java - 如何在 Hibernate 中插入外键定义为 Long 的实体？

Question

我正在使用 Hibernate 3.6.8，并且我在 mysql (5.5) 中定义了一个表，如下所示:

CREATE TABLE mytable
(
    id BIGINT(20) PRIMARY KEY NOT NULL,
    version INT(11),
    description VARCHAR(60),
    scheduled_at DATETIME,
    `from` BIGINT(20),
    `to` BIGINT(20),
    deleted BIT(1) DEFAULT b'0',
    completed BIT(1) DEFAULT b'0',
    delete_from_after_completion BIT(1) DEFAULT b'0',
    CONSTRAINT FK14F71A73C588I54F FOREIGN KEY (`from`) REFERENCES other_table (id),
    CONSTRAINT FK14F71C231C45J198 FOREIGN KEY (`to`) REFERENCES other_table (id)
);
CREATE INDEX FK14F71A73C588I54F ON mytable (`from`);
CREATE INDEX FK14F71C231C45J198 ON mytable (`to`);

Java 实体定义如下:

@Entity
public class MyTable {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    private Long id;
    @Version
    @Column(name = "version")
    private Integer version;
    @Column(name = "description")
    private String description;
    @Column(name = "scheduled_at")
    @Temporal(TemporalType.TIMESTAMP)
    @DateTimeFormat(style = "SM")
    private Date scheduledAt;
    @Column(name = "from")
    private Long fromId;
    @Column(name = "to")
    private Long toId;
    @Column(name = "deleted")
    private boolean deleted;
    @Column(name = "completed")
    private boolean completed;
    @Column(name = "delete_from_after_completion")
    private boolean deleteFromEntityAfterCompletion;

    ...
}

当我尝试使用有效值持久化 MyTable 的实例时，最终出现以下错误:

2016-01-12 10:06:33,443 [qtp2139431292-20] WARN  org.hibernate.util.JDBCExceptionReporter - SQL Error: 1064, SQLState: 42000
2016-01-12 10:06:33,443 [qtp2139431292-20] ERROR org.hibernate.util.JDBCExceptionReporter - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'from, scheduled_at, to, version) values (0, 1, 0, 'Test', 10, '2016-01-13 00:00:' at line 1

我怀疑出现问题是因为我尝试将外键关系(to 和 from)建模为 Long 而不是实体(其他表)。我怀疑这一点，因为如果我注释掉 to 和 from 字段，Hibernate 确实可以保留该实体。请注意，与 to 和 from 实体的关系确实存在于数据库中，因此这不是问题。

如果我尝试使用类似的方法手动插入，它会起作用:

insert into mytable values(3, 0, "desc", '2016-10-10 00:00:', 10, 11, 0, 0, 0);

Answer 1

您有一列是 SQL 保留关键字(“from”)，Hibernate 不会为您引用它。其他 JPA 实现(例如 DataNucleus JPA)会为您处理这些事情。您必须在 JPA 注释信息中的保留字周围添加单引号