Java 玩框架数据库继承

请注意：我是新来玩框架的

信息：

我已经花了几个小时寻找关于使用Play Framework继承的教程或解释

然而，每个例子似乎都忽略了整个例子，这造成了混乱，因此提出这个问题的原因

作为记录，我使用的是MariaDB（aka~MySQL）

研究与文档：

• 文档-播放：不是很有帮助

• 文档-Java:，缺少完整的示例

• Stackoverflow：几个问题，以及

• 博客：缺乏完整的例子，尽管很有见地

• 搜索，对于在PlayFramework中设置eBean非常有用

然而，我可能完全被误解了，但是示例提供了将具有不同名称的列连接到表的方法，没有提及

问题/问题：

我需要利用继承（即外键等）创建一个数据库，在解释的基础上，我如何才能做到这一点

数据库架构：

我目前拥有的：

型号：用户

import io.ebean.Finder;
import io.ebean.Model;
import play.data.validation.Constraints;

import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;

@MappedSuperclass
//@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class User extends Model {

    @Id
    @GeneratedValue
    private Long userId;

    @Constraints.MaxLength(50)
    private String name;
    @Constraints.MaxLength(100)
    private String surname;

    @Constraints.Required
    @Constraints.MinLength(8)
    private String password;

    @Constraints.Email
    @Constraints.Required
    private String email;

    @Constraints.Required
    @Constraints.MaxLength(10)
    @Constraints.MinLength(10)
    @Constraints.Pattern("[0]\\d{2}[- ]{0,1}\\d{3}[- ]{0,1}\\d{4}")
    private String cellNumber;

    private Boolean emailVerified = false;
    private String token;

    public static Finder<String, User> find = new Finder<String, User>(User.class);

    public User(){}

    public User(@Constraints.MinLength(10) @Constraints.MaxLength(10) Long userId, String name, String surname, @Constraints.Required String password, @Constraints.Email @Constraints.Required String email, @Constraints.Required @Constraints.Pattern("[0]\\d{2}[- ]{0,1}\\d{3}[- ]{0,1}\\d{4}") String cellNumber, Boolean emailVerified) {
        this.userId = userId;
        this.name = name;
        this.surname = surname;
        this.password = password;
        this.email = email;
        this.cellNumber = cellNumber;
        this.emailVerified = emailVerified;
    }

import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;

import com.avaje.ebean.Model;

import play.data.validation.Constraints;

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "user_type")
public class User extends Model {

  @Id
  @GeneratedValue
  private Long userId;

  @Constraints.MaxLength(50)
  private String name;
  @Constraints.MaxLength(100)
  private String surname;

  @Constraints.Required
  @Constraints.MinLength(8)
  private String password;

  @Constraints.Email
  @Constraints.Required
  private String email;

  @Constraints.Required
  @Constraints.MaxLength(10)
  @Constraints.MinLength(10)
  @Constraints.Pattern("[0]\\d{2}[- ]{0,1}\\d{3}[- ]{0,1}\\d{4}")
  private String cellNumber;

  private Boolean emailVerified = false;
  private String token;

  public static Finder<String, User> find = new Finder<String, User>(User.class);

  public User(){}

}

但是，它会导致一个错误：

CreationException: Unable to create injector, see the following errors:

1) Error injecting constructor, java.lang.NullPointerException

有关完整堆栈跟踪，请参阅

问题（和TL；DR）：

---

TL；博士：一个基本的全功能，有解释，玩！表示上述数据库架构的框架模型。

不支持继承类型（截至2017年8月18日）

Play使用Ebean ORM，该ORM当前不支持

InheritanceType.TABLE\u PER\u CLASS

或

InheritanceType.JOINED

。这是一个悬而未决的问题

我已经证实了这一点。我复制了您的代码并使用

InheritanceType.TABLE\u PER\u CLASS

运行它。Play创建了用户表和地址表，但没有创建子表、Staff和Customer

作为参考，要消除错误

Error injecting constructor, java.lang.NullPointerException

…您需要向用户添加@Entity注释以及InheritanceType：

@Entity
@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class User extends Model {
...

为了完成，您还需要删除

private Long userId;

…来自员工，因为它是从用户继承的

---

你有什么选择？

1） 您可以将项目重组为，它支持

InheritanceType.TABLE\u PER\u CLASS

和

InheritanceType.JOINED

2） 使用

InheritanceType.SINGLE\u表

。此方法将用户、客户和员工数据存储在一个表User中。它可能不是您理想的实现，但它会起作用：

如果你决定这样做，请注意

单表策略将继承结构的所有实体映射到同一个数据库表。这种方法使多态查询非常有效，并提供最佳性能

但它也有一些缺点。所有实体的属性都映射到同一个数据库表。每个记录只使用可用列的一个子集，并将其余列设置为null。因此，您不能对未映射到所有实体的任何列使用NOTNULL约束。这可能会造成数据完整性问题，您的数据库管理员可能对此不太满意

型号：用户

import io.ebean.Finder;
import io.ebean.Model;
import play.data.validation.Constraints;

import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;

