Hibernate关联关系

1.一对多的关联配置

        数据库：主表从表，通过外键关联

2.懒加载

3.一对多的自关联

4.多对多的关联

一、一对多的关联配置

1、关联指的是类之间的引用关系。

假设有类A与类B，如果AB关联，A引用B，那么被引用的类B将被定义为类A的属性。

2、一对多的关联：
例如：订单和订单项，一个订单有多个订单项；

         但是一个订单项只有一个订单；

3、创建实体类和映射文件
①、实体类：

（1）Order 
 

package com.ty.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）OrderItem

package com.ty.two.entity;
 
public class OrderItem {
//	create table t_hibernate_order_item
//	(
//	  order_item_id int primary key auto_increment,
//	  product_id int not null,
//	  quantity int not null,
//	  oid int not null,
//	  foreign key(oid) references t_hibernate_order(order_id)
//	);
	private Integer orderItemId;
	private Integer productId;
	private Integer quantity;
	private Integer oid;
	
	private Order order;
	public Order getOrder() {
		return order;
	}
	public void setOrder(Order order) {
		this.order = order;
	}
	public Integer getOrderItemId() {
		return orderItemId;
	}
	public void setOrderItemId(Integer orderItemId) {
		this.orderItemId = orderItemId;
	}
	public Integer getProductId() {
		return productId;
	}
	public void setProductId(Integer productId) {
		this.productId = productId;
	}
	public Integer getQuantity() {
		return quantity;
	}
	public void setQuantity(Integer quantity) {
		this.quantity = quantity;
	}
	public Integer getOid() {
		return oid;
	}
	public void setOid(Integer oid) {
		this.oid = oid;
	}
	
}

②、映射文件：

（1）Order.hbm.xml

对于订单来说属于一对多 使用标签one-to-many  class为订单项的全限定名

 name属性是属性名  key表示外键

（2）OrderItem.hbm.xml

核心配置文件（hibernate.cfg.xml）

       
       
工具类

package com.ty.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());
	}
}

①、OrderDao 

package com.ty.two.dao;
 
import java.util.List;
 
import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
 
import com.ty.two.entity.Order;
import com.ty.two.entity.OrderItem;
import com.ty.two.util.SessionFactoryUtil;
 
 
public class OrderDao {
	public com.lsy.two.entity.Order get(com.lsy.two.entity.Order order) {
		Session session = com.lsy.two.util.SessionFactoryUtil.getSession();
		Transaction transaction = session.beginTransaction();
		com.lsy.two.entity.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关联的订单项数据
			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();
	}
}

②、OrderItemDao 

package com.ty.two.dao;
 
import org.hibernate.Session;
import org.hibernate.Transaction;
 
import com.ty.two.entity.OrderItem;
import com.ty.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;
	}
}

OrderDaoTest

package com.ty.two.dao;
 
import java.util.List;
 
import org.junit.Test;
 
import com.ty.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);
	}
 
}

二、懒加载
1、测试
①、orderDaoTest调用查询方法能查询到为7的订单

@Test
    public void testGet() {
        Order order = new Order();
        order.setOrderId(7);
        Order o = this.orderDao.get(order);
        System.out.println(o.getOrderNo());
//        System.out.println(o.getOrderItems());
    }

②、拿到订单对应的订单项

 public void testGet() {
        Order order = new Order();
        order.setOrderId(7);
        Order o = this.orderDao.get(order);
        System.out.println(o.getOrderNo());

//还没加载到，session就关闭了
 System.out.println(o.getOrderItems());        
    }

异常问题

懒加载失败

 解决问题

order.setInitOrderItems(1);

强制加载

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());
	}

 性能调优（解释了hibernate默认采用懒加载的原因）：

1、只需要订单表的数据时，同时会将订单项表的数据查询出来，用到的sql语句量庞大；

2、通过字段控制，所以默认为懒加载为0，需要订单项时将order实体类的initOrderItems字段改为1强制加载

三、一对多的自关联

 1、以前的写法（sql语句繁琐）

 2、实体类（TreeNode）映射文件（TreeNode.hbm.xml）

TreeNode

没有parent_node_id属性是因为他是关联属性

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

 TreeNode.hbm.xml映射文件

①、TreeNodeDao 

package com.ty.two.dao;
 
import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
 
import com.ty.two.entity.TreeNode;
import com.ty.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;
	}
}

配置文件

测试

package com.ty.two.dao;
 
import org.junit.Test;
 
import com.ty.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());
	}
 
}

结果

①、书籍实体类：Book 

package com.ty.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();
	}
	
	
}

 映射文件：book.hbm.xml

②、书籍类别实体类 Category 

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

映射文件：category.hbm.xml

核心配置文件（hibernate.cfg.xml）

dao方法：BookDao 
 

package com.ty.two.dao;
 
import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;
 
import com.ty.two.entity.Book;
import com.ty.two.entity.Category;
import com.ty.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;
//	}
}