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

Question

Is there a specific recommended approach to the inclusion of the spring-boot parent pom into projects that already have a required parent POM?

What do you recommend for projects that need to extend from an organizational parent (this is extremely common and even something many/most projects published to Maven central depending on the feeder repos they come from). Most of the build stuff is related to creating executable JARs (e.g. running embedded Tomcat/Jetty). There are ways to structure things so that you can get all the dependencies without extending from a parent (similar to composition vs. inheritance). You can't get a build stuff that way though.

So is it preferable to include all of the spring-boot parent pom inside of the required parent POM or to simply have a POM dependency within the project POM file.

Other options?

TIA,

Scott

Answer 1

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>

Answer 2

Update 2018-01-04 with 1.5.9.RELEASE.

I have full code and runable example here https://www.surasint.com/spring-boot-with-no-parent-example/

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/.