When you run App.java

java.lang.NoClassDefFoundError: javax/validation/ValidationException
(abridgement)
at com.example.App.main (App.java:34)
Caused by: java.lang.ClassNotFoundException: javax.validation.ValidationException
java.lang.IllegalStateException: Failed to execute CommandLineRunner
(abridgement)
at com.example.App.main (App.java:34)
Caused by: org.springframework.transaction.CannotCreateTransactionException: Could not open JDBC Connection for transaction;nested exception is java.lang.NullPointerException
Caused by: java.lang.NullPointerException: null

Error message is output to the console and it does not work properly.
I would like to know the solution.

package com.example;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import com.example.domain.Customer;
import com.example.repository.CustomerRepository;
import com.example.service.CustomerService;
@EnableAutoConfiguration
@ComponentScan
public class App implements CommandLineRunner {
    @Autowired
    CustomerService customerService;
    @Autowired
    NamedParameterJdbcTemplate jdbcTemplate;
    @Autowired
    CustomerRepository customerRepository;
    @Override
    public void run (String ... strings) throws Exception {
        Customer created = customerRepository.save (new Customer (null, "Hidetoshi", "Dekisugi"));
        System.out.print (created + "is created!");
        customerRepository.findAll (). forEach (System.out :: println);
    }
    public static void main (String [] args) {
        SpringApplication.run (App.class, args);
    }
}

package com.example;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import net.sf.log4jdbc.Log4jdbcProxyDataSource;
import javax.sql.DataSource;@Configuration
public class AppConfig {
    @Autowired
    DataSourceProperties datasourceProperties;
    DataSource datasource;
    @ConfigurationProperties (prefix = "spring.datasource")
    @Bean (destroyMethod = "close")
    DataSource realDataSource () {
        @SuppressWarnings ("rawtypes")
         DataSourceBuilder factory = DataSourceBuilder factory
                .create (this.datasourceProperties.getClassLoader ())
                .url (this.datasourceProperties.getUrl ())
                .username (this.datasourceProperties.getUsername ())
                .password (this.datasourceProperties.getPassword ());
        this.datasource = factory.build ();
        return this.datasource;
}
    @Primary
    @Bean
    Log4jdbcProxyDataSource datasource () {
        return new Log4jdbcProxyDataSource (this.datasource);
    }
}

package com.example.repository;
import java.util.List;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.RowMapper;
import org.springframework.jdbc.core.namedparam.BeanPropertySqlParameterSource;
import org.springframework.jdbc.core.namedparam.MapSqlParameterSource;
import org.springframework.jdbc.core.namedparam.NamedParameterJdbcTemplate;
import org.springframework.jdbc.core.namedparam.SqlParameterSource;
import org.springframework.stereotype.Repository;
import org.springframework.transaction.annotation.Transactional;
import com.example.domain.Customer;
@Repository
@Transactional
public class CustomerRepository {
    @Autowired
    NamedParameterJdbcTemplate jdbcTemplate;
    private static final RowMapper<Customer>customerRowMapper = (rs, i)->{
        Integer id = rs.getInt ("id");
        String firstName = rs.getString ("first_name");
        String lastName = rs.getString ("last_name");
        return new Customer (id, firstName, lastName);
    };
    public List<Customer>findAll () {
        List<Customer>Customers = jdbcTemplate.query ("SELECT id, first_name FROM customers ORDERBY id", customerRowMapper);
        return Customers;
    }
    public Customer findOne (Integer id) {
        SqlParameterSource param = new MapSqlParameterSource (). addValue ("id", id);
        return jdbcTemplate.queryForObject ("SELECT id, first_name, last_name FROM customers WHERE id =: id", param, customerRowMapper);
    }
    public Customer save (Customer customer) {SqlParameterSource param = new BeanPropertySqlParameterSource (customer);
        if (customer.getId () == null) {
            jdbcTemplate.update ("INSERT INTO customers (first_name, last_name) values ​​(: firstName,: lastName,)", param);
        } else {
            jdbcTemplate.update ("UPDATE customers SET first_name =: first_name, last_name =: last_name WHERE is =: id", param);
        }
        return customer;
    }
    public void delete (Integer id) {
        SqlParameterSource param = new MapSqlParameterSource (). addValue ("id", id);
        jdbcTemplate.update ("DELETE FROM customers WHERE id =: id", param);
    }
}

<? 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>       spring-boot-starter-parent</artifactId>    <version>2.3.4.RELEASE</version>    <relativePath /><!-lookup parent from repository-></parent><groupId>com.example</groupId>   hajiboot-layering</artifactId><version>1.0.0-SNAPSHOT</version><name>hajiboot-layering</name><description>Demo project for Spring Boot</description><properties>    <java.version>11</java.version></properties><dependencies>    <dependency>        <groupId>org.lazyluke</groupId>           log4jdbc-remix</artifactId>        <version>0.2.7</version>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>           spring-boot-starter</artifactId>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>           spring-boot-starter-jdbc</artifactId>    </dependency>    <dependency>        <groupId>com.h2database</groupId>           h2</artifactId>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>           spring-boot-starter-data-rest</artifactId>    </dependency>    <dependency><groupId>org.springframework.boot</groupId>           spring-boot-starter-web</artifactId>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>           spring-boot-starter-web-services</artifactId>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>           spring-boot-starter-webflux</artifactId>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>           spring-boot-starter-test</artifactId>        <scope>test</scope>        <exclusions>            <exclusion>                <groupId>org.junit.vintage</groupId>                   junit-vintage-engine</artifactId>            </exclusion>        </exclusions>    </dependency>    <dependency>        <groupId>io.projectreactor</groupId>           reactor-test</artifactId>        <scope>test</scope>    </dependency>    <dependency>        <groupId>org.projectlombok</groupId>           lombok</artifactId>        <version>1.181.12</version><!-$NO-MVN-MAN-VER $->        <scope>provided</scope>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>           spring-boot-configuration-processor</artifactId>        <optional>true</optional>    </dependency>    <dependency>        <groupId>org.springframework.boot</groupId>           spring-boot-configuration-processor</artifactId>        <optional>true</optional>    </dependency></dependencies><build>    <plugins>        <plugin>            <groupId>org.springframework.boot</groupId>               spring-boot-maven-plugin</artifactId>        </plugin>    </plugins></build></project>