【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

===========================================

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;
    }
}

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原文地址：https://www.cnblogs.com/yangchongxing/p/10405151.html