function book_Grounding(){
 var isbn=document.getElementById("book_isbn").value;
 //var b_isbn=parseInt(isbn);
 document.getElementById("bookISbn").value=isbn;
 var form1=document.getElementById("form1");
    form1.submit();
 }

<form action="GroundingServlet" method="post" id="form1">
 <input type="hidden" id="bookISbn" name="book_id" >
</form>

response.setContentType("text/html");
  request.setCharacterEncoding("UTF-8");
  response.setCharacterEncoding("UTF-8");
  
  String book_id=(String)request.getParameter("book_id");
  System.out.println("book_id=["+book_id+"]");

输出的值是：book_id=[]

在JSP中好像都没什么问题，测试过好几次，但在servlet就是接收不到值。