如何在@ManyToMany JPA 关系的一侧反转键值映射类型

Question

我需要关于 KeyStoreEntity 与其 3 个子实体 (KeyPairEntity, SecretKeyEntity, CertificateEntity) 之间的多对多关系的建议。我将在此示例中使用CertificateEntity，因为其他 2 遵循相同的模式/问题。我的扩展类BaseRdbmsEntity 是一个@MappedSuperclass，具有id、name 和description 属性。

我对双方的@ManyToMany 没有任何问题，并在KeystoreEntity 方面使用Map<String, CertificateEntity> 通过他们的别名获取证书，并在CertificateEntity 上使用Map<String, KeyStoreEntity> 来获取别名和相关的密钥库。

然后我意识到我把它搞砸了，因为证书很容易在不同的密钥库中具有相同的别名......因此CertificateEntity 映射键可能会发生冲突，并且一个值会在存储库查询期间清除存储在其中的后续值。

我需要将CertificateEntity 中映射属性的键/值类型反转为Map<KeyStoreEntity, String>。我不清楚我如何使用@MapKeyValue（我意识到这不存在）将别名作为映射中的值......而不是作为键。

我试图通过使用@JoinTable 注释来解决此问题，但我没有看到与@MapKeyColumn 等效的映射值侧。我想要的是KeyStoreEntity 作为键和String alias 作为值。

@Entity(name = "keystores")
@Table(name = "pki_keystores")
public class KeyStoreEntity extends BaseRdbmsSecurityEntity
{
    @MapKeyColumn(name="alias")
    @ManyToMany
    (
        fetch = FetchType.LAZY,
        cascade = {CascadeType.PERSIST, CascadeType.MERGE}
    )
    private Map<String, CertificateEntity> certificates;
    ...snip...
}

@Entity(name = "certificates")
@Table(name = "pki_certificates", uniqueConstraints = {
    @UniqueConstraint(columnNames = {"issuerDn", "serialNumber"})
})
public class CertificateEntity extends BaseRdbmsSecurityEntity
{
    @MapKeyColumn(name="alias")
    @ManyToMany(
        fetch = FetchType.LAZY,
        cascade = {CascadeType.PERSIST, CascadeType.MERGE},
        mappedBy = "certificates",
        targetEntity = KeyStoreEntity.class
    )
    private Map<String, KeyStoreEntity> keystores;
    // Map type for above needs to be <KeyStoreEntity, String>
    ...snip...
}

我希望延迟获取可以在关系的CertificateEntity.keystores 一侧使用反转的 k/v。我的期望是我只需要为keystores 属性调整/添加注释到CertificateEntity。

Answer 1

这是一个单向/双向关系多对多的示例。我希望您能轻松地将其调整为您的代码）这只是List 的简单示例。 Check out this question 也是如此

@ManyToMany

unidirectional:

用户.java

@Entity
public class User {

    @Id
    @GeneratedValue
    @Column(name = "user_id")
    private long id;

    ...

    @ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinTable(name = "user_role", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "role_id"))
    private List<Role> roles = new ArrayList<>();

    public void addRoles(Role role) {
        roles.add(role);
    }

    public void removeRoles(Role role) {
        roles.remove(role);
    }
}

角色.java

@Entity
public class Role {

    @Id
    @GeneratedValue
    @Column(name = "role_id")
    private int id;

    @Column(name = "role")
    private String role;
}

bidirectional:

Trader.java：

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@ToString(exclude = "stockmarkets")
@Table(name = "trader")
public class Trader {

    @Id
    @GeneratedValue
    @Column(name = "trader_id")
    private Long id;

    @Column(name = "trader_name")
    private String traderName;

    @ManyToMany(fetch = FetchType.LAZY,
            cascade = {
            CascadeType.PERSIST,
            CascadeType.MERGE
    })
    @JoinTable(name = "TRADER_STOCKMARKET",
            joinColumns = { @JoinColumn(name = "trader_id") },
            inverseJoinColumns = { @JoinColumn(name = "stockmarket_id") })
    private List<Stockmarket> stockmarkets = new ArrayList<>();


    /*
    We need to add methods below to make everything work correctly
     */

    public void addStockmarket(Stockmarket stockmarket) {
        stockmarkets.add(stockmarket);
        stockmarket.getTraders().add(this);
    }

    public void removeStockmarket(Stockmarket stockmarket) {
        stockmarkets.remove(stockmarket);
        stockmarket.getTraders().remove(this);
    }

}

Stockmarket.java

@Data
@AllArgsConstructor
@NoArgsConstructor
@Entity
@ToString(exclude = "traders")
@Table(name = "stockmarket")
public class Stockmarket{

    @Id
    @GeneratedValue
    @Column(name = "stockmarket_id")
    private Long id;

    @Column(name = "stockmarket_name")
    private String stockmarketName;

    @ManyToMany(mappedBy="stockmarkets")
    private List<Trader> traders = new ArrayList<>();

    /*
    We need to add methods below to make everything work correctly
     */

    public void addTrader(Trader trader) {
        traders.add(trader);
        trader.getStockmarkets().add(this);
    }

    public void removeTrader(Trader trader) {
        traders.remove(trader);
        trader.getStockmarkets().remove(this);
    }

}