Question: 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?

Answer: 
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](http://docs.spring.io/spring-boot/docs/1.4.1.RELEASE/maven-plugin/examples/repackage-classifier.html):

> 
> 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`](http://docs.spring.io/spring-boot/docs/1.4.1.RELEASE/maven-plugin/repackage-mojo.html#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.
use below plugin for spring boot version 2.\*

```
<plugin>
     <groupId>org.springframework.boot</groupId>           
     <artifactId>spring-boot-maven-plugin</artifactId>
     <version>2.2.1.RELEASE</version>
     <configuration>
          <classifier>exec</classifier>
     </configuration>
</plugin>

```