JSP和HTML表单

我想在用户从下拉菜单中选择时运行sql语句.

我的HTML:

          
            Buy
            Hold
            Good
            Sell
          
          
    

我的JSP代码:

<% 
        Dbase db = new Dbase();
        Connection conn = db.connect("jdbc:mysql://localhost:3306/fyp", "root", "");
        ResultSet rs;
        Statement stmt = conn.createStatement();

        String keyword = request.getParameter("item");
        //out.println(keyword);
        if(keyword == "buy"){
            out.println("buy statement");
            String query = "select numberofoccurence from stock WHERE name='buy';";
            rs = stmt.executeQuery(query) ;
            while(rs.next()){
                System.out.println(rs.getString(1));
            }
        }else if(keyword == "sell"){
            String query = "select numberofoccurence from stock WHERE name='sell';";
            rs = stmt.executeQuery(query) ;
            while(rs.next()){
                System.out.println(rs.getString(1));
            }
        }


    %>

它完全没有错误.它只是无法进入if else语句.可能是什么原因 ？我是JSP的新手.

这已经回答了一百万次!总是在字符串中使用equals,所以替换if(keyword == "buy")...为if("buy".equals(keyword)).