Spring JPA 存储库查询过滤器按关系 table

Question

如果我在 JPA 实体之间有如下所示的多对多关系，我如何检索属于特定公司员工的 Person（我对人员属性感兴趣）的列表？

Person和Company之间的关系是多对多的。关系 table Employee 具有指向 Person 和 Company 的 FK，以及 start_date 和 end_date 以指示雇佣开始和结束的时间。

@Entity
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

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

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

@Entity
public class Company {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

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

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

@Entity
public class CompanyEmployee {
    //note this is to model a relationship table. Am I doing this wrong?
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "start_date", nullable = false)
    private LocalDate startDate;

    @Column(name = "end_date", nullable = false)
    private LocalDate endDate;

    @ManyToOne
    private Company company;

    @ManyToOne
    private Person person;
}

我在 CompanyEmployeeJPARepository 上使用 @Query 吗？我该如何应对？

public interface CompanyEmployeeRepository extends JpaRepository<CompanyEmployee,Long> {
//
}

Answer 1

我以前有过 Hibernate JPA 的经验，但没有 spring JPA。根据这些知识，以下查询可能会有用：

select cp.person from CompanyEmployee cp where cp.company.id = ?

Answer 2

巴勃罗，
我们公司正在将我们现有的 Spring / MyBatis 代码转换为 Spring 数据JPA，所以这几周一直在学习Spring Data JPA。我显然不是专家，但我想出了一个类似于你的例子，可能会对你有所帮助。

我有 Person 和 Company class 与您的相似，但是（如 Jens 所述），您需要带有 OneToMany 注释的列表。我使用了一个单独的联接 table（名为 company_person），它只有 companyId、personId 列来维护 多对多关系。请参阅下面的代码。

我没有找到将 start/end 日期放入 company_person 连接 table 的方法，因此我为此单独制作了一个（第 4 个 table）。我用 Java class 实体 EmploymentRecord 称它为 employment_record。它具有组合主键 (companyId, personId) 和 start/end 日期。

您需要 Person、Company 和 EmploymentRecord 的存储库。我扩展了 CrudRepository 而不是 JpaRepository。但是，您不需要用于连接的实体或存储库 table (company_record).

我制作了一个 Spring 启动应用程序 class 来测试它。我在 Person 的 OneToMany 上使用了 CascadeType.ALL。在我的应用程序测试中，我测试了我可以更改分配给一个人的公司，并且 Spring 数据将所有需要的更改传播到 Company 个实体并加入 table。

但是，我不得不通过其存储库手动更新 EmploymentRecord 实体。比如我每次加一个公司给一个人都要加一个start_date。然后，当我从那个人那里删除那个公司时，添加一个 end_date。可能有某种方法可以自动执行此操作。 Spring / JPA 审计功能是可能的，所以检查一下。

您问题的答案：

how can I retrieve a list of Person (I am interested in the person attributes) that are employees of a specific company?

您只需使用 companyRepository 的 findOne(Long id) 方法，然后使用 getPersonList() 方法。

来自 Application.java 的片段：

PersonRepository pRep = context.getBean(PersonRepository.class);
CompanyRepository cRep = context.getBean(CompanyRepository.class);
EmploymentRecordRepository emplRep = context.getBean(EmploymentRecordRepository.class);

...

// fetch a Company by Id and get its list of employees
Company comp = cRep.findOne(5L);
System.out.println("Found a company using findOne(5L), company= " + comp.getName());
System.out.println("People who work at " + comp.getName());
for (Person p : comp.getPersonList()) {
    System.out.println(p);
}

以下是我认为有用的一些参考资料：

Spring Data JPA tutorial
Join Table example

Person.java:

@Entity
public class Person {

    // no-arg constructor
    Person() { }

    // normal use constructor
    public Person(String name, String address) {
        this.name = name;
        this.address = address;
    }

    @Id
    @GeneratedValue
    private Long id;

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

    @Column(name = "address")
    private String address;

    @Version
    private int versionId;

    @OneToMany(cascade=CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinTable(name="company_person",  
    joinColumns={@JoinColumn(name="person_id", referencedColumnName="id")},  
    inverseJoinColumns={@JoinColumn(name="company_id", referencedColumnName="id")})  
    private List<Company> companyList;  

    // Getters / setters

}

Company.java:

@Entity
public class Company {

    // no-arg constructor
    Company() { }

    // normal use constructor
    public Company(String name, String address) {
        this.name = name;
        this.address = address;
    }

    @Id
    @GeneratedValue
    private Long id;

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

    @Column(name = "address")
    private String address;

    @Version
    private int versionId;

