Hibernate一對多自關聯、多對多關聯

本文轉載自查看原文 2019-07-17 20:31 672 Hibernate/ SSH

今天分享hibernate框架的兩個關聯關系

多對多關系注意事項

一定要定義一個主控方
多對多刪除

主控方直接刪除
被控方先通過主控方解除多對多關系，再刪除被控方
禁用級聯刪除

關聯關系編輯，不需要直接操作橋接表，hibernate的主控方會自動維護

重點解析：

數據庫的多對多

數據庫中不能直接映射多對多
處理：創建一個橋接表(中間表)，將一個多對多關系轉換成兩個一對多

hibernate的多對多

hibernate可以直接映射多對多關聯關系(看作兩個一對多)

一：一對多自關聯

設計數據庫

t_hibernate_sys_tree_node表

實體類

TreeNode類

package com.ht.four.entity;

import java.util.HashSet;
import java.util.Set;

public class TreeNode{
    private Integer nodeId;
    private String nodeName;
    private Integer treeNodeType;
    private Integer position;
    private String url;
    private TreeNode parent;
    private Set<TreeNode> children = new HashSet<TreeNode>();
    private Integer initChildren = 0;
    //0懶加載  1.強制加載（子節點） 2.強制加載用戶   3.強制加載兩個

    public Integer getNodeId() {
        return nodeId;
    }

    public void setNodeId(Integer nodeId) {
        this.nodeId = nodeId;
    }

    public String getNodeName() {
        return nodeName;
    }

    public void setNodeName(String nodeName) {
        this.nodeName = nodeName;
    }

    public Integer getTreeNodeType() {
        return treeNodeType;
    }

    public void setTreeNodeType(Integer treeNodeType) {
        this.treeNodeType = treeNodeType;
    }

    public Integer getPosition() {
        return position;
    }

    public void setPosition(Integer position) {
        this.position = position;
    }

    public String getUrl() {
        return url;
    }

    public void setUrl(String url) {
        this.url = url;
    }

    public TreeNode getParent() {
        return parent;
    }

    public void setParent(TreeNode parent) {
        this.parent = parent;
    }

    public Set<TreeNode> getChildren() {
        return children;
    }

    public void setChildren(Set<TreeNode> children) {
        this.children = children;
    }

    public Integer getInitChildren() {
        return initChildren;
    }

    public void setInitChildren(Integer initChildren) {
        this.initChildren = initChildren;
    }

    @Override
    public String toString() {
        return "TreeNode [nodeId=" + nodeId + ", nodeName=" + nodeName + ", treeNodeType=" + treeNodeType
                + ", position=" + position + ", url=" + url + "]";
    }
    

}

對應實體類的配置文件

TreeNode.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.ht.four.entity.TreeNode" table="t_hibernate_sys_tree_node">
        <id name="nodeId" type="java.lang.Integer" column="tree_node_id">
            <generator class="increment" />
        </id>
        <property name="nodeName" type="java.lang.String"
            column="tree_node_name">
        </property>
        <property name="treeNodeType" type="java.lang.Integer"
            column="tree_node_type">
        </property>
        <property name="position" type="java.lang.Integer"
            column="position">
        </property>
        <property name="url" type="java.lang.String"
            column="url">
        </property>
        
        <many-to-one name="parent" class="com.ht.four.entity.TreeNode" column="parent_node_id"/>
        
        <set name="children" cascade="save-update" inverse="true">
            <key column="parent_node_id"></key>
            <one-to-many class="com.ht.four.entity.TreeNode"/>
        </set>
    </class>
</hibernate-mapping>

在核心配置文件hibernate.cfg.xml中添加實體映射文件

<!-- 一對多的自關聯  -->
        <mapping resource="com/ht/four/entity/TreeNode.hbm.xml" />

Dao層

去控制數據庫中數據

package com.ht.four.dao;

import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.ht.four.entity.TreeNode;
import com.ht.two.util.SessionFactoryUtils;

public class TreeNodeDao {
    public TreeNode load(TreeNode treeNode) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        TreeNode t = session.load(TreeNode.class, treeNode.getNodeId());
        if(t != null && new Integer(1).equals(treeNode.getInitChildren())) {
            Hibernate.initialize(t.getChildren());
            Hibernate.initialize(t.getParent());
        }
        transaction.commit();
        session.close();
        return t;
    }
}

