学习笔记之Hibernate_映射关系之一对多映射关系

package hibernates.entities.n21;public class Customer { ???private Integer customerId; ???private String customerName; ???public Integer getCustomerId() { ???????return customerId; ???} ???public void setCustomerId(Integer customerId) { ???????this.customerId = customerId; ???} ???public String getCustomerName() { ???????return customerName; ???} ???public void setCustomerName(String customerName) { ???????this.customerName = customerName; ???} ???public Customer(String customerName) { ???????super(); ???????this.customerName = customerName; ???} ???public Customer() { ???????super(); ???????// TODO Auto-generated constructor stub ???} ???@Override ???public String toString() { ???????return "Customer [customerId=" + customerId + ", customerName=" + customerName + "]"; ???}}

package hibernates.entities.n21;public class Order { ???private Integer orderId; ???private String orderName; ???private Customer customer; ???public Integer getOrderId() { ???????return orderId; ???} ???public void setOrderId(Integer orderId) { ???????this.orderId = orderId; ???} ???public String getOrderName() { ???????return orderName; ???} ???public void setOrderName(String orderName) { ???????this.orderName = orderName; ???} ???public Customer getCustomer() { ???????return customer; ???} ???public void setCustomer(Customer customer) { ???????this.customer = customer; ???} ???public Order(String orderName, Customer customer) { ???????super(); ???????this.orderName = orderName; ???????this.customer = customer; ???} ???public Order() { ???????super(); ???????// TODO Auto-generated constructor stub ???} ???@Override ???public String toString() { ???????return "Order [orderId=" + orderId + ", orderName=" + orderName + ", customer=" + customer + "]"; ???}}

<?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 2017-11-27 21:13:51 by Hibernate Tools 3.5.0.Final --><hibernate-mapping> ???<class name="hibernates.entities.n21.Order" table="ORDERS"> ???????????<id name="orderId" type="java.lang.Integer"> ???????????<column name="ORDERID" /> ???????????<generator class="native" /> ???????</id> ???????????????<property name="orderName" type="java.lang.String"> ???????????<column name="ORDERNAME" /> ???????</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: 一那一端在多的一端对应的数据表中的外键的名字 ???????--> ???????<many-to-one name="customer" class="hibernates.entities.n21.Customer" > ???????????<column name="CUSTOMER_ID" /> ???????</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 2017-11-27 21:13:51 by Hibernate Tools 3.5.0.Final --><hibernate-mapping> ???<class name="hibernates.entities.n21.Customer" table="CUSTOMERS"> ???????????<id name="customerId" type="java.lang.Integer"> ???????????<column name="CUSTOMER_ID" /> ???????????<generator class="native" /> ???????</id> ???????????????<property name="customerName" type="java.lang.String"> ???????????<column name="CUSTOME_RNAME" /> ???????</property> ???????????</class> ???</hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-configuration PUBLIC ???????"-//Hibernate/Hibernate Configuration DTD 3.0//EN" ???????"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration> ???<session-factory> ???????????<!-- 配置连接数据库的基本信息 --> ???????<property name="connection.username">root</property> ???????<property name="connection.password">123456</property> ???????<property name="connection.driver_class">com.mysql.jdbc.Driver</property> ???????<property name="connection.url">jdbc:mysql:///hibernate</property> ???????????????<!-- 配置 hibernate 的基本信息 --> ???????<!-- hibernate 所使用的数据库方言 ????????<property name="dialect">org.hibernate.dialect.MySQLMyISAMDialect</property> ???????????????<property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property> ???????????????<property name="dialect">org.hibernate.dialect.MySQLDialect</property> ???????--> ???????????????<!-- 执行操作时是否在控制台打印 SQL --> ???????<property name="show_sql">true</property> ???????????<!-- 是否对 SQL 进行格式化 --> ???????<property name="format_sql">true</property> ???????????<!-- 指定自动生成数据表的策略 --> ???????<property name="hbm2ddl.auto">update</property> ???????????????<!-- 设置 Hibernate 的事务隔离级别 --> ???????<property name="connection.isolation">2</property> ???????????????<!-- 删除对象后, 使其 OID 置为 null --> ???????<property name="use_identifier_rollback">true</property> ???????????????<!-- 配置 C3P0 数据源 --> ???????<property name="hibernate.c3p0.max_size">10</property> ???????<property name="hibernate.c3p0.min_size">5</property> ???????<property name="c3p0.acquire_increment">2</property> ???????????????<property name="c3p0.idle_test_period">2000</property> ???????<property name="c3p0.timeout">2000</property> ???????????????<property name="c3p0.max_statements">10</property> ???????????????<!-- 指定关联的 .hbm.xml 文件 --> ???????<mapping resource="hibernates/entities/n21/Customer.hbm.xml"/> ???????<mapping resource="hibernates/entities/n21/Order.hbm.xml"/> ???????</session-factory></hibernate-configuration>

