内存分页

public static void convToJSONAndWriteToClient

    (HttpServletResponse response,List ObjectList,int pageNum,int pageSize){

   

    try{

   

if(ObjectList.size()==0){

//没有数据时，rows后面的[]一定要加上，否则页面会保留上一次查询得到的rows内容

String json = "{\"total\":0, \"rows\":[]}";

response.getWriter().write(json);

}else{

int toIndex = 0 ;

   int fromIndex = 0;

   int listSize = ObjectList.size();

if(listSize < pageSize){

//不足一页

toIndex = listSize;

}else if(listSize<=pageNum*pageSize){

//当前页是末页

fromIndex = (pageNum-1)*pageSize;

toIndex = listSize;

}else{

//当前页不是末页

fromIndex = (pageNum-1)*pageSize;

toIndex = pageNum*pageSize;

}

 

//list的截取是通过下标计算的，从0开始

   JSONArray jsonAry=JSONArray.fromObject(ObjectList.subList(fromIndex,toIndex));

response.setContentType("text/json;charset=UTF-8");

String json = "{\"total\":"+ObjectList.size()+" , \"rows\":"+jsonAry.toString()+"}";

response.getWriter().write(json);

}

    } catch (IOException e) {

e.printStackTrace();

}

   

    }