I created a library with Maven and SpringBoot but get an error for JavaServletConfiguration every time I try to use the libraries function

Question

In creating this library, the goal is to end up with a .jar that a user can add to their project to detect garbage collection.

It is my understanding that a library should not have a main class and SpringBoot doesn't require a main, so I've added a runner method which looks like this:

@PostConstruct
public static void runGVApp(String[] args)
{
    SpringApplication.run(GarbageviewApplication.class, args);
}

The error I get when I run this in a simple helloWorld project is "java.lang.IllegalArgumentException: No auto configuration classes found in META-INF/spring.factories. If you are using a custom packaging, make sure that file is correct."

I have added a spring.factories file with the following in it, but I am still getting the same error:

org.springframework.boot.autoconfigure.EnableAutoConfiguration=\ com.garbageview.garbageview.GarbageviewApplication

AutoConfiguration should already be enabled in that class as it is annotated with @SpringApplication.

I've read this page, but cannot seem to get it to work. "No auto configuration classes found in META-INF/spring.factories"

I currently do not have anything in my application.properties folder and think that may be why it's not working. I've added my pom below to see if I have messed anything up there as well.

<?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>com.garbageview</groupId>
    <artifactId>garbageview</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>garbageview</name>
    <description></description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.0.RELEASE</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-undertow</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-tomcat</artifactId>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-rest</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </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>2.1.1.RELEASE</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jar-plugin</artifactId>
                <version>3.1.0</version>
                <configuration>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <classpathPrefix>lib/</classpathPrefix>
                            <!-- Configures the main class of the application -->
                            <mainClass>com.garbageview.garbageview.GarbageviewApplication</mainClass>
                        </manifest>
                    </archive>
                </configuration>
            </plugin>

        </plugins>

    </build>


</project>

Answer 1

Your maven-jar-plugin configuration get's in the way of spring-boot-maven plugin repackaging. As per 71. Spring Boot Maven Plugin additional packaging configuration is not need. Either remove maven-jar-plugin configuration from your pom.xml or don't use spring-boot-maven plugin:repackage goal.

Do note that Spring Boot suggests @SpringBootApplication annotated class with main() method as per 18. Using the @SpringBootApplication Annotation. You can find ways to avoid this annotation but you will be rowing against the tide to make it work.

If this is a simple application don't strive away from Spring Boot conventions. Add the @SpringBootApplication class and use repackage to create a runtime JAR.