Hibernate学习总结----
一、搭建Hibernate环境
1.在src目录下创建hibernate.cfg.xml配置文件
PS:文件的名字不能改！
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"><hibernate-configuration> <session-factory> <!-- configure the database setting --> <property name="connection.username">root</property> <property name="connection.password">1234</property> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost:3306/test</property> <!-- configure the hibernate setting --> <!-- transaction is supported by org.hibernate.dialect.MySQL5InnoDBDialect --> <property name="dialect">org.hibernate.dialect.MySQL5InnoDBDialect</property>
<!-- show sql in the console --> <property name="show_sql">true</property>
<!-- create and update the database automaticlly --> <property name="hbm2ddl.auto">update</property> <!-- javax.persistence.validation.mode默认情况下是auto的，就是说如果不设置的话它是会自动去你的classpath下面找一个 bean-validation**包，但是找不到，所以beanvalitionFactory错误 --> <property name="javax.persistence.validation.mode">none</property> </session-factory></hibernate-configuration>
2. 编写实体类，以Person类为例
package test.Hibernate.model;import java.util.HashSet;import java.util.Set;public class Person { @Override public String toString() { return "Person [id=" + id + ", name=" + name + "]"; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set<String> getAddress() { return address; } public void setAddress(Set<String> address) { this.address = address; } private int id; private String name; private Set<String> address = new HashSet<String>(); }
3.编写Person.hbm.xml实体类配置文件
<?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"><!-- Mapping file autogenerated by MyEclipse Persistence Tools--><hibernate-mapping package="test.Hibernate.model"> <class name="Person" table="person"> <id column="id" name="id" type="int"> <generator class="native"></generator> </id> <property name="name" column="name" length="50" type="string"></property> <set name="address" table="address"> <key column="personId"></key> <element column="address" type="string" length="50"></element> </set> </class></hibernate-mapping>
4.在hibernate.cfg.xml中加入映射信息
<mapping resource="test/Hibernate/model/Person.hbm.xml" />
5.使用MyEclipse生成SessionFactory
package test.Hibernate.SessionFactory;import org.hibernate.HibernateException;import org.hibernate.Session;import org.hibernate.cfg.Configuration;import org.hibernate.service.ServiceRegistry;import org.hibernate.service.ServiceRegistryBuilder;/** * Configures and provides access to Hibernate sessions, tied to the * current thread of execution. Follows the Thread Local Session * pattern, see {@link http://hibernate.org/42.html }. */public class SessionFactory { /** * Location of hibernate.cfg.xml file. * Location should be on the classpath as Hibernate uses * #resourceAsStream style lookup for its configuration file. * The default classpath location of the hibernate config file is * in the default package. Use #setConfigFile() to update * the location of the configuration file for the current session. */ private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>(); private static org.hibernate.SessionFactory sessionFactory; private static Configuration configuration = new Configuration(); private static ServiceRegistry serviceRegistry; static { try { configuration.configure(); serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry(); sessionFactory = configuration.buildSessionFactory(serviceRegistry); } catch (Exception e) { System.err.println("%%%% Error Creating SessionFactory %%%%"); e.printStackTrace(); } } private SessionFactory() { } /** * Returns the ThreadLocal Session instance. Lazy initialize * the <code>SessionFactory</code> if needed. * * @return Session * @throws HibernateException */ public static Session getSession() throws HibernateException { Session session = (Session) threadLocal.get(); if (session == null || !session.isOpen()) { if (sessionFactory == null) { rebuildSessionFactory(); } session = (sessionFactory != null) ? sessionFactory.openSession() : null; threadLocal.set(session); } return session; } /** * Rebuild hibernate session factory * */ public static void rebuildSessionFactory() { try { configuration.configure(); serviceRegistry = new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry(); sessionFactory = configuration.buildSessionFactory(serviceRegistry); } catch (Exception e) { System.err.println("%%%% Error Creating SessionFactory %%%%"); e.printStackTrace(); } } /** * Close the single hibernate session instance. * * @throws HibernateException */ public static void closeSession() throws HibernateException { Session session = (Session) threadLocal.get(); threadLocal.set(null); if (session != null) { session.close(); } } /** * return session factory * */ public static org.hibernate.SessionFactory getSessionFactory() { return sessionFactory; } /** * return hibernate configuration * */ public static Configuration getConfiguration() { return configuration; }}
