Question

大神帮忙解释一下这段代码……

String timeTemp = String.valueOf(new Date().getTime());
DiskFileItemFactory factory = new DiskFileItemFactory();
factory.setSizeThreshold(2048 * 1024);
UploadProgressListener getBarListener = new UploadProgressListener(
request);
ServletFileUpload upload = new ServletFileUpload(factory);
upload.setProgressListener(getBarListener);

List formList = upload.parseRequest(request);
Iterator<Object> formItem = formList.iterator();
while (formItem.hasNext()) {
FileItem item = (FileItem) formItem.next();
if (!item.isFormField()) {

}else{
String fieldName = item.getFieldName();
if (fieldName.equals("user")) {
input_user = item.getString("UTF-8");
}
if (fieldName.equals("password")) {
input_passw = item.getString("UTF-8");
}

if (fieldName.equals("isselect")) {
select_ts = item.getString("UTF-8");
}
}
HttpSession session = request.getSession();

Answer 1

        //定义timeTemp为当前时间距离1970 年1 月1 日0点的毫秒数
        
        String timeTemp = String.valueOf(new Date().getTime());
        
        //new一个DiskFileItemFactory类型的对象factory（文件工厂）
        
        DiskFileItemFactory factory = new DiskFileItemFactory();
        
        //为factory设置是否将上传文件已临时文件的形式保存在磁盘的临界值
        //（以字节为单位的int值）
        
        factory.setSizeThreshold(2048 * 1024);
        
        //文件上传监听器
        
        UploadProgressListener getBarListener = new UploadProgressListener
        (request);
        
        //new一个ServletFileUpload类型的对象upload
        
        ServletFileUpload upload = new ServletFileUpload(factory);
        
        //监听upload
        
        upload.setProgressListener(getBarListener);

        //请求体中获取参数赋值到formList
        
        List formList = upload.parseRequest(request);
        
        //建立迭代器formItem
        
        Iterator<Object> formItem = formList.iterator();
        
        //当formItem序列中还有元素时
        
        while (formItem.hasNext()) {
        
            //建立一个FileItem类的对象item
            
            FileItem item = (FileItem) formItem.next();
            
            //判断item封装的数据是一个普通文本表单字段，
            //还是一个文件上传表单字段，
            //如果是普通表单字段则返回true，否则返回false
            //此处为文件上传表单字段不做任何操作
            
            if (!item.isFormField()) {
                
            }else{//普通文本表单字段
                
                //定义fieldName用于返回表单标签name属性的值
                
                String fieldName = item.getFieldName();
                
                if (fieldName.equals("user")) {//值为user
                    
                    //input_user=item的UTF-8格式
                    
                    input_user = item.getString("UTF-8");
                }
                if (fieldName.equals("password")) {//值为password
                    
                    //input_passw=item的UTF-8格式
                    
                    input_passw = item.getString("UTF-8");
                }

                if (fieldName.equals("isselect")) {//值为isselect
                    
                    //select_ts=item的UTF-8格式
                    
                    select_ts = item.getString("UTF-8");
                }
            }
            
            //定义HttpSession类session用于传送数据到jsp
            
            HttpSession session = request.getSession();