Question

我有两个实体：CollabEntity和TechnoEntity。

协作可以使用多个 technos 。
技术可以由多个合作使用。

我想知道特定合作使用的所有技术。

我的数据库看起来像：

CREATE TABLE collabs(
    co_id INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
    co_firstname VARCHAR(25) NOT NULL,
    co_lastname VARCHAR(30) NOT NULL,
);

CREATE TABLE technos(
    te_id INT PRIMARY KEY NOT NULL AUTO_INCREMENT,
    te_tech VARCHAR(20)
);

CREATE TABLE cote( //Joins Collab & Techno
    co_id INT NOT NULL,
    te_id INT NOT NULL,
    CONSTRAINT fk_cote_co_id FOREIGN KEY(co_id) REFERENCES collabs(co_id),
    CONSTRAINT fk_cote_te_id FOREIGN KEY(te_id) REFERENCES technos(te_id),
    PRIMARY KEY(co_id, te_id)
);

CollabEntity.java

@Entity
@Table(name = "collabs")
public class CollabEntity {
    @Id
    @GeneratedValue
    @Column(name = "co_id")
    private long id;

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

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

    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "technos", 
               joinColumns = {@JoinColumn(name = "co_id", nullable = false, updatable = false)},
               inverseJoinColumns = @JoinColumn(name = "te_id")
    )
    private Set<TechnoEntity> technos = new HashSet<TechnoEntity>();

    protected CollabEntity() {
    }

    public CollabEntity(String firstname, String lastname) {
        this.firstname = firstname;
        this.lastname = lastname;
    }

    public long getId() {
        return id;
    }

    public String getFirstname() {
        return firstname;
    }

    public String getLastname() {
        return lastname;
    }

    public Set<TechnoEntity> getTechnos() {
        return technos;
    }
}

TechnoEntity.java

@Entity
@Table(name = "technos")
public class TechnoEntity {
    @Id
    @GeneratedValue
    @Column(name = "te_id")
    private long id;

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

    @ManyToMany(mappedBy="technos")
    private Set<CollabEntity> collabs = new HashSet<CollabEntity>();

    protected TechnoEntity() {}

    public TechnoEntity(String techno) {
        this.tech = techno;
    }

    public long getId() {
        return id;
    }

    public String getTech() {
        return tech;
    }
}

我在没有找到解决方案的情况下尝试了几个小时。这是我的错误：

线程“main”中的异常 org.springframework.beans.factory.BeanCreationException：错误在类路径中定义名为'entityManagerFactory'的bean resource [fr / xxx / dao / DatabaseConfig.class]：调用init方法失败;嵌套异常是javax.persistence.PersistenceException： [PersistenceUnit：default]无法构建Hibernate SessionFactory

准确地说：

引起：org.hibernate.MappingException：外键（FK_pc2r8qfxqv9jpgsfxrs61kfql：technos [te_id]））必须具有相同的编号列作为引用的主键（technos [co_id，te_id]）

Answer 1

在public ActionResult Index(string id) { db.Configuration.LazyLoadingEnabled = false; string searchString = id; var songs = from m in db.Songs select m; if (!String.IsNullOrEmpty(searchString)) { songs = songs.Where(s => s.Title.Contains(searchString)); } var mappedSongs = songs.Select(it => new { Title = it.Title, Artist = it.Artist }).ToList(); return Json(mappedSongs , JsonRequestBehavior.AllowGet); }中更改多对多的映射。您需要更改连接表名称。即从technos命名为其他名称。

CollabEntity

Hibernate的ManyToMany简单使用

1 个答案: