL_188;

22 SQLException sqle;

23 sqle;

24 sqle.printStackTrace();

25 if(conn != null) try { conn.close();

26 } catch(SQLException sqlce) { sqlce.printStackTrace();

27 } break MISSING_BLOCK_LABEL_188;

28 Exception exception;

29 exception;

30 if(conn != null) try { conn.close();

31 } catch(SQLException sqlce) { sqlce.printStackTrace();

32 } throw exception;

33 return null;

34 }

实际代码如下：

显示代码打印01 public HashMap f5() { Connection conn = null;

02 try { HashMap map = new HashMap();

03 Class.forName("");

04 conn = DriverManager.getConnection("jdbc:odbc:");

05 PreparedStatement pstmt = conn.prepareStatement("select * from table");

06 pstmt.setString(1, "param");

07 ResultSet rs = pstmt.executeQuery();

08 while (rs.next()) { String columnVallue = rs.getString("column");

09 map.put(columnVallue, "");

10 } return map;

11 } catch (ClassNotFoundException cnfe) { cnfe.printStackTrace();

12 } catch (SQLException sqle) { sqle.printStackTrace();

13 } finally { if (conn != null) { try { conn.close();

14 } catch (SQLException sqlce) { sqlce.printStackTrace();

15 } } } return null;

16 }

6、两层异常嵌套代码还原反编译后的代码

显示代码打印01 public int f6() { int i = cal.getTime().compareTo(new Date());

02 System.out.println("finally");

03 return i;

04 Exception e1;

05 e1;

06 e1.printStackTrace();

07 System.out.println("finally");

08 return -1;

09 Exception e2;

10 e2;

11 e2.printStackTrace();

12 System.out.println("finally");

13 return -2;

14 Exception exception;

15 exception;

16 System.out.println("finally");

17 throw exception;

18 }

实际代码

显示代码打印1 public int f6() { try { try { return cal.getTime().compareTo(new Date());

2 } catch (Exception e1) { e1.printStackTrace();

3 return -1;

4 } } catch (Exception e2) { e2.printStackTrace();

5 return -2;

6 } finally { System.out.println("finally");

7 } }

7、非常诡异的代码反编译后的代码

显示代码打印01 public int f7() { int i = cal.getTime().compareTo(new Date());

02 System.out.println("finally");

03 return i;

04 Exception e1;

05 e1;

06 e1.printStackTrace();

07 _L2: System.out.println("finally");

08 return -1;

09 Exception e2;

10 e2;

11 e2.printStackTrace();

12 if(true) goto _L2;

13 else goto _L1 _L1: Exception exception;

14 exception;

15 System.out.println("finally");

16 throw exception;

17 }

原始代码

显示代码打印1 public int f7() { try { try { return cal.getTime().compareTo(new Date());

2 } catch (Exception e1) { e1.printStackTrace();

3 return -1;

4 } } catch (Exception e2) { e2.printStackTrace();

5 return -1;

6 } finally { System.out.println("finally");

7 } }

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