Understanding Spring, I don't understand server errors, please explain?

Question

Java

I’m watching the Devcolibri 7th
lessons , everything starts there at the end, and I get an error when I start it

23-Sep-2017 21:50:15.388 SEVERE [RMI TCP Connection(3)-127.0.0.1] org.apache.catalina.core.StandardContext.startInternal Context [] startup failed due to previous errors
23-Sep-2017 21: 50:15.401 WARNING [RMI TCP Connection(3)-127.0.0.1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [ROOT] registered the JDBC driver [org.postgresql.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.

by trial, the problem disappears if you comment out

package app.config;

import org.apache.commons.dbcp2.BasicDataSource;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import javax.annotation.Resource;
import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;

@Configuration
//@EnableJpaRepositories("app.repository") это и всё что связано с этой папкой
@EnableTransactionManagement
@ComponentScan("app")
@PropertySource("classpath:db.properties")
public class DataBaseConfig {

    @Resource
    private Environment env;

    @Bean
    public DataSource dataSource() {
        BasicDataSource ds = new BasicDataSource();
        ds.setUrl(env.getRequiredProperty("db.url"));
        ds.setDriverClassName(env.getRequiredProperty("db.driver"));
        ds.setUsername(env.getRequiredProperty("db.username"));
        ds.setPassword(env.getRequiredProperty("db.password"));

        ds.setInitialSize(Integer.valueOf(env.getRequiredProperty("db.initialSize")));
        ds.setMinIdle(Integer.valueOf(env.getRequiredProperty("db.minIdle")));
        ds.setMaxIdle(Integer.valueOf(env.getRequiredProperty("db.maxIdle")));
        ds.setTimeBetweenEvictionRunsMillis(Long.valueOf(env.getRequiredProperty("db.timeBetweenEvictionRunsMillis")));
        ds.setMinEvictableIdleTimeMillis(Long.valueOf(env.getRequiredProperty("db.minEvictableIdleTimeMillis")));
        ds.setTestOnBorrow(Boolean.valueOf(env.getRequiredProperty("db.testOnBorrow")));
        ds.setValidationQuery(env.getRequiredProperty("db.validationQuery"));
        return ds;
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean managerFactoryBean() {
        LocalContainerEntityManagerFactoryBean em = new LocalContainerEntityManagerFactoryBean();
        em.setDataSource(dataSource());
        em.setPackagesToScan(env.getRequiredProperty("db.entity.package"));
        em.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
        em.setJpaProperties(getHibernateJpaVendorAdapter());

        return em;
    }

    @Bean
    public PlatformTransactionManager transactionManager(){
        JpaTransactionManager manager = new JpaTransactionManager();
        manager.setEntityManagerFactory(managerFactoryBean().getObject());
        return manager;
    }

    public Properties getHibernateJpaVendorAdapter() {
        try {
            Properties properties = new Properties();
            InputStream is = getClass().getClassLoader().getResourceAsStream("hibernate.properties");
            properties.load(is);
            return properties;
        } catch (IOException e) {
            throw new IllegalArgumentException("Can't find hibernate.properties", e);
        }
    }
}

help!

Answer 1

> startup failed due to previous errors
what is above these lines?