Question

我正在尝试将映射对象插入到具有正确ID的postgresql数据库中。这是我插入的方式：

Session session = Main.getSession();
Transaction rx = session.beginTransaction();
ProductsEntity productsEntity = new ProductsEntity();
productsEntity.setName(nameTextField.getText());
productsEntity.setDescription(descriptionTextArea.getText());
productsEntity.setCategory((ProductCategoriesEntity) categoryComboBox.getSelectedItem());
productsEntity.setPrice(new BigDecimal(1.0));
session.save(productsEntity);
tx.commit();
session.close();

具有已定义序列的类：

@Entity
@Table(name = "products", schema = "public", catalog = "shop")
public class ProductsEntity {
    private int id;
    private String name;
    private String description;
    private BigDecimal price;

    @Id
    @Column(name = "id", nullable = false)
    @SequenceGenerator(name="pk_sequence",sequenceName="products_id_seq")
    @GeneratedValue(strategy=GenerationType.AUTO,generator="pk_sequence")
    public int getId() {
        return id;
    }

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

    @Basic
    @Column(name = "name", nullable = false, length = -1)
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Basic
    @Column(name = "description", nullable = false, length = -1)
    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @Basic
    @Column(name = "price", nullable = false, precision = 2)
    public BigDecimal getPrice() {
        return price;
    }

    public void setPrice(BigDecimal price) {
        this.price = price;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        ProductsEntity that = (ProductsEntity) o;

        if (id != that.id) return false;
        if (name != null ? !name.equals(that.name) : that.name != null) return false;
        if (description != null ? !description.equals(that.description) : that.description != null) return false;
        if (price != null ? !price.equals(that.price) : that.price != null) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = id;
        result = 31 * result + (name != null ? name.hashCode() : 0);
        result = 31 * result + (description != null ? description.hashCode() : 0);
        result = 31 * result + (price != null ? price.hashCode() : 0);
        return result;
    }

    private ProductCategoriesEntity category;

    @ManyToOne
    public ProductCategoriesEntity getCategory() {
        return category;
    }

    public void setCategory(ProductCategoriesEntity category) {
        this.category = category;
    }
}

postgresql序列products_id_seq的最后一个值是4. Hibernate正在插入id = 0的对象，所以第一次插入成功，现在我遇到了唯一的约束违规。

EDIT 我通过添加生成器

使序列工作

<generator class="identity"/>

xml映射定义中的

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="entities.ProductsEntity" table="products" schema="public" catalog="shop">
        <id name="id">
            <column name="id" sql-type="integer"/>
            <generator class="identity"/>
        </id>
        <property name="name">
            <column name="name" sql-type="varchar"/>
        </property>
        <property name="description">
            <column name="description" sql-type="varchar"/>
        </property>
        <property name="price">
            <column name="price" sql-type="numeric(9,2)" precision="9" scale="2"/>
        </property>
        <many-to-one name="category" column="category_id" class="entities.ProductCategoriesEntity" lazy="false"/>
    </class>
</hibernate-mapping>

这不会在课堂上定义序列。我也尝试过使用

@GeneratedValue(strategy=GenerationType.IDENTITY)

在类文件中，但它不起作用。

如果有人有想法，请告诉我为什么只有“xml”方法有效。

Answer 1

序列“products_id_seq”是数据库序列吗？

如果是，请将GenerationType从Auto更改为SEQUENCE。
我对Postgres进行了类似的设置，并将GenerationType设置为SEQUENCE，并为我提供了allocationSize = 1。

另外，请确保您的序列与表格保持同步。如果没有，请立即更改序列，以便进一步更新不会失败。

Hibernate没有使用定义的序列（postgresql）

1 个答案: