TesteJPA não executa | Java e JPA: persista seus objetos com a JPA2 e Hibernate

Quando tento executar o TesteJPA, dá o seguinte erro:

ERROR: HHH000319: Could not get database metadata
com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

Last packet sent to the server was 0 ms ago.
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074)
    at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2120)
    at com.mysql.jdbc.ConnectionImpl.<init>(ConnectionImpl.java:723)
    at com.mysql.jdbc.JDBC4Connection.<init>(JDBC4Connection.java:46)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:500)
    at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:481)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:406)
    at com.mysql.jdbc.ConnectionImpl.getInstance(ConnectionImpl.java:302)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:282)
    at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:677)
    at java.sql/java.sql.DriverManager.getConnection(DriverManager.java:189)
    at org.hibernate.service.jdbc.connections.internal.DriverManagerConnectionProviderImpl.getConnection(DriverManagerConnectionProviderImpl.java:193)
    at org.hibernate.tool.hbm2ddl.SuppliedConnectionProviderConnectionHelper.prepare(SuppliedConnectionProviderConnectionHelper.java:51)
    at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:194)
    at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:178)
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:503)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1750)
    at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:94)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:905)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:890)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:57)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:63)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:47)
    at br.com.caelum.financas.jpa.TesteJPA.main(TesteJPA.java:36)
Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

package br.com.caelum.financas.jpa;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import br.com.caelum.financas.modelo.Conta;

public class TesteJPA {

    public static void main(String[] args) {

        Conta conta = new Conta();
        conta.setTitular("Maria dos Santos");
        conta.setBanco("Caixa");
        conta.setAgencia("043");
        conta.setNumero("54321");

        /**
         * Usando HSQLDB
         */

        // EntityManagerFactory emf = Persistence
        //         .createEntityManagerFactory("contas-hsqldb");

        /**
         * Usando PostgreSQL
         */
        // EntityManagerFactory emf = Persistence
        //         .createEntityManagerFactory("contas-postgres");

        /**
         * Usando MySQL
         */
        EntityManagerFactory emf = Persistence
                .createEntityManagerFactory("contas-mysql");

        EntityManager em = emf.createEntityManager();
        em.getTransaction().begin();

        em.persist(conta);

        em.getTransaction().commit();
        em.close();
    }
}

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