报错ParameterMap cannot be cast to java.util.HashMap的问题

[wch6887164]

代码片段如下

public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String nextPage = "digitalweb/cart_list.jsp";
		HttpSession session = request.getSession();
		HashMap<String,String[]> map=(HashMap<String, String[]>) request.getParameterMap();
		ArrayList<Cart> cartList = (ArrayList<Cart>) session.getAttribute("cartList");
		if(map.get("type")[0].equals("add")){
			Cart cart = new Cart();
			cart.setId(Integer.parseInt(map.get("id")[0]));
			cart.setName(map.get("name")[0]);
			cart.setSale(Double.parseDouble(map.get("sale")[0]));
			cart.setPrice(Double.parseDouble(map.get("price")[0]));
			cart.setPic(map.get("pic")[0]);
			cart.setNum(Integer.parseInt(map.get("num")[0]));
			if(cartList==null){
				cartList = new ArrayList<Cart>();
				session.setAttribute("cartList", cartList);
			}
			//判断是否又相同的商品
			boolean hasCart = false;
			for(Cart c:cartList){
				if(c.getId() == cart.getId()){
					c.setNum(c.getNum()+cart.getNum());
					hasCart=true;
					break;
				}
			}
			if(!hasCart)
				cartList.add(cart);
		}
		response.sendRedirect(nextPage);
	}

这是一个购物车跳转的servlet，在前一个jsp界面点击跳转之后输出如下错误

应该是HashMap<String,String[]> map=(HashMap<String, String[]>) request.getParameterMap();出了问题
request.getParameterMap()返回的是一个Map，想把它转换为HashMap操作应该怎么办呢

[清晨v]

request.getParameter("key"); 这样取出来再放到Map中不行吗

[a584429317]

Map 和hashMap 是不一样的

[hp961218]

HashMap<String,String[]> map=(HashMap<String, String[]>) request.getParameterMap(); 这个，绝对是这句话报错

[mmmmm12342]

这样转
if (method.getName().equals("getParameterMap")) {
Map<String,String[]> map1= (Map<String, String[]>) method.invoke(req, args);
Map<String,String[]> map = new HashMap<String, String[]>(map1);

[别闹腰不好]

引用 3 楼 hp961218 的回复:

HashMap<String,String[]> map=(HashMap<String, String[]>) request.getParameterMap(); 这个，绝对是这句话报错

Map<String,String[]> map= request.getParameterMap(); 这就可以了

[别闹腰不好]

这个工具类，比你那一坨好多了 protected <T> T getBean(HttpServletRequest request, Class<T> c) { try { T obj = c.newInstance(); BeanUtils.copyProperties(obj, getBean(request)); return obj; } catch (Exception e) { logger.error(e); } return null; } protected Map getBean(HttpServletRequest request) { Map bm = new HashMap(); Map<String, String[]> tmp = request.getParameterMap(); if (tmp != null) { for (String key : tmp.keySet()) { String[] values = tmp.get(key); bm.put(key, values.length == 1 ? values[0].trim() : values); } } return bm; }

[cuichuanjin]

我也遇到了，tomcat版本过高，换为低版本解决！