package hibernates.entities.n21;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.boot.MetadataSources;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.service.ServiceRegistry;import org.junit.After;import org.junit.Before;import org.junit.Test;public class HibernateTest { ???????????Session session; ???SessionFactory sessionFactory; ???Transaction transaction; ???????@Before ???public void init() { ???????ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().configure().build(); ???????sessionFactory = new MetadataSources(serviceRegistry).buildMetadata().buildSessionFactory(); ???????session = sessionFactory.openSession(); ???????transaction = session.beginTransaction(); ???} ???????@After ???public void destroy() { ???????transaction.commit(); ???????session.close(); ???????sessionFactory.close(); ???} ???????@Test ???public void testMany2OneSave() { ???????Customer customer = new Customer(); ???????customer.setCustomerName("小明"); ???????Order order1 = new Order(); ???????order1.setOrderName("AA"); ???????Order order2 = new Order(); ???????order2.setOrderName("BB"); ???????????????//设定关联关系 ???????order1.setCustomer(customer); ???????order2.setCustomer(customer); ???????????????//执行 ?save 操作: 先插入 Customer, 再插入 Order, 3 条 INSERT ???????//先插入 1 的一端, 再插入 n 的一端, 只有 INSERT 语句.// ???????session.save(customer);// ???????session.save(order1);// ???????session.save(order2); ???????????????//先插入 Order, 再插入 Customer. 3 条 INSERT, 2 条 UPDATE ???????//先插入 n 的一端, 再插入 1 的一端, 会多出 UPDATE 语句! ???????//因为在插入多的一端时, 无法确定 1 的一端的外键值. 所以只能等 1 的一端插入后, 再额外发送 UPDATE 语句. ???????//推荐先插入 1 的一端, 后插入 n 的一端 ???????session.save(order1); ???????session.save(order2); ???????session.save(customer); ???????????} ???????@Test ???public void testMany2OneGet() { ???????//1. 若查询多的一端的一个对象, 则默认情况下, 只查询了多的一端的对象. 而没有查询关联的 ???????//1 的那一端的对象! ???????Order order = session.get(Order.class, 1); ???????System.out.println(order); ???????System.out.println(order.getCustomer().getClass().getName()); ???????????????session.close(); ???????????????//2. 在需要使用到关联的对象时, 才发送对应的 SQL 语句. ????????Customer customer = order.getCustomer(); ???????System.out.println(customer); ???????????????//3. 在查询 Customer 对象时, 由多的一端导航到 1 的一端时, ????????//若此时 session 已被关闭, 则默认情况下 ???????//会发生 LazyInitializationException 异常 ???????????????//4. 获取 Order 对象时, 默认情况下, 其关联的 Customer 对象是一个代理对象! ???????????} ???????@Test ???public void testUpdate() { ???????Order order = session.get(Order.class, 1); ???????order.getCustomer().setCustomerName("555"); ???} ???????????@Test ???public void testDelete() { ???????//在不设定级联关系的情况下, 且 1 这一端的对象有 n 的对象在引用, 不能直接删除 1 这一端的对象 ???????Customer customer = session.get(Customer.class, 1); ???????session.delete(customer); ???}}

