javax.servlet.jsp.PageContext cannot be resolved to a type

javax.servlet.jsp.PageContext cannot be resolved to a type问题，今天做jsp开发，在jsp页面中调用${pageContext.request.contextPath}时，报上述错误。上网找原因发现，系jar缺失，在页面使用EL表达式时要导入 jsp-api.jar包。代码如下：

<form action="${pageContext.request.contextPath}/servlet/RegisterServlet}" method="post">
	<table>
		<tr>
			<td>用户名</td>
			<td><input type="text" name="username"></td>

		</tr>
		<tr>
			<td>密码</td>
			<td><input type="password" name="password"></td>

		</tr>
		<tr>
			<td>确认密码</td>
			<td><input type="password" name="password2"></td>

		</tr>
		<tr>
			<td>邮箱</td>
			<td><input type="text" name="password2"></td>

		</tr>
		<tr>
			<td>生日</td>
			<td><input type="text" name="birthday"></td>

		</tr>
		<tr>
			<td><input type="reset" value="清空"></td>
			<td><input type="submit" value="注册"></td>

		</tr>

	</table>
	</form>