Can't run Spring Boot application trough the command line

Question

I am trying to run my Spring Boot application through the command line but I am getting this error

MigrationsApplication.java:3: error: package org.springframework.boot does not exist
import org.springframework.boot.SpringApplication;
                               ^
MigrationsApplication.java:4: error: package org.springframework.boot.autoconfigure does not exist
import org.springframework.boot.autoconfigure.SpringBootApplication;
                                             ^
MigrationsApplication.java:8: error: cannot find symbol
@SpringBootApplication
 ^
  symbol: class SpringBootApplication
MigrationsApplication.java:15: error: cannot find symbol
        SpringApplication.run(MigrationsApplication.class, args);
        ^
  symbol:   variable SpringApplication
  location: class MigrationsApplication
4 errors

when I try to build it using the command javac MigrationsApplication.java

pom File

<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>2.4.3</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <groupId>com.migrations</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Migrations</name>
    <description>Demonstration of some migrations</description>
    <properties>
        <java.version>15</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.liquibase</groupId>
            <artifactId>liquibase-core</artifactId>
            <version>4.3.1</version>
        </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>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
    </dependencies>

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

</project>

Main Class

package com.migrations.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import java.io.IOException;

@SpringBootApplication
public class MigrationsApplication {

    public static void main(String[] args) {


        //if entered the command run in the command line
        SpringApplication.run(MigrationsApplication.class, args);

        //if entered the command create in the command line
        /*MigrationGenerator generator=new MigrationGenerator();
        try {
            generator.generateMigrationFile("TEST2");
        } catch (IOException e) {
            System.out.println("There was an error generating the file");
        }*/
    }

}

I also have this "error " Select Run/Debug Configuration

How can I fix this? Maybe I imported my project from start.io in a wrong way or is it because I don't have Maven installed?

Updating pom

<?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>2.4.3</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.migrations</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>MigrationsApp</name>
    <description>Migrations</description>
    <properties>
        <java.version>15</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>

        <dependency>
            <groupId>org.liquibase</groupId>
            <artifactId>liquibase-core</artifactId>
            <version>4.3.1</version>
        </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>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-configuration-processor</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>com.company.common</groupId>
            <artifactId>common-files</artifactId>
            <version>0.0.1-SNAPSHOT</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <fork>true</fork>
                    <mainClass>${start-class}</mainClass>
                </configuration>

                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <artifactId>maven-assembly-plugin</artifactId>
                <configuration>
                    <archive>
                        <manifest>
                            <addClasspath>true</addClasspath>
                            <mainClass>migrations.MigrationsAppApplication</mainClass>
                        </manifest>
                    </archive>
                    <descriptorRefs>
                        <descriptorRef>jar-with-dependencies</descriptorRef>
                    </descriptorRefs>
                </configuration>
                <executions>
                    <execution>
                        <id>assemble-all</id>
                        <phase>package</phase>
                        <goals>
                            <goal>single</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

Answer 1

This will not work. Because If one class is dependent on another class that hasn't been compiled yet, the program won't run

  javac *.java // compliles all java files in the dir

  java MigrationsApplication // runs the particular file

So you should compile all files before trying to run the program dependent on other files.

If your files are packaged, then something like this

javac com.mypackage/.*java

java com.mypackage.MigrationsApplication 

For Error in your debug configuration, Check what is missing or wrongly provided in the configuration.

Also, I suggest to create a sprint boot project and run it as a Spring boot JAR from the command line either or from the IDE itself

To run it as a JAR:

 java -jar target/your.jar