java class文件准确的反编译思路

推荐两款工具 结合使用

1、Java Decompiler

这款反编译器叫 “Java Decompiler”, 由 Pavel Kouznetsov开发，目前最新版本为0.2.5. 它由 C++开发，并且官方可以下载 windows、linux和苹果Mac Os三个平台的可执行程序。

官方网站：http://jd.benow.ca/

2、Java 反编译器 JD-GUI

JD-GUI 是一个用 C++ 开发的 Java 反编译工具，由 Pavel Kouznetsov开发，支持Windows、Linux和苹果Mac Os三个平台。而且提供了Eclipse平台下的插件JD-Eclipse。JD-GUI不需要安装，直接点击运行，可以反编译jar,class文件。

官方网站：http://jd.benow.ca/

JD-GUI

主要使用 JD-gui, 因为他可以编译整个文件夹class文件非常方便

但是会偶尔地方报错，需要自己分析代码，比如创建一些  没有必要的局部变量

出错实例如下

  public boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object h)
    throws Exception
  {
    String servletPath = req.getServletPath().toLowerCase();
    boolean isContains = (servletPath.contains("add")) || (servletPath.contains("create"));
    boolean pass;
    if (isContains) {
      String name = this.userService.getStaffNameByStaffId((Long)req.getAttribute("sid"));
      boolean pass;
      if (StringUtils.isNotBlank(name)) {
        pass = true;
      } else {
        boolean pass = false;
        JSON.writeDataToStream(res.getOutputStream(), I18NResult.failure(ErrorType.USERNAM_NONE));
      }
    } else {
      pass = true;
    }


    return pass;
  }
}

pass 多处创建 调整后如下

  public boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object h)
/*    */     throws Exception
/*    */   {
/* 24 */     String servletPath = req.getServletPath().toLowerCase();
/* 25 */     boolean isContains = (servletPath.contains("add")) || (servletPath.contains("create"));
/*    */     boolean pass;
/* 26 */     if (isContains) {
/* 27 */       String name = this.userService.getStaffNameByStaffId((Long)req.getAttribute("sid"));
/* 28 */       if (StringUtils.isNotBlank(name)) {
/* 29 */         pass = true;
/*    */       } else {
/* 31 */         pass = false;
/* 32 */         JSON.writeDataToStream(res.getOutputStream(), I18NResult.failure(ErrorType.USERNAM_NONE));
/*    */       }
/*    */     } else {
/* 35 */       pass = true;
/*    */     }
/*    */ 
/* 38 */     return pass;
/*    */   }
/*    */ }

