spring-boot without parent pom.xml cannot generate war packaging

Question

I used the example gs-convert-jar-to-war provided by spring-io. It describes how to generate war packaging within a spring boot project.

The spring-boot documentation allows for using own parent poms, thus omitting the predefined parent pom for all spring-boot projects. The following dependency has to be added:

<dependencyManagement>
    <dependencies>
        <dependency>
            <!-- Import dependency management from Spring Boot -->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>1.0.1.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

I applied this change (and only this change) to the example. Afterwards it is no longer possible to generate the war. I get following error message:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-war-plugin:2.1.1:war (default-war) on project gs-convert-jar-to-war: Error assembling WAR: webxml attribute is required (or pre-existing WEB-INF/web.xml if executing in update mode) -> [Help 1]

Here is the complete listing of the modified pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<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>org.springframework-sample</groupId>
    <artifactId>gs-convert-jar-to-war</artifactId>
    <version>0.1.0</version>
    <packaging>war</packaging>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <!-- Import dependency management from Spring Boot -->
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-parent</artifactId>
                <version>1.0.1.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
            </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
            </dependency>
    </dependencies>

    <properties>
        <start-class>hello.Application</start-class>
    </properties>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>http://repo.spring.io/libs-milestone</url>
        </repository>
    </repositories>

    <pluginRepositories>
        <pluginRepository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>http://repo.spring.io/libs-milestone</url>
        </pluginRepository>
    </pluginRepositories>

</project>

Is there any idea to overcome the problem?

In my project I will use my own parent pom, because it defines a lot of stuff regarding the company.

Answer 1

You removed the parent, so you lost its declaration of the WAR plugin configuration. Here it is:

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

See here for the source code.

N.B. this is not necessary with Spring Boot 2.0 parent pom and above (the war plugin version is different), or if you use the latest war plugin.