h2 数据库保留数据但在应用程序启动时重置

Question

我有一个嵌入式数据库的基本测试，我正试图为一个 java 项目工作。就目前而言，我可以使用我的实体存储库对象将行保存到数据库中，并且在应用程序完成运行ning 后，我可以使用 intellij 连接到数据库并看到那些行仍然存在。但是，如果我注释掉 save 方法并再次运行它，当我在完成后检查数据库时，数据库是空的。

实体

package closet.utilities.entities;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name = "outfits")
public class Outfit {

    @Id
    @Column(name = "id")
    String id;

    @Column(name = "inv_name")
    String invName;

    @Column(name = "display_name")
    String displayName;

    @Column(name = "owner")
    String owner;

    public Outfit() {
    }

    public Outfit(String id, String invName, String displayName, String owner) {
        this.id = id;
        this.invName = invName;
        this.displayName = displayName;
        this.owner = owner;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getInvName() {
        return invName;
    }

    public void setInvName(String invName) {
        this.invName = invName;
    }

    public String getDisplayName() {
        return displayName;
    }

    public void setDisplayName(String displayName) {
        this.displayName = displayName;
    }

    public String getOwner() {
        return owner;
    }

    public void setOwner(String owner) {
        this.owner = owner;
    }

    @Override
    public String toString() {
        return "Outfit{" +
                "id='" + id + '\'' +
                ", invName='" + invName + '\'' +
                ", displayName='" + displayName + '\'' +
                ", owner='" + owner + '\'' +
                '}';
    }
}

存储库

package closet.utilities.repositories;

import closet.utilities.entities.Outfit;

import javax.persistence.EntityManager;
import java.util.List;
import java.util.Optional;

public class OutfitRepository {

    private EntityManager entityManager;

    public OutfitRepository(EntityManager entityManager) {
        this.entityManager = entityManager;
    }

    public Optional<Outfit> findById(String id) {
        Outfit outfit = entityManager.find(Outfit.class, id);
        return outfit != null ? Optional.of(outfit) : Optional.empty();
    }

    public List<Outfit> findAll() {
        return entityManager.createQuery("from Outfit").getResultList();
    }

    public Optional<Outfit> save(Outfit outfit) {
        try {
            entityManager.getTransaction().begin();
            entityManager.persist(outfit);
            entityManager.getTransaction().commit();
            return Optional.of(outfit);
        } catch (Exception e) {
            // TODO logging
            e.printStackTrace();
        }
        return Optional.empty();
    }
}

主要方法

package closet.utilities;

import closet.utilities.entities.Outfit;
import closet.utilities.repositories.OutfitRepository;
import org.hibernate.Session;
import org.hibernate.Transaction;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import java.util.List;

public class Runnable {

    public static void main(String[] args) {

        // Create our entity manager
        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("closet");
        EntityManager entityManager = entityManagerFactory.createEntityManager();


        Outfit outfit = new Outfit("Ramesh", "Fadatare", "rameshfadatare@javaguides.com", "");
        Outfit outfit1 = new Outfit("John", "Cena", "john@javaguides.com", "");
        OutfitRepository outfitRepository = new OutfitRepository(entityManager);
        //outfitRepository.save(outfit);
        //outfitRepository.save(outfit1);

        List<Outfit> outfits = outfitRepository.findAll();

        for (Outfit o : outfits) {
            System.out.println(o.getInvName());
        }

    }
}

persistence.xml

<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"
             version="2.0" xmlns="http://java.sun.com/xml/ns/persistence">

    <persistence-unit name="closet" transaction-type="RESOURCE_LOCAL">
        <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
        <class>closet.utilities.entities.Outfit</class>
        <properties>
            <property name="javax.persistence.jdbc.driver" value="org.h2.Driver" />
            <property name="javax.persistence.jdbc.url"    value="jdbc:h2:./data/closet" />
            <property name="javax.persistence.jdbc.user" value="sa" />
            <property name="javax.persistence.jdbc.password" value="" />

            <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
            <property name="hibernate.hbm2ddl.auto" value="create-drop" />
            <property name="show_sql" value="true"/>
            <property name="hibernate.temp.use_jdbc_metadata_defaults" value="false"/>
        </properties>
    </persistence-unit>
</persistence>

hibernate.cfg.xml

<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <!-- JDBC Database connection settings -->
        <property name="connection.driver_class">org.h2.Driver</property>
        <property name="connection.url">jdbc:h2:./data/closet</property>
        <property name="connection.username">sa</property>
        <property name="connection.password"></property>
        <!-- JDBC connection pool settings ... using built-in test pool -->
        <property name="connection.pool_size">1</property>
        <!-- Select our SQL dialect -->
        <property name="dialect">org.hibernate.dialect.H2Dialect</property>
        <!-- Echo the SQL to stdout -->
        <property name="show_sql">true</property>
        <!-- Set the current session context -->
        <property name="current_session_context_class">thread</property>
        <!-- Drop and re-create the database schema on startup -->
        <property name="hbm2ddl.auto">create-drop</property>
        <!-- dbcp connection pool configuration -->
        <property name="hibernate.dbcp.initialSize">5</property>
        <property name="hibernate.dbcp.maxTotal">20</property>
        <property name="hibernate.dbcp.maxIdle">10</property>
        <property name="hibernate.dbcp.minIdle">5</property>
        <property name="hibernate.dbcp.maxWaitMillis">-1</property>
        <mapping class="closet.utilities.entities.Outfit" />
    </session-factory>
</hibernate-configuration>

我只是按照 this tutorial 此处作为指南来弄清楚如何让它全部工作。基于此我看不出我做错了什么。

Answer 1

您使用：

<property name="hbm2ddl.auto">create-drop</property>

如 documentation 中所述：

create-drop

Drop the schema and recreate it on SessionFactory startup. Additionally, drop the schema on SessionFactory shutdown.

所以，这是预期的行为。

h2 数据库保留数据但在应用程序启动时重置

h2 database persists data but resets on application start

java

hibernate

jpa

h2

embedded-database

实体

存储库

主要方法

persistence.xml

hibernate.cfg.xml