Java Play Framework-Ebean-没有为类注册ScalarType“；“类名”；

我在MySQL数据库中构建了一些表，使用持久性API和Ebean将自定义Java对象表示为表。现在，我尝试通过在Ebean.find（）查询我想要的对象时作为参数传递来恢复存储的条目，但是每次都会抛出

javax.persistence.PersistenceException

---

让我解释一下层次结构和结构：

有一个机器类：

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "MACHINE_TYPE")
public class Machine extends Model
{
    @Id
    @Column(name = "id")
    private Long _machineID;

    @Column(name = "name", unique = true)
    private String _name;

    @Column(name = "info")
    private String _info;

    // rest of code
}

@Entity
@Table(name = "machine")
@DiscriminatorValue("Container")
public class Container extends Machine
{
@Column(name = "dockerID", unique = true)
   private String _dockerID;

   @ManyToOne
   @JoinColumn(name = "host", insertable = true, updatable = true)
   private Server _host;

   @Column(name = "currentSize")
   private String _currentSize;

   @Column(name = "additionalInfo")
   private String _additionalInfo;

   @Column(name = "last_login")
   private String _lastLogin;

   // rest of code
}

有两个子类。服务器类扩展机器如下：

@Entity
@Table(name = "machine")
@DiscriminatorValue("Server")
public class Server extends Machine
{
   @Column(name = "ip")
   private String _ip;

   @Column(name = "port")
   private Integer _port;

   @Column(name = "user_name")
   private String _userName;

   @Column(name = "password")
   private String _password;

   @Column(name = "clock")
   private Integer _clock;

   @Column(name = "ram")
   private Integer _ram;

   // rest of code
}

`machine` (
  `machine_type` varchar(31) NOT NULL,
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `info` mediumtext,
  `dockerID` varchar(255) DEFAULT NULL,
  `host` bigint(20) DEFAULT NULL,
  `currentSize` varchar(255) DEFAULT NULL,
  `additionalInfo` text,
  `last_login` varchar(255) DEFAULT NULL,
  `ip` varchar(255) DEFAULT NULL,
  `port` int(11) DEFAULT NULL,
  `user_name` varchar(255) DEFAULT NULL,
  `password` varchar(255) DEFAULT NULL,
  `clock` int(11) DEFAULT NULL,
  `ram` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `uq_machine_dockerID` (`dockerID`),
  KEY `ix_machine__host_4` (`host`),
  CONSTRAINT `fk_machine__host_4` FOREIGN KEY (`host`) REFERENCES `machine` (`id`)
)

@ManyToOne(targetEntity = Server.class) // explicitly specify the target class
@JoinColumn(name = "host", insertable = true, updatable = true)
private Server host;

和容器类：

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "MACHINE_TYPE")
public class Machine extends Model
{
    @Id
    @Column(name = "id")
    private Long _machineID;

    @Column(name = "name", unique = true)
    private String _name;

    @Column(name = "info")
    private String _info;

    // rest of code
}

@Entity
@Table(name = "machine")
@DiscriminatorValue("Container")
public class Container extends Machine
{
@Column(name = "dockerID", unique = true)
   private String _dockerID;

   @ManyToOne
   @JoinColumn(name = "host", insertable = true, updatable = true)
   private Server _host;

   @Column(name = "currentSize")
   private String _currentSize;

   @Column(name = "additionalInfo")
   private String _additionalInfo;

   @Column(name = "last_login")
   private String _lastLogin;

   // rest of code
}

---

这段代码在MySQL数据库中构建了一个machine表，如下所示：

@Entity
@Table(name = "machine")
@DiscriminatorValue("Server")
public class Server extends Machine
{
   @Column(name = "ip")
   private String _ip;

   @Column(name = "port")
   private Integer _port;

   @Column(name = "user_name")
   private String _userName;

   @Column(name = "password")
   private String _password;

   @Column(name = "clock")
   private Integer _clock;

   @Column(name = "ram")
   private Integer _ram;

   // rest of code
}

`machine` (
  `machine_type` varchar(31) NOT NULL,
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `info` mediumtext,
  `dockerID` varchar(255) DEFAULT NULL,
  `host` bigint(20) DEFAULT NULL,
  `currentSize` varchar(255) DEFAULT NULL,
  `additionalInfo` text,
  `last_login` varchar(255) DEFAULT NULL,
  `ip` varchar(255) DEFAULT NULL,
  `port` int(11) DEFAULT NULL,
  `user_name` varchar(255) DEFAULT NULL,
  `password` varchar(255) DEFAULT NULL,
  `clock` int(11) DEFAULT NULL,
  `ram` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `uq_machine_dockerID` (`dockerID`),
  KEY `ix_machine__host_4` (`host`),
  CONSTRAINT `fk_machine__host_4` FOREIGN KEY (`host`) REFERENCES `machine` (`id`)
)

@ManyToOne(targetEntity = Server.class) // explicitly specify the target class
@JoinColumn(name = "host", insertable = true, updatable = true)
private Server host;

这似乎是正确的。但是，如果我在数据库中添加一个条目并尝试执行

...
Server server = Server.getServerByName(serverName); // this returns a Server object correctly
List<Container> testCase = Ebean.find(Container.class)
                    .where()
                    .eq("host", server)
                    .findList(); // this throws the exception

