今日课程：
一、对多的关联配置 Order与Order_item（一个订单对应的多个订单项，但一个订单项只有一个订单）1，一对多的关联配置（数据库：主表从表，通过外键关联）将数据库中表与表之间的关系给映射到实体类里面
2，懒加载
3，一对多的自关联
4，多对多的关联，数据库中不能直接映射多对多（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）
示例（片段）：
①、创建实体类（订单Order）package com.zxy.two.entity;
import java.util.HashSet;
import java.util.Set;
public class Order {
// create table t_hibernate_order
// (
// order_id int primary key auto_increment,
// order_no varchar(50) not null
// );
private Integer orderId;
private String orderNo;
//注意：变量属性一定用接口进行接受
private Set orderItems = new HashSet<>();
private Integer initOrderItems = 0;//0代表懒加载，1代表强制加载
public Integer getInitOrderItems() {
return initOrderItems;
}
public void setInitOrderItems(Integer initOrderItems) {
this.initOrderItems = initOrderItems;
}
public Set getOrderItems() {
return orderItems;
}
public void setOrderItems(Set orderItems) {
this.orderItems = orderItems;
}
public Integer getOrderId() {
return orderId;
}
public void setOrderId(Integer orderId) {
this.orderId = orderId;
}
public String getOrderNo() {
return orderNo;
}
public void setOrderNo(String orderNo) {
this.orderNo = orderNo;
}
}
package com.zxy.two.entity;
import java.util.HashSet;
import java.util.Set;
public class Order {
// create table t_hibernate_order
// (
// order_id int primary key auto_increment,
// order_no varchar(50) not null
// );
private Integer orderId;
private String orderNo;
//注意：变量属性一定用接口进行接受
private Set orderItems = new HashSet<>();
private Integer initOrderItems = 0;//0代表懒加载，1代表强制加载
public Integer getInitOrderItems() {
return initOrderItems;
}
public void setInitOrderItems(Integer initOrderItems) {
this.initOrderItems = initOrderItems;
}
public Set getOrderItems() {
return orderItems;
}
public void setOrderItems(Set orderItems) {
this.orderItems = orderItems;
}
public Integer getOrderId() {
return orderId;
}
public void setOrderId(Integer orderId) {
this.orderId = orderId;
}
public String getOrderNo() {
return orderNo;
}
public void setOrderNo(String orderNo) {
this.orderNo = orderNo;
}
}
②、订单项（OrderItem ）
第二步：配置映射文件
Order.hbm.xml
OrderItem.hbm.xml
二、懒加载
①导入工具类
package com.zxy.two.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class SessionFactoryUtil {
static SessionFactory sessionFactory;
static {
Configuration configure = new Configuration().configure("hibernate.cfg.xml");
sessionFactory = configure.buildSessionFactory();
}
public static Session getSession() {
Session session = sessionFactory.getCurrentSession();
if(session == null) {
session = sessionFactory.openSession();
}
return session;
}
public static void main(String[] args) {
Session session = SessionFactoryUtil.getSession();
// Calling method 'isConnected' is not valid without an active transaction (Current status: NOT_ACTIVE)
session.beginTransaction();
System.out.println(session.isConnected());
session.close();
System.out.println(session.isConnected());
}
}
②dao方法（OrderDao 、OrderItemDao）
package com.zxy.two.dao;
import java.util.List;
import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.zxy.two.entity.Order;
import com.zxy.two.entity.OrderItem;
import com.zxy.two.util.SessionFactoryUtil;
public class OrderDao {
public Order get(Order order) {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
Order o = session.get(Order.class, order.getOrderId());
// 并且想要查询出关联的订单项的数据是，采用强制加载
if(o != null && new Integer(1).equals(order.getInitOrderItems())) {
// 强制加载订单O管理的订单项数据
Hibernate.initialize(o.getOrderItems());
}
transaction.commit();
session.close();
return o;
}
public List list() {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
List list = session.createQuery("from Order").list();
for (Order o: list) {
