Unable to find a suitable main class, please add a 'mainClass' property, Spring boot

Question

Hi friends i am developing a spring boot maven based project and and i have created a maven submodules but when i try to run my project it gives an error

[ERROR] Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:1.2.5.RELEASE:run (default-cli) on project demo-jhipster: Unable to find a suitable main class, please add a 'mainClass' property -> [Help 1] org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.springframework.boot:spring-boot-maven-plugin:1.2.5.RELEASE:run (default-cli) on project demo-jhipster: Unable to find a suitable main class, please add a 'mainClass' property         at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:216)         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:120)         at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:355)         at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:155)         at org.apache.maven.cli.MavenCli.execute(MavenCli.java:584)         at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:216)         at org.apache.maven.cli.MavenCli.main(MavenCli.java:160) 

my parent pom and child pom is

<?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 http://maven.apache.org/maven-v4_0_0.xsd">     <modelVersion>4.0.0</modelVersion>      <parent>         <artifactId>spring-boot-starter-parent</artifactId>         <groupId>org.springframework.boot</groupId>         <version>1.2.5.RELEASE</version>         <relativePath />     </parent>      <groupId>com.aquevix.demo</groupId>     <artifactId>demo-jhipster</artifactId>     <version>0.0.1-SNAPSHOT</version>     <packaging>pom</packaging>      <name>demo_jhipster</name>      <prerequisites>         <maven>3.0.0</maven>     </prerequisites>     <modules>         <module>JhipsterSubmodule</module>     </modules>      <properties>         <assertj-core.version>3.1.0</assertj-core.version>         <awaitility.version>1.4.0</awaitility.version>         <commons-io.version>2.4</commons-io.version>         <commons-lang.version>2.6</commons-lang.version>         <gatling-maven-plugin.version>2.1.6</gatling-maven-plugin.version>         <gatling.version>2.1.6</gatling.version>         <hibernate.version>4.3.10.Final</hibernate.version>         <hikaricp.version>2.4.0</hikaricp.version>         <jacoco-maven-plugin.version>0.7.4.201502262128</jacoco-maven-plugin.version>         <java.version>1.8</java.version>         <javax.inject.version>1</javax.inject.version>         <joda-time-hibernate.version>1.4</joda-time-hibernate.version>         <liquibase-hibernate4.version>3.5</liquibase-hibernate4.version>         <liquibase-slf4j.version>1.2.1</liquibase-slf4j.version>         <liquibase.version>3.4.1</liquibase.version>         <mapstruct.version>1.0.0.CR1</mapstruct.version>         <maven-enforcer-plugin.version>1.3.1</maven-enforcer-plugin.version>         <maven-sortpom-plugin.version>2.3.0</maven-sortpom-plugin.version>         <maven.build.timestamp.format>yyyyMMddHHmmss</maven.build.timestamp.format>         <maven.compiler.source>${java.version}</maven.compiler.source>         <maven.compiler.target>${java.version}</maven.compiler.target>         <metrics-spark-reporter.version>1.2</metrics-spark-reporter.version>         <metrics-spring.version>3.1.2</metrics-spring.version>         <!-- Sonar properties -->         <project.testresult.directory>${project.build.directory}/test-results</project.testresult.directory>         <run.addResources>false</run.addResources>         <sonar-maven-plugin.version>2.6</sonar-maven-plugin.version>         <sonar.exclusions>src/main/webapp/assets/**/*.*, src/main/webapp/bower_components/**/*.*, src/main/webapp/dist/**/*.*</sonar.exclusions>         <sonar.jacoco.itReportPath>${project.testresult.directory}/coverage/jacoco/jacoco-it.exec</sonar.jacoco.itReportPath>         <sonar.jacoco.reportPath>${project.testresult.directory}/coverage/jacoco/jacoco.exec</sonar.jacoco.reportPath>         <sonar.java.codeCoveragePlugin>jacoco</sonar.java.codeCoveragePlugin>          <sonar.javascript.jstestdriver.reportsPath>${project.testresult.directory}/karma</sonar.javascript.jstestdriver.reportsPath>         <sonar.javascript.lcov.reportPath>${project.testresult.directory}/coverage/report-lcov/lcov.info</sonar.javascript.lcov.reportPath>          <sonar.sources>${project.basedir}/src/main/</sonar.sources>         <sonar.surefire.reportsPath>${project.testresult.directory}/surefire-reports</sonar.surefire.reportsPath>         <sonar.tests>${project.basedir}/src/test/</sonar.tests>         <spring-security.version>4.0.2.RELEASE</spring-security.version>         <springfox.version>2.0.3</springfox.version>         <usertype-core.version>4.0.0.GA</usertype-core.version>      </properties>      <dependencies>         // dependencies..     </dependencies>     <build>         <resources>             <resource>                 <filtering>true</filtering>                 <directory>src/main/resources</directory>                 <includes>                     <include>**/*.xml</include>                 </includes>             </resource>             <resource>                 <filtering>false</filtering>                 <directory>src/main/resources</directory>                 <excludes>                     <exclude>**/*.xml</exclude>                 </excludes>             </resource>         </resources>         <plugins>             <plugin>                 <groupId>com.google.code.sortpom</groupId>                 <artifactId>maven-sortpom-plugin</artifactId>                 <version>${maven-sortpom-plugin.version}</version>                 <executions>                     <execution>                         <phase>verify</phase>                         <goals>                             <goal>sort</goal>                         </goals>                     </execution>                 </executions>                 <configuration>                     <sortProperties>true</sortProperties>                     <nrOfIndentSpace>4</nrOfIndentSpace>                     <sortDependencies>groupId,artifactId</sortDependencies>                     <sortPlugins>groupId,artifactId</sortPlugins>                     <keepBlankLines>true</keepBlankLines>                     <expandEmptyElements>false</expandEmptyElements>                 </configuration>             </plugin>             <plugin>                 <groupId>io.gatling</groupId>                 <artifactId>gatling-maven-plugin</artifactId>                 <version>${gatling-maven-plugin.version}</version>                 <configuration>                     <configFolder>src/test/gatling/conf</configFolder>                     <dataFolder>src/test/gatling/data</dataFolder>                     <resultsFolder>target/gatling/results</resultsFolder>                     <bodiesFolder>src/test/gatling/bodies</bodiesFolder>                     <simulationsFolder>src/test/gatling/simulations</simulationsFolder>                     <!