Question

所以我有两个类，一个是Route，一个是BusStop。路线＆＃39;使用＆＃39;两个BusStop对象，一个作为开始，一个作为目标。我需要通过连接表映射这种关系，＆＃39;使用＆＃39;。

此联接表不需要区分BusStop是用于起点还是目的地。基本上我只需要在这个连接表中使用start和destination成为一个列（允许重复），这样我就可以得到一个完整的映射，显示哪些路由停止使用。

以下是我设置的方法（假设有吸气剂和固定剂）：

public class Route {
    @Id
    private String number;

    @Column(nullable = false)
    private int frequency;

    @ManyToOne
    @JoinTable(
        name = "Uses",
        joinColumns = @JoinColumn(name = "number"),
        inverseJoinColumns = @JoinColumn(name = "id")
    )
    private BusStop start;

    @ManyToOne
    @JoinTable(
        name = "Uses",
        joinColumns = @JoinColumn(name = "number"),
        inverseJoinColumns = @JoinColumn(name = "id")
    )
    private BusStop destination;
    ...
}

public class BusStop {
    @Id
    private int id;

    @Column(nullable = false)
    private String description;

    @OneToMany
    @JoinTable(
        name = "Uses",
        joinColumns = @JoinColumn(name = "id"),
        inverseJoinColumns = @JoinColumn(name = "number")
    )
    private Set<Route> routes;
    ...
}

现在我遇到的问题是，这导致了“使用”问题。只有每个Route id之一的表，尽管它成功地保留了重复的stop id。我假设它与我有关，试图创造两个用途＆＃39; Route类中的表？

那么究竟如何正确地解决这个问题呢？

Answer 1

我会采用更清洁的方式来做到这一点。

这是我的实体。

package com.ansh.entity;

import lombok.Getter;
import lombok.Setter;

import javax.persistence.*;

@Entity
@Table(name = "routes")
@Getter @Setter
public class Route {

    @Id
    @Column(name = "number")
    private String number;

    @Column(name = "frequency", nullable = false)
    private int frequency;

    @ManyToOne
    @JoinColumn(name = "start_id")
    private BusStop start;

    @ManyToOne
    @JoinColumn(name = "destination_id")
    private BusStop destination;
}

AND

package com.ansh.entity;

import com.google.common.collect.Sets;
import lombok.Getter;
import lombok.Setter;

import javax.persistence.*;
import java.util.Set;

@Entity
@Table(name = "bus_stops")
@Getter @Setter
public class BusStop {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

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

    @OneToMany(mappedBy = "start")
    private Set<Route> outgoingRoutes = Sets.newHashSet();

    @OneToMany(mappedBy = "destination")
    private Set<Route> incomingRoutes = Sets.newHashSet();

    public Set<Route> getRoutes() {
        return Sets.union(outgoingRoutes, incomingRoutes);
    }
}

JPA Annotations - 如何将两个字段合并为一个连接表的列？

1 个答案: