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.