boolean boo=new BookManageBiz().delete(bm);
    String info=boo?"删除成功":"删除失败";
    String str="<script type=‘text/javascript‘>alert(‘"+info+"‘);window.location.href="http://www.mamicode.com/+req.getContextPath()+"/findall.do‘;</script>";
    PrintWriter out=resp.getWriter();
    out.print(str);
    out.flush();
    out.close();

<a href="javascript:mydelete(${b.b_Id})">删除</a>
        
<script type="text/javascript">
        function mydelete(id){
            if(confirm("你确定要删除吗?")){
                window.location.href="/20170519/delete.do?id="+id;
            }
        }
</script>

<script type="text/javascript">
        window.onload = function() {
        document.getElementById("myForm").onsubmit = function() {
            var arr=["b_name","b_author","b_time"];
            var a=["图书名称不能为空","作者姓名不能为空","购买日期不能为空"];
            for(var i=0;i<arr.length;i++){
                if(myId(arr[i]).length==0){
                    alert(a[i]);
                    return false;
                }
            }
            if(myId("b_time").length>0){
                var reg=/\d{4}-([1-12]|\d{2})-([1-9]|\d{2})/;
                if(!reg.test(myId("b_time"))){
                    alert("日期格式错误，必须为yyyy-MM-dd");
                    return false;
                }
            }
            return true;
        }
        function myId(id){
            return document.getElementById(id).value;
        }
    }
</script>