"Unable to find main class" with Maven on spring-boot project in Eclipse

Question

I am pretty desperate since I no longer can compile my Maven projects. I have one logical project split into 7 maven modules which so far compiled fine, but today I introduced a feature, whereby I accidentally generated a circular maven dependency. Therefore I refactored the code and eliminated the circular dependency. Ever since I updated the pom files to reflect the fix my project doesn't build anymore. When I run maven with "-X clean install" I get the following java.lang.IllegalStateException: Unable to find main class

[INFO] Error stacktraces are turned on.
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO] 
[INFO] agiletunes-parent
[INFO] agiletunes-util
[INFO] agiletunes-security-common
[INFO] agiletunes-marketing-persistence
[INFO] agiletunes-common-ui
[INFO] agiletunes-security-client
[INFO] agiletunes-marketing-application
[INFO] agiletunes-security-server
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building agiletunes-parent 0.0.1
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- spring-boot-maven-plugin:1.5.2.RELEASE:repackage (default) @ agiletunes-parent ---
[INFO] 
[INFO] --- maven-install-plugin:2.5.2:install (default-install) @ agiletunes-parent ---
[INFO] Installing C:\Users\Alexander\Documents\Development\agileTunes\agiletunes-parent\pom.xml to C:\Users\Alexander\Documents\Development\mavenArtifacts\com\agiletunes\agiletunes-parent\0.0.1\agiletunes-parent-0.0.1.pom
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building agiletunes-util 0.0.1
[INFO] ------------------------------------------------------------------------
[INFO] 
[INFO] --- maven-resources-plugin:2.6:resources (default-resources) @ agiletunes-util ---
[INFO] Using 'UTF-8' encoding to copy filtered resources.
[INFO] skip non existing resourceDirectory C:\Users\Alexander\Documents\Development\agileTunes\agiletunes-util\src\main\resources
[INFO] skip non existing resourceDirectory C:\Users\Alexander\Documents\Development\agileTunes\agiletunes-util\src\main\resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:compile (default-compile) @ agiletunes-util ---
[INFO] Nothing to compile - all classes are up to date
[INFO] 
[INFO] --- maven-resources-plugin:2.6:testResources (default-testResources) @ agiletunes-util ---
[INFO] Not copying test resources
[INFO] 
[INFO] --- maven-compiler-plugin:3.1:testCompile (default-testCompile) @ agiletunes-util ---
[INFO] Not compiling test sources
[INFO] 
[INFO] --- maven-surefire-plugin:2.18.1:test (default-test) @ agiletunes-util ---
[INFO] Tests are skipped.
[INFO] 
[INFO] --- maven-jar-plugin:2.6:jar (default-jar) @ agiletunes-util ---
[INFO] 
[INFO] --- spring-boot-maven-plugin:1.5.2.RELEASE:repackage (default) @ agiletunes-util ---
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO] 
[INFO] agiletunes-parent .................................. SUCCESS [  1.492 s]
[INFO] agiletunes-util .................................... FAILURE [  1.095 s]
[INFO] agiletunes-security-common ......................... SKIPPED
[INFO] agiletunes-marketing-persistence ................... SKIPPED
[INFO] agiletunes-common-ui ............................... SKIPPED
[INFO] agiletunes-security-client ......................... SKIPPED
[INFO] agiletunes-marketing-application ................... SKIPPED
[INFO] agiletunes-security-server ......................... SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.674 s
[INFO] Finished at: 2017-03-21T21:53:04+01:00
[INFO] Final Memory: 31M/309M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:repackage (default) on project agiletunes-util: Execution default of goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:repackage failed: Unable to find main class -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:repackage (default) on project agiletunes-util: Execution default of goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:repackage failed: Unable to find main class
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
    at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
    at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
    at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
    at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
    at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
    at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
    at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
    at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
    at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default of goal org.springframework.boot:spring-boot-maven-plugin:1.5.2.RELEASE:repackage failed: Unable to find main class
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:145)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
    ... 20 more
Caused by: java.lang.IllegalStateException: Unable to find main class
    at org.springframework.boot.loader.tools.Repackager.buildManifest(Repackager.java:354)
    at org.springframework.boot.loader.tools.Repackager.repackage(Repackager.java:273)
    at org.springframework.boot.loader.tools.Repackager.repackage(Repackager.java:258)
    at org.springframework.boot.loader.tools.Repackager.repackage(Repackager.java:190)
    at org.springframework.boot.maven.RepackageMojo.repackage(RepackageMojo.java:212)
    at org.springframework.boot.maven.RepackageMojo.execute(RepackageMojo.java:199)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
    ... 21 more
[ERROR] 
...