有时候JD-GUI编译出来的代码莫名其妙，这个时候可以结合

Java Decompiler 编译后的代码综合分析

下面给出一个class 文件的一个函数

由 jd-gui编译的函数 （有问题）

@RequestMapping({"/getMyProjectTaskList", "/getMeProjectTasks"})
/*     */   @ResponseBody
/*     */   public Output getMetasks(@RequestParam("projectId") Long projectId, @Sid Long sid) {
/*     */     try {
/* 141 */       metasks = this.taskService.getMetasks(projectId, sid);
/*     */     }
/*     */     catch (Exception e)
/*     */     {
/*     */       List metasks;
/* 143 */       throw new RuntimeException(e);
/*     */     }
/* 147 */     List metasks;
/* 146 */     List metaskRess = new ArrayList(metasks.size());
/* 147 */     for (Iterator localIterator = metasks.iterator(); localIterator.hasNext(); ) { metask = (MetaskBo)localIterator.next();
/* 148 */       MetaskRes metaskVo = new MetaskRes();
/*     */ 
/* 150 */       metaskVo.setTaskId(ObjectUtils.toString(metask.getTaskId()));
/* 151 */       metaskVo.setIsLeafTask(ObjectUtils.toString(metask.getIsLeafTask()));
/* 152 */       metaskVo.setTaskName(ObjectUtils.toString(metask.getTaskName()));
/* 153 */       srt = metask.getStartDateTime();
/* 154 */       Date end = metask.getEndDateTime();
/* 155 */       metaskVo.setSrtDate(DateUtil.defaultDateToString(srt));
/* 156 */       metaskVo.setEndDate(DateUtil.defaultDateToString(end));
/* 157 */       metaskVo.setIsFinished(ObjectUtils.toString(metask.getIsFinished()));
/* 158 */       metaskVo.setBetween((srt.getTime() <= metask.getCurrentDateTime().longValue()) && (metask.getCurrentDateTime().longValue() <= end.getTime()) ? "1" : "0");
/* 159 */       metaskVo.setTaskDesStatus(ObjectUtils.toString(metask.getTaskDesStatus()));
/* 160 */       metaskVo.setTaskStatus(ObjectUtils.toString(metask.getTaskStatus()));
/* 161 */       metaskVo.setRemindTime(ObjectUtils.toString(metask.getRemindTime()));
/* 162 */       metaskVo.setWatcherSid(ObjectUtils.toString(metask.getWatcherSid()));
/* 163 */       metaskVo.setAuditorSid(ObjectUtils.toString(metask.getAuditorSid()));
/*     */ 
/* 165 */       metaskRess.add(metaskVo);
/*     */     }
/* 169 */     Date srt;
/* 168 */     List taskInfos = this.taskProgressService.calcTaskProgress(projectId);
/* 169 */     for (MetaskBo metask = taskInfos.iterator(); metask.hasNext(); ) { taskInfo = (TaskInfo)metask.next();
/* 170 */       for (MetaskRes metaskRes : metaskRess)
/* 171 */         if (taskInfo.getTaskId().toString().equals(metaskRes.getTaskId())) {
/* 172 */           metaskRes.setPlanProgress(ObjectUtils.toString(Float.valueOf(taskInfo.getPlanProgress())));
/* 173 */           float undoneProgress = taskInfo.getPlanProgress() - taskInfo.getProgress();
/* 174 */           metaskRes.setUndoneProgress(ObjectUtils.toString(Float.valueOf(undoneProgress < 0.0F ? 0.0F : undoneProgress)));
/* 175 */           metaskRes.setActualProgress(ObjectUtils.toString(Float.valueOf(taskInfo.getProgress())));
/* 176 */           break;
/*     */         }
/*     */     }
/*     */     TaskInfo taskInfo;
/* 181 */     return Result.success(metaskRess);
/*     */   }

由

dj java Decompiler工具分析出来的结果(也有问题) 

 @RequestMapping(value={"/getMyProjectTaskList", "/getMeProjectTasks"})
    @ResponseBody
    public Output getMetasks(@RequestParam(value="projectId") Long projectId, @Sid Long sid)
    {
        List metasks;
        try
        {
            metasks = taskService.getMetasks(projectId, sid);
        }
        catch(Exception e)
        {
            throw new RuntimeException(e);
        }
        List metaskRess = new ArrayList(metasks.size());
        MetaskRes metaskVo;
        for(Iterator iterator = metasks.iterator(); iterator.hasNext(); metaskRess.add(metaskVo))
        {
            MetaskBo metask = (MetaskBo)iterator.next();
            metaskVo = new MetaskRes();
            metaskVo.setTaskId(ObjectUtils.toString(metask.getTaskId()));
            metaskVo.setIsLeafTask(ObjectUtils.toString(metask.getIsLeafTask()));
            metaskVo.setTaskName(ObjectUtils.toString(metask.getTaskName()));
            Date srt = metask.getStartDateTime();
            Date end = metask.getEndDateTime();
            metaskVo.setSrtDate(DateUtil.defaultDateToString(srt));
            metaskVo.setEndDate(DateUtil.defaultDateToString(end));
            metaskVo.setIsFinished(ObjectUtils.toString(metask.getIsFinished()));
            metaskVo.setBetween(srt.getTime() > metask.getCurrentDateTime().longValue() || metask.getCurrentDateTime().longValue() > end.getTime() ? "0" : "1");
            metaskVo.setTaskDesStatus(ObjectUtils.toString(metask.getTaskDesStatus()));
            metaskVo.setTaskStatus(ObjectUtils.toString(metask.getTaskStatus()));
            metaskVo.setRemindTime(ObjectUtils.toString(metask.getRemindTime()));
            metaskVo.setWatcherSid(ObjectUtils.toString(metask.getWatcherSid()));
            metaskVo.setAuditorSid(ObjectUtils.toString(metask.getAuditorSid()));
        }