    //@OneToMany(cascade=CascadeType.ALL)
    @OneToMany(fetch = FetchType.EAGER)
    @JoinTable(name="company_person",  
    joinColumns={@JoinColumn(name="company_id", referencedColumnName="id")},  
    inverseJoinColumns={@JoinColumn(name="person_id", referencedColumnName="id")})  
    private List<Person> personList;  

    // Getters / Setters
}

EmploymentRecord.java:

@Entity
@IdClass(EmploymentRecordKey.class)
public class EmploymentRecord {

    // no-arg constructor
    EmploymentRecord() { }

    // normal use constructor
    public EmploymentRecord(Long personId, Long companyId, Date startDate, Date endDate) {
        this.startDate = startDate;
        this.endDate = endDate;
        this.companyId = companyId;
        this.personId = personId;
    }

    // composite key
    @Id
    @Column(name = "company_id", nullable = false)
    private Long companyId;

    @Id
    @Column(name = "person_id", nullable = false)
    private Long personId;

    @Column(name = "start_date")
    private Date startDate;

    @Column(name = "end_date")
    private Date endDate;

    @Version
    private int versionId;

    @Override
    public String toString() {
        return
                " companyId=" + companyId +
                " personId=" + personId +
                " startDate=" + startDate +
                " endDate=" + endDate +
                " versionId=" + versionId;
    }

    // Getters/Setters

}

// Class to wrap the composite key
class EmploymentRecordKey implements Serializable {

    private long companyId;
    private long personId;

    // no arg constructor
    EmploymentRecordKey() { }

    @Override
    public int hashCode() {
        return (int) ((int) companyId + personId);
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) return false;
        if (obj == this) return true;
        if (!(obj instanceof EmploymentRecordKey)) return false;
        EmploymentRecordKey pk = (EmploymentRecordKey) obj;
        return pk.companyId == companyId && pk.personId == personId;
    }

    // Getters/Setters
}

MySql 脚本，createTables.sql:

DROP TABLE IF EXISTS `test`.`company_person`;
DROP TABLE IF EXISTS `test`.`employment_record`;
DROP TABLE IF EXISTS `test`.`company`;
DROP TABLE IF EXISTS `test`.`person`;

CREATE TABLE `company` (
  `id` int NOT NULL AUTO_INCREMENT,
  `name` varchar(128) NOT NULL DEFAULT '',
  `address` varchar(500) DEFAULT '',
  `version_id` int NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `person` (
  `id` int NOT NULL AUTO_INCREMENT,
  `name` varchar(128) NOT NULL DEFAULT '',
  `address` varchar(500) DEFAULT '',
  `version_id` int NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

/* Join table */
CREATE TABLE `company_person` (
  `company_id` int NOT NULL,
  `person_id` int NOT NULL,
  PRIMARY KEY (`person_id`,`company_id`),
  KEY `company_idx` (`company_id`),
  KEY `person_idx` (`person_id`),
  CONSTRAINT `fk_person` FOREIGN KEY (`person_id`) REFERENCES `person` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `fk_company` FOREIGN KEY (`company_id`) REFERENCES `company` (`id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

/* Employment records */
CREATE TABLE `employment_record` (
  `company_id` int NOT NULL,
  `person_id` int NOT NULL,
  `start_date` datetime,
  `end_date` datetime,
  `version_id` int NOT NULL,
  PRIMARY KEY (`person_id`,`company_id`),
  KEY `empl_company_idx` (`company_id`),
  KEY `empl_person_idx` (`person_id`),
  CONSTRAINT `fk_empl_person` FOREIGN KEY (`person_id`) REFERENCES `person` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `fk_empl_company` FOREIGN KEY (`company_id`) REFERENCES `company` (`id`) ON DELETE CASCADE ON UPDATE CASCADE

) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Answer 3

您不需要为关系 table 创建一个单独的实体。

可以在两个实体内维护关系，

所以如果A和B是多对多关系，

@Entity
class A {

@Id
Long id;
...

@ManyToMany(fetch=FetchType.LAZY)
@JoinTable(name="a_b",
            joinColumns={@JoinColumn(name="id_a", referencedColumnName="id")},
            inverseJoinColumns={@JoinColumn(name="id_b", referencedColumnName="id")})
List<B> bList;

...

}


@Entity
class B {

@Id
Long id;
...

@ManyToMany(fetch=FetchType.LAZY)
@JoinTable(name="a_b",
            joinColumns={@JoinColumn(name="id_b", referencedColumnName="id")},
            inverseJoinColumns={@JoinColumn(name="id_a", referencedColumnName="id")})
List<A> aList;

...

}

您现在可以在任一实体存储库上使用存储库查询，或者如果您在两个实体存储库上都有带参数的查询，则可以在其中一个存储库中创建自定义查询。

Spring JPA 存储库查询过滤器按关系 table

Spring JPA Repository query filter by a relationship table

java

spring

jpa

spring-data

spring-data-jpa