package com.hibernate.n21;import java.util.HashSet;
import java.util.Set;public class Manager {private Integer mgrId;private String mgrName;/** 1. 声明集合类型时, 需使用接口类型, 因为 hibernate 在获取* 集合类型时, 返回的是 Hibernate 内置的集合类型, 而不是 JavaSE 一个标准的* 集合实现. * 2. 需要把集合进行初始化, 可以防止发生空指针异常*/private Set<Worker> workers = new HashSet<>();public Integer getMgrId() {return mgrId;}public void setMgrId(Integer mgrId) {this.mgrId = mgrId;}public String getMgrName() {return mgrName;}public void setMgrName(String mgrName) {this.mgrName = mgrName;}public Set<Worker> getWorkers() {return workers;}public void setWorkers(Set<Worker> workers) {this.workers = workers;}}package com.hibernate.n21;public class Worker {private Integer id;private String name;private Manager manager;public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Manager getManager() {return manager;}public void setManager(Manager manager) {this.manager = manager;}@Overridepublic String toString() {return "Worker [id=" + id + ", name=" + name + ", manager=" + manager + "]";}}

<!--1这一端-->
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-8-10 7:47:59 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping><class name="com.hibernate.n21.Manager" table="MANAGER"><id name="mgrId" type="java.lang.Integer"><column name="MGR_ID" /><generator class="native" /></id><property name="mgrName" type="java.lang.String"><column name="MGR_NAME" /></property><!-- 映射 1 对多的那个集合属性 --><!-- set: 映射 set 类型的属性, table: set 中的元素对应的记录放在哪一个数据表中. 该值需要和多对一的多的那个表的名字一致 --><!-- inverse: 指定由哪一方来维护关联关系. 通常设置为 true, 以指定由多的一端来维护关联关系 --><!-- order-by 在查询时对集合中的元素进行排序, order-by 中使用的是表的字段名, 而不是持久化类的属性名  --><set name="workers" table="WORKER" inverse="true"><!-- 执行多的表中的外键列的名字 --><key><column name="MGR_ID" /></key><!-- 指定映射类型 --><one-to-many class="com.hibernate.n21.Worker" /></set></class>
</hibernate-mapping>

<!--多这端-->
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-8-10 7:47:59 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping><class name="com.hibernate.n21.Worker" table="WORKER"><id name="id" type="java.lang.Integer"><column name="ID" /><generator class="native" /></id><property name="name" type="java.lang.String"><column name="NAME" /></property><!-- 映射多对一的关联关系。 使用 many-to-one 来映射多对一的关联关系 name: 多这一端关联的一那一端的属性的名字class: 一那一端的属性对应的类名column: 一端对应的数据表中的外键的名字--><many-to-one name="manager" class="com.hibernate.n21.Manager" fetch="join"><column name="MGR_ID" /></many-to-one></class>
</hibernate-mapping>

package com.hibernate.n21;import static org.junit.Assert.*;import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;public class Test {private SessionFactory sessionFactory;private Session session;private Transaction transaction;@Beforepublic void init(){Configuration configuration = new Configuration().configure();ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();sessionFactory = configuration.buildSessionFactory(serviceRegistry);session = sessionFactory.openSession();transaction = session.beginTransaction();}@Afterpublic void destroy(){transaction.commit();session.close();sessionFactory.close();}@org.junit.Testpublic void test() {fail("Not yet implemented");}@org.junit.Testpublic void testMany2OneGet(){//1. 若查询多的一端的一个对象(Worker), 则默认情况下, 只查询了多的一端的对象,不查询一的一端对象(Manager)Worker worker = (Worker) session.get(Worker.class, 1);System.out.println(worker.getName());System.out.println(worker.getManager().getClass());//session.close();//2. 在需要使用到关联的对象时, 才发送对应的 SQL 语句. /*Manager manager = worker.getManager();System.out.println(manager.getMgrName());*/ //3. 在查询对象时, 由多的一端导航到 1 的一端时, //若此时 session 已被关闭, 会发生 LazyInitializationException 异常//4. 获取 Worker 对象时, 默认情况下, 其关联的 Manager对象是一个代理对象!
        }@org.junit.Testpublic void testMany2OneSave() {Worker worker = new Worker();worker.setName("worker-1");Worker worker2 = new Worker();worker2.setName("worker-2");Worker worker3 = new Worker();worker3.setName("worker-3");System.out.println(worker);System.out.println(worker2);System.out.println(worker3);Manager manager = new Manager();manager.setMgrName("MMM");//设定关联关系
        worker.setManager(manager);worker2.setManager(manager);worker3.setManager(manager);//先插入 1 的一端, 再插入 n 的一端, 只有 INSERT 语句.//反过来插入开始Manner的mgrId未生成会产生update语句
        session.save(manager);session.save(worker);session.save(worker2);session.save(worker3);}}