        List taskInfos = taskProgressService.calcTaskProgress(projectId);
        Iterator iterator1 = taskInfos.iterator();
label0:
        do
        {
            if(!iterator1.hasNext())
                break;
            TaskInfo taskInfo = (TaskInfo)iterator1.next();
            Iterator iterator2 = metaskRess.iterator();
            MetaskRes metaskRes;
            do
            {
                if(!iterator2.hasNext())
                    continue label0;
                metaskRes = (MetaskRes)iterator2.next();
            } while(!taskInfo.getTaskId().toString().equals(metaskRes.getTaskId()));
            metaskRes.setPlanProgress(ObjectUtils.toString(Float.valueOf(taskInfo.getPlanProgress())));
            float undoneProgress = taskInfo.getPlanProgress() - taskInfo.getProgress();
            metaskRes.setUndoneProgress(ObjectUtils.toString(Float.valueOf(undoneProgress >= 0.0F ? undoneProgress : 0.0F)));
            metaskRes.setActualProgress(ObjectUtils.toString(Float.valueOf(taskInfo.getProgress())));
        } while(true);
        return Result.success(metaskRess);
    }

结合二者的优点 回避各自缺点

最终分析出来的结果

/*     */   @RequestMapping({"/getMyProjectTaskList", "/getMeProjectTasks"})
/*     */   @ResponseBody
/*     */   public Output getMetasks(@RequestParam("projectId") Long projectId, @Sid Long sid) {
		      List<MetaskBo> metasks;
/*     */     try {
/* 141 */       metasks = this.taskService.getMetasks(projectId, sid);
/*     */     }
/*     */     catch (Exception e)
/*     */     {
/* 143 */       throw new RuntimeException(e);
/*     */     }
/* 147 */     
/* 146 */     List<MetaskRes> metaskRess = new ArrayList<MetaskRes>(metasks.size());
/* 147 */     for (Iterator localIterator = metasks.iterator(); localIterator.hasNext(); ) 
			  { 
				MetaskBo metask = (MetaskBo)localIterator.next();
/* 148 */       MetaskRes metaskVo = new MetaskRes();
/*     */ 
/* 150 */       metaskVo.setTaskId(ObjectUtils.toString(metask.getTaskId()));
/* 151 */       metaskVo.setIsLeafTask(ObjectUtils.toString(metask.getIsLeafTask()));
/* 152 */       metaskVo.setTaskName(ObjectUtils.toString(metask.getTaskName()));
/* 153 */       Date srt = metask.getStartDateTime();
/* 154 */       Date end = metask.getEndDateTime();
/* 155 */       metaskVo.setSrtDate(DateUtil.defaultDateToString(srt));
/* 156 */       metaskVo.setEndDate(DateUtil.defaultDateToString(end));
/* 157 */       metaskVo.setIsFinished(ObjectUtils.toString(metask.getIsFinished()));
/* 158 */       metaskVo.setBetween((srt.getTime() <= metask.getCurrentDateTime().longValue()) && (metask.getCurrentDateTime().longValue() <= end.getTime()) ? "1" : "0");
/* 159 */       metaskVo.setTaskDesStatus(ObjectUtils.toString(metask.getTaskDesStatus()));
/* 160 */       metaskVo.setTaskStatus(ObjectUtils.toString(metask.getTaskStatus()));
/* 161 */       metaskVo.setRemindTime(ObjectUtils.toString(metask.getRemindTime()));
/* 162 */       metaskVo.setWatcherSid(ObjectUtils.toString(metask.getWatcherSid()));
/* 163 */       metaskVo.setAuditorSid(ObjectUtils.toString(metask.getAuditorSid()));
/*     */ 
/* 165 */       metaskRess.add(metaskVo);
/*     */     }
/* 168 */     List<TaskInfo> taskInfos = this.taskProgressService.calcTaskProgress(projectId);
/* 169 */     for (Iterator iterator1= taskInfos.iterator(); iterator1.hasNext(); ) {
				TaskInfo taskInfo = (TaskInfo)iterator1.next();
/* 170 */       for (MetaskRes metaskRes : metaskRess)
/* 171 */         if (taskInfo.getTaskId().toString().equals(metaskRes.getTaskId())) {
/* 172 */           metaskRes.setPlanProgress(ObjectUtils.toString(Float.valueOf(taskInfo.getPlanProgress())));
/* 173 */           float undoneProgress = taskInfo.getPlanProgress() - taskInfo.getProgress();
/* 174 */           metaskRes.setUndoneProgress(ObjectUtils.toString(Float.valueOf(undoneProgress < 0.0F ? 0.0F : undoneProgress)));
/* 175 */           metaskRes.setActualProgress(ObjectUtils.toString(Float.valueOf(taskInfo.getProgress())));
/* 176 */           break;
/*     */         }
/*     */     }
/* 181 */     return Result.success(metaskRess);
/*     */   }