已經排查了一小時了，實在是找不出毛病了，一查詢就錯，Parameter index out of range (1 > number of parameters, which is 0).我看也沒少問號啊

public?void?doGet(HttpServletRequest?req,?HttpServletResponse?resp)
			throws?ServletException,?IOException?{
		try?{
			req.setCharacterEncoding("UTF-8");
			String?command?=?req.getParameter("command");
			String?description?=?req.getParameter("description");
			req.setAttribute("command",?command);
			req.setAttribute("description",?description);
			System.out.println(command+description);
			Class.forName("com.mysql.jdbc.Driver");
			Connection?ct?=?DriverManager.getConnection("jdbc:mysql:///wechat?useUnicode=true&characterEncoding=UTF-8",
					"root",?"qxqx");
			StringBuilder?sql?=?new?StringBuilder(
					"select?ID,COMMAND,DESCRIPTION,CONTENT?from?message?where?1=1?");
			PreparedStatement?ps?=?ct.prepareStatement(sql.toString());
			List<String>?paramList?=?new?ArrayList<String>();
			if?(command?!=?null?&&?!"".equals(command.trim()))?{
				sql.append("?and?COMMAND='?'?");
				paramList.add(command);
			}
			if?(description?!=?null?&&?!"".equals(description.trim()))?{
				sql.append("?and?DESCRIPTION?like?'%'???'%'?");
				paramList.add(description);
			}
			for?(int?i?=?0;?i?<?paramList.size();?i++)?{

				ps.setString(i?+?1,?paramList.get(i));
			}
			System.out.println(ps.toString());
			ResultSet?rs?=?ps.executeQuery();
			List<Message>?messageList?=?new?ArrayList<Message>();

			while?(rs.next())?{
				Message?message?=?new?Message();
				//?容器里加入的都是引用，不是對象本身，所以后續的set方法依然有用
				messageList.add(message);
				message.setId(rs.getString("ID"));
				message.setCommand(rs.getString("COMMAND"));
				message.setDescription(rs.getString("DESCRIPTION"));
				message.setContent(rs.getString("CONTENT"));
			}
			req.setAttribute("messageList",?messageList);
		}?catch?(Exception?e)?{
			//?TODO?Auto-generated?catch?block
			e.printStackTrace();
		}

		req.getRequestDispatcher("/WEB-INF/jsp/back/list.jsp").forward(req,
				resp);
	}

還有一個小問題，為什么doPost（）方法用super.doGet（req,resp）會出現405錯誤，用doPost（req,resp）就可以了

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第一個問題解決了，把PreparedStatement ps = ct.prepareStatement(sql.toString());放到for循環前一行