Hibernate：多对多新增

案例：

1：实体类：

package com.crud.five.entity;

import java.util.HashSet;
import java.util.Set;

public class Book {
	private Integer bookId;
	private String bookName;
	private Float price;
	
	//创建关联
	private Set<Category> categorys=new HashSet<Category>();
	
	//强制立即加载
	private Integer initCagetorys=0;
	
	public Integer getInitCagetorys() {
		return initCagetorys;
	}
	public void setInitCagetorys(Integer initCagetorys) {
		this.initCagetorys = initCagetorys;
	}
	public Set<Category> getCategorys() {
		return categorys;
	}
	public void setCategorys(Set<Category> categorys) {
		this.categorys = categorys;
	}
	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;
	}
	
	

}

package com.crud.five.entity;

import java.util.HashSet;
import java.util.Set;

public class Category {
	
	private Integer categoryId;
	private String categoryName;
	
	//创建关联
	private Set<Book> books=new HashSet<Book>();
	
	//强制立即加载
	private Integer initBooks=0;
	
	public Integer getInitBooks() {
		return initBooks;
	}
	public void setInitBooks(Integer initBooks) {
		this.initBooks = initBooks;
	}
	public Set<Book> getBooks() {
		return books;
	}
	public void setBooks(Set<Book> books) {
		this.books = books;
	}
	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;
	}
	
	

}

2.配置文件：

<?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">
    
    <!--   多对多SQL形成过程：
    session.get(Book.class,5);
    以前的做法：select * from t_hibernate_book where bookId=?(5)
    得到：resultSet->
       值： 5  a  10
   建模之后找到Book类实例：
  Book book= 	Class.forName("com.crud.five.entity.Book").newInstance();
  拿到属性对象： field    可以把resultlset里的属性全都设值进去
  book.setBookId(5);
  book.setBookName(a);    通过反射做的
  book.setPrice(12);
    
  categorys为什么有值？
  1.建模之后，通过当前实体类的映射文件找到set标签中table属性
  	形成SQL语句：select * from t_hibernate_book_category
  2.继续读取配置文件，拿到set标签中的子标签key的column属性（当前类对应的表主键在桥接表中的外键）
  	进一步生成SQL语句：select * from t_hibernate_book_category where bid=?(bookId=4)
  	sql语句之后，又形成一个：resultSet 
  			1   古典
  			2  神话
  	EntityBaseDao中的executeQuery方法，对result进行处理，最终返回
  	
     -->
    <hibernate-mapping>
    	<class table="t_hibernate_book" name="com.crud.five.entity.Book">
    		<id name="bookId" type="java.lang.Integer" column="book_id ">
    			<generator class="increment"></generator>
    		</id>
    		<property name="bookName" type="java.lang.String" column="book_name "></property>
    		<property name="price" type="java.lang.Float" column="price "></property>
    		
    		<!-- table:中间连接表
    		name="categorys"：Book实体类里的类属性
    		 -->
    	    <set table="t_hibernate_book_category" name="categorys" cascade="save-update" inverse="false">
    	    	<!-- one -->
    			<key column="bid"></key>
    			<!-- many -->
    			<many-to-many column="cid" class="com.crud.five.entity.Category"></many-to-many>
    		</set> 
    		
    		
    	</class>
    </hibernate-mapping>

<?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 table="t_hibernate_category" name="com.crud.five.entity.Category">
    		<id name="categoryId" type="java.lang.Integer" column="category_id ">
    			<generator class="increment"></generator>
    		</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.crud.five.entity.Book"></many-to-many>
    		</set> 
    	
    	</class>
    </hibernate-mapping>

3.dao方法：

/**
	 * 增加书籍
	 * @param book
	 * @return
	 */
	public Integer add(Book book) {
		Session session = SessionFactoryUtils.getSession();
		Transaction transaction = session.beginTransaction();
		Integer s =(Integer) session.save(book);
		transaction.commit();
		session.close();
		return s;
	}

/**
	 * 增加书籍的同时，选好类别
	 * 
	 * book.hbm.xml:inverse="false"      主控方：书籍
	 * category.hbm.xml:inverse="true"    被控方：书籍类别
	 */
	@Test
	public void testAdd() {
		book.setBookName("斗破苍穹11");
		book.setPrice(23f);
		category.setCategoryId(5);
		book.getCategorys().add(this.categoryDao.getCategory(category));
		this.bookDao.add(book);
	}