Junit測試類（用於測試映射關系的測試類）

TreeNodeDaoTest類

package com.ht.four.dao;

import org.junit.Test;

import com.ht.four.entity.TreeNode;

public class TreeNodeDaoTest {
    private TreeNodeDao treeNodeDao = new TreeNodeDao();


    @Test
    public void testLoad() {
        TreeNode treeNode = new TreeNode();
        treeNode.setNodeId(6);
        treeNode.setInitChildren(1);
        
        TreeNode t = this.treeNodeDao.load(treeNode);
        System.out.println(t);
        System.out.println(t.getParent());
        System.out.println(t.getChildren());
    }

}

運行結果如下圖：

二：Hibernate多對多測試案例

多對多級聯查詢書籍表、書籍類別表

設計數據庫表

t_hibernate_book表

t_hibernate_category表

實體類

Book類

package com.ht.four.entity;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

public class Book implements Serializable{
//    book_id int primary key auto_increment,
//       book_name varchar(50) not null,
//       price float not null
    private Integer bookId;
    private String bookName;
    private Float price;
    
    private Set<Category> categories = new HashSet<Category>();
    private Integer initCategories = 0;

    public Integer getInitCategories() {
        return initCategories;
    }

    public void setInitCategories(Integer initCategories) {
        this.initCategories = initCategories;
    }

    public Integer getBookId() {
        return bookId;
    }

    public void setBookId(Integer bookId) {
        this.bookId = bookId;
    }

    public String getBookName() {
        return bookName;
    }

    public void setBookName(String bookName) {
        this.bookName = bookName;
    }

    public Float getPrice() {
        return price;
    }

    public void setPrice(Float price) {
        this.price = price;
    }

    public Set<Category> getCategories() {
        return categories;
    }

    public void setCategories(Set<Category> categories) {
        this.categories = categories;
    }

    @Override
    public String toString() {
        return "Book [bookId=" + bookId + ", bookName=" + bookName + ", price=" + price + "]";
    }

    public Book(Integer bookId, String bookName) {
        super();
        this.bookId = bookId;
        this.bookName = bookName;
    }

    public Book() {
        super();
    }
    
    
}

Category類

package com.ht.four.entity;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

public class Category implements Serializable{
//    category_id int primary key auto_increment,
//       category_name varchar(50) not null
    private Integer categoryId;
    private String categoryName;
    private Set<Book> books = new HashSet<Book>();
    public Integer getCategoryId() {
        return categoryId;
    }
    public void setCategoryId(Integer categoryId) {
        this.categoryId = categoryId;
    }
    public String getCategoryName() {
        return categoryName;
    }
    public void setCategoryName(String categoryName) {
        this.categoryName = categoryName;
    }
    public Set<Book> getBooks() {
        return books;
    }
    public void setBooks(Set<Book> books) {
        this.books = books;
    }
    @Override
    public String toString() {
        return "Category [categoryId=" + categoryId + ", categoryName=" + categoryName + "]";
    }
    
}

對應實體映射文件

book.hnm.xml

package com.ht.four.entity;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

public class Book implements Serializable{
//    book_id int primary key auto_increment,
//       book_name varchar(50) not null,
//       price float not null
    private Integer bookId;
    private String bookName;
    private Float price;
    
    private Set<Category> categories = new HashSet<Category>();
    private Integer initCategories = 0;

    public Integer getInitCategories() {
        return initCategories;
    }

    public void setInitCategories(Integer initCategories) {
        this.initCategories = initCategories;
    }

    public Integer getBookId() {
        return bookId;
    }

    public void setBookId(Integer bookId) {
        this.bookId = bookId;
    }

    public String getBookName() {
        return bookName;
    }

    public void setBookName(String bookName) {
        this.bookName = bookName;
    }

    public Float getPrice() {
        return price;
    }

    public void setPrice(Float price) {
        this.price = price;
    }

    public Set<Category> getCategories() {
        return categories;
    }

    public void setCategories(Set<Category> categories) {
        this.categories = categories;
    }

