Question

我是Hibernate Annotations的新手，我想尝试一个例子。

我有两个类（Node和HyperEdge），当我运行我的应用程序时，它只为Node创建一个表而不是为HyperEdge创建一个表。

这是我开发的代码：

节点：

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

@Entity
@Table(name="Node")
public class Node {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;

    @Column
    private String name;

    @Column(name="\"group\"")
    private Integer group;

    public Node() {
        super();
        // TODO Auto-generated constructor stub
    }

    public Node(Integer id, String name, Integer group) {
        super();
        this.id = id;
        this.name = name;
        this.group = group;
    }

    public Integer getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getGroup() {
        return group;
    }

    public void setGroup(Integer group) {
        this.group = group;
    }

}

HyperEdge：

import javax.persistence.Column;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Table(name="HyperEdge")
public class HyperEdge {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Integer id;

    @Column
    private String title;

    public HyperEdge() {
        super();
        // TODO Auto-generated constructor stub
    }
    public HyperEdge(Integer id, String title) {
        super();
        this.id = id;
        this.title = title;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }

}

hibernate.cfg.xml：

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>
        <!-- Database connection settings -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/exhiber</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>

        <property name="connection.pool_size">1</property>
        <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
        <property name="current_session_context_class">thread</property>
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
        <property name="show_sql">true</property>
        <property name="hbm2ddl.auto">create</property>

        <mapping class="com.hib.ex.entity.Node" />
        <mapping class="com.hib.ex.entity.HyperEdge" />

    </session-factory>

</hibernate-configuration>

HibernateDao：

import java.util.List;

import org.hibernate.Session;
import org.hibernate.SessionFactory;

import com.hib.ex.entity.HyperEdge;
import com.hib.ex.entity.Node;

public class HibExDao {

    public void saveNode(Node noeud) {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();
        session.beginTransaction();

        session.save(noeud);

        session.getTransaction().commit();
        session.close();

    }

    public List listNode() {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();

        List nodes = session.createQuery("FROM Node").list();
        session.close();
        return nodes;

    }

    public Node readNode(Integer id) {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();

        Node noeud = (Node) session.get(Node.class, id);
        session.close();
        return noeud;

    }

    public void saveHyperEdge(HyperEdge he, String chaine) {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();
        session.beginTransaction();

        he.setTitle(chaine);

        session.save(he);
        session.getTransaction().commit();
        session.close();

    }

    public List listHyperEdge() {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();

        List hyperedges = session.createQuery("FROM HyperEdge").list();
        session.close();
        return hyperedges;

    }

    public HyperEdge readHyperEdge(Integer id) {

        SessionFactory sf = HibExUtil.getSessionFactory();
        Session session = sf.openSession();

        HyperEdge hyperEdge = (HyperEdge) session.get(HyperEdge.class, id);
        session.close();
        return hyperEdge;

    }

}

主要班级：

import java.util.List;

import com.hib.ex.dao.HibExDao;
import com.hib.ex.entity.HyperEdge;
import com.hib.ex.entity.Node;

public class Run {


    public static void main(String[] args) {

        HibExDao dao = new HibExDao();

        System.out.println("****************WRITING****************");
        Node n1 = new Node();
        n1.setName("toto");
        dao.saveNode(n1);
        System.out.println("Node saved!");
        Node n2 = new Node();
        n2.setName("lala");
        dao.saveNode(n2);
        System.out.println("Node saved!");

        System.out.println("\n****************READING****************");
        List nodes = dao.listNode();
        System.out.println("Name in Node number 2 is: " + dao.readNode(2).getName());

    }

}

有什么问题？我该如何解决？

谢谢！

Answer 1

也许您必须将@Entity注释添加到HyperEdge类

Answer 2

您的@Entity课程中缺少

HyperEdge注释

@Entity注释用于将此类标记为实体bean 。所以该类至少应该有一个包范围无参构造函数。

@Table注释用于指定要保留数据的表。 name属性引用表名。如果未指定@Table注释，则Hibernate默认使用类名作为表名。

Answer 3

在HyperEdge类中，您必须添加@Entity注释，以便hibernate可以将其视为要与数据库中的表HyperEdge进行映射的实体。

@Entity
@Table(name="HyperEdge")
public class HyperEdge {

Hibernate没有创建表

3 个答案: