Question

试图使用冬眠/ jpa 与 scala 。遇到有趣的问题。

这是我的实体定义。

@Entity
class Product(n: String, d: Double) extends EntityBase {

  def this() = this("", 0)
  def this(n: String) = this(n, 0)

  var name: String = n
  var price: Double = d

  @ManyToOne
  @JoinColumn(name="orderId")
  var order: Order = _

  override def toString = "Product: " + id + " " + name
}

当我进行冬眠查询时,我得到以下例外:

[SQLGrammarException: ERROR: column this_.bitmap$init$0 does not exist Position: 29]

显然 jpa 默认地创建 scala 自动生成的位图字段 $0 的映射。我不知道是什么导致 scala 生成它。但是无论有什么办法可以让 jpa 忽略它? 或者把它从冬眠映射中移除。或者其他的。

Answer 1

我不知道自动生成的字段来自何方, 但你可以试着简化您的课程, 以减少字段 :

@Entity
class Product(var name: String = "", var price: Double = 0) extends EntityBase {

  @ManyToOne
  @JoinColumn(name="orderId")
  var order: Order = _

  override def toString = "Product: " + id + " " + name
}

Answer 2

发现了一些有趣的事情关于这个问题。

我的应用程序中有这个 < code> 模式 < /code> 类 :

@Entity
@Table(name="users")
class User extends Model{
  @Id
  @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="users_id_seq")
  @Column(name="id", updatable=false, nullable=false)
  val id:Long = 0L

  @BeanProperty var name:String = _
  @BeanProperty var email:String = _

时时

此类编译为名为 User 的 java 类, 其定义如下:

@Entity
@Table(name="users")
@ScalaSignature(bytes=long array of bytes)
public class User extends Model
   implements ScalaObject, EntityBean
{

   @Id
   @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="users_id_seq")
   @Column(name="id", updatable=false, nullable=false)
   private final long id;
   private String name;
   private String email;
   private volatile int bitmap$init$0;
   private static String _EBEAN_MARKER = "models.User";

   ...

   public long id()
  {
    if ((_ebean_get_bitmap$init$0() & 0x1) != 0)
    {
        _ebean_get_id(); return _ebean_get_id(); 
   时 时 
   throw new 
         UninitializedFieldError("Uninitialized field: User.scala: 17".toString());
    时 时

   public String name()
   {
   if ((_ebean_get_bitmap$init$0() & 0x2) != 0)
   {
     _ebean_get_name(); return _ebean_get_name();
   时 时 throw new 
           UninitializedFieldError("Uninitialized field: User.scala: 19".toString()); 
   时 时 

   public void name_$eq(String paramString) { 
     _ebean_set_name(paramString); 
      _ebean_set_bitmap$init$0(_ebean_get_bitmap$init$0() | 0x2);
   时 时

  ....

The bitmap$init$0 actually comes from a class enhancement, and I thought that the responsible was the Ebean library, which I m currently using. But after reading your post I went to investigate if JPA itself was doing some sort of bytecode enhancement on this object. In order to check this out, I created a copy project, but in Java. The generated code for the User class happens to have no bitmap$init$0 field, as follow:

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="users")
public class User
{

  @Id
  @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="users_id_seq")
  @Column(name="id", updatable=false, nullable=false)
  private Long id;
  private String name;
  private String email;

 public void setId(Long id)
 {
    this.id = id;
 时 时

 public Long getId() {
   return this.id;
 时 时

public String getName() {
   return this.name;
 时 时
 public void setName(String name) {
   this.name = name;
 时 时
 public String getEmail() {
    return this.email;
 时 时
 public void setEmail(String email) {
    this.email = email;
  时 时
时 时

所有这些麻烦导致我来到这个 rel=“nofollow norefererr”> post ,我非常肯定地同意。似乎将JPA与Scala Ebean/Hibertnate结合是一种真正的痛苦。我仍然不明白, Ebean 或其他东西是否将这个 bittmap$ini0 字段注入了类位元代码。

似乎你可以试图绕过这种行为,将注解()与生成的爪哇字节码联系起来,首先为 java 编译代码,然后到 Scala 编译代码,类似于< a href=> https://stackoverflow.com/ questions/11493543/compiliting-java-annotions-with-sbt” 。但我真的不认为这很值得!

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