两个实体之间的多个多对多关系

Question

我有两个对象。

值：

@Table(name = "random_value")
@Entity(name = "random_value")
public class RandomValue
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    protected long id;

    @Column(name = "random_value", nullable = false)
    private String value;

    public RandomValue()
    {
    }

    public long getId()
    {
        return id;
    }

    public void setId(long id)
    {
        this.id = id;
    }

    public String getValue()
    {
        return value;
    }

    public void setValue(String value)
    {
        this.value = value;
    }
}

和实体：

@Table(name = "entity")
@Entity(name = "entity")
public class Entity
{
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    protected long id;

    @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinTable(name = "entity_value_list", joinColumns = {
            @JoinColumn(referencedColumnName = "id", nullable = false)}, inverseJoinColumns = {
            @JoinColumn(referencedColumnName = "id", nullable = false)})
    @Fetch(FetchMode.SELECT)
    private List<RandomValue> values;

    @ManyToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinTable(name = "hidden_entity_value_list", joinColumns = {
            @JoinColumn(referencedColumnName = "id", nullable = false)}, inverseJoinColumns = {
            @JoinColumn(referencedColumnName = "id", nullable = false)})
    @Fetch(FetchMode.SELECT)
    private List<RandomValue> hiddenValues;

    public Entity()
    {
    }

    public List<RandomValue> getValues()
    {
        return values;
    }

    public void setValues(List<RandomValue> values)
    {
        this.values = values;
    }

    public List<RandomValue> getHiddenValues()
    {
        return values;
    }

    public void setHiddenValues(List<RandomValue> hiddenValues)
    {
        this.hiddenValues = hiddenValues;
    }
}

我也有四张表：

一个代表值:

CREATE TABLE `random_value`
(
    `id`  INT          NOT NULL AUTO_INCREMENT,
    `random_value` VARCHAR(127) NOT NULL UNIQUE,
    PRIMARY KEY (`id`)
);

实体一个：

CREATE TABLE `entity`
(
    `id`      INT          NOT NULL AUTO_INCREMENT,
    PRIMARY KEY (`id`)
);

并且两个表要有多对多的关系

CREATE TABLE `entity_value_list`
(
    `entity_id` INT NOT NULL,
    `values_id`  INT NOT NULL,
    PRIMARY KEY (`entity_id`, `values_id`),
    CONSTRAINT `entity_id`
        FOREIGN KEY (`entity_id`)
            REFERENCES `entity` (`id`),
    CONSTRAINT `values_id`
        FOREIGN KEY (`values_id`)
            REFERENCES `random_value` (`id`)
);


CREATE TABLE `hidden_entity_value_list`
(
    `entity_id` INT NOT NULL,
    `values_id`  INT NOT NULL,
    PRIMARY KEY (`entity_id`, `values_id`),
    CONSTRAINT `entity_id`
        FOREIGN KEY (`entity_id`)
            REFERENCES `entity` (`id`),
    CONSTRAINT `values_id`
        FOREIGN KEY (`values_id`)
            REFERENCES `random_value` (`id`)
);

当我尝试运行我的 spring 引导项目时，它使用休眠和运行创建的 h2 数据库，我收到一条错误消息。

Caused by: org.h2.jdbc.JdbcSQLSyntaxErrorException: Constraint "ENTITY_ID" already exists; SQL statement:
CREATE TABLE `hidden_entity_value_list`
(
    `entity_id` INT NOT NULL,
    `values_id`  INT NOT NULL,
    PRIMARY KEY (`entity_id`, `values_id`),
    CONSTRAINT `entity_id`
        FOREIGN KEY (`entity_id`)
            REFERENCES `entity` (`id`),
    CONSTRAINT `values_id`
        FOREIGN KEY (`values_id`)
            REFERENCES `random_value` (`id`)
); [90045-200]
    at org.h2.message.DbException.getJdbcSQLException(DbException.java:576) ~[h2-1.4.200.jar:1.4.200]

据我了解，因为 hidden_entity_value_list 中的字段看起来像 entity_value_list 中的字段，所以它在抱怨。我该如何解决这个问题并使整个事情正常进行？

Answer 1

约束名称在架构范围内必须是唯一的。

您在两个表中都使用了 CONSTRAINT 名称 entity_id。所以只需重命名两者中的一个即可。

两个实体之间的多个多对多关系

Multiple many-to-many relations between two entities

sql

database

hibernate

h2

spring-boot