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 ret 7、JVM INSTR tableswitch 1 3: default 269、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 = Calen

2、dar.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、fin ally代码的还

3、原反编译后的Java代码如下： 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 boolea

4、n f2() try return cal.getTime().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.

5、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 :

6、label 的还原反编译后的代码 publicStringf4()throwsExceptionlabel0: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

7、String f4() throws Exception try Integeri = new Integer (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 = nul

8、l;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(columnV

9、allue, ) columnVallue = rs.getString(column); hashmap = map; if(conn != 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; s

10、qle; 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

11、： 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() Str

12、ing columnVallue = rs.getString(column); map.put(columnVallue, ); return map; catch (SQLException 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.prin

13、tStackTrace(); 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; 1.printStackTrace(); return -1; catch (Exception e2) e 2.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