javaclass反编译后的代码还原

1、javaclass利用jad反编译之后，偶尔回碰到一些不正常的代码，例如：label0:_L1MISSING_BLOCK_LABEL_30、 JVM INSTR ret7、JVM INSTR tableswitch 1 3: default269、JVM INSTR monitorexit JVM INSTR monitorente，这些一般是由特殊 的for循环、try catchfinally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 = Calendar.get

2、Instance();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、fin ally代码的还原反编译后的Java代码如下：

3、publicbooleanf2()booleanflag=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 boolean f2() try return cal.getTime

4、().after(new Date(); catch (Exception e) e.printStackTrace();return false; finally System.out.println(finally); 3、missing_block_labEL还原反编译后的代码 publicObjectf22()Datedate=cal.getTime();system.out.println(finally);return date;Exception e;e;e.printStackTrace();System.out.println(finally);break MISSING_B

5、LOCK_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 :label 的还原反编译后的代码publicStringf4()throwsExcepti

6、onlabel0:try Integer i = new Integer(1);if(Value() 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：public String f4() throws Exception try Integeri = new Inte

7、ger(1);if (Value() 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 public HashMap f5() Connection conn = null;HashMap hashmap;HashMap map = new HashMap();Class.forN

8、ame();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

9、 != null) try conn.close(); catch(SQLException sqlce) sqlce.printStackTrace(); return hashmap;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(SQL

10、Exception 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：public HashMap f5() Connection conn = null;try HashMap map = new HashMap();Cl

11、ass.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 (S

12、QLException sqle) sqle.printStackTrace(); finally if (conn != null) try conn.close(); catch (SQLException sqlce) sqlce.printStackTrace(); return null;System.out.println(finally);return i;Exception e1;e1;e1.printStackTrace();System.out.println(finally);return -1;Exception e2;e2;e2.printStackTrace();S

13、ystem.out.println(finally);return -2;Exception exception;exception;System.out.println(finally);throw exception;1.printStackTrace();return -1; catch (Exception e2) e2.printStackTrace();return -2; finally System.out.println(finally);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 got