Spring Boot multi module Maven project deployment

Question

We have multi module Maven project with following modules:

• Commons
• Model
• Repository
• Service
• Web

We've googled around and we didn't found a solution how to make one executable jar when project has this kind of structure.

Here is the parent pom.xml:

<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>...</groupId>
    <artifactId>...</artifactId>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>Model</module>
        <module>Web</module>
        <module>Service</module>
        <module>Repository</module>
        <module>Common</module>
    </modules>
    <packaging>pom</packaging>

    <name>Api</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>

        <mssql.jdbc.driver.version>4.2</mssql.jdbc.driver.version>

        <apache.commons.lang.version>3.3.2</apache.commons.lang.version>
        <apache.commons.collection.utils.version>4.1</apache.commons.collection.utils.version>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.1.RELEASE</version>
    </parent>

    <dependencies>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-envers</artifactId>
        </dependency>

        <dependency>
            <groupId>com.fasterxml.jackson.datatype</groupId>
            <artifactId>jackson-datatype-jsr310</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>

    </dependencies>

</project>

So, very basic parent pom.xml. We know that we can't use Spring Boot Maven plugin when packaging is pom, so we've defined it in pom.xml from Web module:

<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">
    <parent>
        <artifactId>...</artifactId>
        <groupId>...</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <groupId>...</groupId>
    <artifactId>...</artifactId>
    <packaging>jar</packaging>

    <name>...</name>

    <dependencies>

        <dependency>
            <groupId>...</groupId>
            <artifactId>Service</artifactId>
            <version>${project.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <version>1.4.1.RELEASE</version>
                <configuration>
                    <mainClass>...App</mainClass>
                </configuration>
                <!--<executions>-->
                    <!--<execution>-->
                        <!--<goals>-->
                            <!--<goal>repackage</goal>-->
                        <!--</goals>-->
                    <!--</execution>-->
                <!--</executions>-->
            </plugin>
        </plugins>
    </build>

</project>

The rest of pom.xmls from other modules are pretty much the same: Service's pom.xml includes Repository.jar, Repository includes Model and Common.

Problem 1: when we run mvn install, plugin creates fat jar in target folder of web module. But when we try to run it with java -jar name-of-jar it gives java.lang.NoClassDefFoundError about some class from Service module - and you can see from Web's pom.xml that Service module is included (there is also a Service.jar packed as library in Web.jar)

Problem 2: what's interesting is that Service.jar inside of Web.jar also contains pretty much all the dependencies that are already present in Web.jar - basically they are duplicated.

Did anyone managed to create executable fat jar using Spring Boot Maven plugin and Maven Module project structure?

Answer 1

Problem 1 & 2

You should not have devtools as dependency in your parent pom. Move the following to the web/spring-boot module:

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-devtools</artifactId>
</dependency>

If you look at devtools's pom, it includes the following:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-autoconfigure</artifactId>
</dependency>

So your service jar ends up with some spring boot dependencies.