    @Override
    public String toString() {
        return "Book [bookId=" + bookId + ", bookName=" + bookName + ", price=" + price + "]";
    }

    public Book(Integer bookId, String bookName) {
        super();
        this.bookId = bookId;
        this.bookName = bookName;
    }

    public Book() {
        super();
    }
    
    
}

book.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.ht.four.entity.Book" table="t_hibernate_book">
        <cache usage="read-only" region="com.ht.four.entity.Book"/>
        <id name="bookId" type="java.lang.Integer" column="book_id">
            <generator class="increment" />
        </id>
        <property name="bookName" type="java.lang.String"
            column="book_name">
        </property>
        <property name="price" type="java.lang.Float"
            column="price">
        </property>
        <!--  
            table:代表中間表
            name:書籍類的屬性
            inverse：代表中間表交於對方維護
            key:當前類對應的表列段在中間表中的外鍵
            many-to-many:
                column:對應的是上面key查出來的另一張表的主鍵
                class:上述查出來的主鍵對應的實體類
                
                
             流程：以查詢 book_id=8這本書為例
             1.通過建模反射自動生成sql，可以拿到book_id=8這條記錄的基本信息    
             2.book_id=8 必讀=8去查詢中間表 t_hibernate_book_category
                 拿到了cid=8,9
             3.cid=8,9  t_hibernate_category的category_id=8,9
             4.拿到了當前book實例對應的category的集合
             5.最終{book_id=8,book_name=聖墟，price=40}    
        -->
        <set table="t_hibernate_book_category" name="categories" cascade="save-update" inverse="false">
            <!-- one -->
            <key column="bid"></key>
            <!-- many -->
            <many-to-many column="cid" class="com.ht.four.entity.Category"></many-to-many>
        </set>
    </class>
</hibernate-mapping>

category.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC 
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
    <class name="com.ht.four.entity.Category" table="t_hibernate_category">
        <id name="categoryId" type="java.lang.Integer" column="category_id">
            <generator class="increment" />
        </id>
        <property name="categoryName" type="java.lang.String"
            column="category_name">
        </property>
        
        <set table="t_hibernate_book_category" name="books" cascade="save-update" inverse="true">
            <key column="cid"></key>
            <many-to-many column="bid" class="com.ht.four.entity.Book"></many-to-many>
        </set>
    </class>
</hibernate-mapping>

在核心文件hibernate.cfg.xml中配置實體映射文件

<!-- 多對多實體配置文件 -->
        <mapping resource="com/ht/four/entity/book.hbm.xml" />
        <mapping resource="com/ht/four/entity/category.hbm.xml" />

dao層

控制數據庫中的數據

package com.ht.four.dao;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.query.Query;

import com.ht.four.entity.Book;
import com.ht.four.entity.Category;
import com.ht.two.util.SessionFactoryUtils;

public class BookDao{
    public Integer addBook(Book book) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Integer bid = (Integer) session.save(book);
        transaction.commit();
        session.close();
        return bid;
    }
    
    public Integer addCategory(Category category) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Integer cid = (Integer) session.save(category);
        transaction.commit();
        session.close();
        return cid;
    }
    
    public Category getCategory(Category category) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Category c = session.get(Category.class, category.getCategoryId());
        transaction.commit();
        session.close();
        return c;
    }
    
    public Book getBook(Book book) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Book b = session.get(Book.class, book.getBookId());
        if (b != null && new Integer(1).equals(book.getInitCategories())) {
            Hibernate.initialize(b.getCategories());
        }
        transaction.commit();
        session.close();
        return b;
    }
    
    public void delBook(Book book) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        session.delete(book);
        transaction.commit();
        session.close();
    }
    
    public void delCategory(Category category) {
        Session session = SessionFactoryUtils.openSession();
        Transaction transaction = session.beginTransaction();
        Category c = session.get(Category.class, category.getCategoryId());
        if(c!=null) {
            for (Book b : c.getBooks()) {
//                通過在被控方通過主控方來解除關聯關系，最后被控方再做刪除
                b.getCategories().remove(c);
            }
        }
        session.delete(c);
        transaction.commit();
        session.close();
    }
}

junit測試類（給dao層測試他所寫的方法是否正確）

BookDaotext類

package com.ht.four.dao;

import org.junit.Test;

import com.ht.four.entity.Book;
import com.ht.four.entity.Category;

public class BookDaoTest {
    private BookDao bookDao = new BookDao();

    @Test
    public void testGetBook() {
        Book book = new Book();
        book.setBookId(3);
        book.setInitCategories(1);
        Book b = this.bookDao.getBook(book );
        System.out.println(b.getBookName());
        System.out.println(b.getCategories());
    }
    
