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);
} }