maven新建web项目提示The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path

在pom.xml中添加下面代码来下载servlet-api:

<dependency>  
    <groupId>javax.servlet</groupId>  
    <artifactId>servlet-api</artifactId>  
    <version>2.5</version>  
    <scope>provided</scope>  
</dependency>