This is the pom.xml of my maven parent project:

<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.agiletunes</groupId>
<artifactId>agiletunes-parent</artifactId>
<version>0.0.1</version>

<packaging>pom</packaging>
<name>agiletunes-parent</name>
<description>Maven parent project of agiletunes</description>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.2.RELEASE</version>
    <relativePath></relativePath>
</parent>

<modules>
    <module>../agiletunes-common-ui</module>
    <module>../agiletunes-marketing-application</module>
    <module>../agiletunes-marketing-persistence</module>
    <module>../agiletunes-security-client</module>
    <module>../agiletunes-security-common</module>
    <module>../agiletunes-security-server</module>
    <module>../agiletunes-util</module>
</modules>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <!-- Java -->
    <java.version>1.8</java.version>

    <!-- Spring -->
    <spring.boot.version>1.5.2.RELEASE</spring.boot.version>

    <!-- persistence -->
    <mysql-connector-java.version>6.0.5</mysql-connector-java.version>

    <!-- util -->
    <guava.version>17.0</guava.version>

    <!-- testing -->
    <mockito.version>1.9.5</mockito.version>

</properties>

<dependencies>

    <!-- Spring -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>${mysql-connector-java.version}</version><!--$NO-MVN-MAN-VER$ -->
        <scope>runtime</scope>
    </dependency>

    <!-- utils -->
    <dependency>
        <groupId>com.google.guava</groupId>
        <artifactId>guava</artifactId>
        <version>${guava.version}</version>
    </dependency>

    <!-- unit test framework -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.mockito</groupId>
        <artifactId>mockito-core</artifactId>
        <version>${mockito.version}</version>
        <scope>test</scope>
    </dependency>

</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

What do I need to do, to fix this? Please let me know, should you need additional information. Thank you in advance.

Pifer

Possible duplicate of How do I tell Spring Boot which main class to use for the executable jar? – Reisfield

What lets you think that it is a problem of the branch? I could go back, since I have a git versioning. But I wonder if the eclipse version is the problem? – Pifer

Dear asettouf, thank you for the feedback. From the maven parent perspective I have a number of main methods since multiple - but not all - of the modules have a main as they can be used within another maven projects or standalone. I thought that this was doable with Maven and so far that was never a problem. The util module, were the built stops, has really no main. So, I am afraid the other post you pointed out, is not solving the issue since to my understanding it requires only one main method in the entire project. – Pifer

Dear Ortomala Lokni. I hesitated to reset the branch, but you were right. After the reset everything works fine again. Thank you so much! – Pifer

Answer 1

Just for someone who faced with similar problem. I added spring-boot-maven-plugin in parent POM in section pluginManagement section like this:

 <build>
    <pluginManagement>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </pluginManagement>
</build>

Then I added the plugin only in the modules using it (in plugin section).The project has been successfully built after that.

Crass

i was adding plugins without <pluginManagement? – Enrobe

Answer 2

You should have this

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

only in those modules that you want to run, but not in the parent pom.

Threephase

Mind explaining why doesn't it get inherited from parent pom and have to be exclusively included in child pom ? – Vernissage

Because in a multi-module project, not all sub-modules should be executable. – Kath

Thanks man! So this plugin defines which module is executable, right? – Cobra

I did this one, still having same issue – Watershed

Works like a charm when you want to write a lib! – Osborn

Answer 3

if you don't have a main class in springboot project, you can execution spring-boot-maven-plugin by follow

         <build>
            <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                    <configuration>
                        <skip>true</skip>
                    </configuration>
                </plugin>
            </plugins>
        </build>

Kimmy

This is great answer when you don't have a main class in a non executable spring-boot app.Thank you. – Educator

Answer 4

You can try adding this in the properties section of your pom

<start-class>your.package.main</start-class>

Ramshackle

Oh no, it helped me but after deploying it, app crashes because of " Exception in thread "main" java.lang.ClassNotFoundException: my.package.main":( – Nicosia

How to tell if jar is not an executable , rather a simple library jar or dependency jar. I am getting main class not found error on 2.1.3.RELEASE but its not comming on 2.0.8 – Constantine

In previous version, start-class was not required :( – Nils

Answer 5

I had the same problem. It ended being a spring boot mvn plugin declaration on a subproject that does not actually run (no main class). I just removed the spring boot mvn plugin from the submodule and everything ran fine

Dodge

Simple and good answer. It is worked for me as for no run library project. – Lusty

What he means is remove <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> from parent POM and add it to POM of the runnable modules. Thanks Man – Demurrage

Answer 6

In project agiletunes-util pom.xml add

<properties>
   <spring-boot.repackage.skip>true</spring-boot.repackage.skip>
</properties>

Zandrazandt

Answer 7

add property to maven properties like this

<properties>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
    <start-class>org.roshan.Application</start-class>
</properties>

Anaanabaena

What if I do not have main class. just a library jar. – Constantine

Answer 8

I had a similar problem in the pom.xml created for separating my data model into a new module.

Reading this tread I discovered I had accidentally put the <configuration><skip>true</skip></configuration> inside the <executions> block. Below is my corrected pom.xml build section. FYI, there is no <packaging> entry in my pom.xml.

