Hibernate复合主键映射

    通常做法是将主键相关字段放到一个单独的类中，但是这样类是有要求的：
* 必须实现序列化接口
* 覆盖equals和hashcode方法

    示例：TObject类有复合主键aPK、bPK
    TObject类：

public class TObject {
	private CompositePK compositePK;
	private String name;
	
	public CompositePK getCompositePK() {
		return compositePK;
	}
	public void setCompositePK(CompositePK compositePK) {
		this.compositePK = compositePK;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}	
}

    CompositePK类：

public class CompositePK implements Serializable {
	private int aPK;
	private int bPK;
	
	public int getaPK() {
		return aPK;
	}

	public void setaPK(int aPK) {
		this.aPK = aPK;
	}

	public int getbPK() {
		return bPK;
	}

	public void setbPK(int bPK) {
		this.bPK = bPK;
	}

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + aPK;
		result = prime * result + bPK;
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		final CompositePK other = (CompositePK) obj;
		if (aPK != other.aPK)
			return false;
		if (bPK != other.bPK)
			return false;
		return true;
	}
}

    TObject.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="com.zero.hibernate.vo.TObject" table="t_tobject">
		<composite-id name="compositePK">
			<key-property name="aPK"/>
			<key-property name="bPK"/>
		</composite-id>
		<property name="name" />
	</class>
</hibernate-mapping>

    生成的建表语句：

    drop table if exists t_tobject

    create table t_tobject (
        aPK integer not null,
        bPK integer not null,
        name varchar(255),
        primary key (aPK, bPK)
    )

    测试：

TObject tObject = new TObject();
CompositePK pk = new CompositePK();
pk.setaPK(1234);
pk.setbPK(1235);
tObject.setCompositePK(pk);

session.save(tObject);

CompositePK pk = new CompositePK();
pk.setaPK(1234);
pk.setbPK(1235);

TObject tObject=(TObject) session.load(TObject.class, pk);
System.out.println(tObject.getName());

//Hibernate: select tobject0_.aPK as aPK1_0_0_, tobject0_.bPK as bPK2_0_0_, tobject0_.name as name3_0_0_ from t_tobject tobject0_ where tobject0_.aPK=? and tobject0_.bPK=?
//zero