[英]Java JPA flush() doesn't update database in one to many relationship?
[英]JPA - why my one to many relationship does not appear in database
我正在學習JPA,我有2個實體(Customer和CheckingAccount),其中第一個實體與第二個實體具有一對多關系。 CheckingAccount子類是BankAccount類。 我正在使用MySQL。
我在一個測試程序中創建2個支票帳戶,並將它們都分配給我創建的一位客戶。
堅持一切並檢查數據庫后,我希望在CheckingAccount表中看到2行,在Customer表中看到2行,表明該客戶有2個支票帳戶,但我只看到一行,並且Accounts列的值為“ blob”,我希望看到一個帳號。
我是否應該在“客戶”表中看到2行以表明該客戶有2個支票帳戶?
這是我的客戶實體...
package com.gmail.gmjord;
import java.io.Serializable;
import java.lang.String;
import java.util.ArrayList;
import java.util.List;
import javax.persistence.*;
/**
* Entity implementation class for Entity: Customer
*
*/
@Entity
public class Customer implements Serializable {
@Id
@GeneratedValue
private String id;
@Column(nullable = false)
private String name;
@Column(nullable = false)
private List<BankAccount> accounts;
@Column(nullable = false)
private String infoId;
@Column(nullable = false)
private String pin;
private static final long serialVersionUID = 1L;
public Customer() {
super();
accounts = new ArrayList<BankAccount>();
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public int getAccountsLength() {
return this.accounts.size();
}
public boolean isAccountsNull() {
if (accounts == null) {
return true;
} else {
return false;
}
}
public List<BankAccount> getAccounts() {
return accounts;
}
public void setAccounts(List<BankAccount> accounts) {
this.accounts = accounts;
}
public String getInfoId() {
return this.infoId;
}
public void setInfoId(String infoId) {
this.infoId = infoId;
}
public String getPin() {
return this.pin;
}
public void setPin(String pin) {
this.pin = pin;
}
}
這是我的CheckingAccount實體...
package com.gmail.gmjord;
import com.gmail.gmjord.BankAccount;
import java.io.Serializable;
import javax.persistence.*;
/**
* Entity implementation class for Entity: CheckingAccount
*
*/
@Entity
public class CheckingAccount extends BankAccount implements Serializable {
private static final long serialVersionUID = 1L;
public CheckingAccount() {
super();
}
}
這是我的CheckingAccount的BankAccount超類...
package com.gmail.gmjord;
import java.io.Serializable;
import java.lang.String;
import javax.persistence.*;
/**
* Entity implementation class for Entity: BankAccount
*
*/
@MappedSuperclass
public abstract class BankAccount implements Serializable {
@Id
@Column(nullable=false)
private String accountNum;
@Column(nullable=false)
private String balance;
@Column(nullable=false)
private String accountType;
private static final long serialVersionUID = 1L;
public BankAccount() {
super();
}
public String getAccountNum() {
return this.accountNum;
}
public void setAccountNum(String accountNum) {
this.accountNum = accountNum;
}
public String getBalance() {
return this.balance;
}
public void setBalance(String balance) {
this.balance = balance;
}
public String getAccountType() {
return this.accountType;
}
public void setAccountType(String accountType) {
this.accountType = accountType;
}
}
當您將“一對多”用於2個支票帳戶和一個客戶時,數據庫中將具有以下結構(僅是一個任意示例-我使用json格式只是為了更好地解釋,但將其屬性想象為列):
客戶= [{id:1,姓名:安德森先生}]
CheckingAccount = [{{id:1,值:$ 100,id_customer:1},{id:2,值:$ 250,id_customer:1}]
客戶表中不需要兩行。 當您具有一對多關系時,您在多關系方表中具有外鍵。
知道了..有意義嗎?
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