【hibernate】映射继承关系

转载：https://www.cnblogs.com/yangchongxing/p/10405151.html

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

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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