SpringBoot: Unable to find a single main class from the following candidates

Question

I\'ve generated a Spring Boot web application using Spring Initializer, embedded Tomcat, Thymeleaf template engine.Technologies used: Spring Boot 1.4.2.RELEASE, Spring 4.3.4

Answer 1

To disambiguate the entry point of a spring boot application, you can add the following directive to your Gradle build file

springBoot {
    mainClassName = 'your.org.bla.TestKt'
}

Answer 2

or simply hard code the main class in plugin configuration.

        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <executions>
                <execution>
                    <goals>
                        <goal>repackage</goal>
                    </goals>
                    <configuration>
                        <mainClass>your.main.class.MainClass</mainClass>
                    </configuration>
                </execution>
            </executions>
        </plugin>

Answer 3

Sometimes this error is given when you do mvn install without doing mvn clean.

Answer 4

I was building a spring boot library project, so I don't need a main starter class, so I faced the same issue while building the project with maven, so I removed the maven plugin to compile successfully

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

For a more detailed example. find it here https://spring.io/guides/gs/multi-module/

Answer 5

Define single main class via start-class property

<properties>
      <start-class>com.may.Application</start-class>
</properties>

Alternatively, define the main class in the spring-boot-maven-plugin

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <mainClass>com.may.Application</mainClass>
            </configuration>
        </plugin>
    </plugins>
</build>

Or via profiles

<profiles>
        <profile>
            <id>profile1</id>
            <properties>
                <spring.boot.mainclass>com.may.Application1</spring.boot.mainclass>
            </properties>
        </profile>
        <profile>
            <id>profile2</id>
            <properties>
                <spring.boot.mainclass>com.may.Application2</spring.boot.mainclass>
            </properties>
        </profile>
<profiles>

<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>