java MAVEN 项目出现红叉

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.ps</groupId>
<artifactId>gczj</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>war</packaging>
<name>gczj Maven Webapp</name>
<url>http://maven.apache.org</url>
<description>工程造价</description>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>

<dependency>
<groupId>jstl</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>

<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.0-b01</version>
</dependency>

</dependencies>
<build>
<finalName>gczj</finalName>

<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<configuration>
<source>1.8</source><!-- 这个1.8是jdk的版本，下面那个也是-->
<target>1.8</target>
</configuration>
</plugin>
</plugins>

</build>
</project>

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee">

</web-app>