java - thymeleaf 中对 @OneToMeny 和 @ManyToOne 类的无尽 hibernate 查询

Question

各位，我自己创建了两个正在流通的类(class)。

添加剂类

@Entity
@Table(name = "additive", schema = "dbo")
@Data
@NoArgsConstructor
public class Additive{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "additive_id")
    private Integer id;

    @ManyToOne(targetEntity = AdditiveType.class, fetch = FetchType.LAZY)
    @JoinColumn(name = "additive_type_id")
    private AdditiveType additiveType;

    private String description;
    private BigDecimal price;
}

以及带有类型的类

@Entity
@Table(name = "additive_type", schema = "dbo")
@Data
@NoArgsConstructor
public class AdditiveType{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "additive_type_id")
    private Integer id;

    @OneToMany(targetEntity = Additive.class, fetch = FetchType.LAZY)
    @JoinColumn(name = "additive_type_id")
    private Set<Additive> additives;

    private String description;
}

当我尝试使用 thymeleaf 显示代码时

<div th:each="aType:${types}">
    <h2 th:text="${aType.description}">type</h2>
    <div>
        <div th:each="additive:${aType.additives}">
            <div>
                <img alt="${additive.description}"
                     src="...">
                <div>
                    <h5 th:text="${additive.description}">additive description</h5>
                </div>
                <div>
                    <form method="post"
                          th:action="...">
                        <input name="id" th:value="${additive.id}" type="hidden"/>
                        <button type="submit">select this</button>
                    </form>
                </div>
            </div>
        </div>
    </div>
</div>

即使提取类型被标记为惰性fetch = FetchType，我也会从一个表additive一次从另一个additive_type对数据库进行无休止的查询。懒惰

如何解决这个问题？

更新

不幸的是，@JsonIgnoreProperties 和 @JsonIgnore 都没有导致循环查询中断。我在其余服务中使用了这些注释并且它在那里工作。在 thymeleaf 这里，它没有带来预期的效果。

Answer 1

我认为您遇到了循环序列化问题。

您有一个Additive有AdditiveTypes与 Additives 相关有AdditiveTypes与 Additives 相关....等等，等等。

解决该问题的一种方法是用 @JsonIgnoreProperties 注释您的类属性之一。例如:

@Entity
@Table(name = "additive_type", schema = "dbo")
@Data
@NoArgsConstructor
public class AdditiveType{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "additive_type_id")
    private Integer id;

    @OneToMany(targetEntity = Additive.class, fetch = FetchType.LAZY)
    @JoinColumn(name = "additive_type_id")
    @JsonIgnoreProperties("additiveType")
    private Set<Additive> additives;

    private String description;
}

所以当序列化 AdditiveType 时，内部的additiveTypes不会被序列化。

更新

而且我认为如果你只用 @JsonIgnore 进行注释然后Additives AdditiveTypes的根本不会被序列化