Hibernate: @ManyToMany - relacja jedno i dwukierunkowa

Relacja @ManyToMany jest to połączenie dwóch tabel za pomocą relacji trzeciej tabeli.

Stworzenie tabel w bazie danych
Stworzenie klas Entity
Klasa testująca dodawanie obiektu
Klasa testująca usuwanie obiektu
Klasa testująca odczytywanie obiektu

✅ Stworzenie tabel w bazie danych

CREATE DATABASE IF NOT EXISTS `bazatestowa2`;

USE `bazatestowa2`;

CREATE TABLE IF NOT EXISTS recipe (

recipe_id INT AUTO_INCREMENT,

recipe_name VARCHAR(40) DEFAULT NULL,

PRIMARY KEY (recipe_id)

) ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS ingredient (

ingredient_id INT AUTO_INCREMENT,

ingredient_name VARCHAR(40) DEFAULT NULL,

PRIMARY KEY (ingredient_id)

) ENGINE=InnoDB;

CREATE TABLE IF NOT EXISTS recipe_ingredient (

recipe_id int NOT NULL,

ingredient_id int NOT NULL,

PRIMARY KEY (recipe_id, ingredient_id),

CONSTRAINT FK_RECIPE FOREIGN KEY (recipe_id)

REFERENCES recipe (recipe_id) ON DELETE NO ACTION ON UPDATE NO ACTION,

CONSTRAINT FK_INGREDIENT FOREIGN KEY (ingredient_id)

REFERENCES ingredient (ingredient_id) ON DELETE NO ACTION ON UPDATE NO ACTION

) ENGINE=InnoDB;

✅ Stworzenie klas Entity

👉 Entity Recipe

package myhibernate.direction.entity;
import java.util.ArrayList;
import java.util.List;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.ManyToMany;
import javax.persistence.Table;

@Entity
@Table(name = "recipe")
public class Recipe {
@Id
@Column(name = "recipe_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long recipeId;

@Column(name = "recipe_name")
private String recipeName;

public Recipe() {
}

public Recipe(String recipeName) {
this.recipeName = recipeName;
}
public String getRecipeName() {
return recipeName;
}
public void setRecipeName(String recipeName) {
this.recipeName = recipeName;
}
public List<Ingredient> getIngredients() {
return ingredients;
}
public void addIngredient(Ingredient ingredient) {
if (ingredients == null) {
ingredients = new ArrayList<Ingredient>();
}
ingredients.add(ingredient);
}
public void setIngredients(List<Ingredient> ingredients) {
this.ingredients = ingredients;
}
@Override
public String toString() {
return "Recipe [recipeId=" + recipeId + ", recipeName=" + recipeName + "]";
}
}

👉 Entity Ingredient

@Entity
@Table(name = "ingredient")
public class Ingredient {
@Id
@Column(name = "ingredient_id")
@GeneratedValue(strategy = GenerationType.IDENTITY)
private long ingredientId;

@Column(name = "ingredient_name")
private String ingredientName;

@ManyToMany(fetch = FetchType.LAZY, cascade = { CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST, CascadeType.REFRESH })
@JoinTable(name = "recipe_ingredient", joinColumns = @JoinColumn(name = "ingredient_id"), inverseJoinColumns = @JoinColumn(name = "recipe_id"))
List<Recipe> recipes;

public Ingredient() {
}

public Ingredient(String ingredientName) {
this.ingredientName = ingredientName;
}
public String getIngredientName() {
return ingredientName;
}
public void setIngredientName(String ingredientName) {
this.ingredientName = ingredientName;
}
public List<Recipe> getRecipes() {
return recipes;
}
public void setRecipes(List<Recipe> recipes) {
this.recipes = recipes;
}

public void addRecipe(Recipe recipe) {
if (recipes == null) {
recipes = new ArrayList<Recipe>();
}

recipes.add(recipe);
}
@Override
public String toString() {
return "Ingredient [ingredientId=" + ingredientId + ", ingredientName=" + ingredientName + "]";
}
}

✅ Klasa testująca dodawanie obiektu

👉 Klasa testująca

package myhibernate.direction;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import myhibernate.direction.entity.Recipe;

import myhibernate.direction.entity.Ingredient;

public class AddManyToManyApp {

public static void main(String[] args) {

Configuration conf = new Configuration();

conf.configure("hibernate.cfg.xml");

conf.addAnnotatedClass(Recipe.class);

conf.addAnnotatedClass(Ingredient.class);

SessionFactory factory = conf.buildSessionFactory();

Session session = factory.getCurrentSession();

session.beginTransaction();

