休眠外键问题：执行DDL“更改表...”时出错

Question

我有一个非常简单的对象结构，这给我一个我无法解决的错误。做了大量的搜索，我认为这一定是一个很常见的用例，所以不确定是什么问题。我有以下三个课程：

@Entity
public class Widget {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int idd;
    private Date date;
    private String type;
    private int ownerId;

    @OneToOne(cascade = CascadeType.ALL)
    private Rating rating;


    @OneToMany(cascade = CascadeType.ALL)
    private List<Tag> tagList;


}


@Entity
public class Rating {
public enum ChartType  {RADAR, BAR, LINE, STAR};

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private int ratingId;
private String name;

@Enumerated(EnumType.STRING)
private ChartType chartType;
private double normalizedValue;

@OneToMany(cascade = CascadeType.ALL, orphanRemoval = true)
private List<RatingComponent> componentList = new ArrayList<>();


public Rating() {
    buildNormalizedValue();
}
}


@Entity
public class RatingComponent {


@Id
@GeneratedValue()
private int compId;

private String name;
private double value;
private double maxValue;

}

在DAO中保存时，出现了我不太了解的错误，例如

2018-07-23 11:43:07,208 WARN o.h.t.s.i.ExceptionHandlerLoggedImpl [main] GenerationTarget encountered exception accepting command : 
Error executing DDL "alter table Rating_RatingComponent drop foreign key FKaudjguwlo1i8tm2jgli5bbnq6" via JDBC Statement
org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "alter table Rating_RatingComponent drop foreign key FKaudjguwlo1i8tm2jgli5bbnq6" via JDBC Statement

再往下走

2018-07-23 11:43:07,644 WARN o.h.t.s.i.ExceptionHandlerLoggedImpl [main] GenerationTarget encountered exception accepting command : Error executing DDL "create table RatingComponent (compId integer not null, maxValue double precision not null, name varchar(255), value double precision not null, primary key (compId)) engine=InnoDB" via JDBC Statement
org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "create table RatingComponent (compId integer not null, maxValue double precision not null, name varchar(255), value double precision not null, primary key (compId)) engine=InnoDB" via JDBC Statement

我的配置中有这些属性

    <property name="hibernate.hbm2ddl.auto">create</property>
    <property name="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property> 

我以为我已经非常仔细地浏览了文档，并且认为这是一个非常简单的对象设计...有关如何解决的任何想法，以及我应该在文档中的何处更仔细地研究以了解根本原因？

谢谢！

Answer 1

我使用了 SQL 保留字'order'作为实体名称，因此我收到了类似的错误。重命名它为我解决了这个问题。看看你的实体名称，其中是否使用了任何保留字？

Answer 2

替换

<property name="hibernate.dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>

经过

<property name="hibernate.dialect">org.hibernate.dialect.MySQL8InnoDBDialect</property>

会成功的