Hibernate父子实体更新策略：高效管理关联集合变更

import jakarta.persistence.*;

@Entity
@Table(name = "ingredients")
public class Ingredient {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    // 构造函数
    public Ingredient() {}
    public Ingredient(String name) { this.name = name; }

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Ingredient that = (Ingredient) o;
        return id != null && id.equals(that.id);
    }

    @Override
    public int hashCode() {
        return id != null ? id.hashCode() : 0;
    }
}

import jakarta.persistence.*;
import java.io.Serializable;

@Entity
@Table(name = "recipe_ingredients")
public class RecipeIngredient implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id; // 使用单一主键简化，也可以使用复合主键

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "recipe_id")
    private Recipe recipe;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "ingredient_id")
    private Ingredient ingredient;

    private Integer quantity; // 例如：配料数量

    // 构造函数
    public RecipeIngredient() {}
    public RecipeIngredient(Recipe recipe, Ingredient ingredient, Integer quantity) {
        this.recipe = recipe;
        this.ingredient = ingredient;
        this.quantity = quantity;
    }

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public Recipe getRecipe() { return recipe; }
    public void setRecipe(Recipe recipe) { this.recipe = recipe; }
    public Ingredient getIngredient() { return ingredient; }
    public void setIngredient(Ingredient ingredient) { this.ingredient = ingredient; }
    public Integer getQuantity() { return quantity; }
    public void setQuantity(Integer quantity) { this.quantity = quantity; }

    // 确保equals和hashCode基于业务唯一性，如果使用id作为主键，则基于id
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        RecipeIngredient that = (RecipeIngredient) o;
        return id != null && id.equals(that.id);
    }

    @Override
    public int hashCode() {
        return id != null ? id.hashCode() : 0;
    }
}

import jakarta.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Entity
@Table(name = "recipes")
public class Recipe {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String title;

    @OneToMany(mappedBy = "recipe", cascade = CascadeType.ALL, orphanRemoval = true, fetch = FetchType.LAZY)
    private Set<RecipeIngredient> recipeIngredients = new HashSet<>();

    // 构造函数
    public Recipe() {}
    public Recipe(String title) { this.title = title; }

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getTitle() { return title; }
    public void setTitle(String title) { this.title = title; }
    public Set<RecipeIngredient> getRecipeIngredients() { return recipeIngredients; }
    public void setRecipeIngredients(Set<RecipeIngredient> recipeIngredients) { this.recipeIngredients = recipeIngredients; }

    // 辅助方法，用于维护双向关联的一致性
    public void addRecipeIngredient(RecipeIngredient recipeIngredient) {
        recipeIngredients.add(recipeIngredient);
        recipeIngredient.setRecipe(this);
    }

    public void removeRecipeIngredient(RecipeIngredient recipeIngredient) {
        recipeIngredients.remove(recipeIngredient);
        recipeIngredient.setRecipe(null); // 解除关联
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Recipe that = (Recipe) o;
        return id != null && id.equals(that.id);
    }

    @Override
    public int hashCode() {
        return id != null ? id.hashCode() : 0;
    }
}

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.stream.Collectors;

// 假设存在 RecipeRequest DTO 和 RecipeIngredientRequest DTO
// public class RecipeRequest { private Long id; private String title; private Set<RecipeIngredientRequest> recipeIngredients; ... }
// public class RecipeIngredientRequest { private Long ingredientId; private Integer quantity; ... }

@Service
public class RecipeService {

    private final RecipeRepository recipeRepository;
    private final IngredientRepository ingredientRepository;

    public RecipeService(RecipeRepository recipeRepository, IngredientRepository ingredientRepository) {
        this.recipeRepository = recipeRepository;
        this.ingredientRepository = ingredientRepository;
    }

    @Transactional // 确保整个操作在一个事务中
    public void updateRecipe(RecipeRequest request) {
        // 1. 加载现有 Recipe 实体
        final Recipe existingRecipe = recipeRepository.findById(request.getId())
                .orElseThrow(() -> new NoSuchElementException("Recipe not found with ID: " + request.getId()));

        // 2. 更新 Recipe 的基本属性
        existingRecipe.setTitle(request.getTitle()); // 假设有 capitalizeFully 方法，这里简化

        // 3. 清空现有子实体集合
        // 这一步是核心。由于配置了 orphanRemoval = true，
        // 集合中原有的 RecipeIngredient 实例在从集合中移除后，将被Hibernate自动删除。
        existingRecipe.getRecipeIngredients().clear();

        // 4. 根据请求添加新的/更新的子实体
        request.getRecipeIngredients().forEach(recipeIngredientRequest -> {
            // 查找 Ingredient 实体
            final Ingredient ingredient = ingredientRepository.findById(recipeIngredientRequest.getIngredientId())
                    .orElseThrow(() -> new NoSuchElementException("Ingredient not found with ID: " + recipeIngredientRequest.getIngredientId()));

            // 创建新的 RecipeIngredient 实例
            RecipeIngredient newRecipeIngredient = new RecipeIngredient(
                existingRecipe, // 关联到当前 Recipe
                ingredient,
                recipeIngredientRequest.getQuantity()
            );

            // 将新的 RecipeIngredient 添加到 Recipe 的集合中
            // addRecipeIngredient 辅助方法会维护双向关联
            existingRecipe.addRecipeIngredient(newRecipeIngredient);
        });

        // 5. 保存父实体
        // Hibernate 会检测到 existingRecipe 集合的变化，并根据 cascade 和 orphanRemoval 规则
        // 执行必要的 INSERT 和 DELETE 操作。
        recipeRepository.save(existingRecipe);
    }
}