【hibernate】映射继承关系
转载：https://www.cnblogs.com/yangchongxing/p/10405151.html
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1、每个带有隐式多态的具体类使用一个表
2、每个带有联合的具体类使用一个表
3、每个类层次结构使用一个表
4、每个带有联结的子类使用一个表
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1、每个带有隐式多态的具体类使用一个表
@MappedSuperclass 超类的属性被忽略不会被持久化
package cn.ycx.study.hibernate.entity;
import javax.persistence.MappedSuperclass;
@MappedSuperclass
public abstract class BillingDetails {
protected String owner;
public String getOwner() {
return owner;
}
public void setOwner(String owner) {
this.owner = owner;
}
}
子类
package cn.ycx.study.hibernate.entity; import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
@Entity
public class CreditCard extends BillingDetails {
@Id
@GeneratedValue(generator="id_generator")
protected Long id;
protected String cardNumber;
protected String expMonth;
protected String expYear;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getCardNumber() {
return cardNumber;
}
public void setCardNumber(String cardNumber) {
this.cardNumber = cardNumber;
}
public String getExpMonth() {
return expMonth;
}
public void setExpMonth(String expMonth) {
this.expMonth = expMonth;
}
public String getExpYear() {
return expYear;
}
public void setExpYear(String expYear) {
this.expYear = expYear;
}
}
子类
package cn.ycx.study.hibernate.entity;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
@Entity
public class BankAccount extends BillingDetails {
@Id
@GeneratedValue(generator="id_generator")
protected Long id;
protected String account;
protected String bankname;
protected String swift;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getAccount() {
return account;
}
public void setAccount(String account) {
this.account = account;
}
public String getBankname() {
return bankname;
}
public void setBankname(String bankname) {
this.bankname = bankname;
}
public String getSwift() {
return swift;
}
public void setSwift(String swift) {
this.swift = swift;
}
}
生成的 SQL 表结构
CREATE TABLE `creditcard` (
`id` BIGINT(20) NOT NULL,
`owner` VARCHAR(255) NULL DEFAULT NULL,
`cardNumber` VARCHAR(255) NULL DEFAULT NULL,
`expMonth` VARCHAR(255) NULL DEFAULT NULL,
`expYear` VARCHAR(255) NULL DEFAULT NULL,
PRIMARY KEY (`id`)
)
COLLATE='utf8mb4_general_ci'
ENGINE=InnoDB
; CREATE TABLE `bankaccount` (
`id` BIGINT(20) NOT NULL,
`owner` VARCHAR(255) NULL DEFAULT NULL,
`account` VARCHAR(255) NULL DEFAULT NULL,
`bankname` VARCHAR(255) NULL DEFAULT NULL,
`swift` VARCHAR(255) NULL DEFAULT NULL,
PRIMARY KEY (`id`)
)
COLLATE='utf8mb4_general_ci'
ENGINE=InnoDB
;
2、每个带有联合的具体类使用一个表
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS) 策略
package cn.ycx.study.hibernate.entity;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
@Entity
@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)
public abstract class BillingDetails {
@Id
@GeneratedValue(generator="id_generator")
protected Long id;
protected String owner;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getOwner() {
return owner;
}
public void setOwner(String owner) {
this.owner = owner;
}
}
子类
package cn.ycx.study.hibernate.entity; import javax.persistence.Entity;
@Entity
public class CreditCard extends BillingDetails {
protected String cardNumber;
protected String expMonth;
protected String expYear;
public String getCardNumber() {
return cardNumber;
}
public void setCardNumber(String cardNumber) {
this.cardNumber = cardNumber;
}
public String getExpMonth() {
return expMonth;
}
public void setExpMonth(String expMonth) {
this.expMonth = expMonth;
}
public String getExpYear() {
return expYear;
}
public void setExpYear(String expYear) {
this.expYear = expYear;
}
}
子类
package cn.ycx.study.hibernate.entity;
import javax.persistence.Entity;
@Entity
public class BankAccount extends BillingDetails {
protected String account;
protected String bankname;
protected String swift;
public String getAccount() {
return account;
}
public void setAccount(String account) {
this.account = account;
}
public String getBankname() {
return bankname;
}
public void setBankname(String bankname) {
this.bankname = bankname;
}
public String getSwift() {
return swift;
}
public void setSwift(String swift) {
this.swift = swift;
}
}
生成的 SQL 表结构
CREATE TABLE `bankaccount` (
`id` BIGINT(20) NOT NULL,
`owner` VARCHAR(255) NULL DEFAULT NULL,
`account` VARCHAR(255) NULL DEFAULT NULL,
`bankname` VARCHAR(255) NULL DEFAULT NULL,
`swift` VARCHAR(255) NULL DEFAULT NULL,
PRIMARY KEY (`id`)
)
COLLATE='utf8mb4_general_ci'
ENGINE=InnoDB
; CREATE TABLE `creditcard` (
