The superclass "javax.servlet.http.HttpServlet" was not found

<build>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.3</version>
<configuration>
<source>1.7</source>
<target>1.7</target>
</configuration>
</plugin>
</plugins>
</build>
<dependencies>
<!-- Servlet 3.1 -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
</dependency>
<!-- JSP 2.2 -->
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>jsp-api</artifactId>
<version>2.2</version>
</dependency>
<!-- JSTL 1.2 -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<!-- SLF4J + Log4j -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-log4j12</artifactId>
<version>1.7.7</version>
</dependency>
</dependencies>
src/main/webapp/WEB-INF/web.xml(Servlet 3.0 版本)<web-app xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
xmlns="https://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="https://java.sun.com/xml/ns/javaee https://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0">
</web-app>
切換到 Navigator 視圖,編輯 .settings/org.eclipse.wst.common.project.facet.core.xml:
<installed facet="jst.web" version="3.0"/>
Alt + F5 → 勾選 Force Update of Snapshots/Releases → OK