EntityManagerFactory 未初始化

我没有使用 EJB/Spring 等。

只有 Jpa + Servlet。

我正在尝试初始化

public abstract class AbstractEntityManagerFactory {

    private static final EntityManagerFactory emf = Persistence.createEntityManagerFactory("HibernateTask");

    public static EntityManager getEntityManager(){
        return emf.createEntityManager();
    }

当我运行它时public static void main(String[] args)- 一切都很好。

但是如果我使用 Tom Cat 9.0.58 - 我会收到一个错误：

05-Apr-2022 22:58:58.985 INFO [http-nio-8080-exec-4] org.hibernate.service.internal.AbstractServiceRegistryImpl.stopService HHH000369: Error stopping service [class org.hibernate.hikaricp.internal.HikariCPConnectionProvider]
        java.lang.NullPointerException: Cannot invoke "com.zaxxer.hikari.HikariDataSource.close()" because "this.hds" is null
            at org.hibernate.hikaricp.internal.HikariCPConnectionProvider.stop(HikariCPConnectionProvider.java:122)
            at org.hibernate.service.internal.AbstractServiceRegistryImpl.stopService(AbstractServiceRegistryImpl.java:390)
            at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.cleanup(EntityManagerFactoryBuilderImpl.java:1449)
            at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1508)
            at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:56)
            at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79)
            at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54)
            at com.aimprosoft.hopak.factory.AbstractEntityManagerFactory.<clinit>(AbstractEntityManagerFactory.java:9)

持久性.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0"
             xmlns="http://java.sun.com/xml/ns/persistence"
             xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
             http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">

    <persistence-unit name="HibernateTask">
        <properties>
            <property name="javax.persistence.jdbc.driver" value="com.mysql.cj.jdbc.Driver"/>
            <property name="hibernate.hikari.jdbcUrl" value="jdbc:mysql://localhost:3306/Departments"/>
            <property name="hibernate.hikari.username" value="root"/>
            <property name="hibernate.hikari.password" value="ISBN97859910"/>
            <property name="hibernate.show_sql" value="true"/>
            <property name="hibernate.format_sql" value="true"/>

            <property name="hibernate.connection.provider_class" value="org.hibernate.hikaricp.internal.HikariCPConnectionProvider"/>
            <property name="hibernate.hikari.connectionTimeout" value="20000"/>
            <property name="hibernate.hikari.idleTimeout" value="150000"/>
            <property name="hibernate.hikari.maximumPoolSize" value="10"/>
            <property name="hibernate.hikari.poolName" value="HikariPool"/>

            <property name="hibernate.hikari.autoCommit" value="true"/>
            <property name="hibernate.hikari.maxLifetime" value="90000"/>

        </properties>
    </persistence-unit>

</persistence>

我认为这与一些特殊的 EntityManagerFactory 声明有关。

我有一个纯 jdbc 实现。如果我先对其进行查询。然后在魔术的帮助下，一切都会初始化。

目前我在页面上有 2 个按钮。

部门 - (JDBC) 员工 - (JPA)

如果我立即点击 Employee(JPA) - 我得到NullPointerException，但如果首先点击 Department(JDBC)，然后点击 Employee(JPA) - 一切都像时钟一样工作。

也许静态初始化有问题？

称呼

public class JpaTransactionManager {

    public static <T> T doInTransaction(JpaTransactionCallback<T> callback) {

        EntityManager em = AbstractEntityManagerFactory.getEntityManager(); // Попытка инициализации
        T result = null;

        em.getTransaction().begin();
        result = callback.execute(em);
        em.getTransaction().commit();

        Log.logger.info("Transaction is done");
        em.close();
        return result;
    }
}

pom.xml

<dependencies>
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
            <version>${slf4j.version}</version>
        </dependency>

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-simple</artifactId>
            <version>${slf4j.version}</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.28</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-core</artifactId>
            <version>5.6.7.Final</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-entitymanager</artifactId>
            <version>5.6.7.Final</version>
        </dependency>

        <dependency>
            <groupId>com.zaxxer</groupId>
            <artifactId>HikariCP</artifactId>
            <version>5.0.1</version>
        </dependency>

        <dependency>
            <groupId>org.hibernate</groupId>
            <artifactId>hibernate-hikaricp</artifactId>
            <version>5.6.7.Final</version>
        </dependency>

    </dependencies>