无法写入内容：未能懒惰地初始化角色集合

Question

@Entity
@Table(name = "catalog")
public class Catalog {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "catalog_id")
    private int catalog_id;

    @NotEmpty
    @Size(min = 3, max = 255)
    @Column(name = "name", nullable = false)
    private String name;

    @OneToMany(mappedBy="mycatalogorder")
    private List<Order> orders;

    @OneToMany(mappedBy="mycatalog")
    private List<CatalogItem> items;

    // setters and getters
}

 @Entity
 @Table(name = "catalogitem")
 public class CatalogItem {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "catalogitem_id")
    private int catalogitem_id;

    @NotEmpty
    @Size(min = 3, max = 255)
    @Column(name = "name", nullable = false)
    private String name;

    @NotEmpty
    @Column(name = "price", nullable = false)
    private Double price;

    @OneToOne(mappedBy="ordercatalogitem", cascade=CascadeType.ALL)
    private OrderItem morderitem;

    @ManyToOne
    @JoinColumn(name="catalog_id", nullable=false)
    private Catalog mycatalog;

    // setters and getters
}

@Entity
@Table(name = "orders")
public class Order {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "order_id")
    private int order_id;

    @NotEmpty
    @Size(min = 3, max = 255)
    @Column(name = "name", nullable = false)
    private String name;

    @NotEmpty
    @Size(min = 3, max = 1024)
    @Column(name = "note", nullable = false)
    private String note;

    @Temporal(TemporalType.TIMESTAMP)
    @DateTimeFormat(pattern = "ddmmYYYY HH:mm:ss")
    @Column(name = "created", nullable = false)
    private Date created;

    @OneToMany(mappedBy="myorder")
    private Set<OrderItem> orderItems;

    @ManyToOne
    @JoinColumn(name="catalog_id", nullable=false)
    private Catalog mycatalogorder;

    @PrePersist
    protected void onCreate() {
        created = new Date();
    }

    // setters and getters
}

@Entity
@Table(name = "orderitem")
public class OrderItem {

    @Id
    @Column(name="catalogitem_id", unique=true, nullable=false)
    @GeneratedValue(generator="gen")
    @GenericGenerator(name="gen", strategy="foreign", parameters=@Parameter(name="property", value="catalogitem"))
    private int catalogitem_id;

    @Column(name = "quantity")
    private int quantity;

    @OneToOne
    @PrimaryKeyJoinColumn
    private CatalogItem ordercatalogitem;

    @ManyToOne
    @JoinColumn(name="order_id", nullable=false)
    private Order myorder;
     // setters and getters
}

我的版本是：

• SpringFramework 4.2.4.发布
• Hibernate4.3.11.final
• 杰克逊2.7.4
• 杰克逊类型2.7.1

Answer 1

这是正常的冬眠行为

在一对多关系中，hibernate加载父实体（在本例中为目录），但它将以惰性模式加载子实体列表（在本例中为列表项和列表顺序）

这意味着您不能访问这些对象，因为它们只是代理而不是真正的对象

这是有用的，以避免在执行查询时加载完整的数据库

您有两个解决方案：

1. 在EAGER模式下加载子实体（我强烈建议您不要这样做，因为您可以加载完整的DB...，但这与您的场景有关
2. 不使用com.fasterxml.jackson.annotation.jsonIgnore属性在JSON中序列化子实体