Dynamic Web Module 3.0 -- 3.1

I had similar troubles in eclipse and the only way to fix it for me was to

• Remove the web module
• Apply
• Change the module version
• Add the module
• Configure (Further configuration available link at the bottom of the dialog)
• Apply

Just make sure you configure the web module before applying it as by default it will look for your web files in /WebContent/ and this is not what Maven project structure should be.

EDIT:

Here is a second way in case nothing else helps

• Exit eclipse, go to your project in the file system, then to .settings folder.
• Open the org.eclipse.wst.common.project.facet.core.xml , make backup, and remove the web module entry.
• You can also modify the web module version there, but again, no guarantees.

I had the same problem and fixed this by editing org.eclipse.wst.common.project.facet.core.xml.

In this file, I was able to change the following line

<installed facet="jst.web" version="3.1"/>

back to

<installed facet="jst.web" version="3.0"/>

That seemed to fix the problem for me.

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.

This is how it should look like:

<?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" 
         xmlns:web="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>2.6</version>
    <configuration>
        ...
    </configuration>
</plugin>

and

<dependency>
    <groupId>javax.servlet</groupId>
    <artifactId>javax.servlet-api</artifactId>
    <version>3.1.0</version>
    <scope>provided</scope>
</dependency>

Finally, you should compile with Java 7 or 8:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-compiler-plugin</artifactId>
    <version>3.3</version>
    <configuration>
        <source>1.7</source>
        <target>1.7</target>
    </configuration>
</plugin>