Hibernate 备忘录

Hibernate关联映射

最新推荐文章于 2025-12-01 14:38:10 发布

最新推荐文章于 2025-12-01 14:38:10 发布 · 118 阅读

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#Hibernate #XML #数据结构

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本文详细介绍Hibernate中一对一关联映射的实现方式，包括外键关联、主键关联和联合主键等场景，并对比了XML配置与Annotation配置的区别。

1. 生成表

两种方法，方法一，在Hibernate.cfg.xml配置文件中添加如下配置，则App运行过程中如数据库中表不存在，或根据相关条件生成新表，配置如下

<property name="hbm2ddl.auto">update</property>

方法二，运用SchemaExport生成新表，如下代码

public static void main(String[] args) {
SchemaExport se = new SchemaExport(new AnnotationConfiguration().configure());
se.create(true, true);
}

为了和Hibernate 备忘录-续风格统一，这里对本文做一修改，本文包括一对一外键单向关联、一对一外键双向关联、一对一主键单向关联、一对一主键双向关联、联合主键5个部分，每部分包括：描述、Annotation配置、结果说明，老版本Hibernate的XML配置；

2. 一对一单向外键关联

2.1 如下图所示为一个一对一关系的映射，这里所有都用这个映射为例；

如上图，Husband和Wife为一对一关系，

2.2Annotation配置代码

@Entity
public class Husband {
	private int id;
	private String name;
	private Wife wife;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@OneToOne(cascade=CascadeType.ALL)
	@JoinColumn(name="wifeId")
	public Wife getWife() {
		return wife;
	}
	public void setWife(Wife wife) {
		this.wife = wife;
	}	
}

@Entity
public class Wife {
	private int id;
	private String name;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

2.3、此配置下数据库中生成表结构如下：

2.4、老版本HibernateＸＭＬ配置

<hibernate-mapping>
	<class name="com.kylin.test.Husband" dynamic-update="true">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
		<many-to-one name="wife" column="wideId" unique="true"></many-to-one>
    </class>
</hibernate-mapping>

<hibernate-mapping>
	<class name="com.kylin.test.Wife" dynamic-update="true">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
    </class>
</hibernate-mapping>

3. 一对一双向外键关联

3.1 同上一Husband Wife来描述一对一双向外键关联

3.2 给出Annotation配置代码

@Entity
public class Husband {
	private int id;
	private String name;
	private Wife wife;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@OneToOne
	@JoinColumn(name="wifeId") 
	public Wife getWife() {
		return wife;
	}
	public void setWife(Wife wife) {
		this.wife = wife;
	}	
}

@Entity
public class Wife {
	private int id;
	private String name;
	private Husband husband;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@OneToOne(mappedBy="wife") 
	public Husband getHusband() {
		return husband;
	}
	public void setHusband(Husband husband) {
		this.husband = husband;
	}
}

3.3、数据库中生成表如下

3.4、老版本XML

<hibernate-mapping>
	<class name="com.kylin.test.Husband" dynamic-update="true">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
		<many-to-one name="wife" column="wideId" unique="true"></many-to-one>
    </class>
</hibernate-mapping>

<hibernate-mapping>
	<class name="com.kylin.test.Wife" dynamic-update="true">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
		<one-to-one name="husband" property-ref="wife"></one-to-one>
    </class>
</hibernate-mapping>

3.5比较。运行结果和上面2导出的表相同；

总结比较Annotation配置和XML配置，

第一、使用XML配置核心要注意点：

<many-to-one name="wife" column="wideId" unique="true"></many-to-one>

<one-to-one name="husband" property-ref="wife"></one-to-one>

如上分别为Husband.hbm.xml和Wife.hbm.xml上指定一对一双向映射的配置，其中Wife中property-ref值必须与Husband中name值相同

第二、明显Annotation配置更容易明白，XML配置比较难理解，所以一般采取Annotation；

4. 一对一单向主键关联

4.1 用Husband及Wife为例说明

4.2 Annotation配置代码

@Entity
public class Husband {
	private int id;
	private String name;
	private Wife wife;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@OneToOne(cascade=CascadeType.ALL)
	@PrimaryKeyJoinColumn
	public Wife getWife() {
		return wife;
	}
	public void setWife(Wife wife) {
		this.wife = wife;
	}	
}

@Entity
public class Wife {
	private int id;
	private String name;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

4.3.导出的表结构

4.4XML配置

<hibernate-mapping>
	<class name="com.kylin.test.Husband" dynamic-update="true">
		<id name="id">
			<generator class="foreign">
				<param name="property">wife</param>
			</generator>
		</id>
		<property name="name"/>
		<one-to-one name="wife" constrained="true"></one-to-one>
    </class>
</hibernate-mapping>

<hibernate-mapping>
	<class name="com.kylin.test.Wife" dynamic-update="true">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
    </class>
</hibernate-mapping>

5. 一对一双向主键关联

5.1、同上一Husband Wife为例

5.2、给出配置代码

@Entity
public class Husband {
	private int id;
	private String name;
	private Wife wife;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@OneToOne(cascade=CascadeType.ALL)
	@PrimaryKeyJoinColumn
	public Wife getWife() {
		return wife;
	}
	public void setWife(Wife wife) {
		this.wife = wife;
	}	
}

@Entity
public class Wife {
	private int id;
	private String name;
	private Husband husband;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@OneToOne  
    @PrimaryKeyJoinColumn 
	public Husband getHusband() {
		return husband;
	}
	public void setHusband(Husband husband) {
		this.husband = husband;
	}
}

5.3表结构

5.4、老版本XML

<hibernate-mapping>
	<class name="com.kylin.test.Husband" dynamic-update="true">
		<id name="id">
			<generator class="foreign">
				<param name="property">wife</param>
			</generator>
		</id>
		<property name="name"/>
		<one-to-one name="wife" constrained="true"></one-to-one>
    </class>
</hibernate-mapping>

<hibernate-mapping>
	<class name="com.kylin.test.Wife" dynamic-update="true">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
		<one-to-one name="husband" property-ref="wife"></one-to-one>
    </class>
</hibernate-mapping>

6. 联合主键

6.1 同上，但这里只给出Annotation配置例子：

6.2.配置代码

@Entity
public class Husband {
	private int id;
	private String name;
	private Wife wife;
	@Id
	@GeneratedValue
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	@OneToOne
	@JoinColumns(
			{
				@JoinColumn(name="wifeId", referencedColumnName="id"),
				@JoinColumn(name="wifeName", referencedColumnName="name")
			}
		)
	public Wife getWife() {
		return wife;
	}
	public void setWife(Wife wife) {
		this.wife = wife;
	}
}

@Entity
@IdClass(WifePK.class)
public class Wife {
	private int id;
	private String name;
	private int age;
	@Id
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	@Id
	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;
	}
}

public class WifePK {
	private int id;
	private String name;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
}

6.3，表结构如下