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How to solve Error assembling WAR webxml attribute is required exception when building spring boot wars

Cowrie
Cowrie
Dev @ Bswen

1. The purpose of this post

When build springboot app as war file, sometime we encounter this exception:

Terminal window
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-war-plugin:2.2:war (default-war) on project: Error assembling WAR: webxml attribute is required (or pre-existing WEB-INF/web.xml if executing in update mode) -> [Help 1]

The error shows that :

  • it needs a webxml attribute to construct the WAR file
  • Or you should provide a WEB-INF/web.xml to build the WAR file

2. Environments

  • spring boot 1.x and 2.x

3. The solution

3.1 The original pom.xml

Before solve , we can look at the original pom.xml

pom.xml
<build>
    <finalName>${artifactId}</finalName>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <executions>
                <execution>
                    <goals>
                        <goal>repackage</goal>
                    </goals>
                    <configuration>
                        <classifier>exec</classifier>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </build>

We use the spring-boot-maven-plugin to execute the goal repackage with exec classifier.

The classifier, which uses exec here, indicating that the generated jar file will have a -EXEC suffix.

In summary, this configuration uses spring-boot-maven-plugin plug-in to reintegrate the project and generate a executable jar file with the -EXEC suffix.

But, we want to WAR file to be generated, not a executable jar file!

So , we need to change the pom.xml to generate a WAR.

3.2 The right pom.xml

We should add maven-war-plugin to build springboot as a WAR file:

pom.xml
<build>
    <finalName>${artifactId}</finalName>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <executions>
                <execution>
                    <goals>
                        <goal>repackage</goal>
                    </goals>
                    <configuration>
                        <classifier>exec</classifier>
                    </configuration>
                </execution>
            </executions>
        </plugin>


        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-war-plugin</artifactId>
            <version>3.0.0</version>
        </plugin>
    </plugins>
</build>

Please pay attention to the version of the maven-war-plugin, it must be 3.0.0+, or else you must add as follows:

<plugin>
  <artifactId>maven-war-plugin</artifactId>
  <version>2.6</version>
  <configuration>
    <failOnMissingWebXml>false</failOnMissingWebXml>
  </configuration>
</plugin>

Hope it helps for you.

Final Words + More Resources

My intention with this article was to help others who might be considering solving such problem. So I hope that’s been the case here. If you still have any questions, don’t hesitate to ask me by email: [email protected].

Here are also the most important links from this article along with some further resources that will help you in this scope:

Oh, and if you found these resources useful, don’t forget to support me by starring the repo on GitHub!