java - Hibernate一对多映射注释问题

Question

我是 Hibernate 新手。我有两个表 Team(父)和 Product(子)，其中 TEAM_ID 列作为关系，每个团队将有多个产品，每个产品将有一个团队。我在 Team 类中创建了带有 @OneToMany 映射的实体类，在 Product 类中创建了带有 @ManyToOne 映射的实体类。

我需要掩盖以下场景，

1. 在新团队成立时保存产品和团队
2. 如果团队已经可用，则仅保存产品

当我尝试保存产品时，它尝试再次保存团队抛出约束错误。请帮忙。

Team:

@Entity
@Table(name = "TEAM")
public class Team implements Serializable{

private static final long serialVersionUID = 5819170381583611288L;

@Id
@SequenceGenerator(name="teamIdSeq",sequenceName="team_id_seq",allocationSize=1)
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="teamIdSeq")
@Column(name="TEAM_ID", updatable = false, nullable = false, unique = true)
private int teamId;

@Column(name="NAME", nullable = false, unique = true)
private String teamName;

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

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

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

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

@Temporal(TemporalType.DATE)
@Column(name="CREATED_ON", nullable = false)
private Date createdOn;

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

@Temporal(TemporalType.DATE)
@Column(name="MODIFIED_ON", nullable = false)
private Date modifiedOn;

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

@OneToMany(fetch = FetchType.LAZY, mappedBy="team", cascade = CascadeType.ALL)
private Set<Product> products;

//setters and getters   
}

Product:

@Entity
@Table(name = "PRODUCT", uniqueConstraints = {@UniqueConstraint(columnNames = {"PRODUCT_ID", "TEAM_ID"})})
public class Product implements Serializable{

private static final long serialVersionUID = 5819170381583611288L;

@Id
@SequenceGenerator(name="productIdSeq", sequenceName="product_id_seq",allocationSize=1)
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="productIdSeq")
@Column(name="PRODUCT_ID", updatable = false, nullable = false)
private int productId;

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "TEAM_ID")
private Team team;

@Column(name="NAME", nullable = false, unique = true)
private String productName;

@Column(name="DESCRIPTION", nullable = true)
private String productDesc;

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

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

@Temporal(TemporalType.DATE)
@Column(name="CREATED_ON", nullable = false)
private Date createdOn;

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

@Temporal(TemporalType.DATE)
@Column(name="MODIFIED_ON", nullable = false)
private Date modifiedOn;

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

@OneToMany(fetch = FetchType.LAZY, mappedBy="product")
private Set<Form> forms;
//setters and getters   
}

DAO:

@Repository
@EnableTransactionManagement
public class KMDBDAOImpl implements KMDBDAO {

@Autowired
private SessionFactory sessionFactory;

public void addTeam(Team team) {
    Product product = new Product(team, "BMA" + Math.random(), "UI Tool", "test", 
            1, new Date(), "test", new Date(), "test");
    Set<Product> products = new HashSet<Product>();
    products.add(product);
    team.setProducts(products);
    if(getTeam(team.getTeamName()) != null) {
        product.setTeam(getTeam(team.getTeamName()));
        sessionFactory.getCurrentSession().saveOrUpdate(product);
    } else {
        sessionFactory.getCurrentSession().saveOrUpdate(team);
    }
}

public Team getTeam(String teamName) {
    Query query = sessionFactory.getCurrentSession().createQuery("from Team where teamName = :name");  
    query.setString("name", "teamName");
    return (query.list().size() > 0 ? (Team) query.list().get(0) : null);
}

Answer 1

只有当团队是一个新实体时，您才应该在团队上设置产品列表。所以:

Set<Product> products = new HashSet<Product>();
products.add(product);
if(getTeam(team.getTeamName()) != null) {
    product.setTeam(getTeam(team.getTeamName()));
    sessionFactory.getCurrentSession().saveOrUpdate(product);
} else {
    team.setProducts(products);
    sessionFactory.getCurrentSession().saveOrUpdate(team);
}