@MappedSuperclass的用法

最新推荐文章于 2024-08-14 10:16:54 发布

转载最新推荐文章于 2024-08-14 10:16:54 发布 · 251 阅读

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本文探讨了Java Hibernate框架中实体类通过继承@MappedSuperclass与@Entity注解时的不同表现，具体分析了如何影响数据库表的生成及字段映射。

实体类baseEntity.java

package com.rock.cft.hibernate;
import java.util.Date;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;
//@MappedSuperclass 用在父类上面。当这个类肯定是父类时，加此标注。如果改成@Entity，则继承后，多个类继承，只会生成一个表，而不是多个继承，生成多个表
@MappedSuperclass
public abstract class BaseEntity {
  private Integer id;// 数据库主键
 private Date creationTime;//创建时间
 private Date modificationTime;//修改时间
 
 @Id
 @GeneratedValue(strategy = GenerationType.AUTO)
 public Integer getId() {
  return id;
 }
 public void setId(Integer id) {
  this.id = id;
 }
 public Date getCreationTime() {
  return creationTime;
 }
 public void setCreationTime(Date creationTime) {
  this.creationTime = creationTime;
 }
 public Date getModificationTime() {
  return modificationTime;
 }
 public void setModificationTime(Date modificationTime) {
  this.modificationTime = modificationTime;
 }
 
}

实体类Test_No1.java
 package com.rock.cft.test.model;
import java.io.Serializable;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table;
import com.rock.cft.hibernate.BaseEntity;
@Entity
@Table(name="test_no2")
public class Test_No1 extends BaseEntity implements Serializable {
 

 private String name;
 private int age;
 
 public String getName() {
  return name;
 }
 public void setName(String name) {
  this.name = name;
 }
 public int getAge() {
  return age;
 }
 public void setAge(int age) {
  this.age = age;
 }
  
}
实体类Test_NO2.javapackage com.rock.cft.test.model;
import java.io.Serializable;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Table;
import com.rock.cft.hibernate.BaseEntity;
@Entity
@Table(name="test_no2")
public class Test_NO2 extends BaseEntity implements Serializable {
 
 
 private Date testBri;
 
 private String testAdr;
 
 public Date getTestBri() {
  return testBri;
 }
 public void setTestBri(Date testBri) {
  this.testBri = testBri;
 }
 public String getTestAdr() {
  return testAdr;
 }
 public void setTestAdr(String testAdr) {
  this.testAdr = testAdr;
 }
 
 

 
 
} 
 
这样在生成表的时候只生成了：test_no1、test_no2两张表，而且两张表中都含有id、creationTime、modificationTime三个属性
 
但是如果把@MappedSuperclass换成@Entity那么就会另外在生成一张baseEntity的表