关于java的。求好心人给我解释下什么意思。新手不懂

private void kaoqintongji(HttpServletRequest request,

HttpServletResponse response) {

String begdate=request.getParameter("begindate");//定义一个字符串型数据用来获取开始日期

String enddate=request.getParameter("enddate");//结束日期

String zgname=request.getParameter("zgname");

String SQL="select zgname,idcardno,status ,count(*) 天数 from kaoqin where 1=1 ";

if(begdate!=null)

SQL+=MessageFormat.format(" and kqdate>=''{0}'' ", begdate);

if(enddate!=null)

SQL+=MessageFormat.format(" and kqdate<=''{0}'' ",enddate);

if(zgname!=null)

SQL+=MessageFormat.format(" and zgname like ''%{0}%'' ",zgname)；

SQL+=" group by zgname,idcardno,status";

List tongjilist=DALBase.runNativeSQL(SQL)；

dispatchParams(request, response);

request.setAttribute("tongjilist", tongjilist);

String forwardurl=request.getParameter("forwardurl");
最好能每行注释一下。谢谢

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