請問我的Statement.setString(1,"查看");不工作？很無語 就算我把這里的第二個參數(shù)變成常量字符串也沒辦法工作，查詢不出東西 ?求解!!!!!!急

req.setCharacterEncoding("UTF-8");

String command=req.getParameter("command");

String description=req.getParameter("description");

Class.forName("com.mysql.jdbc.Driver");

Connection conn=DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/micro_message","root","123456");

StringBuilder sql=new StringBuilder();

sql.append("select * from message where 1=1");

List<String> paramList=new ArrayList<>();

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);

}

PreparedStatement Statement= conn.prepareStatement(sql.toString());

for(int i=0;i<paramList.size();i++){

Statement.setString(i+1,paramList.get(i));

}

ResultSet rs=Statement.executeQuery();

List<Message> messageList=new ArrayList<>();

while (rs.next()) {

Message message=new Message();

message.setId(rs.getInt("ID"));

message.setCommand(rs.getString("COMMAND"));

message.setContent(rs.getString("CONTENT"));

message.setDescription(rs.getString("DESCRIPTION"));

messageList.add(message);

}

req.setAttribute("messageList", messageList);

} catch (ClassNotFoundException e) {

// TODO Auto-generated catch block

e.printStackTrace();

} catch (SQLException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

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