Create Spring Boot Runnable JAR file

May 27, 2021 No comments Spring Boot Jar Runnable

1. Introduction

In this article, we are going to present how to create a runnable JAR file out of a Spring Boot application. One of the best features of Spring Boot is embedded web containers which allow us to pack the whole application with dependencies into a single jar file ready to deploy and run.

2. Maven configuration

To create a fat jar with Spring Boot we need an additional spring-boot-maven-plugin in our pom.xml file:

<?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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <!-- Inherit defaults from Spring Boot -->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.5.0</version>
        <relativePath/>
    </parent>

    <groupId>com.frontbackend.springboot</groupId>
    <artifactId>getting-started</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>getting-started</name>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <!-- Add typical dependencies for a web application -->
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

    <!-- Package as an executable jar -->
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

With that Maven configuration, we can build our Spring Boot project using mvn clean install. To run our application we simply executing generated jar file in the target directory.

java -jar target/getting-started-0.0.1-SNAPSHOT.jar

we should see Spring Boot starting output logs on the console:

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.5.0)

2021-05-27 22:20:05.735  INFO 567 --- [           main] c.f.s.GettingStartedApplication          : Starting GettingStartedApplication v0.0.1-SNAPSHOT using Java 1.8.0_231 on frontbackend with PID 567 (/home/tutorials/spring-boot/getting-started/target/getting-started-0.0.1-SNAPSHOT.jar started by marcinw in /home/tutorials/spring-boot/getting-started/target)
2021-05-27 22:20:05.737  INFO 567 --- [           main] c.f.s.GettingStartedApplication          : No active profile set, falling back to default profiles: default
2021-05-27 22:20:06.768  INFO 567 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2021-05-27 22:20:06.781  INFO 567 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2021-05-27 22:20:06.781  INFO 567 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.46]
2021-05-27 22:20:06.839  INFO 567 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2021-05-27 22:20:06.839  INFO 567 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 1033 ms
2021-05-27 22:20:07.232  INFO 567 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2021-05-27 22:20:07.246  INFO 567 --- [           main] c.f.s.GettingStartedApplication          : Started GettingStartedApplication in 1.872 seconds (JVM running for 2.291)
2021-05-27 22:20:07.247  INFO 567 --- [           main] o.s.b.a.ApplicationAvailabilityBean      : Application availability state LivenessState changed to CORRECT
2021-05-27 22:20:07.249  INFO 567 --- [           main] o.s.b.a.ApplicationAvailabilityBean      : Application availability state ReadinessState changed to ACCEPTING_TRAFFIC

To stop the application we need to find that process and terminates it:

> ps aux | grep java

frontbackend    567 11.6  0.8 12252152 289796 pts/14 Sl+ 22:20   0:09 java -jar getting-started-0.0.1-SNAPSHOT.jar

> sudo kill -9 567

3. Additional Maven configuration

If we are not inheriting spring-boot-starter-parent in the pom.xml file we could still create executable Spring Boot jar bu adding a main class in the Maven plugin:

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
        <mainClass>com.frontbackend.springboot.GettingStartedApplication</mainClass>
        <layout>ZIP</layout>
    </configuration>
</plugin>

We could also point that class in properties section:

<properties>
    <start-class>com.frontbackend.springboot.GettingStartedApplication</start-class>
</properties>

Note that if we are using correct annotations and in the pom.xml file we inherited from spring-boot-starter-parent we don't need to add main-class related values.

4. Conclusion

In this article, we presented a simple way to build Spring Boot in a runnable JAR file.

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