java - 保留具有双向关系的嵌套实体(一对多)

Question

我正在创建一个 Spring Boot Web 应用程序，该应用程序应该通过 HTTP 接收 JSON 文档，将其解析为相应的实体类，并保留该对象。 JSON 是 Recipe 实例的表示，一个配方可以有多个与其关联的 Step 对象。

Recipe.java

@Entity
public class Recipe {

    @Id
    @GeneratedValue
    private Long id;

    @NotNull
    private String name;

    @OneToMany(mappedBy = "recipe", cascade = CascadeType.ALL)
    private Set<Step> steps;

    // Additional attributes, constructors, getters and setters omitted
}

Step.java

@Entity
public class Step {

    @Id
    @GeneratedValue
    private Long id;

    @NotNull
    private String name;

    @ManyToOne
    @JoinColumn(name = "RECIPE_ID")
    private Recipe recipe;

    // Additional attributes, constructors, getters and setters omitted
}

但是，当将以下 JSON 文档发送到应用程序时，外键引用 RECIPE_ID步骤对象内是 null ，因此配方与其步骤之间没有联系。

{
    "name": "Test recipe",
    "description": "Test description",
    "type": "Test",
    "cookingTime": 45,
    "preparationTime": 30,
    "thumbnail": "",
    "steps": [
        {
            "number": 1,
            "name": "First step",
            "content": "Test content",
            "image": ""
        },
        {
            "number": 2,
            "name": "Second step",
            "content": "Test content",
            "image": ""
        }
    ]
}

自 CascadeType.ALL 起，嵌套步骤对象不应该也被持久化吗？已指定？另外，我正在使用 RestController处理请求和 JpaRepository坚持不懈的类(class)。

Answer 1

您可以在@ManyToOne端添加@JsonBackReference注释，在@OneToMany端添加@JsonManagedReference注释。

@Entity
public class Recipe {

    @Id
    @GeneratedValue
    private Long id;

    @NotNull
    private String name;

    @OneToMany(mappedBy = "recipe", cascade = CascadeType.ALL)
    @JsonManagedReference("recipe_steps")
    private Set<Step> steps;

    // Additional attributes, constructors, getters and setters omitted
}


@Entity
public class Step {

    @Id
    @GeneratedValue
    private Long id;

    @NotNull
    private String name;

    @ManyToOne
    @JoinColumn(name = "RECIPE_ID")
    @JsonBackReference("recipe_steps")
    private Recipe recipe;

    // Additional attributes, constructors, getters and setters omitted
}