//create ingredients

Ingredient ingredient1 = new Ingredient("mleko");

Ingredient ingredient2 = new Ingredient("proszek do pieczenia");

Ingredient ingredient3 = new Ingredient("biały ser");

Ingredient ingredient4 = new Ingredient("czekolada");

//create recipes

Recipe recipe1 = new Recipe("sernik");

recipe1.addIngeredient(ingredient1);

recipe1.addIngeredient(ingredient2);

recipe1.addIngeredient(ingredient3);

Recipe recipe2 = new Recipe("tort czekoladowy");

recipe2.addIngeredient(ingredient1);

recipe2.addIngeredient(ingredient2);

recipe2.addIngeredient(ingredient4);

//utrwalenie obiektu w bazie

session.persist(recipe1);

session.persist(recipe2);

session.getTransaction().commit();

factory.close();

}

❗ Wynik działania w konsoli:

❗Wynik w bazie danych:

1. tabela recipe

2. tabela ingredient

3. tabela recipe_ingredient

✅ Klasa testująca usuwanie obiektu

❗ Aktualy stan w bazie danych:

1. tabela recipe

2. tabela ingredient

3. tabela recipe_ingredient

👉 Klasa testująca

package myhibernate.direction;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import org.hibernate.query.Query;

import myhibernate.direction.entity.Ingredient;

import myhibernate.direction.entity.Recipe;

public class DeleteManyToManyApp {

public static void main(String[] args) {

Configuration conf = new Configuration();

conf.configure("hibernate.cfg.xml");

conf.addAnnotatedClass(Recipe.class);

conf.addAnnotatedClass(Ingredient.class);

SessionFactory factory = conf.buildSessionFactory();

Session session = factory.getCurrentSession();

session.beginTransaction();

String sql = "select distinct r from Recipe r join fetch r.ingredients where r.recipeName= :recipeName ";

Query<Recipe> query = session.createQuery(sql);

query.setParameter("recipeName", "sernik");

Recipe recipe = query.getSingleResult();

System.out.println("Recipe istnieje w baze:" + recipe);

for(Ingredient ingredient : recipe.getIngredients()) {

System.out.println("Ingredient: " + ingredient);

//kasujemy tylko składniki należące do przepisu sernik

if (ingredient.getRecipes().size() == 1) {

System.out.println("kasuje Ingredient: " + ingredient);

session.delete(ingredient);

}

session.delete(recipe);

session.getTransaction().commit();

factory.close();

}

❗ Wynik działania w konsoli:

❗ Wynik w bazie danych:

1. tabela recipe

2. tabela ingredient

3. tabela recipe_ingredient

✅ Klasa testująca odczytywanie obiektu

❗ Aktualy stan w bazie danych:

1. tabela recipe

2. tabela ingredient

3. tabela recipe_ingredient

👉 Klasa testująca

package myhibernate.direction;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import org.hibernate.query.Query;

import myhibernate.direction.entity.Ingredient;

import myhibernate.direction.entity.Recipe;

public class ReadManyToManyApp {

public static void main(String[] args) {

Configuration conf = new Configuration();

conf.configure("hibernate.cfg.xml");

conf.addAnnotatedClass(Recipe.class);

conf.addAnnotatedClass(Ingredient.class);

SessionFactory factory = conf.buildSessionFactory();

Session session = factory.getCurrentSession();

session.beginTransaction();

String sql = "select distinct r from Recipe r join fetch r.ingredients ";

Query<Recipe> query = session.createQuery(sql);

for(Recipe recipe : query.list()) {

System.out.println("Recipe istnieje w baze:" + recipe);

for(Ingredient ingredient : recipe.getIngredients()) {

System.out.println("Ingredient: " + ingredient);

}

session.getTransaction().commit();

factory.close();

}

❗ Wynik działania w konsoli:

SELECT DISTINCT recipe0_.recipe_id AS recipe_i1_1_0_,

ingredient2_.ingredient_id AS ingredie1_0_1_,

recipe0_.recipe_name AS recipe_n2_1_0_,

ingredient2_.ingredient_name AS ingredie2_0_1_,

ingredient1_.recipe_id AS recipe_i2_2_0__,

ingredient1_.ingredient_id AS ingredie1_2_0__

FROM recipe recipe0_

INNER JOIN recipe_ingredient ingredient1_

ON recipe0_.recipe_id = ingredient1_.recipe_id

INNER JOIN ingredient ingredient2_

ON ingredient1_.ingredient_id = ingredient2_.ingredient_id

Hibernate

@ManyToMany - relacja jedno i dwukierunkowa

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