FailOnMissingWebXml error when validating pom.xml in Eclipse

Everything in Maven revolves around plugins. Plugins are the programs that execute some behavior within the build process. Some plugin inclusions are implied without us having to declare anything.

These implied plugins have default configurations. For example, the maven-compiler-plugin is included in all projects without having to declare it. To override the default configurations we need to declare the plugin in our pom.xml file and set the configurations. For instance, you will see a lot of projects override the default version on the maven-compiler-plugin which has it's source and target set to Java 1.5. We can change to 1.8

<build>
  <plugins>
      <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.1</version>
          <configuration>
              <source>1.8</source>
              <target>1.8</target>
          </configuration>
      </plugin>
  </plugins>
</build>

This is just some theory behind the plugins to give you an idea of what's going on.

With that being said, in order to use <packaging>war<packaging>, the maven-war-plugin is used without us having to declare anything. Just like when using <packaging>jar</packaging>, the maven-jar-plugin's inclusion is implied.

The default configuration for the maven-war-plugin is to fail where there is no web.xml (that configuration property being failOnMissingWebXml). So if we want to override this default, we need to declare the plugin, then set the value for the property to false (not fail)

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <version>2.4</version>
            <configuration>
                <failOnMissingWebXml>false</failOnMissingWebXml>    
            </configuration>
        </plugin>
    </plugins>
</build>

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UPDATE

The war plugin now allows you to just use a property that it will lookup. This allows you to simply declare the property without having to override the plugin. To add this property, you would simply add the property failOnMissingWebXml with a value of false to the project <properties>

<properties>
    <failOnMissingWebXml>false</failOnMissingWebXml>
</properties>

Just by adding this, if you have no further configurations you need to add to the compiler plugin, you will no longer have to override and declare the compiler plugin in your pom.

---

UPDATE 2

So if you declare the maven-war-plugin and use a <version> 3.0.0+, the default for no web.xml failure will be set to false, so we no longer have to override the configuration property, though we still need to declare the plugin.

1. Do:

   mvn clean eclipse:clean
   

2. Add this to your POM:

   <packaging>war</packaging>
   <properties>
       <failOnMissingWebXml>false</failOnMissingWebXml>
   </properties>