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1、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，Calendar cal
2、= Calendar.getInstance();1、Exceptioin 的还原反编译后的代码如下： public boolean f1() return cal.getTime().after(new Date();Exception e; e;e.printStackTrace();return false; 还原后的 Java 代码 public boolean f1() try return cal.getTime().after(new Date(); catch (Exception e) e.printStackTrace(); return false; 2、finally
3、代码的还原 反编译后的 Java 代码如下： 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： public bo
4、olean 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 public Object f22() Date date = cal.getTime();System.out.println(finally);return date;Exception e;e;e.printStackTrace();Sy
5、stem.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 public Object f22() try return cal.getTime(); catch (Exception e) e.printStackTrace(); finally System.out.println(finally); return null;4、异常中:lab
6、el 的还原反编译后的代码 public String f4() throws Exception labelO: try Integer i = new Integer(1);if(i.intValue() O) System.out.println(i);break labelO; 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：public Str
7、ing f4() throws Exception try Integer i = new Integer(1);if (i.intValue() O) 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 public HashMap f5() Connection conn = null; Has
8、hMap 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, ) colu
9、mnVallue = 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 MIS
10、SING_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()
11、; throw exception; return null; 实际代码如下： 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.exec
12、uteQuery();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.prin
13、tStackTrace(); return null;6、 两层异常嵌套代码 还原 反编 译后的代 码 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;E
14、xception exception;exception;System.out.println(finally);throw exception; 实际代码 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
15、译后的代码 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.prin