    /**
     * book.hbm.xml    inverse=fasle
     * category.hbm.xml inverse=true
     * 數據添加正常
     * 書籍表、橋接表各新增一條數據
     */
    @Test
    public void test1() {
        Book book = new Book();
        book.setBookName("本是青燈不歸客");
        book.setPrice(10f);
        Category category = new Category();
        category.setCategoryId(5);
//        直接將category對象加入到新建的book中是錯誤的，因為此時的category是臨時態的，hibernate是不會管理的
//        book.getCategories().add(category);
        Category c = this.bookDao.getCategory(category);
//        c.getBooks().add(book);
        book.getCategories().add(c);
        this.bookDao.addBook(book);
    }

    /**
     * book.hbm.xml    inverse=true
     * category.hbm.xml inverse=true
     * 只增加書籍表數據
     * 橋接表不加數據
     * 原因：雙方都沒有去維護關系
     */
    @Test
    public void test2() {
        Book book = new Book();
        book.setBookName("c");
        book.setPrice(10f);
        Category category = new Category();
        category.setCategoryId(5);
        Category c = this.bookDao.getCategory(category);
        
        book.getCategories().add(c);
        this.bookDao.addBook(book);
//        c.getBooks().add(book);
    }
    
    
}

我們來一個一個測試

首先測試查詢方法可不可行

       @Test
    public void testGetBook() {
        Book book = new Book();
        book.setBookId(3);
        book.setInitCategories(1);
        Book b = this.bookDao.getBook(book );
        System.out.println(b.getBookName());
        System.out.println(b.getCategories());
}

運行結果如下：

我們再來看新增方法可不可行

/**
     * book.hbm.xml    inverse=fasle
     * category.hbm.xml inverse=true
     * 數據添加正常
     * 書籍表、橋接表各新增一條數據
     */
    @Test
    public void test1() {
        Book book = new Book();
        book.setBookName("本是青燈不歸客");
        book.setPrice(10f);
        Category category = new Category();
        category.setCategoryId(5);
//        直接將category對象加入到新建的book中是錯誤的，因為此時的category是臨時態的，hibernate是不會管理的
//        book.getCategories().add(category);
        Category c = this.bookDao.getCategory(category);
//        c.getBooks().add(book);
        book.getCategories().add(c);
        this.bookDao.addBook(book);
    }

運行結果如下：

配置inverse屬性去增加

　　category.hbm.xml、book.hbm.xml中inverse屬性皆為默認值true

　　只增加書籍表數據
橋接表不加數據
原因：雙方都沒有去維護關系

cateagory.hbm.xml

<set table="t_hibernate_book_category" name="books" cascade="save-update" inverse="true">

book.hbm.xml

<set table="t_hibernate_book_category" name="categories" cascade="save-update" inverse="true">
            <!-- one -->
            <key column="bid"></key>
            <!-- many -->
            <many-to-many column="cid" class="com.ht.four.entity.Category"></many-to-many>
        </set>

謝謝觀看！！！

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猜您在找 【SSH進階之路】Hibernate映射——一對多關聯映射（七） Hibernate一對多關聯關系保存時的探究 SpringData JPA一對多多對一多對多關聯 JPA 單向一對多關聯關系 Hibernate一對多關系操作 Hibernate入門（三）—— 一對多、多對多關系 hibernate中一對多關系的映射 TP5一對一、一對多關聯模型的使用【Hibernate框架】關聯映射（一對多，多對一） Mybatis @Many注解一對多關聯映射

Hibernate一對多自關聯、多對多關聯

多對多關系注意事項

重點解析：

數據庫的多對多

hibernate的多對多

一：一對多自關聯

二：Hibernate多對多測試案例

設計數據庫表

實體類

對應實體映射文件

book.hnm.xml

book.hbm.xml

category.hbm.xml

在核心文件hibernate.cfg.xml中配置實體映射文件

dao層

junit測試類（給dao層測試他所寫的方法是否正確）

BookDaotext類

我們來一個一個測試

首先測試查詢方法可不可行

運行結果如下：

我們再來看新增方法可不可行

運行結果如下：

配置inverse屬性去增加

category.hbm.xml、book.hbm.xml中inverse屬性皆為默認值true

免責聲明！

　　category.hbm.xml、book.hbm.xml中inverse屬性皆為默認值true