package com.hibernate.n21;public class Department {private Integer deptId;private String deptName;private Manager mgr;public Integer getDeptId() {return deptId;}public void setDeptId(Integer deptId) {this.deptId = deptId;}public String getDeptName() {return deptName;}public void setDeptName(String deptName) {this.deptName = deptName;}public Manager getMgr() {return mgr;}public void setMgr(Manager mgr) {this.mgr = mgr;}}package com.hibernate.n21;import java.util.HashSet;
import java.util.Set;public class Manager {private Integer mgrId;private String mgrName;/** 1. 声明集合类型时, 需使用接口类型, 因为 hibernate 在获取* 集合类型时, 返回的是 Hibernate 内置的集合类型, 而不是 JavaSE 一个标准的* 集合实现. * 2. 需要把集合进行初始化, 可以防止发生空指针异常*/private Set<Worker> workers = new HashSet<>();private Department dept; //在上面的代码上加了这行public Integer getMgrId() {return mgrId;}public void setMgrId(Integer mgrId) {this.mgrId = mgrId;}public String getMgrName() {return mgrName;}public void setMgrName(String mgrName) {this.mgrName = mgrName;}public Set<Worker> getWorkers() {return workers;}public void setWorkers(Set<Worker> workers) {this.workers = workers;}public Department getDept() {return dept;}public void setDept(Department dept) {this.dept = dept;}}

<!--在部门这端生成外键--><?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-8-10 9:04:21 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping><class name="com.hibernate.n21.Department" table="DEPARTMENT"><id name="deptId" type="java.lang.Integer"><column name="DEPTID" /><generator class="native" /></id><property name="deptName" type="java.lang.String"><column name="DEPTNAME" /></property><!-- 使用 many-to-one 的方式来映射 1-1 关联关系 --><many-to-one name="mgr" class="com.hibernate.n21.Manager" column="MGR_ID" unique="true"></many-to-one></class>
</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-8-10 7:47:59 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping><class name="com.hibernate.n21.Manager" table="MANAGER"><id name="mgrId" type="java.lang.Integer"><column name="MGR_ID" /><generator class="native" /></id><property name="mgrName" type="java.lang.String"><column name="MGR_NAME" /></property><!-- 映射 1 对多的那个集合属性 --><!-- set: 映射 set 类型的属性, table: set 中的元素对应的记录放在哪一个数据表中. 该值需要和多对一的多的那个表的名字一致 --><!-- inverse: 指定由哪一方来维护关联关系. 通常设置为 true, 以指定由多的一端来维护关联关系 --><!-- order-by 在查询时对集合中的元素进行排序, order-by 中使用的是表的字段名, 而不是持久化类的属性名  --><set name="workers" table="WORKER" inverse="true"><!-- 执行多的表中的外键列的名字 --><key><column name="MGR_ID" /></key><!-- 指定映射类型 --><one-to-many class="com.hibernate.n21.Worker" /></set><!-- 映射 1-1 的关联关系: 在对应的数据表中已经有外键了, 当前持久化类使用 one-to-one 进行映射 --><!-- 没有外键的一端需要使用one-to-one元素，该元素使用 property-ref 属性指定使用被关联实体主键以外的字段作为关联字段--><!-- 在原来的代码上加上一对一关系 --><one-to-one name="dept" class="com.hibernate.n21.Department"property-ref="mgr"></one-to-one></class>
</hibernate-mapping>