即使我试图用

List<Container> testcase = Ebean.find(Container.class)
                    .where()
                    .eq("host", server.getMachineId()) // pass the serverID
                    .findList();

---

---

任何帮助，至少是关于遵循什么方向的帮助，都将不胜感激。因此，经过一些测试，我发现如果您想使用对象访问数据库表，您需要遵循对象映射中的一些规则，而我显然没有。在文档中我也找不到这个。这个解决方案是失败和尝试的结果

---

首先，变量的名称必须与列的名称相同！如果我将

Container.class

和

Server.class

变量更改为：

@ManyToOne
@JoinColumn(name = "host", insertable = true, updatable = true)
private Server host; // notice the name is the same as the column name

一切正常，我可以在查询中传递

Server.class

对象，如：

Ebean.find(Container.class)
      .where()
      .eq("host", server)
      .findList();

因此，要映射对象实体，列名必须与变量名完全相同，反之亦然

---

其次，据我在文档中所读，我们可以在

@ManyToOne

注释中指定目标实体，如下所示：

@Entity
@Table(name = "machine")
@DiscriminatorValue("Server")
public class Server extends Machine
{
   @Column(name = "ip")
   private String _ip;

   @Column(name = "port")
   private Integer _port;

   @Column(name = "user_name")
   private String _userName;

   @Column(name = "password")
   private String _password;

   @Column(name = "clock")
   private Integer _clock;

   @Column(name = "ram")
   private Integer _ram;

   // rest of code
}

`machine` (
  `machine_type` varchar(31) NOT NULL,
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `info` mediumtext,
  `dockerID` varchar(255) DEFAULT NULL,
  `host` bigint(20) DEFAULT NULL,
  `currentSize` varchar(255) DEFAULT NULL,
  `additionalInfo` text,
  `last_login` varchar(255) DEFAULT NULL,
  `ip` varchar(255) DEFAULT NULL,
  `port` int(11) DEFAULT NULL,
  `user_name` varchar(255) DEFAULT NULL,
  `password` varchar(255) DEFAULT NULL,
  `clock` int(11) DEFAULT NULL,
  `ram` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `uq_machine_dockerID` (`dockerID`),
  KEY `ix_machine__host_4` (`host`),
  CONSTRAINT `fk_machine__host_4` FOREIGN KEY (`host`) REFERENCES `machine` (`id`)
)

@ManyToOne(targetEntity = Server.class) // explicitly specify the target class
@JoinColumn(name = "host", insertable = true, updatable = true)
private Server host;

---

在我的例子中，这并不是主要问题，因为Java读取

host

字段的类类型并自动传递目标实体。但是这里最好是安全的。

因此，经过一些测试，我发现如果您想使用对象访问数据库表，您需要在对象映射中遵循一些规则，而我显然没有。在文档中我也找不到这个。这个解决方案是失败和尝试的结果

---

首先，变量的名称必须与列的名称相同！如果我将

Container.class

和

Server.class

变量更改为：

@ManyToOne
@JoinColumn(name = "host", insertable = true, updatable = true)
private Server host; // notice the name is the same as the column name

一切正常，我可以在查询中传递

Server.class

对象，如：

Ebean.find(Container.class)
      .where()
      .eq("host", server)
      .findList();

因此，要映射对象实体，列名必须与变量名完全相同，反之亦然

---

其次，据我在文档中所读，我们可以在

@ManyToOne

注释中指定目标实体，如下所示：

@Entity
@Table(name = "machine")
@DiscriminatorValue("Server")
public class Server extends Machine
{
   @Column(name = "ip")
   private String _ip;

   @Column(name = "port")
   private Integer _port;

   @Column(name = "user_name")
   private String _userName;

   @Column(name = "password")
   private String _password;

   @Column(name = "clock")
   private Integer _clock;

   @Column(name = "ram")
   private Integer _ram;

   // rest of code
}

`machine` (
  `machine_type` varchar(31) NOT NULL,
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) DEFAULT NULL,
  `info` mediumtext,
  `dockerID` varchar(255) DEFAULT NULL,
  `host` bigint(20) DEFAULT NULL,
  `currentSize` varchar(255) DEFAULT NULL,
  `additionalInfo` text,
  `last_login` varchar(255) DEFAULT NULL,
  `ip` varchar(255) DEFAULT NULL,
  `port` int(11) DEFAULT NULL,
  `user_name` varchar(255) DEFAULT NULL,
  `password` varchar(255) DEFAULT NULL,
  `clock` int(11) DEFAULT NULL,
  `ram` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`),
  UNIQUE KEY `uq_machine_dockerID` (`dockerID`),
  KEY `ix_machine__host_4` (`host`),
  CONSTRAINT `fk_machine__host_4` FOREIGN KEY (`host`) REFERENCES `machine` (`id`)
)

@ManyToOne(targetEntity = Server.class) // explicitly specify the target class
@JoinColumn(name = "host", insertable = true, updatable = true)
private Server host;

在我的例子中，这并不是主要问题，因为Java读取

host

字段的类类型并自动传递目标实体。但这里最好安全