Hibernate.initialize(o.getOrderItems());
}
transaction.commit();
session.close();
return list;
}
public void delete(Order order) {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
Order o = session.get(Order.class, order.getOrderId());
for(OrderItem oi:o.getOrderItems()) {
session.delete(oi);
}
session.delete(o);
transaction.commit();
session.close();
}
}
OrderItemDao
package com.zxy.two.dao;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.zxy.two.entity.OrderItem;
import com.zxy.two.util.SessionFactoryUtil;
public class OrderItemDao {
public OrderItem get(OrderItem orderItem) {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
OrderItem oi = session.get(OrderItem.class, orderItem.getOrderItemId());
transaction.commit();
session.close();
return oi;
}
}
③测试类（OrderDaoTest）
package com.zxy.two.dao;
import java.util.List;
import org.junit.Test;
import com.zxy.two.entity.Order;
public class OrderDaoTest {
private OrderDao orderDao = new OrderDao();
@Test
public void testGet() {
Order order = new Order();
order.setOrderId(7);
order.setInitOrderItems(1);
Order o = this.orderDao.get(order);
System.out.println(o.getOrderNo());
System.out.println(o.getOrderItems());
}
@Test
public void testList() {
List list = this.orderDao.list();
for (Order o : list) {
System.out.println(o.getOrderNo());
// System.out.println(o.getOrderItems().size());
}
}
@Test
public void testDelete() {
Order order = new Order();
order.setOrderId(6);
this.orderDao.delete(order);
}
}
当此状态运行时
运行结果：正常拿到
当我们需要一并拿到订单项是，解开注释
输出结果并没有拿到，而且还会出现错误
问题：默认使用懒加载，在执行完上面那个输出时就已经关闭session了，所以会报错，该错误是需要强制加载，就是强制加载与订单关联的订单项数据
解决：解开注释，并设置为一，强制加载
运行结果：正常拿到
运行该查询方法：
产生大量SQL语句，如果数据多，会严重拖慢性能
性能优化（当数据非常多的时候）
假如只需要使用订单表数据，我们就使用懒加载，如果同时需要两个表的数据那么就不使用懒加载，该为强制加载，也就是要用的东西就查，不用的东西就不查
三、一对多的自关联分析（模拟环境：树形菜单）：
一对多的自关联是指自己可以有多个子节点，但父节点只有一个，并且是在自己本身的表里
SQL语句分析：
--查询出权限管理节点的相关信息
SELECT * FROM t_hibernate_sys_tree_node where
tree_node_id=6;
--当前节点的父节点信息（当前节点的父id是父节点的id）
SELECt * FROM t_hibernate_sys_tree_node where
tree_node_id=1;
--当前节点的子节点信息（当前节点的id是子节点的父id）
SELECt * FROM t_hibernate_sys_tree_node where
parent_node_id=6;
①、实体类（TreeNode）
package com.zxy.two.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 children = new HashSet();
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 getChildren() {
return children;
}
public void setChildren(Set 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 + "]";
}
}
第一个为父节点（父节点只有一个）
第二个为子节点（子节点可能有多个所以用集合包起来）
第三个为懒加载（0为懒加载，1为强制加载）
②、对应的映射关系
③、dao方法 TreeNodeDao
package com.zxy.two.dao;
import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.zxy.two.entity.TreeNode;
import com.zxy.two.util.SessionFactoryUtil;
public class TreeNodeDao {
public TreeNode load(TreeNode treeNode) {
Session session = SessionFactoryUtil.getSession();
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;
}
}
④、测试 TreeNodeDaoTest
package com.zxy.two.dao;
import org.junit.Test;
import com.zxy.two.entity.TreeNode;
public class TreeNodeDaoTest {
private TreeNodeDao treeNodeDao = new TreeNodeDao();
// @Before
// public void setUp() throws Exception {
// }
//
// @After
// public void tearDown() throws Exception {
// }
@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：成功拿到
四、多对多的关联
①、实体类
package com.zxy.two.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 categories = new HashSet();
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 getCategories() {
return categories;
}
public void setCategories(Set 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();
}
}
②、Category
package com.zxy.two.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 books = new HashSet();
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 getBooks() {