Using Ubuntu 20.04 LTS, Java 11.0.7, maven 3.6.3, Spring Starter 2.3.2.RELEASE, IntelliJ 2020.2

Working build configuration for pom.xml of my data model module

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <skip>true</skip>
                </configuration>
            </plugin>
        </plugins>
    </build>

Sauger

Thanks, worked for me. Had the same problem. – Eb

Answer 9

I solved that,

Add the following code to pom file,

<profiles>
    <profile>
        <id>profile1</id>
        <properties>
            <spring.boot.mainclass>com.detaysoft.Application</spring.boot.mainclass>
        </properties>
    </profile>
</profiles>

Then build the build tag as follows,

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                        <configuration>
                            <mainClass>${spring.boot.mainclass}</mainClass>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

Montelongo

It only worked when the configuration tag was out side instead of under executions. – Odontograph

Answer 10

Wouldn't you simply tell it by using the annotation @SpringBootApplication?

https://docs.spring.io/spring-boot/docs/current/reference/html/using-boot-using-springbootapplication-annotation.html

Many Spring Boot developers always have their main class annotated with @Configuration, @EnableAutoConfiguration and @ComponentScan. Since these annotations are so frequently used together (especially if you follow the best practices above), Spring Boot provides a convenient @SpringBootApplication alternative.

Cicelycicenia

Answer 11

If you have multi modules maven project, as first workaround simply disable repackage to avoid this exception :

<properties>
    <spring-boot.repackage.skip>true</spring-boot.repackage.skip>
</properties>

Other workarouds :

<executions>
      <execution>
          <goals>
               <goal>repackage</goal>
           </goals>
      </execution>
</executions>
<configuration>
      <skip>true</skip>
</configuration>

As solution:

<properties>
 <spring.boot.mainclass>ir.shaparak.Application</spring.boot.mainclass>
</properties>

Another solution: In parent POM do as follows:

<build>
    <pluginManagement>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </pluginManagement>
</build>

In sub modules(runable moudles) should be as follows

   <build>
          <plugins>
                <plugin>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-maven-plugin</artifactId>
                </plugin>
           </plugins>
    </build>

Rachellrachelle

Answer 12

I was also facing the same issue is resolved by adding <id>repackage</id>.

        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <id>repackage</id>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                        <configuration>
                            <skip>true</skip>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>

Pensioner

Answer 13

I had the same issue for multi module project and I added <mainClass>package-name-in-which-main-method-resides</mainClass> and it worked.

<build>
<plugins>
    <plugin>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-maven-plugin</artifactId>
    <configuration>
    <mainClass>package-name-where-@SpringBootApplication-main-method-is(com.agiletunes)</mainClass>
    </configuration>
    </plugin>
</plugins>
</build>

A

Answer 14

I also stumbled across this issue, and it turned out that packaging type was wrong. When I changed packaging from pom to jar, everything started to work correctly.

Barometry

Answer 15

In my case I had to add the "sourceDirectory" and my pom.xml changed from:

...

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

...

to

...

<build>
    <sourceDirectory>src</sourceDirectory>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

...

Kesselring

Answer 16

In my case, I had a code source file named java even though I was explicitly using kotlin:

<sourceDirectory>${project.basedir}/src/main/kotlin</sourceDirectory>
<testSourceDirectory>${project.basedir}/src/test/kotlin</testSourceDirectory>

Firstrate

Answer 17

In my case, I had missed bellow tag in progect pom:

<packaging>jar</packaging>

or

<packaging>war</packaging>

so, I added and it worked fine.

Corenecoreopsis

Answer 18

In my case, I had a kotlin project but the src dir was named java instead of kotlin by the IDE. refactoring the name fixed the issue.

Imposition

Answer 19

under

<artifactId></artifactId>

tag write this property

    <properties>
        <spring-boot.repackage.skip>true</spring-boot.repackage.skip>
    </properties>

it is helped me

Popular

Answer 20

<properties>
  <spring-boot.repackage.skip>true</spring-boot.repackage.skip>
</properties>

This will work for your pom.xml as your program is trying to find a main class so that it can repackage all the dependencies into a single fat jar but if your module does not contain a main class then you need to specify it with the above code in your module's pom file.

Thermoelectrometer

Answer 21

If you manually build your Sprint Boot project by using maven then make sure your project has a class like " class Application extends SpringBootServletInitializer " with main method in that.

Aceves

Answer 22

With Maven you can tell which is the main class by:

<build>
  <plugins>
    <plugin>
      <configuration>
        <mainClass>com.xxx.yyy.mainApplication<mainClass>
      <configuration>
    <plugin>
  <plugins>
</build>

Senarmontite

Answer 23

In my case error was hidden under mistake in folder structure. It should be

src/main/java

but in my case I've made a mistake during files copy and ended up with

main/java

So, do not hesitate to check manually what is inside .jar built by spring-boot-maven-plugin. In my case it contains only spring classes and none of mine classes.

Versieversification

Answer 24

I also had same issue, and solved by adding Application class as

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

i missed adding application start point during configuration of project.

Prickly

Answer 25

There are 2 ways to solve the issue:

1. Create Main class:

public class Main {public static void main(String[] args){}}

2. Remove plugin from pom.xml:

<plugin>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-maven-plugin</artifactId>
</plugin>

Dodi