java 具有空值的 JPA 复合主键
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JPA composite primary key with null value
提问by Matsu Q.
I have a table containing customer data in an oracle database. Here is a simplified definition:
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：
CUSTOMER (CUSTOMER_ID NUMBER NOT NULL,
SOURCE_SYSTEM VARCHAR2(30),
FULL_NAME VARCHAR2(360),
PHONE_NUMBER VARCHAR2(240)
)
The primary key for this table is (CUSTOMER_ID, SOURCE_SYSTEM).
该表的主键是(CUSTOMER_ID, SOURCE_SYSTEM)。
The table has numerous rows for which SOURCE_SYSTEMis 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:
该表有许多SOURCE_SYSTEM为空的行。在数据库级别，没有问题，但是当我尝试通过 JPA 实体访问这些行中的任何一行时，它会导致许多问题：
1: Using em.find()to fetch a row with a null SOURCE_SYSTEMalways results in a null being returned.
1：使用em.find()空值获取一行SOURCE_SYSTEM总是导致返回空值。
2: Using em.merge()to upsert a row with a null SOURCE_SYSTEMsucceeds if the record does not exist in the table, but fails on subsequent updates because the merge ALWAYS results in an insert being run.
2：如果记录不存在于表中，则使用em.merge()更新插入具有空值的行会SOURCE_SYSTEM成功，但在后续更新时失败，因为合并总是会导致运行插入。
3: Using em.createQuery()to explicitly query for a row with a null causes the following exception:
3：使用em.createQuery()显式查询具有空值的行会导致以下异常：
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))")
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.
不幸的是，“主键不能包含空值”似乎是最终的。我无法找到有关此错误的解决方法的太多信息，这使得似乎没有解决方案。
THE QUESTION: I would like to know if anyone has any Java code-based solutionthat don't involve making changes to the database. My current workaround is to use ROW_IDas the @Idof the table, but this means I can no longer use em.merge()or em.find().
问题：我想知道是否有人有任何不涉及对数据库进行更改的基于 Java 代码的解决方案。我目前的解决办法是使用ROW_ID的@Id表，但是这意味着我可以不再使用em.merge()或em.find()。
Here are my Java classes:
这是我的 Java 类：
Customer.java:
客户.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
客户 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
...
}
回答by James
Primary keys cannot contain null (in JPA or in databases). Use a different value such as "" or " ".
主键不能包含 null（在 JPA 或数据库中）。使用不同的值，例如“”或“”。
Is the customer_id unique? if so then just remove the sourceSystem from the Id.
customer_id 是唯一的吗？如果是这样，那么只需从 Id 中删除 sourceSystem。
Otherwise, you could try logging a bug to have support for null ids added.
否则，您可以尝试记录错误以添加对空 ID 的支持。