-- This will force Gatling to ask which simulation to run                       This is useful when you have multiple simulations -->                     <simulationClass>*</simulationClass>                 </configuration>             </plugin>             <plugin>                 <groupId>org.apache.maven.plugins</groupId>                 <artifactId>maven-eclipse-plugin</artifactId>                 <configuration>                     <downloadSources>true</downloadSources>                     <downloadJavadocs>true</downloadJavadocs>                 </configuration>             </plugin>             <plugin>                 <groupId>org.apache.maven.plugins</groupId>                 <artifactId>maven-enforcer-plugin</artifactId>                 <version>${maven-enforcer-plugin.version}</version>                 <executions>                     <execution>                         <id>enforce-versions</id>                         <goals>                             <goal>enforce</goal>                         </goals>                     </execution>                 </executions>                 <configuration>                     <rules>                         <requireMavenVersion>                             <message>You are running an older version of Maven. JHipster requires at least Maven 3.0</message>                             <version>[3.0.0,)</version>                         </requireMavenVersion>                         <requireJavaVersion>                             <message>You are running an older version of Java. JHipster requires at least JDK ${java.version}</message>                             <version>[${java.version}.0,)</version>                         </requireJavaVersion>                     </rules>                 </configuration>             </plugin>             <plugin>                 <groupId>org.apache.maven.plugins</groupId>                 <artifactId>maven-surefire-plugin</artifactId>                 <configuration>                     <argLine>-Xmx256m ${surefireArgLine}</argLine>                     <!-- Force alphabetical order to have a reproducible build -->                     <runOrder>alphabetical</runOrder>                 </configuration>             </plugin>             <plugin>                 <groupId>org.apache.maven.plugins</groupId>                 <artifactId>maven-war-plugin</artifactId>                 <configuration>                     <packagingExcludes>WEB-INF/lib/tomcat-*.jar</packagingExcludes>                 </configuration>             </plugin>             <plugin>                 <groupId>org.bsc.maven</groupId>                 <artifactId>maven-processor-plugin</artifactId>                 <version>2.2.4</version>                 <executions>                     <execution>                         <id>process</id>                         <phase>generate-sources</phase>                         <goals>                             <goal>process</goal>                         </goals>                     </execution>                 </executions>                 <dependencies>                     <dependency>                         <groupId>org.mapstruct</groupId>                         <artifactId>mapstruct-processor</artifactId>                         <version>${mapstruct.version}</version>                     </dependency>                 </dependencies>                 <configuration>                     <defaultOutputDirectory>${project.build.directory}/generated-sources</defaultOutputDirectory>                     <processors>                         <processor>org.mapstruct.ap.MappingProcessor</processor>                     </processors>                     <options>                         <mapstruct.suppressGeneratorTimestamp>true</mapstruct.suppressGeneratorTimestamp>                         <mapstruct.defaultComponentModel>spring</mapstruct.defaultComponentModel>                     </options>                 </configuration>             </plugin>             <plugin>                 <groupId>org.codehaus.mojo</groupId>                 <artifactId>sonar-maven-plugin</artifactId>                 <version>${sonar-maven-plugin.version}</version>             </plugin>             <plugin>                 <groupId>org.jacoco</groupId>                 <artifactId>jacoco-maven-plugin</artifactId>                 <version>${jacoco-maven-plugin.version}</version>                 <executions>                     <execution>                         <id>pre-unit-tests</id>                         <goals>                             <goal>prepare-agent</goal>                         </goals>                         <configuration>                             <!-- Sets the path to the file which contains the execution data. -->                             <destFile>${project.testresult.directory}/coverage/jacoco/jacoco.exec</destFile>                             <!-- Sets the name of the property containing the settings for JaCoCo runtime agent. -->                             <propertyName>surefireArgLine</propertyName>                         </configuration>                     </execution>                     <!