具有空值的JPA复合主键 [英] JPA composite primary key with null value

问题描述

我在oracle数据库中有一个包含客户数据的表。这是一个简化的定义：

I have a table containing customer data in an oracle database. Here is a simplified definition:

CUSTOMER (CUSTOMER_ID NUMBER NOT NULL,
          SOURCE_SYSTEM VARCHAR2(30),
          FULL_NAME VARCHAR2(360),
          PHONE_NUMBER VARCHAR2(240)
          )

该表的主键是（CUSTOMER_ID，SOURCE_SYSTEM）。

该表有许多行 SOURCE_SYSTEM 为空。在数据库级别，没有问题，但是当我尝试通过JPA实体访问任何这些行时，它会导致许多问题：

The table has numerous rows for which SOURCE_SYSTEM is null. At the database level, there is no issue, however when I try to access any of these rows via JPA Entity, it causes a number of issues:

1：使用 em.find（）获取一个空的行 SOURCE_SYSTEM 总是会返回null。

1: Using em.find() to fetch a row with a null SOURCE_SYSTEM always results in a null being returned.

2：使用 em.merge（）来插入一个空行 SOURCE_SYSTEM 成功，但后续更新失败，因为合并ALWAYS导致插入正在运行。

2: Using em.merge() to upsert a row with a null SOURCE_SYSTEM succeeds if the record does not exist in the table, but fails on subsequent updates because the merge ALWAYS results in an insert being run.

3：使用 em.createQuery（）显式查询带有null的行会导致以下异常：

3: Using em.createQuery() to explicitly query for a row with a null causes the following exception:

Exception [EclipseLink-6044] (Eclipse Persistence Services - 2.3.1.v20111018-r10243):
   org.eclipse.persistence.exceptions.QueryException
Exception Description: The primary key read from the row [ArrayRecord(
CUSTOMER.CUSTOMER_ID => 1
CUSTOMER.FULL_NAME => GUY PERSON
CUSTOMER.PHONE_NUMBER => 555-555-1234
CUSTOMER.SOURCE_SYSTEM => null)] during the execution of the query was detected to be null.
   Primary keys must not contain null.
Query: ReadAllQuery(referenceClass=Customer sql="SELECT CUSTOMER_ID, FULL_NAME, PHONE_NUMBER, SOURCE_SYSTEM FROM CUSTOMER WHERE ((CUSTOMER_ID = ?) AND (SOURCE_SYSTEM IS NULL))")

不幸的是，主键不能包含null似乎是最终的。我无法找到有关此错误的变通方法的太多信息，这使得它似乎没有解决方案。

Unfortunately, "Primary keys must not contain null" seems pretty final. I was unable to find too much information on workarounds for this error, which makes it seem like there is no solution.

问题：我想知道是否有人有任何 基于Java代码的解决方案 不涉及对数据库进行更改。我目前的解决方法是使用 ROW_ID 作为表的 @Id ，但这意味着我无法再使用 em.merge（）或 em.find（）。

THE QUESTION: I would like to know if anyone has any Java code-based solution that don't involve making changes to the database. My current workaround is to use ROW_ID as the @Id of the table, but this means I can no longer use em.merge() or em.find().

以下是我的Java类：

Here are my Java classes:

Customer.java：

Customer.java:

@Entity
@Table(name = "CUSTOMER")
public class Customer implements Serializable {
  private static final long serialVersionUID = 1L;

  @EmbeddedId
  private Customer_Id key;

  @Column(name = "CUSTOMER_ID", nullable = false, insertable = false, updatable = false)
  private Long customerId;
  @Column(name = "SOURCE_SYSTEM", length = 30, insertable = false, updatable = false)
  private String sourceSystem;

  @Column(name = "FULL_NAME", length = 360)
  private String fullName;
  @Column(name = "PHONE_NUMBER", length = 240)
  private String phoneNumber;

  //Setters, Getters, etc
  ...
}

Customer_Id.java

Customer_Id.java

@Embeddable
public class Customer_Id implements Serializable {
  private static final long serialVersionUID = 1L;

  @Column(name = "CUSTOMER_ID", nullable = false)
  private Long customerId;
  @Column(name = "SOURCE_SYSTEM", length = 30)
  private String sourceSystem;

  //Setters, Getters, etc
  ...
}

推荐答案

主键不能包含null（在JPA或数据库中）。使用不同的值，例如或。

Primary keys cannot contain null (in JPA or in databases). Use a different value such as "" or " ".

customer_id是唯一的吗？如果是这样，那么只需从Id中删除sourceSystem。

Is the customer_id unique? if so then just remove the sourceSystem from the Id.

否则，您可以尝试记录错误以支持添加空ID。

Otherwise, you could try logging a bug to have support for null ids added.

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