<?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 2017-12-1 19:54:01 by Hibernate Tools 3.5.0.Final --><hibernate-mapping> ???<class name="hibernates.entities.n21.both.Order" table="BOTHORDERS"> ???????<id name="orderId" type="java.lang.Integer"> ???????????<column name="ORDERID" /> ???????????<generator class="native" /> ???????</id> ???????<property name="orderName" type="java.lang.String"> ???????????<column name="ORDERNAME" /> ???????</property> ???????<many-to-one name="customer" class="hibernates.entities.n21.both.Customer" fetch="join" ???????????????cascade="delete"> ???????????<column name="CUSTOMERID" /> ???????</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 2017-12-1 19:54:01 by Hibernate Tools 3.5.0.Final --><hibernate-mapping> ???<class name="hibernates.entities.n21.both.Customer" table="BOTHCUSTOMERS"> ???????<id name="customerId" type="java.lang.Integer"> ???????????<column name="CUSTOMERID" /> ???????????<generator class="native" /> ???????</id> ???????<property name="customerName" type="java.lang.String"> ???????????<column name="CUSTOMERNAME" /> ???????</property> ???????<set name="orders" table="BOTHORDERS" inverse="true" cascade="delete" order-by="CUSTOMERID DESC"> ???????????<key> ???????????????<column name="CUSTOMERID" /> ???????????</key> ???????????<one-to-many class="hibernates.entities.n21.both.Order" />
 ???????</set> ???</class></hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC ???????"-//Hibernate/Hibernate Configuration DTD 3.0//EN" ???????"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration> ???<session-factory> ???????????<!-- 配置连接数据库的基本信息 --> ???????<property name="connection.username">root</property> ???????<property name="connection.password">123456</property> ???????<property name="connection.driver_class">com.mysql.jdbc.Driver</property> ???????<property name="connection.url">jdbc:mysql:///hibernate</property> ???????????????<!-- 配置 hibernate 的基本信息 --> ???????<!-- hibernate 所使用的数据库方言 ????????<property name="dialect">org.hibernate.dialect.MySQLMyISAMDialect</property> ???????????????<property name="dialect">org.hibernate.dialect.MySQLDialect</property> ???--> ???????????????<property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property> ???????????????????<!-- 执行操作时是否在控制台打印 SQL --> ???????<property name="show_sql">true</property> ???????????<!-- 是否对 SQL 进行格式化 --> ???????<property name="format_sql">true</property> ???????????<!-- 指定自动生成数据表的策略 --> ???????<property name="hbm2ddl.auto">update</property> ???????????????<!-- 设置 Hibernate 的事务隔离级别 --> ???????<property name="connection.isolation">2</property> ???????????????<!-- 删除对象后, 使其 OID 置为 null --> ???????<property name="use_identifier_rollback">true</property> ???????????????<!-- 配置 C3P0 数据源 --> ???????<property name="hibernate.c3p0.max_size">10</property> ???????<property name="hibernate.c3p0.min_size">5</property> ???????<property name="c3p0.acquire_increment">2</property> ???????????????<property name="c3p0.idle_test_period">2000</property> ???????<property name="c3p0.timeout">2000</property> ???????????????<property name="c3p0.max_statements">10</property> ???????????????<!-- 指定关联的 .hbm.xml 文件 --> ???????<!-- ????????<mapping resource="hibernates/entities/n21/Customer.hbm.xml"/> ???????<mapping resource="hibernates/entities/n21/Order.hbm.xml"/>--> ???????<mapping resource="hibernates/entities/n21/both/Order.hbm.xml"/> ????????<mapping resource="hibernates/entities/n21/both/Customer.hbm.xml"/> ????????</session-factory></hibernate-configuration>

package hibernates.entities.n21.both;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.Transaction;import org.hibernate.boot.MetadataSources;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.service.ServiceRegistry;import org.junit.After;import org.junit.Before;import org.junit.Test;public class HibernateTest { ???????????????????Session session; ???SessionFactory sessionFactory; ???Transaction transaction; ???????@Before ???public void init() { ???????ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().configure().build(); ???????sessionFactory = new MetadataSources(serviceRegistry).buildMetadata().buildSessionFactory(); ???????session = sessionFactory.openSession(); ???????transaction = session.beginTransaction(); ???????Customer customer1 = new Customer(); ???????customer1.setCustomerName("AA"); ???????Customer customer2 = new Customer(); ???????customer2.setCustomerName("BB"); ???????Order order1 = new Order(); ???????Order order2 = new Order(); ???????customer1.getOrders().add(order1); ???????customer1.getOrders().add(order2); ???????customer2.getOrders().add(order1); ???????customer2.getOrders().add(order2); ???????order1.setCustomer(customer1); ???????order2.setCustomer(customer1); ???????order1.setCustomer(customer2); ???????order2.setCustomer(customer2); ???????session.save(customer1); ???????session.save(customer2); ???????session.save(order1); ???????session.save(order2); ???} ???????@After ???public void destroy() { ???????transaction.commit(); ???????session.close(); ???????sessionFactory.close(); ???} ???????@Test ???public void testInverse() { ???????//1.可以在 1 的一端的 set 节点指定 inverse=true, 来使 1 的一端放弃维护关联关系! ???????//2.通过多的一端改变来改变表中的数据： ???????Order order3 = session.get(Order.class, 1); ???????order3.setOrderName("HH"); ???????order3.getCustomer().setCustomerName("BB"); ???????//3.通过一的一端来修改表中的数据： ???????Customer customer3 = session.get(Customer.class, 1); ???????customer3.setCustomerName("DD"); ???????customer3.getOrders().iterator().next().setCustomer(customer3); ???????System.out.println(customer3.getOrders()); ???????????} ???????@Test ???public void testCascade() { ???????//当<set> 中的 cascade的属性值为delete时一的一端的数据被删除时，它所关联的多的一端也被删除,<many-to-one>中的 ???????//cascade也具有同样的功能 ???????Customer customer3 = session.get(Customer.class, 1); ???????session.delete(customer3); ???????Order order3 = session.get(Order.class, 1); ???????session.delete(order3); ???} ???????@Test ???public void testOrderBy() { ???????//下面两句输出语句都会使Hibernate查询customer关联的order表，然后按照order-by的设定排序查询 ???????Customer customer3 = session.get(Customer.class, 1); ???????System.out.println(customer3.getOrders()); ???????System.out.println(customer3.getCustomerName()); ???} ???}