Question

我想构建一个小型控制台应用程序，它是通过学习Hibernate目的的测试来执行的。不幸的是，hibernate返回时没有数据，当列表应该被实体填充时，它会抛出outofindex异常。我假设没有结果回来。我一直在阅读这里的教程和问题，但我找不到为什么会这样。

JDBC连接运行良好，它是从DataGrip复制的。

还应该检查更详细的其他内容？对不起，我在这个世界上完全缺乏经验。

请找到以下代码。

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
        <property name="hibernate.dialect">org.hibernate.dialect.PostgreSQL95Dialect</property>
        <property name="connection.url" >jdbc:postgresql://localhost:5432/digitallibraryreports</property>
        <property name="connection.driver_class">org.postgresql.Driver</property>
        <property name="connection.username">postgres</property>
        <property name="connection.password">postgres</property>

        <property name="connection.pool_size">1</property>
        <property name="show_sql">true</property>
        <property name="format_sql">true</property>
        <property name="use_sql_comments">true</property>
        <!-- DB schema will be updated if needed -->
        <!-- <property name="hbm2ddl.auto">update</property> -->
    </session-factory>
</hibernate-configuration>

来源：

public class ETL {

    private static SessionFactory factory;

    public ETL(){
        try{
            factory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable ex){
            System.err.println("Failed to create sessionfactory" + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    public SessionFactory getSessionFactory() {
        return factory;
    }
}

类提取内容：

public class FeatureFetcher {

    private static SessionFactory sessionFactory;

    public FeatureFetcher() {
        ETL etl = new ETL();
        sessionFactory = etl.getSessionFactory();
    }

    public void fetchFeatures() {

        Session session = sessionFactory.openSession();
        EntityManager em = sessionFactory.createEntityManager();

        try {
            em.getTransaction().begin();
            List<Test> testEntityList = em.createQuery("FROM Test", Test.class).getResultList();

            if (testEntityList.size() > 0) {
                for (Iterator<Test> iterator = testEntityList.iterator(); iterator.hasNext(); ) {
                    Test testEntity = (Test) iterator.next();

                    System.out.println("Test Entity name: " + testEntity.getName());
                    System.out.println("Test Entity id: " + testEntity.getId());
                }

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

        } catch (HibernateException e) {
            em.getTransaction().rollback();
            e.printStackTrace();
        } finally {
            em.close();
        }

    }
}

实体：

@Entity
@Table(name = "test", schema = "public")
public class Test {

    @javax.persistence.Id
    @GeneratedValue
    @Column(name = "id")
    public Integer Id;

    @Column(name = "name")
    public String Name;

    public Integer getId() {
        return Id;
    }

    public void setId(Integer id) {
        Id = id;
    }

    public String getName() {
        return Name;
    }

    public void setName(String name) {
        Name = name;
    }
}

SQL：

CREATE TABLE public.TEST
(
    Id INT PRIMARY KEY,
    Name VARCHAR(255)
);

日志：

May 14, 2017 9:20:30 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate Core {5.2.10.Final}
May 14, 2017 9:20:30 PM org.hibernate.cfg.Environment <clinit>
INFO: HHH000206: hibernate.properties not found
May 14, 2017 9:20:31 PM org.hibernate.annotations.common.reflection.java.JavaReflectionManager <clinit>
INFO: HCANN000001: Hibernate Commons Annotations {5.0.1.Final}
May 14, 2017 9:20:31 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using Hibernate built-in connection pool (not for production use!)
May 14, 2017 9:20:31 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001005: using driver [org.postgresql.Driver] at URL [jdbc:postgresql://localhost:5432/digitallibraryreports]
May 14, 2017 9:20:31 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {user=postgres, password=****}
May 14, 2017 9:20:31 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
May 14, 2017 9:20:31 PM org.hibernate.engine.jdbc.connections.internal.PooledConnections <init>
INFO: HHH000115: Hibernate connection pool size: 1 (min=1)
May 14, 2017 9:20:31 PM org.hibernate.dialect.Dialect <init>
INFO: HHH000400: Using dialect: org.hibernate.dialect.PostgreSQL95Dialect
May 14, 2017 9:20:31 PM org.hibernate.engine.jdbc.env.internal.LobCreatorBuilderImpl useContextualLobCreation
INFO: HHH000424: Disabling contextual LOB creation as createClob() method threw error : java.lang.reflect.InvocationTargetException
May 14, 2017 9:20:31 PM org.hibernate.type.BasicTypeRegistry register
INFO: HHH000270: Type registration [java.util.UUID] overrides previous : org.hibernate.type.UUIDBinaryType@6253c26
May 14, 2017 9:20:31 PM org.hibernate.hql.internal.QuerySplitter concreteQueries
WARN: HHH000183: no persistent classes found for query class: FROM Test
May 14, 2017 9:20:31 PM org.hibernate.hql.internal.QueryTranslatorFactoryInitiator initiateService
INFO: HHH000397: Using ASTQueryTranslatorFactory

Answer 1

您需要在SessionFactory中注册entites。您可以通过以下方式编辑hibernate.cfg.xml来完成此操作：

<session-factory>
  ...
  <mapping class="some.pack.Test" />
  ...
</session-factory>

您也可以使用Spring扫描包以添加entites。或者，出于测试目的，来自here的EntityScanner。

请删除与EntityManager相关的所有行并使用Session。删除它：

EntityManager em = sessionFactory.createEntityManager();

Answer 2

Hibernate SessionFactory不知道你的实体。您需要将以下资源添加到标记内的hibernate.cfg.xml文件中，并使用正确的hbm.xml文件名替换Entity。

<session-factory>
.
.
.
<mapping resource="Entity.hbm.xml"/> 
</session-factory>

为什么hibernate不从db返回实体，但是给定的表有数据？

2 个答案: