今天分享hibernate框架的两个关联关系

多对多关系注意事项

一定要定义一个主控方
多对多删除

主控方直接删除
被控方先通过主控方解除多对多关系，再删除被控方
禁用级联删除

关联关系编辑，不需要直接操作桥接表，hibernate的主控方会自动维护

重点解析：

数据库的多对多

数据库中不能直接映射多对多
处理：创建一个桥接表(中间表)，将一个多对多关系转换成两个一对多

hibernate的多对多

hibernate可以直接映射多对多关联关系(看作两个一对多)

一：一对多自关联

设计数据库

t_hibernate_sys_tree_node表

实体类

TreeNode类

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懒加载  1.强制加载（子节点） 2.强制加载用户   3.强制加载两个

    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 + "]";

    }

}

对应实体类的配置文件

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中添加实体映射文件

<!-- 一对多的自关联  -->

        <mapping resource="com/ht/four/entity/TreeNode.hbm.xml" />

Dao层

去控制数据库中数据

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测试类（用于测试映射关系的测试类）

TreeNodeDaoTest类

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());

    }

}

运行结果如下图：

二：Hibernate多对多测试案例

多对多级联查询书籍表、书籍类别表

设计数据库表

t_hibernate_book表

Hibernate一对多自关联、多对多关联-LMLPHP

t_hibernate_category表

实体类

Book类

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类

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 + "]";

    }

}

对应实体映射文件

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:代表中间表

            name:书籍类的属性

            inverse：代表中间表交于对方维护

            key:当前类对应的表列段在中间表中的外键

            many-to-many:

                column:对应的是上面key查出来的另一张表的主键

                class:上述查出来的主键对应的实体类

             流程：以查询 book_id=8这本书为例

             1.通过建模反射自动生成sql，可以拿到book_id=8这条记录的基本信息

             2.book_id=8 必读=8去查询中间表 t_hibernate_book_category

                 拿到了cid=8,9

             3.cid=8,9  t_hibernate_category的category_id=8,9

             4.拿到了当前book实例对应的category的集合

             5.最终{book_id=8,book_name=圣墟，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中配置实体映射文件

<!-- 多对多实体配置文件 -->

        <mapping resource="com/ht/four/entity/book.hbm.xml" />

        <mapping resource="com/ht/four/entity/category.hbm.xml" />

dao层

控制数据库中的数据

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()) {

//                通过在被控方通过主控方来解除关联关系，最后被控方再做删除

                b.getCategories().remove(c);

            }

        }

        session.delete(c);

        transaction.commit();

        session.close();

    }

}

junit测试类（给dao层测试他所写的方法是否正确）

BookDaotext类

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

     * 数据添加正常

     * 书籍表、桥接表各新增一条数据

     */

    @Test

    public void test1() {

        Book book = new Book();

        book.setBookName("本是青灯不归客");

        book.setPrice(10f);

        Category category = new Category();

        category.setCategoryId(5);

//        直接将category对象加入到新建的book中是错误的，因为此时的category是临时态的，hibernate是不会管理的

//        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

     * 只增加书籍表数据

     * 桥接表不加数据

     * 原因：双方都没有去维护关系

     */

    @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);

    }

}

我们来一个一个测试

首先测试查询方法可不可行

       @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());

}

运行结果如下：

Hibernate一对多自关联、多对多关联-LMLPHP

我们再来看新增方法可不可行

/**

     * book.hbm.xml    inverse=fasle

     * category.hbm.xml inverse=true

     * 数据添加正常

     * 书籍表、桥接表各新增一条数据

     */

    @Test

    public void test1() {

        Book book = new Book();

        book.setBookName("本是青灯不归客");

        book.setPrice(10f);

        Category category = new Category();

        category.setCategoryId(5);

//        直接将category对象加入到新建的book中是错误的，因为此时的category是临时态的，hibernate是不会管理的

//        book.getCategories().add(category);

        Category c = this.bookDao.getCategory(category);

//        c.getBooks().add(book);

        book.getCategories().add(c);

        this.bookDao.addBook(book);

    }

运行结果如下：

Hibernate一对多自关联、多对多关联-LMLPHP

配置inverse属性去增加

　　category.hbm.xml、book.hbm.xml中inverse属性皆为默认值true

　　只增加书籍表数据
桥接表不加数据
原因：双方都没有去维护关系

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>

Hibernate一对多自关联、多对多关联-LMLPHP

谢谢观看！！！

对多

Hibernate一对多自关联、多对多关联

多对多关系注意事项

重点解析：

数据库的多对多

hibernate的多对多

一：一对多自关联

二：Hibernate多对多测试案例

设计数据库表

实体类

对应实体映射文件

book.hnm.xml

book.hbm.xml

category.hbm.xml

在核心文件hibernate.cfg.xml中配置实体映射文件

dao层

junit测试类（给dao层测试他所写的方法是否正确）

BookDaotext类

我们来一个一个测试

首先测试查询方法可不可行

运行结果如下：

我们再来看新增方法可不可行

运行结果如下：

配置inverse属性去增加

category.hbm.xml、book.hbm.xml中inverse属性皆为默认值true

　　category.hbm.xml、book.hbm.xml中inverse属性皆为默认值true