用myeclipse的Hibernate 反向引擎 生成 数据库的 entity

把 Myeclipse 转到DB Browser

新建一个Database Connection driver

然后找到要反向工程的表

右键->Hibernate Reverse Engineering

然后，选好entity缩放的目录

对 Create POJO<>DB Table mapping information 打钩

然后点选 AddHibernate mapping annotations to POJO

再点选Update Hibernate configuration with mapping resource location

其他钩全部去掉，点击下一步，直至结束就可以

这样生成的entity

这里只说一对多和多对一

例：用户和组为多对一关系，双向

用户类：

package com.hibernate.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

/**
 * Tuser entity. @author MyEclipse Persistence Tools
 */
@Entity
@Table(name = "tuser", catalog = "test")
public class Tuser implements java.io.Serializable {

  // Fields

  /**
   * 
   */
  private static final long serialVersionUID = -7792597282750540598L;
  private Integer id;
  private Tgroup tgroup;
  private String name;

  // Constructors

  /** default constructor */
  public Tuser() {
  }

  /** full constructor */
  public Tuser(Tgroup tgroup, String name) {
    this.tgroup = tgroup;
    this.name = name;
  }

  // Property accessors
  @Id
  @GeneratedValue
  @Column(name = "id", unique = true, nullable = false)
  public Integer getId() {
    return this.id;
  }

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

  @ManyToOne(fetch = FetchType.LAZY)
  @JoinColumn(name = "groupid")
  public Tgroup getTgroup() {
    return this.tgroup;
  }

  public void setTgroup(Tgroup tgroup) {
    this.tgroup = tgroup;
  }

  @Column(name = "name")
  public String getName() {
    return this.name;
  }

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

}

组类：

package com.hibernate.entity;

import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;

/**
 * Tgroup entity. @author MyEclipse Persistence Tools
 */
@Entity
@Table(name = "tgroup", catalog = "test")
public class Tgroup implements java.io.Serializable {

  // Fields

  /**
   * 
   */
  private static final long serialVersionUID = -7208715716759269846L;
  private Integer id;
  private String name;
  private Set<Tuser> tusers = new HashSet<Tuser>(0);

  // Constructors

  /** default constructor */
  public Tgroup() {
  }

  /** full constructor */
  public Tgroup(String name, Set<Tuser> tusers) {
    this.name = name;
    this.tusers = tusers;
  }

  // Property accessors
  @Id
  @GeneratedValue
  @Column(name = "id", unique = true, nullable = false)
  public Integer getId() {
    return this.id;
  }

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

  @Column(name = "name")
  public String getName() {
    return this.name;
  }

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

  @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "tgroup")
  public Set<Tuser> getTusers() {
    return this.tusers;
  }

  public void setTusers(Set<Tuser> tusers) {
    this.tusers = tusers;
  }

}

<?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">

<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>

  <session-factory>
    <property name="dialect">
      org.hibernate.dialect.MySQLDialect
    </property>
    <property name="connection.url">
      jdbc:mysql://localhost/test
    </property>
    <property name="connection.username">root</property>
    <property name="connection.password">root</property>
    <property name="connection.driver_class">
      com.mysql.jdbc.Driver
    </property>

    <!-- JDBC connection pool (use the built-in) -->
    <property name="connection.pool_size">1</property>



    <!-- Enable Hibernate's automatic session context management -->
    <property name="current_session_context_class">thread</property>

    <!-- Disable the second-level cache  -->
    <property name="cache.provider_class">
      org.hibernate.cache.NoCacheProvider
    </property>

    <!-- Echo all executed SQL to stdout -->
    <property name="show_sql">true</property>

    <property name="format_sql">true</property>
    <!--
      <mapping class="com.hibernate.entity.Husband" />
      <mapping class="com.hibernate.entity.Wife" />
      ===================================================
      <mapping class="com.hibernate.entity.Teacher" />
      <mapping class="com.hibernate.entity.Student" />
    -->

    <mapping class="com.hibernate.entity.Tgroup" />
    <mapping class="com.hibernate.entity.Tuser" />
  </session-factory>

</hibernate-configuration>

这里会抛错，原因是user类中没有写cascade = CascadeType.ALL

在Tuser类的@ManyToOne(fetch = FetchType.LAZY)中加上cascade = CascadeType.ALL就可以了

@Test
  public void saveUser() {
    Tgroup g = new Tgroup();
    g.setName("g1");
    
    Tuser u = new Tuser();
    u.setName("u1");
    u.setTgroup(g);
    
    Session s = sessionFactory.getCurrentSession();
    s.beginTransaction();
    s.save(u);
    s.getTransaction().commit();//这里会抛错，原因是user类中没有写cascade = CascadeType.ALL
，而默认是不写的。 }

这个方法也可以持久化两个类

@Test
  public void saveGroup() {
    Tgroup g = new Tgroup();
    g.setName("g1");
    
    Tuser u = new Tuser();
    u.setName("u1");
    u.setTgroup(g);
    
    g.getTusers().add(u);
    
    Session s = sessionFactory.getCurrentSession();
    s.beginTransaction();
    s.save(g);
    
    s.getTransaction().commit();
  }