hibernate关联关系 (多对多)

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

 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

一对多的自关联

映射文件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.MavenHibernate.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.MavenHidernate.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.MavenHidernate.four.entity.TreeNode"/>
         </set>
     </class>
 </hibernate-mapping>

映射文件TreeNode.hbm.xml对应的实体类TreeNode.java

 package com.MavenHidernate.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;
 
     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 + ", children=" + children + "]";
 //    }
 
     @Override
     public String toString() {
         return "TreeNode [nodeId=" + nodeId + ", nodeName=" + nodeName + ", treeNodeType=" + treeNodeType
                 + ", position=" + position + ", url=" + url + ", parent=" + parent + ", children=" + children
                 + ", initChildren=" + initChildren + "]";
     }
 
 }

TreeNodeDao方法

 package com.MavenHibernate.four.dao;
 
 import org.hibernate.Hibernate;
 import org.hibernate.Session;
 import org.hibernate.Transaction;
 
 import com.MavenHibernate.two.util.SessionFactoryUtils;
 import com.MavenHibernate.four.entity.TreeNode;
 
 public class TreeNodeDao {
     public TreeNode load(TreeNode treeNode) {
         Session session = SessionFactoryUtils.openSession();
         Transaction transaction = session.beginTransaction();
         TreeNode treenode = session.load(TreeNode.class, treeNode.getNodeId());
         if(treenode != null && new Integer(1).equals(treeNode.getInitChildren())) {
             Hibernate.initialize(t.getChildren());
             Hibernate.initialize(t.getParent());
         }
         transaction.commit();
         session.close();
         return treenode;
     }
 }

junit测试TreeNodeDao

TreeNodeDaoTest

 package com.MavenHibernate.four.dao;
 
 import org.junit.Test;
 
 import com.MavenHibernate.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());
     }
 
 }

多对多关联关系

映射文件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.MavenHibernate.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.MavenHibernate.four.entity.Book"></many-to-many>
         </set>
     </class>
 </hibernate-mapping>

映射文件category.hbm.xml对应的实体类category

 package com.MavenHibernate.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 + "]";
     }
 
 }

映射文件book.hbm.xml

  set标签
           table:对应的是中间表，没有实体类的，意味着靠两张主表对应的映射文件联合管理数据
           name：当前映射文件对应的实体类对应的属性
           cascade:级联新增修改，说白了就是当前实体类对应的表删除能否影响到关联表的数据
           inberse:中间表的数据维护的权利交给对方
  key标签
           column：当前表t_hibernate_book_category的主键book_id在中间表的列段bid
           many-to-many:
           column:代表中间表对应的除去当前表t_hibernate_book的非主键的中间列段cid
            class:cid对应的类      

 <?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.MavenHibernate.four.entity.Book" table="t_hibernate_book">
         <cache usage="read-only" region="com.zking.five.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>
         <!--
         set标签
              table:对应的是中间表，没有实体类的，意味着靠两张主表对应的映射文件联合管理数据
              name：当前映射文件对应的实体类对应的属性
              cascade:级联新增修改，说白了就是当前实体类对应的表删除能否影响到关联表的数据
              inberse:中间表的数据维护的权利交给对方
         key标签
              column：当前表t_hibernate_book_category的主键book_id在中间表的列段bid
              many-to-many:
              column:代表中间表对应的除去当前表t_hibernate_book的非主键的中间列段cid
              class:cid对应的类
          -->
         <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.MavenHibernate.four.entity.Category"></many-to-many>
         </set>
     </class>
 </hibernate-mapping>

映射文件book.hbm.xml对应的实体类book

 package com.MavenHibernate.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();
     }
 
 }

hibernate.cfg.xml中配置映射文件

BookDao

 package com.MavenHibernate.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.MavenHibernate.two.util.SessionFactoryUtils;
 import com.MavenHibernate.four.entity.Book;
 import com.MavenHbernate.four.entity.Category;
 import com.mysql.jdbc.StringUtils;
 
 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BookDao

BookDaoTest

 package com.MavenHibernate.four.dao;
 
 import org.junit.Test;
 
 import com.MavenHibernate.four.entity.Book;
 import com.MavenHbernate.four.entity.Category;
 
 public class BookDaoTest {
     private BookDao bookDao = new BookDao();
 
     @Test
     public void testGetBook() {
         Book book = new Book();
         book.setBookId(8);
         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("jt5555555");
         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=false
      * 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("T226");
         book.setPrice(10);
         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);
     }
 
 }