servlet处理抛的异常

发布于 2022-09-04 07:06:55 字数 6796 浏览 11 评论 0

商品列表jsp主要代码：<%
List<String[]> vgoods=(List<String[]>)request.getAttribute("vgoods");
if(vgoods==null){

  Pages pages=new Pages();
  pages.setCurPage(1);
  String gsql="select Gimgurl,Gname,Gintro,Gclass,"+"Gprice,Gid,Gdate from GoodsInfo";
  int totalpage=DBUtil.getTotalPages("select count(*) from goodsinfo");
  pages.setTotalPage(totalpage);
  pages.setSql(gsql);
  vgoods=DBUtil.getPageContent(1, gsql);
  request.setAttribute("vgoods", vgoods);
  session.setAttribute("pages", pages);

}

%>
</head>

<a href="${pageContext.request.contextPath}/GoodsDetail?gid=${goods[5]}">

${goods[1]}
<h4>${fn:replace(goods[2],'|',' ')}</h4>
<h4>所属分类:${goods[3]}</h4>
<h4>定价:￥${goods[4]}</h4>

<h4>上架日期:${goods[6]}</h4>
<div class="btn_div">

<button class="button bg-sub padding float-right
margin-big-top button-block">修改/删除商品</button>

从这进去商品详情JSP页面：
<% List<String[]> vgoods=(List<String[]>)request.getAttribute("vgoods");

%>
</head>
<body>
<div class="layout">
<div class="line padding-big-top padding-big-bottom navbar bg-blue bg-inverse">
<div class="x2">
<button class="button icon-navicon float-right " data-target="#header-demo3"></button>
<img src="${pageContext.request.contextPath}/img/jclogo(2).png" width="150" class="padding" height="50"/>

</div>
<%@include file="../user/top.jsp" %>
</div>

</div>
<c:forEach var="goods" items="${vgoods}">
<div class="container-layout">
<div class="line border padding-big margin-big-top">
<div class="x3 padding-big">
<img width="100%" class="img-responsive" src="${goods[0]}">

</div>
<div class="x9 float-right padding-big">
<h1>${goods[1]}</h1>
<h4>
<span>${fn:replace(goods[2],'|','') }</span>
</h4>
<h4>所属分类:${goods[3]}</h4>
<h4>定价：￥${goods[4]}</h4>

<h3>商品简述:</h3>
<p>${goods[6]}</p>

<img src="${pageContext.request.contextPath}/img/other/buy.png" border="0"/>

，点击超链接进BuyGoods servlet去处理

BuyGoods.java:
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    // TODO Auto-generated method stub
    doPost(request,response);
}

/**
 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
 */
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    HttpSession session=request.getSession();
    Pages pages=(Pages)session.getAttribute("pages");
    Cart cart=(Cart)session.getAttribute("cart");
    if(pages==null){
        pages=new Pages();
    }
    if(cart==null){
        cart=new Cart();
    }
    //得到要购买的东西的ID
    String gid=request.getParameter("gid").trim();
    //判断在哪里购买，0-在缩略图中购买，1-在详细信息中购买
    String flag=request.getParameter("flag").trim();
    cart.buy(gid);
    //得到搜索当前内容的sql
    String sql=pages.getSql();
    int page=pages.getCurPage();
    session.setAttribute("pages", pages);
    session.setAttribute("cart", cart);
    String url="";
    if(flag.equals("0")){
        url="/index.jsp";
    }
    else{
        url="/jsp/good/gooddetail.jsp";
        sql="select Gimgurl,Gname,Gintro,Gclass,Gprice,"+"Gid,Gbrief from GoodsInfo where Gid="+gid;
        page=1;
    }
    //返回后，得到页面内容
    List<String[]> vgoods=DBUtil.getPageContent(page, sql);
    if(vgoods.size()==0){
        String msg="对不起，没有搜索到你要的商品！！！";
        request.setAttribute("msg", msg);
    }
    if(flag.equals("0")){
        request.setAttribute("vgoods", vgoods);
    }
    else{
        request.setAttribute("vgoods", vgoods.get(0));
    }
    //forward 到要去的页面
    ServletContext sc=getServletContext();
    RequestDispatcher rd=sc.getRequestDispatcher(url);
    rd.forward(request, response);
    
}

}
结果抛出异常我查了一下说是转型问题，搞了半天还是没弄出来，望各位大神指点迷津
异常如下：message java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.util.List

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.util.List

org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:556)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
com.wywydo.BuyGoods.doPost(BuyGoods.java:91)
com.wywydo.BuyGoods.doGet(BuyGoods.java:40)
javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
com.wywy.filter.CharsetFilter.doFilter(CharsetFilter.java:48)

root cause

java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.util.List

org.apache.jsp.jsp.good.gooddetail_jsp._jspService(gooddetail_jsp.java:113)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
com.wywydo.BuyGoods.doPost(BuyGoods.java:91)
com.wywydo.BuyGoods.doGet(BuyGoods.java:40)

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