`id` BIGINT(20) NOT NULL,
`owner` VARCHAR(255) NULL DEFAULT NULL,
`cardNumber` VARCHAR(255) NULL DEFAULT NULL,
`expMonth` VARCHAR(255) NULL DEFAULT NULL,
`expYear` VARCHAR(255) NULL DEFAULT NULL,
PRIMARY KEY (`id`)
)
COLLATE='utf8mb4_general_ci'
ENGINE=InnoDB
;
3、每个类层次结构使用一个表
@Inheritance(strategy=InheritanceType.SINGLE_TABLE) 策略
@DiscriminatorColumn(name="bd_type") 指定识别器列名，不指定默认时 DTYPE。
@DiscriminatorValue("CC") 指定识别器值，每种一个，
package cn.ycx.study.hibernate.entity;
import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
@Entity
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="bd_type")
public abstract class BillingDetails {
@Id
@GeneratedValue(generator="id_generator")
protected Long id;
protected String owner;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getOwner() {
return owner;
}
public void setOwner(String owner) {
this.owner = owner;
}
}
子类，识别器值 @DiscriminatorValue("CC")
package cn.ycx.study.hibernate.entity; import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
@Entity
@DiscriminatorValue("CC")
public class CreditCard extends BillingDetails {
protected String cardNumber;
protected String expMonth;
protected String expYear;
public String getCardNumber() {
return cardNumber;
}
public void setCardNumber(String cardNumber) {
this.cardNumber = cardNumber;
}
public String getExpMonth() {
return expMonth;
}
public void setExpMonth(String expMonth) {
this.expMonth = expMonth;
}
public String getExpYear() {
return expYear;
}
public void setExpYear(String expYear) {
this.expYear = expYear;
}
}
子类，识别器值 @DiscriminatorValue("BA")
package cn.ycx.study.hibernate.entity;
import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
@Entity
@DiscriminatorValue("BA")
public class BankAccount extends BillingDetails {
protected String account;
protected String bankname;
protected String swift;
public String getAccount() {
return account;
}
public void setAccount(String account) {
this.account = account;
}
public String getBankname() {
return bankname;
}
public void setBankname(String bankname) {
this.bankname = bankname;
}
public String getSwift() {
return swift;
}
public void setSwift(String swift) {
this.swift = swift;
}
}
生成的 SQL 表结构
CREATE TABLE `billingdetails` (
`bd_type` VARCHAR(31) NOT NULL,
`id` BIGINT(20) NOT NULL,
`owner` VARCHAR(255) NULL DEFAULT NULL,
`cardNumber` VARCHAR(255) NULL DEFAULT NULL,
`expMonth` VARCHAR(255) NULL DEFAULT NULL,
`expYear` VARCHAR(255) NULL DEFAULT NULL,
`account` VARCHAR(255) NULL DEFAULT NULL,
`bankname` VARCHAR(255) NULL DEFAULT NULL,
`swift` VARCHAR(255) NULL DEFAULT NULL,
PRIMARY KEY (`id`)
)
COLLATE='utf8mb4_general_ci'
ENGINE=InnoDB
;
4、每个带有联结的子类使用一个表
@Inheritance(strategy=InheritanceType.JOINED) 联结
@PrimaryKeyJoinColumn(name = "ba_id") 可以不指定，它会自动继承父类主键。
package cn.ycx.study.hibernate.entity;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
@Entity
@Inheritance(strategy=InheritanceType.JOINED)
public abstract class BillingDetails {
@Id
@GeneratedValue(generator="id_generator")
protected Long id;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
} protected String owner;
public String getOwner() {
return owner;
}
public void setOwner(String owner) {
this.owner = owner;
}
}
子类
package cn.ycx.study.hibernate.entity; import javax.persistence.Entity;
import javax.persistence.PrimaryKeyJoinColumn;
@Entity
@PrimaryKeyJoinColumn(name = "cc_id")
public class CreditCard extends BillingDetails {
protected String cardNumber;
protected String expMonth;
protected String expYear; public String getCardNumber() {
return cardNumber;
}
public void setCardNumber(String cardNumber) {
this.cardNumber = cardNumber;
}
public String getExpMonth() {
return expMonth;
}
public void setExpMonth(String expMonth) {
this.expMonth = expMonth;
}
public String getExpYear() {
return expYear;
}
public void setExpYear(String expYear) {
this.expYear = expYear;
}
}
子类
package cn.ycx.study.hibernate.entity;
import javax.persistence.Entity;
import javax.persistence.PrimaryKeyJoinColumn;
@Entity
@PrimaryKeyJoinColumn(name = "ba_id")
public class BankAccount extends BillingDetails {
protected String account;
protected String bankname;
protected String swift;
public String getAccount() {
return account;
}
public void setAccount(String account) {
this.account = account;
}
public String getBankname() {
return bankname;
}
public void setBankname(String bankname) {
this.bankname = bankname;
}
public String getSwift() {
return swift;
}
public void setSwift(String swift) {
this.swift = swift;
}
}