If you want to use version 3.1 you need to use the following schema:

• http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd

Note that 3.0 and 3.1 are different: in 3.1 there's no Sun mentioned, so simply changing 3_0.xsd to 3_1.xsd won't work

<?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>

Also, make sure you're depending on the latest versions in your pom.xml. That is,

<plugin>

    <groupId>org.apache.maven.plugins</groupId>

    <artifactId>maven-war-plugin</artifactId>

    <version>2.4</version>

    <configuration>

        ...

    </configuration>

</plugin>

and

<dependency>

    <groupId>javax.servlet</groupId>

    <artifactId>javax.servlet-api</artifactId>

    <version>3.1.0</version>

    <scope>provided</scope>

</dependency>

Also, you should compile with Java 7 or 8:

<plugin>

    <groupId>org.apache.maven.plugins</groupId>

    <artifactId>maven-compiler-plugin</artifactId>

    <version>3.1</version>

    <configuration>

        <source>1.7</source>

        <target>1.7</target>

    </configuration>

</plugin>