Question

我有一个@GenericGenerator的实体：

@Entity
public class Report {
    @Id
    @GenericGenerator(name = "generator", strategy = "foreign",
            parameters = @Parameter(name = "property", value = "examrequisitions"))
    // @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(nullable = false, unique = true)
    private Long id;

    ... // outcome, status
}

当我保存该实体时，它会显示以下异常：

Caused by: Exception [EclipseLink-4002] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.DatabaseException
Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'id' cannot be null
Error Code: 1048
Call: INSERT INTO SystemCardiologyReports.REPORTS (ID, OUTCOME, STATUS) VALUES (?, ?, ?)
    bind => [3 parameters bound]
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Column 'id' cannot be null

为什么ID null - 尽管@GenericGenerator？

Answer 1

GenericGenerator注释只是在代码中的某处声明了一个生成器。您可以将其添加到任何包，类型，字段或方法。这并不意味着生成器应该用于带注释的元素。

您需要将@GeneratedValue添加到要使用它的字段，并按名称引用它：

@Id
@GenericGenerator(name = "genericGenerator" ...))
@GeneratedValue(generator = "genericGenerator")
private Long id;

GenericGenerator不生成值

1 个答案: