Spring Boot - parent pom when you already have a parent pom

Update 2022-05-29 with 1.5.9.RELEASE.

I have full code and runable example here https://github.com/surasint/surasint-examples/tree/master/spring-boot-jdbi/9_spring-boot-no-parent (see README.txt to see that you can try)

You need this as a basic

   <dependencyManagement>
        <dependencies>
            <dependency>
                <!-- Import dependency management from Spring Boot -->
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-dependencies</artifactId>
                <version>${springframework.boot.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

But that is not enough, you also need explicitly define goal for spring-boot-maven-plugin (If you use Spring Boot as parent, you do not have to explicitly define this)

    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <version>${springframework.boot.version}</version>
            <executions>
                <execution>
                    <goals>
                        <goal>repackage</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>

Otherwise you cannot build as executable jar or war.

Not yet, if you are using JSP, you need to have this:

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

Otherwise, you will get this error message:

    [ERROR] Failed to execute goal org.apache.maven.plugins:maven-war-plugin:2.2:war (default-war) on project spring-boot-09: Error assembling WAR: webxml attribute is required (or pre-existing WEB-INF/web.xml if executi
ng in update mode) -> [Help 1]

NO NO , this is still not enough if you are using Maven Profile and Resource Filter with Spring Boot with "@" instead of "${}" (like this example https://www.surasint.com/spring-boot-maven-resource-filter/). Then you need to explicitly add this in

    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <filtering>true</filtering>
        </resource>
    </resources>

And this in

        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-resources-plugin</artifactId>
            <version>2.7</version>
            <configuration>
                <delimiters>
                    <delimiter>@</delimiter>
                </delimiters>
                <useDefaultDelimiters>false</useDefaultDelimiters>
            </configuration>
        </plugin>

See the example in the link https://www.surasint.com/spring-boot-with-no-parent-example/.

You can use the spring-boot-starter-parent like a "bom" (c.f. Spring and Jersey other projects that support this feature now), and include it only in the dependency management section with scope=import.That way you get a lot of the benefits of using it (i.e. dependency management) without replacing the settings in your actual parent.

The 2 main other things it does are

1. define a load of properties for quickly setting versions of dependencies that you want to override
2. configure some plugins with default configuration (principally the Spring Boot maven plugin). So those are the things you will have to do manually if you use your own parent.

Example provided in Spring Boot documentation:

<dependencyManagement>
    <dependencies>
        <dependency>
            <!-- Import dependency management from Spring Boot -->
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>2.1.3.RELEASE</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>