-- Ensures that the code coverage report for unit tests is created after unit tests have been run -->                     <execution>                         <id>post-unit-test</id>                         <phase>test</phase>                         <goals>                             <goal>report</goal>                         </goals>                         <configuration>                             <dataFile>${project.testresult.directory}/coverage/jacoco/jacoco.exec</dataFile>                             <outputDirectory>${project.testresult.directory}/coverage/jacoco</outputDirectory>                         </configuration>                     </execution>                 </executions>             </plugin>             <plugin>                 <groupId>org.liquibase</groupId>                 <artifactId>liquibase-maven-plugin</artifactId>                 <version>${liquibase.version}</version>                 <dependencies>                     <dependency>                         <groupId>org.javassist</groupId>                         <artifactId>javassist</artifactId>                         <version>3.18.2-GA</version>                     </dependency>                     <dependency>                         <groupId>org.liquibase.ext</groupId>                         <artifactId>liquibase-hibernate4</artifactId>                         <version>${liquibase-hibernate4.version}</version>                     </dependency>                     <dependency>                         <groupId>org.springframework.boot</groupId>                         <artifactId>spring-boot-starter-data-jpa</artifactId>                         <version>${project.parent.version}</version>                     </dependency>                 </dependencies>                 <configuration>                     <changeLogFile>src/main/resources/config/liquibase/master.xml</changeLogFile>                     <diffChangeLogFile>src/main/resources/config/liquibase/changelog/${maven.build.timestamp}_changelog.xml</diffChangeLogFile>                     <driver />                     <url />                     <defaultSchemaName />                     <username />                     <password />                     <referenceUrl>hibernate:spring:com.aquevix.demo.domain?dialect=</referenceUrl>                     <verbose>true</verbose>                     <logging>debug</logging>                 </configuration>             </plugin>             <plugin>                 <groupId>org.springframework.boot</groupId>                 <artifactId>spring-boot-maven-plugin</artifactId>                 <configuration>                     <jvmArguments>-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=5005</jvmArguments>                     <arguments>                         <argument>--spring.profiles.active=dev</argument>                     </arguments>                 </configuration>             </plugin>         </plugins>     </build>      <profiles>         <profile>             <id>dev</id>             <activation>                 <activeByDefault>true</activeByDefault>             </activation>             <properties>                 <!-- log configuration -->                 <logback.loglevel>DEBUG</logback.loglevel>             </properties>             <dependencies>                 <dependency>                     <groupId>org.springframework.boot</groupId>                     <artifactId>spring-boot-starter-tomcat</artifactId>                 </dependency>             </dependencies>         </profile>         <profile>             <id>fast</id>             <build>                 <plugins>                     <plugin>                         <groupId>org.springframework.boot</groupId>                         <artifactId>spring-boot-maven-plugin</artifactId>                         <configuration>                             <arguments>                                 <argument>--spring.profiles.active=dev,fast</argument>                             </arguments>                         </configuration>                     </plugin>                 </plugins>             </build>             <properties>                 <!-- log configuration -->                 <logback.loglevel>DEBUG</logback.loglevel>             </properties>             <dependencies>                 <dependency>                     <groupId>org.springframework.boot</groupId>                     <artifactId>spring-boot-starter-undertow</artifactId>                 </dependency>             </dependencies>         </profile>         <profile>             <id>prod</id>             <build>                 <plugins>                     <plugin>                         <groupId>com.github.trecloux</groupId>                         <artifactId>yeoman-maven-plugin</artifactId>                         <version>0.4</version>                         <executions>                             <execution>                                 <id>run-frontend-build</id>                                 <phase>generate-resources</phase>                                 <goals>                                     <goal>build</goal>                                 </goals>                                 <configuration>                                     <buildTool>grunt</buildTool>                                     <buildArgs>build --force --no-color</buildArgs>                                 </configuration>                             </execution>                         </executions>                         <configuration>                             <yeomanProjectDirectory>${project.basedir}</yeomanProjectDirectory>                         </configuration>                     </plugin>                     <plugin>                         <artifactId>maven-clean-plugin</artifactId>                         <version>2.5</version>                         <configuration>                             <filesets>                                 <fileset>                                       <directory>src/main/webapp/dist</directory>                                 </fileset>                                 <fileset>                                     <directory>.tmp</directory>                                 </fileset>                                 <fileset>                                     <directory>node_modules</directory>                                 </fileset>                             </filesets>                         </configuration>                     </plugin>                     <plugin>                         <groupId>org.springframework.boot</groupId>                         <artifactId>spring-boot-maven-plugin</artifactId>                         <configuration>                             <arguments>                                 <argument>--spring.profiles.active=prod</argument>                             </arguments>                         </configuration>                     </plugin>                 </plugins>             </build>             <properties>                 <!-- log configuration -->                 <logback.loglevel>INFO</logback.loglevel>             </properties>             <dependencies>                 <dependency>                     <groupId>org.springframework.boot</groupId>                     <artifactId>spring-boot-starter-tomcat</artifactId>                 </dependency>             </dependencies>         </profile>     </profiles> </project> 

