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

Question

I totally understand this error message meaning, but how to fix it? Intellij doesn't allow me to click on the main application class.

org.springframework.boot:spring-boot-maven-plugin:2.1.7.RELEASE:run (default-cli) on project XprojApplication: Unable to find a suitable main class, please add a 'mainClass' property -> [Help 1]

pom.xml

    <?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>
        <parent>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-parent</artifactId>
            <version>2.1.7.RELEASE</version>
            <relativePath/> <!-- lookup parent from repository -->
        </parent>
        <groupId>dev.house</groupId>
        <artifactId>xproj</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <name>15house</name>

        <description>Demo project for Spring Boot</description>

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

        <packaging>war</packaging>
        <dependencies>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-web</artifactId>
                <exclusions>
                    <exclusion>
                        <groupId>org.springframework.boot</groupId>
                        <artifactId>spring-boot-starter-tomcat</artifactId>
                    </exclusion>
                </exclusions>

            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-tomcat</artifactId>
                <scope>provided</scope>
            </dependency>
            <dependency>
                <groupId>org.apache.tomcat</groupId>
                <artifactId>tomcat-servlet-api</artifactId>
                <version>8.0.36</version>
                <scope>provided</scope>
            </dependency>

            <dependency>
                <groupId>com.h2database</groupId>
                <artifactId>h2</artifactId>
                <scope>runtime</scope>
            </dependency>
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <scope>runtime</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-test</artifactId>
                <scope>test</scope>
            </dependency>
            <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-databind</artifactId>
                <version>2.9.4</version>
            </dependency>

            <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-core</artifactId>
                <version>2.9.4</version>
            </dependency>

            <dependency>
                <groupId>com.fasterxml.jackson.core</groupId>
                <artifactId>jackson-annotations</artifactId>
                <version>2.9.4</version>
            </dependency>
        </dependencies>

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

                <plugin>
                    <artifactId>maven-assembly-plugin</artifactId>
                    <executions>
                        <execution>
                            <phase>package</phase>
                            <goals>
                                <goal>single</goal>
                            </goals>
                        </execution>
                    </executions>
                    <configuration>
    <!--                    <archive>-->
    <!--                        <manifest>-->
    <!--                            <addClasspath>true</addClasspath>-->
    <!--                            <mainClass>dev.house.XprojApplication</mainClass>-->
    <!--                        </manifest>-->
    <!--                    </archive>-->
                        <descriptorRefs>
                            <descriptorRef>jar-with-dependencies</descriptorRef>
                        </descriptorRefs>
                    </configuration>
                </plugin>

            </plugins>
            <directory>/Users/poc/workspace/tw-real-estate-service-manager/webapps/15house</directory>
            <finalName>15house</finalName>
        </build>

    </project>

See https://stackoverflow.com/a/43319356/104891 and https://stackoverflow.com/a/42660624/104891. Try to delete `.idea` directory and reimport from `pom.xml`. What's the full path to the source root? Is it under `src/main/java`? — CrazyCoder, Oct 20 '19 at 18:45

score 0 · Answer 1 · answered Oct 20 '19 at 18:47

0

It does not seem that your directories are marked properly.

Since you're using Maven, I assume you have the following structure.

Please ensure to mark the java directory as Sources Root by right-clicking on the folder and following the Mark Directory as submenu. You might want to do the same for the resources directory, marking it as Resources Root.

answered Oct 20 '19 at 18:47

Matthew Formosa

468
3
9

He's using Maven, so any manual changes to the project source roots will be discarded on the next project refresh. – CrazyCoder Oct 20 '19 at 18:48
To be fair since he's using Maven, the IDE should have marked the directories automatically. – Matthew Formosa Oct 20 '19 at 18:49

score 0 · Answer 2 · answered Oct 20 '19 at 20:09

If you want bootable jar for spring boot, you can simply use below configuration in your pom.xml, you don't need maven-assembly-plugin

<plugin>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-maven-plugin</artifactId>
    <executions>
        <execution>
            <goals>
                <goal>repackage</goal>
            </goals>
            <configuration>
                <start-class>org.springframework.boot.loader.JarLauncher</start-class>
            </configuration>
        </execution>
    </executions>
</plugin>

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

pom.xml

2 Answers2