请查看为什么ajax不能接受json返回的数据

烦请老师检查代码：我在searchbook 的servlet中可以打印出搜索的结果，说明servlet本身应该没错，不明白为什么json返回的数值取不出来，还有怎么打印ajax的数据，便于debug？

用flag尝试测试也不能跳转页面。

这是我的searchbook jsp的代码

<body>
    <center>
        <h1>图书查询</h1>
        <p>
            图书ID：<input type="text" name="bookID">
            图书名：<input type="text" name="bookName">
            分类：<input type="text" name="catgoryName">
            <input type="button" value="查询" id="search">
        </p>
        <hr>
        <table width="800px" cellspacing="0px" cellpadding="0px" border="1px">
            <thead>
                <tr>
                    <th>图书ID</th>
                    <th>书名</th>
                    <th>分类</th>
                    <th>价格</th>
                    <th>描述</th>
                </tr>
            </thead>
            <tbody id="cont">
                   <c:forEach items="${booklist }" var="book">
                    <tr>
                        <td>${book.getId()}</td>
                        <td>${book.getBookName()}</td>
                        <td>${book.getCatgoryName()}</td>
                        <td>${book.getPrice()}</td>
                        <td>${book.getDescride()}</td>
                    </tr>
                </c:forEach>            
          </tbody>
        </table>
    </center>
</body>
<script type="text/javascript" >
$("#search").click(function(){
    //单击查询按钮的时候触发ajax事件
    $.ajax({
        url:"<%=basePath%>/searchBook",
        type:"post",
        data:{
            bookID:$("input[name=bookID]").val(),
            bookName:$("input[name=bookName]").val(),
            catgoryName:$("input[name=catgoryName]").val()
        },
        dataType:"json",
        success:function(result){//result里封装了servlet给ajax返回的结果
              /*var flag=result.flag;
              if(flag==true) {
                     //System.out.println("json返回成功！");
                     response.sendRedirect(request.getContextPath()+"/BookManage/showBooks.jsp");
              }*/
              var list= eval(result);
              var s = null;
              for (var i in list){
                  var id = list[i].id;
                  var bookName = list[i].bookname;
                  var bookCategory = list[i].bookCategory;
                  var price = list[i].price;
                  var description = list[i].description;
              s = s+ "<tr><td>" + id +"</td><td>"+bookname+"</td><td>"+bookcategory+"</td><td>"+price+"</td><td>"+
              description+ "</td></tr>";
              $("#cont>tr").remove();
              }
              $("#cont").html(s);
              }
    });
});
</script>

这是我的searchbook servlet代码：

public class searchBook extends HttpServlet {
    public List<Book> booklist;
    public List<Book> result;
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String bookID = request.getParameter("bookID");
        String bookName = request.getParameter("bookName");
        String catgoryName = request.getParameter("catgoryName");
        //System.out.println("bookID "+bookID+"bookName "+bookName+" catgoryName "+catgoryName);
        if(request.getSession().getAttribute("booklist")!=null) {
             booklist= (List<Book>) request.getSession().getAttribute("booklist");
        }
        result=new ArrayList<>();
        for(Book b: booklist) {
            if(b.getBookname().equals(bookName)||b.getCatgoryName().equals(catgoryName)||(b.getId()+"").equals(bookID))
                result.add(b);
        }
        for(Book b:result) {
            System.out.println(b.toString());
        }
        //JSONObject jsonobject= new JSONObject("{flag:true}");
        JSONArray jsonarray= new JSONArray(result);
        //response.getOutputStream().write(jsonobject.toString().getBytes("UTF-8"));
        response.getOutputStream().write(jsonarray.toString().getBytes("UTF-8"));
        //response.sendRedirect(request.getContextPath()+"/BookManage/searchBooks.jsp");
    }