@MappedSuperclass
//@Inheritance(strategy = InheritanceType.TABLE_PER_CLASS)
public class User extends Model {

    @Id
    @GeneratedValue
    private Long userId;

    @Constraints.MaxLength(50)
    private String name;
    @Constraints.MaxLength(100)
    private String surname;

    @Constraints.Required
    @Constraints.MinLength(8)
    private String password;

    @Constraints.Email
    @Constraints.Required
    private String email;

    @Constraints.Required
    @Constraints.MaxLength(10)
    @Constraints.MinLength(10)
    @Constraints.Pattern("[0]\\d{2}[- ]{0,1}\\d{3}[- ]{0,1}\\d{4}")
    private String cellNumber;

    private Boolean emailVerified = false;
    private String token;

    public static Finder<String, User> find = new Finder<String, User>(User.class);

    public User(){}

    public User(@Constraints.MinLength(10) @Constraints.MaxLength(10) Long userId, String name, String surname, @Constraints.Required String password, @Constraints.Email @Constraints.Required String email, @Constraints.Required @Constraints.Pattern("[0]\\d{2}[- ]{0,1}\\d{3}[- ]{0,1}\\d{4}") String cellNumber, Boolean emailVerified) {
        this.userId = userId;
        this.name = name;
        this.surname = surname;
        this.password = password;
        this.email = email;
        this.cellNumber = cellNumber;
        this.emailVerified = emailVerified;
    }

import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;

import com.avaje.ebean.Model;

import play.data.validation.Constraints;

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "user_type")
public class User extends Model {

  @Id
  @GeneratedValue
  private Long userId;

  @Constraints.MaxLength(50)
  private String name;
  @Constraints.MaxLength(100)
  private String surname;

  @Constraints.Required
  @Constraints.MinLength(8)
  private String password;

  @Constraints.Email
  @Constraints.Required
  private String email;

  @Constraints.Required
  @Constraints.MaxLength(10)
  @Constraints.MinLength(10)
  @Constraints.Pattern("[0]\\d{2}[- ]{0,1}\\d{3}[- ]{0,1}\\d{4}")
  private String cellNumber;

  private Boolean emailVerified = false;
  private String token;

  public static Finder<String, User> find = new Finder<String, User>(User.class);

  public User(){}

}

模型客户：

import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.OneToOne;

import play.data.validation.Constraints;

@Entity
@DiscriminatorValue("customer")
public class Customer extends User {

    @Constraints.Required
    @OneToOne(mappedBy = "customer")
    private Address address;
    private Boolean isStudent = false;

    public Customer(){}

    public static final Finder<String, Customer> find = new Finder<String, Customer>(Customer.class);
}

@OneToOne

已将客户映射添加到地址

使用间隙2.5.10进行验证

import javax.persistence.DiscriminatorColumn;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;

import com.avaje.ebean.Model;

import play.data.validation.Constraints;

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "user_type")
public class User extends Model {

  @Id
  @GeneratedValue
  private Long userId;

  @Constraints.MaxLength(50)
  private String name;
  @Constraints.MaxLength(100)
  private String surname;

  @Constraints.Required
  @Constraints.MinLength(8)
  private String password;

  @Constraints.Email
  @Constraints.Required
  private String email;

  @Constraints.Required
  @Constraints.MaxLength(10)
  @Constraints.MinLength(10)
  @Constraints.Pattern("[0]\\d{2}[- ]{0,1}\\d{3}[- ]{0,1}\\d{4}")
  private String cellNumber;

  private Boolean emailVerified = false;
  private String token;

  public static Finder<String, User> find = new Finder<String, User>(User.class);

  public User(){}

}

import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;

import play.data.validation.Constraints;

@Entity
@DiscriminatorValue("staff")
public class Staff extends User {

    @Constraints.Required
    private Boolean isKitchenStaff;

    public static Finder<String, Staff> find = new Finder<String, Staff>(Staff.class);

    public Staff() {}
}

import javax.persistence.DiscriminatorValue;
import javax.persistence.Entity;
import javax.persistence.OneToOne;

import play.data.validation.Constraints;

@Entity
@DiscriminatorValue("customer")
public class Customer extends User {

    @Constraints.Required
    @OneToOne(mappedBy = "customer")
    private Address address;
    private Boolean isStudent = false;

    public Customer(){}

    public static final Finder<String, Customer> find = new Finder<String, Customer>(Customer.class);
}

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;

import com.avaje.ebean.Model;

import play.data.validation.Constraints;

@Entity
public class Address extends Model {

    @Id
    @Constraints.Required
    @GeneratedValue
    @Constraints.Max(15)
    private Long addressId;
    @Constraints.Required
    private String unitNumber;
    @Constraints.Required
    private String streetName;
    private String communityName;
    private Boolean isCommunity;

    @OneToOne
    @JoinColumn(name = "user_id")
    private Customer customer;

    public Address(){}

    public static Finder<String, Address> find = new Finder<String, Address>(Address.class);
}