How to add a dependency to a Spring Boot Jar in another project?

jar, maven, spring-boot, spring-boot-maven-plugin

Solution

By default, Spring Boot repackages your JAR into an executable JAR, and it does that by putting all of your classes inside `BOOT-INF/classes`, and all of the dependent libraries inside `BOOT-INF/lib`. The consequence of creating this fat JAR is that you can no longer use it as a dependency for other projects.

From Custom repackage classifier:

By default, the `repackage` goal will replace the original artifact with the repackaged one. That's a sane behaviour for modules that represent an app but if your module is used as a dependency of another module, you need to provide a classifier for the repackaged one.

The reason for that is that application classes are packaged in `BOOT-INF/classes` so that the dependent module cannot load a repackaged jar's classes.

If you want to keep the original main artifact in order to use it as a dependency, you can add a `classifier` in the `repackage` goal configuration:

<plugin>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-maven-plugin</artifactId>
  <version>1.4.1.RELEASE</version>
  <executions>
    <execution>
      <goals>
        <goal>repackage</goal>
      </goals>
      <configuration>
        <classifier>exec</classifier>
      </configuration>
    </execution>
  </executions>
</plugin>

With this configuration, the Spring Boot Maven Plugin will create 2 JARs: the main one will be the same as a usual Maven project, while the second one will have the classifier appended and be the executable JAR.

Problem

I have a Spring Boot application and I have created a Jar out of that. Following is my `pom.xml`: ``` <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-mail</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId> </dependency> <dependency> <groupId>org.thymeleaf.extras</groupId> <artifactId>thymeleaf-extras-java8time</artifactId> <version>2.1.0.RELEASE</version> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-actuator</artifactId> </dependency> <!-- WebJars --> <dependency> <groupId>javax.mail</groupId> <artifactId>mail</artifactId> <version>1.4.7</version> </dependency> <dependency> <groupId>com.google.code.gson</groupId> <artifactId>gson</artifactId> <version>2.6.2</version> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> ``` I want to use this Jar in my other application so added this jar to my application. But when I am calling a method in that Jar, it is throwing a `ClassNotFoundException`. How can I fix this issue? How can I add a dependency to a Spring Boot JAR?

Original source