JPA复合主键使用

原文链接：https://blog.csdn.net/mypop/article/details/6149538
数据库表
create table RENT_CERT_VENDOR_TYPE
(
CERT_TYPE_ID NUMBER not null,
VENDOR_ID NUMBER not null,
CERT_TYPE_VENDOR_ID NUMBER not null
)
;
alter table RENT_CERT_VENDOR_TYPE
add constraint PK_RENT_CERT_VENDOR_TYPE primary key (CERT_TYPE_ID, VENDOR_ID);
alter table RENT_CERT_VENDOR_TYPE
add constraint FK_CERT_VENDOR_CERT_TYPE_ID foreign key (CERT_TYPE_ID)
references RENT_CERT_TYPE (ID);
alter table RENT_CERT_VENDOR_TYPE
add constraint FK_CERT_VENDOR_VENDOR_ID foreign key (VENDOR_ID)
references RENT_VENDOR (ID);

一、使用@EmbeddedId

eclipse生成的复合主键类
@Embeddable
public class RentCertVendorTypePK implements Serializable {
//default serial version id, required for serializable classes.
private static final long serialVersionUID = 1L;

@Column(name="CERT_TYPE_ID")
private long certTypeId;

@Column(name="VENDOR_ID")
private long vendorId;

public RentCertVendorTypePK() {
}
public long getCertTypeId() {
	return this.certTypeId;
}
public void setCertTypeId(long certTypeId) {
	this.certTypeId = certTypeId;
}
public long getVendorId() {
	return this.vendorId;
}
public void setVendorId(long vendorId) {
	this.vendorId = vendorId;
}

public boolean equals(Object other) {
	if (this == other) {
		return true;
	}
	if (!(other instanceof RentCertVendorTypePK)) {
		return false;
	}
	RentCertVendorTypePK castOther = (RentCertVendorTypePK)other;
	return 
		(this.certTypeId == castOther.certTypeId)
		&& (this.vendorId == castOther.vendorId);

}

public int hashCode() {
	final int prime = 31;
	int hash = 17;
	hash = hash * prime + ((int) (this.certTypeId ^ (this.certTypeId >>> 32)));
	hash = hash * prime + ((int) (this.vendorId ^ (this.vendorId >>> 32)));
	
	return hash;
}

}

主键类必需满足下列条件：
(1)必需被序列化
(2)必需有一个公共的无参构造方法
(3)必需实现equals()和hashCode()方法

使用主键类
@Entity
@Table(name=“RENT_CERT_VENDOR_TYPE”)
public class RentCertVendorType implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private RentCertVendorTypePK id;

@Column(name="CERT_TYPE_VENDOR_ID")
private BigDecimal certTypeVendorId;

//bi-directional many-to-one association to RentCertType
@ManyToOne
@JoinColumn(name="CERT_TYPE_ID")
private RentCertType rentCertType;

public RentCertVendorType() {
}

public RentCertVendorTypePK getId() {
	return this.id;
}

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

public BigDecimal getCertTypeVendorId() {
	return this.certTypeVendorId;
}

public void setCertTypeVendorId(BigDecimal certTypeVendorId) {
	this.certTypeVendorId = certTypeVendorId;
}

public RentCertType getRentCertType() {
	return this.rentCertType;
}

public void setRentCertType(RentCertType rentCertType) {
	this.rentCertType = rentCertType;
}

}

使用eclipse生成JPA实体的向导界面中，复合主键类的key generator指定为auto，则插件会自动识别数据库表中的复合主键，并生成复合主键类。

这种方法在Entity中获取复合主键中的某列属性如VENDOR_ID时，需要rentCertVendorType.getRentCertVendorTypePK().getVendorId()，其中rentCertVendorType为RentCertVendorType类对象。

二、使用@IdClass

主键类
public class RentCertVendorTypePK implements Serializable {
//default serial version id, required for serializable classes.
private static final long serialVersionUID = 1L;

private long certTypeId;

private long vendorId;

public RentCertVendorTypePK() {
}
public long getCertTypeId() {
	return this.certTypeId;
}
public void setCertTypeId(long certTypeId) {
	this.certTypeId = certTypeId;
}
public long getVendorId() {
	return this.vendorId;
}
public void setVendorId(long vendorId) {
	this.vendorId = vendorId;
}

public boolean equals(Object other) {
	if (this == other) {
		return true;
	}
	if (!(other instanceof RentCertVendorTypePK)) {
		return false;
	}
	RentCertVendorTypePK castOther = (RentCertVendorTypePK)other;
	return 
		(this.certTypeId == castOther.certTypeId)
		&& (this.vendorId == castOther.vendorId);

}

public int hashCode() {
	final int prime = 31;
	int hash = 17;
	hash = hash * prime + ((int) (this.certTypeId ^ (this.certTypeId >>> 32)));
	hash = hash * prime + ((int) (this.vendorId ^ (this.vendorId >>> 32)));
	
	return hash;
}

}

Entity
@IdClass(RentCertVendorTypePK.class)
@Entity
@Table(name=“RENT_CERT_VENDOR_TYPE”)
public class RentCertVendorType implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Column(name=“CERT_TYPE_ID”)
private long certTypeId;

@Id
    @Column(name="VENDOR_ID")
private long vendorId;

@Column(name="CERT_TYPE_VENDOR_ID")
private BigDecimal certTypeVendorId;

//bi-directional many-to-one association to RentCertType
@ManyToOne
@JoinColumn(name="CERT_TYPE_ID")
private RentCertType rentCertType;

public RentCertVendorType() {
}

public RentCertVendorTypePK getId() {
	return this.id;
}

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

public BigDecimal getCertTypeVendorId() {
	return this.certTypeVendorId;
}

public void setCertTypeVendorId(BigDecimal certTypeVendorId) {
	this.certTypeVendorId = certTypeVendorId;
}

public RentCertType getRentCertType() {
	return this.rentCertType;
}

public void setRentCertType(RentCertType rentCertType) {
	this.rentCertType = rentCertType;
}

}

这种方法在Entity中获取复合主键中的某列属性如VENDOR_ID时，只需要rentCertVendorType.getVendorId()，其中rentCertVendorType为RentCertVendorType类对象。