@org.junit.Testpublic void testGet(){//1. 默认情况下对关联属性使用懒加载Department dept = (Department) session.get(Department.class, 1);System.out.println(dept.getDeptName()); //2. 会出现懒加载异常的问题.
//        session.close();//3. 查询 Manager 对象的连接条件应该是 dept.manager_id = mgr.manager_id
//而不应该是 dept.dept_id = mgr.manager_id所以在xml文件中加入property-ref="mgr"Manager mgr = dept.getMgr();System.out.println(mgr.getMgrName()); }@org.junit.Testpublic void testSave(){Department department = new Department();department.setDeptName("DEPT-BB");Manager manager = new Manager();manager.setMgrName("MGR-BB");//设定关联关系
        department.setMgr(manager);manager.setDept(department);//保存操作//建议先保存没有外键列的那个对象. 这样会减少 UPDATE 语句
        session.save(manager);session.save(department);}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2017-8-10 9:04:21 by Hibernate Tools 3.4.0.CR1 -->
<hibernate-mapping><class name="com.hibernate.n21.Department" table="DEPARTMENT"><id name="deptId" type="java.lang.Integer"><column name="DEPT_ID" /><!-- 使用外键的方式来生成当前的主键 --><generator class="foreign"><!-- property 属性指定使用当前持久化类的哪一个属性的主键作为外键 --><param name="property">mgr</param></generator></id><property name="deptName" type="java.lang.String"><column name="DEPTNAME" /></property><!-- 使用 many-to-one 的方式来映射 1-1 关联关系 --><!--  采用 foreign 主键生成器策略的一端增加 one-to-one 元素映射关联属性,其 one-to-one 节点还应增加 constrained=true 属性, 以使当前的主键上添加外键约束--><one-to-one name="mgr" class="com.hibernate.n21.Manager" constrained="true"></one-to-one></class>
</hibernate-mapping>

public class Category {private Integer id;private String name;private Set<Item> items = new HashSet<>();public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Set<Item> getItems() {return items;}public void setItems(Set<Item> items) {this.items = items;}}public class Item {private Integer id;private String name;private Set<Category> categories = new HashSet<>();public Integer getId() {return id;}public void setId(Integer id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Set<Category> getCategories() {return categories;}public void setCategories(Set<Category> categories) {this.categories = categories;}}@Testpublic void testGet(){Category category = (Category) session.get(Category.class, 1);System.out.println(category.getName()); //需要连接中间表Set<Item> items = category.getItems();System.out.println(items.size()); }@Testpublic void testSave(){Category category1 = new Category();category1.setName("C-AA");Category category2 = new Category();category2.setName("C-BB");Item item1 = new Item();item1.setName("I-AA");Item item2 = new Item();item2.setName("I-BB");//设定关联关系
        category1.getItems().add(item1);category1.getItems().add(item2);category2.getItems().add(item1);category2.getItems().add(item2);item1.getCategories().add(category1);item1.getCategories().add(category2);item2.getCategories().add(category1);item2.getCategories().add(category2);//执行保存操作
        session.save(category1);session.save(category2);session.save(item1);session.save(item2);}

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.hibernate.n2n"><class name="Category" table="CATEGORIES"><id name="id" type="java.lang.Integer"><column name="ID" /><generator class="native" /></id><property name="name" type="java.lang.String"><column name="NAME" /></property><!-- table: 指定中间表 --><set name="items" table="CATEGORIES_ITEMS"><key><column name="C_ID" /></key><!-- 使用 many-to-many 指定多对多的关联关系. column 执行 Set 集合中的持久化类在中间表的外键列的名称  --><many-to-many class="Item" column="I_ID"></many-to-many></set></class>
</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"><hibernate-mapping package="com.hibernate.n2n"><class name="Item" table="ITEMS"><id name="id" type="java.lang.Integer"><column name="ID" /><generator class="native" /></id><property name="name" type="java.lang.String"><column name="NAME" /></property><set name="categories" table="CATEGORIES_ITEMS" inverse="true"><key column="I_ID"></key><many-to-many class="Category" column="C_ID"></many-to-many></set></class>
</hibernate-mapping>