return books;
}
public void setBooks(Set books) {
this.books = books;
}
@Override
public String toString() {
return "Category [categoryId=" + categoryId + ", categoryName=" + categoryName + "]";
}
}
③、对应的映射配置（book.hbm.xml）
④、category.hbm.xml
table：中间表
name：关联属性
key：当前表的主键在关联表的外键
inverse属性为反转，数据的维护
false表示中间表的数据由自己维护
true表示中间表的数据由对方维护
两表一定是一个为true一个为false，这样中间表才有数据
⑤、dao方法 BookDao
package com.zxy.two.dao;
import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.zxy.two.entity.Book;
import com.zxy.two.entity.Category;
import com.zxy.two.util.SessionFactoryUtil;
public class BookDao {
public Integer addBook(Book book) {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
Integer bid = (Integer) session.save(book);
transaction.commit();
session.close();
return bid;
}
public Integer addCategory(Category category) {
Session session = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
Integer cid = (Integer) session.save(category);
transaction.commit();
session.close();
return cid;
}
public Category getCategory(Category category) {
Session session = SessionFactoryUtil.getSession();
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 = SessionFactoryUtil.getSession();
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 = SessionFactoryUtil.getSession();
Transaction transaction = session.beginTransaction();
session.delete(book);
transaction.commit();
session.close();
}
public void delCategory(Category category) {
Session session = SessionFactoryUtil.getSession();
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();
}
// public List list(Book book, PageBean pageBean) {
// Session session = SessionFactoryUtil.getSession();
// Transaction transaction = session.beginTransaction();
// String hql = "from Book where 1 = 1";
//
// if (StringUtils.isNotBlank(book.getBookName())) {
// hql += " and bookName like :bookName";
// }
//
// Query query = session.createQuery(hql);
//
// if (StringUtils.isNotBlank(book.getBookName())) {
// query.setParameter("bookName", book.getBookName());
// }
//
// if (pageBean != null && pageBean.isPagination()) {
// query.setFirstResult(pageBean.getStartIndex());
// query.setMaxResults(pageBean.getRows());
// }
// List list = query.list();
// transaction.commit();
// session.close();
// return list;
//
// }
// public List list2(Book book, PageBean pageBean) {
// Session session = SessionFactoryUtil.getSession();
// Transaction transaction = session.beginTransaction();
// String hql = "from Book where 1 = 1";
// Map map = new HashMap();
//
// if (StringUtils.isNotBlank(book.getBookName())) {
// hql += " and bookName like :bookName";
// map.put("bookName", book.getBookName());
// }
// List list = super.executeQuery(session, hql, map, pageBean);
// transaction.commit();
// session.close();
// return list;
// }
// public List list3(Book book, PageBean pageBean) {
String sql = "select b.*,o.* from t_hibernate_book b,t_hibernate_Order o";
// String sql = "select * from t_hibernate_book";
// Session session = SessionFactoryUtil.getSession();
// Transaction transaction = session.beginTransaction();
// List list = session.createSQLQuery(sql).list();
// transaction.commit();
// session.close();
// return list;
// }
}
⑥、测试 BookDaoTest
package com.zxy.two.dao;
import org.junit.Test;
import com.zxy.two.entity.Book;
import com.zxy.two.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());
}
@Test
public void test1() {
Book book = new Book();
book.setBookName("bbbb");
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);
}
@Test
public void test2() {
Book book = new Book();
book.setBookName("dddd");
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);
}
}
运行结果：
