属性 说明
    ${param.name}} 相当于request.getParameter(“name”)
    ${name} 相当于request.getAttribute(“name”) 
    1. ${param.name}是得到将表单或者url的参数传递过来的值
    2. ${name}是得到域中的对象
    3. ${requestScope.name}是在request域中查找
    4. ${sessionScope.name}是在session域中查找
    5. ${applicationScope.name}是在application域中查找
    6. ${pageScop.name}是在page域中查找