java - Hibernate 生成额外的表

Question

我有一个这样的实体

@Entity
@Table(name = "past_price")
public class PastPrice {

    @Id
    private String symbol;
    @OneToMany(fetch = FetchType.EAGER,cascade = CascadeType.ALL)
    private Set<Price> prices = null;

    public String getSymbol() {
        return symbol;
    }

    public void setSymbol(String symbol) {
        this.symbol = symbol;
    }

    public Set<Price> getPrices() {
        return prices;
    }

    public void setPrices(Set<Price> prices) {
        this.prices = prices;
    }

}

Price实体是这样的

@Entity
public class Price {
    @Id
    @Temporal(TemporalType.TIMESTAMP)
    private Date date;
    private String price;

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public String getPrice() {
        return price;
    }

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

}

我想做的是，创建一个名为 past_price 的表，它与 Price 实体有 OneToMany 关系。我有 hibernate 属性 spring.jpa.hibernate.ddl-auto=update 所以每当我运行它时都会创建 3 个表 1。过去的价格 2。 past_price_prices 和 3。价格。但我只是想创建 2 个表 past_price 和 price。任何帮助，将不胜感激。谢谢

Answer 1

使用@JoinColumn 告诉hibernate 在价格表中创建一个列并将其用于连接。将您的代码更改为以下内容:

@OneToMany(fetch = FetchType.EAGER,cascade = CascadeType.ALL)
@JoinColumn(name = "fk_past_price")
private Set<Price> prices = null;

这将在价格表中创建一个名为 fk_past_price 的列，并且不会创建第三个表。

P.S.:如果没有充分的理由使用单向关联，请改用双向关联。如下所示:

@Entity
@Table(name = "past_price")
public class PastPrice {

    @Id
    private String symbol;
    @OneToMany(mappedBy = "pastPrice", cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    private Set<Price> prices = null;

    public String getSymbol() {
        return symbol;
    }

    public void setSymbol(String symbol) {
        this.symbol = symbol;
    }

    public Set<Price> getPrices() {
        return prices;
    }

    public void setPrices(Set<Price> prices) {
        this.prices = prices;
    }

}

价格:

@Entity
public class Price {
    @Id
    @Temporal(TemporalType.TIMESTAMP)
    private Date date;
    private String price;

    @ManyToOne
    @JoinColumn(name = "past_price_symbol", nullable = false)
    private PastPrice pastPrice;

    public PastPrice getPastPrice() {
      return pastPrice;
    }

    public void setPastPrice(PastPrice pastPrice) {
      this.pastPrice = pastPrice;
    }

    public Date getDate() {
        return date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    public String getPrice() {
        return price;
    }

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

}