具有双向关系的java持久化嵌套实体（onetomany）

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，并持久化该对象。JSON是一个配方实例的表示，一个配方可以有多个与其关联的步骤对象

食谱。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
}

一步。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
}

然而，当向应用程序发送以下JSON文档时，step对象中引用RECIPE_ID的外键是null，因此配方与其步骤之间没有连接

{
    "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": ""
        }
    ]
}

既然指定了CascadeType.ALL，嵌套的步骤对象是否也应该被持久化？此外，我使用RestController来处理请求，使用JpaRepository类来持久化

Answer 1

在你的控制器中，你将不得不这样做

for (Step step : recipe.getSteps()) {
    step.setRecipe(recipe);
}

你基本上错过了Step object中的back引用，当你发帖时它就是null

Answer 2

您可以在@many一侧添加@JsonBackReference注释，在@OneToMany一侧添加@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
}