and chile pom is

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">     <modelVersion>4.0.0</modelVersion>     <parent>         <artifactId>demo-jhipster</artifactId>         <groupId>com.aquevix.demo</groupId>         <version>0.0.1-SNAPSHOT</version>     </parent>     <artifactId>JhipsterSubmodule1</artifactId> </project> 

I have googled but not found any solution please help in this regard!

Answer 1

I believe the issue I was having is similar to yours. I have a multi module app using Spring Boot and only one Application.java (with main method).

I was struggling with it trying to start it up using Maven and I got the same result as yours (unable to find a suitable main class).

I spent several hours trying and changing stuff and after adding the property mainClass to the pom, it couldn't find it.

Then I decided to run the project not from the root project but from the project where the Application class is.

By doing this I was able to start up Spring Boot and everything works like a charm.

Updated

If you want to package the whole thing to be executed with java -jar file you can run the command below from the root project:

mvn clean package spring-boot:repackage  

Don't forget to add the spring-boot-maven-plugin to your pom.

Answer 2

In my case i had in main pom:

<parent>     <groupId>org.springframework.boot</groupId>     <artifactId>spring-boot-starter-parent</artifactId>     <version>2.0.3.RELEASE</version> </parent> 

whitch includes plugin spring-boot-maven-plugin

I had to add to main pom to skip it:

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

and then in module with ma Application class:

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