JPA 定义需要类型转换的字段上的关系

发布于 2024-10-04 15:03:13 字数 348 浏览 1 评论 0原文

我想在“供应商”列上加入两个表，在发票表中，供应商类型为整数，在供应商表中，供应商类型为 varchar(10)。

是否可以进行类型转换并且也有关系？

@Entity
public class Vendor
{
    private String id;

    @Id(Column="vendor")
    public String getId(){ ... }
}

@Entity
public class Invoice
{
    private Vendor vendor;

    @One-to-one
    public Vendor getVendor() { ... }
}

原文

I want to join two tables on column "vendor",
In invoice table vendor type is integer, in vendor table, vendor is type varchar(10).

Is it possible to do a type conversion and also have a relationship?

@Entity
public class Vendor
{
    private String id;

    @Id(Column="vendor")
    public String getId(){ ... }
}

@Entity
public class Invoice
{
    private Vendor vendor;

    @One-to-one
    public Vendor getVendor() { ... }
}

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你如我软肋 2024-10-11 15:03:13

据我所知，使用数据透视表（就像表示多对多关系一样）是正确的方法。

像这样的东西应该可以工作：

@Entity
public class Invoice
{
    @JoinTable(name = "invoice_vendor", joinColumns = {
        @JoinColumn(name = "invoice", referencedColumnName = "vendor_id")}, inverseJoinColumns = {
        @JoinColumn(name = "vendor", referencedColumnName = "id")})
    @OneToOne
    private Vendor vendor;
}

其中invoice_vendor表在id列中有整数id，在vendor_id列中有varchar引用。

另外，我猜想您希望供应商之间存在多对一关系，但您已经编写了一对一的关系，因此我将其保留为原样。

As far as I know, using a pivot table (as you would do to represent a many-to-many relationship) would be the right way to do that.

Something like this should work:

@Entity
public class Invoice
{
    @JoinTable(name = "invoice_vendor", joinColumns = {
        @JoinColumn(name = "invoice", referencedColumnName = "vendor_id")}, inverseJoinColumns = {
        @JoinColumn(name = "vendor", referencedColumnName = "id")})
    @OneToOne
    private Vendor vendor;
}

Where the invoice_vendor table has the integer id in id column and varchar reference in vendor_id column.

Also I surmise you would like a ManyToOne relationship between vendors, but you've written one to one, so I have left that as such.

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她比我温柔 2024-10-11 15:03:13

也许这可以使用瞬态字段来完成

@Entity
public class Employee {
    ...
    private boolean isActive;
    ...
    @Transient
    public boolean getIsActive() {
        return isActive;
    }
    public void setIsActive(boolean isActive) {
        this.isActive = isActive;
    }
    @Basic
    private String getIsActiveValue() {
        if (isActive) {
            return "T";
        } else {
            return "F";
        }
    }
    private void setIsActiveValue(String isActive) {
        this.isActive = "T".equals(isActive);
    }
}

http://en.wikibooks.org/wiki/ Java_Persistence/Basic_Attributes#Conversion

Maybe this can be done using a transient field

@Entity
public class Employee {
    ...
    private boolean isActive;
    ...
    @Transient
    public boolean getIsActive() {
        return isActive;
    }
    public void setIsActive(boolean isActive) {
        this.isActive = isActive;
    }
    @Basic
    private String getIsActiveValue() {
        if (isActive) {
            return "T";
        } else {
            return "F";
        }
    }
    private void setIsActiveValue(String isActive) {
        this.isActive = "T".equals(isActive);
    }
}

http://en.wikibooks.org/wiki/Java_Persistence/Basic_Attributes#Conversion

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