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jesmith17
Asked: 2024-12-21 13:20:52 +0800 CST

@MappedSuperclass 被分配给 @OneToMany spring-data

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我正在开发一款用于跟踪客户帐户的应用程序。每个客户可以拥有多个帐户。挑战在于帐户对象是多态的。有一个抽象类，Account其中包含 2-3 种方法，并且目前有 2 个子类型SavingsAccount和CreditAccount。

我尝试让Account对象使用@MappedSuperclass注释，然后每个具体类@Entity都像正常一样有注释。

问题似乎是我的客户对象的映射

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinColumn(name="customer_id", referencedColumnName = "id")
    List<Account> accounts = new ArrayList<>();

当我使用它时，我在 IDE 中收到来自 Spring 的警告，但在运行时我收到此错误。

com.example.models.Customer.accounts' targets the type 'com.example.models.Account' which is not an '@Entity' type

有没有办法对多态对象列表进行 @OneToMany 映射？即使它们存储在同一张表中？

spring-data-jpa

1 个回答

  1. Best Answer

    @MappedSuperclass用于在@Entity带注释的类之间重用公共属性，并不直接适用于您当前的情况。但是，@MappedSuperclass您的情况的正确用法示例如下：

    @MappedSuperclass
public abstract class MyMappedSuperclass {

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

    // getter/setter
}

    并让Customer继承MyMappedSuperclass。

    您需要使用和Account注释基类。这将启用多态查询，您可以查询基类并检索其所有子类。如果对所有子类使用单个表，则该类可能如下所示：@Entity @InheritanceAccount

    import jakarta.persistence.*;

@Entity
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "account_type")
public abstract class Account {

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

    @ManyToOne
    @JoinColumn(name = "customer_id", nullable = false)
    private Customer customer;

    // getters and setters
}

    你的子类将如下所示

    import jakarta.persistence.DiscriminatorValue;

@DiscriminatorValue("SAVINGS")
public class SavingsAccount extends Account {
}

@DiscriminatorValue("CREDIT")
public class CreditAccount extends Account {
}

    我通过此客户实现验证了上述代码：

    import jakarta.persistence.*;

import java.util.ArrayList;
import java.util.List;

@Entity
public class Customer {

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

    @OneToMany(mappedBy = "customer", cascade = CascadeType.ALL)
    private List<Account> accounts = new ArrayList<>();

    public void addAccount(Account account) {
        account.setCustomer(this);
        accounts.add(account);
    }

    // getters/setters
}

    客户资料库

    import org.springframework.data.repository.CrudRepository;

public interface CustomerRepository extends CrudRepository<Customer, Long> {
}

    Flyway 迁移（Postgresql）

    CREATE TABLE customer
(
    id SERIAL PRIMARY KEY
);

CREATE TABLE account
(
    id           SERIAL PRIMARY KEY,
    account_type VARCHAR(16) NOT NULL,
    customer_id  INT         NOT NULL,
    CONSTRAINT fk_customer FOREIGN KEY (customer_id) REFERENCES customer (id)
);

    PostgresTestContainer配置

    import org.springframework.boot.test.context.TestConfiguration;
import org.springframework.boot.testcontainers.service.connection.ServiceConnection;
import org.springframework.context.annotation.Bean;
import org.testcontainers.containers.PostgreSQLContainer;

@TestConfiguration
public class PostgresTestContainerConfig {

    @Bean
    @ServiceConnection
    public PostgreSQLContainer<?> postgreSQLContainer() {
        return new PostgreSQLContainer<>("postgres:15-alpine");
    }
}

    测试

    import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.jdbc.AutoConfigureTestDatabase;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
import org.springframework.context.annotation.Import;

import static org.junit.jupiter.api.Assertions.*;

@DataJpaTest
@AutoConfigureTestDatabase
@Import(no.vicx.database.PostgresTestContainerConfig.class)
class CustomerRepositoryTest {

    @Autowired
    TestEntityManager entityManager;

    @Autowired
    CustomerRepository sut;

    @Test
    void testInserts() {
        Customer customer = new Customer();
        customer.addAccount(new SavingsAccount());
        customer.addAccount(new CreditAccount());

        sut.save(customer);

        assertEquals(2, getAccountCountInDb());

        var customerInDb = entityManager.find(Customer.class, customer.getId());

        assertInstanceOf(SavingsAccount.class, customerInDb.getAccounts().getFirst());
        assertInstanceOf(CreditAccount.class, customerInDb.getAccounts().getLast());
    }

    long getAccountCountInDb() {
        return (long) entityManager.getEntityManager()
                .createQuery("SELECT COUNT(1) FROM Account ")
                .getSingleResult();
    }
}
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