6.编写测试类
package test.Hibernate.dao;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.Test;import test.Hibernate.SessionFactory.SessionFactory;import test.Hibernate.model.Person;public class PersonDao { @Test public void add(){ Session session = SessionFactory.getSession(); Transaction tr = session.beginTransaction(); //---------------------------------------------- Person p = new Person(); p.setName("test"); p.getAddress().add("firstAddr"); p.getAddress().add("secondAddr"); p.getAddress().add("thirdAddr"); p.getAddress().add("fourthAddr"); session.save(p); //---------------------------------------------- tr.commit(); SessionFactory.closeSession(); } @Test public void get(){ Session session = SessionFactory.getSession(); Transaction tr = session.beginTransaction(); //---------------------------------------------- Person p = (Person)session.get(Person.class, 2); System.out.println(p); //---------------------------------------------- tr.commit(); SessionFactory.closeSession(); }}
二、主键生成策略
identity：使用数据库的自动增长策略，不是所有数据库都支持，比如oracle就不支持。
sequence：在 DB2，PostgreSQL，Oracle，SAP DB，McKoi 中使用序列（sequence）在使用Oracle数据库时可以使用这一个。
hilo:使用高低位算法生成主键值。只需要一张额外表，所有的数据都支持。
native:根据底层数据库的能力选择 identity、sequence 或者 hilo中的一个。
assigned：手工指定主键值。
uuid：由Hibernate自动生成UUID并指定为主键值。
三、Hibernate映射关系配置
1.一对一映射（以主键关联作为示例）User与IdCard（有外键方）的XML配置：
<?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"><!-- Mapping file autogenerated by MyEclipse Persistence Tools--><hibernate-mapping package="test.Hibernate.model"> <class name="User" table="user"> <id name="id" type="int" column="id"> <generator class="native"></generator> </id> <property name="name" type="string" column="name"/> <set name="address" table="address"> <key column="userId"></key> <element column="address" type="string"></element> </set> <one-to-one name="idCard" class="IdCard" cascade="all"></one-to-one> </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"><!-- Mapping file autogenerated by MyEclipse Persistence Tools--><hibernate-mapping package="test.Hibernate.model"> <class name="IdCard" table="idCard"> <id name="id" type="int" column="id"> <generator class="foreign"> <param name="property">user</param> </generator> </id> <property name="number" type="string" column="number"/> <one-to-one name="user" class="User" constrained="true"></one-to-one> </class></hibernate-mapping>
2.一对多，多对一（以Father和Children为例）
<?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 package="test.Hibernate.model"> <class name="Father" table="father"> <id name="id" type="int" column="id" > <generator class="native"></generator> </id> <property name="name" type="string" column="name"/> <set name="children" cascade="all"> <key column="fatherId"></key> <one-to-many class="Children"/> </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 package="test.Hibernate.model"> <class name="Children" table="children"> <id name="id" type="int" column="id" > <generator class="native"></generator> </id> <property name="name" type="string" column="name"/> <many-to-one name="father" class="Father" column="fatherId"></many-to-one> </class></hibernate-mapping>
3.多对多（以Student和Teacher为例）
PS:有一方的set集合要标明inverse=true（后面会讲）
<?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"><!-- Mapping file autogenerated by MyEclipse Persistence Tools--><hibernate-mapping package="test.Hibernate.model"> <class name="Student" table="student"> <id name="id" type="int" column="id"> <generator class="native"></generator> </id> <property name="name" type="string" column="name" length="20"/> <set name="teachers" table="student_teacher" inverse="false" > <key column="studentId"></key> <many-to-many class="Teacher" column="teacherId"></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"><!-- Mapping file autogenerated by MyEclipse Persistence Tools--><hibernate-mapping package="test.Hibernate.model"> <class name="Teacher" table="teacher"> <id name="id" type="int" column="id"> <generator class="native"></generator> </id> <property name="name" column="name" type="string" length="20"></property> <set name="students" table="student_teacher" inverse="true" cascade="all"> <key column="teacherId"></key> <many-to-many class="Student" column="studentId"></many-to-many> </set> </class></hibernate-mapping>
四、inverse和cascade的区别（个人总结，有不对还望指正）
1.inverse=false在一对多删除时是把孩子的外键设置为null，然后删除父亲，孩子不删除，而casecade=all在一对多删除时是把孩子的外键设置为null，然后删除父亲，然后再删除孩子
2.many to many的时候由一方维护，所以一方要设置inverse=false，但是inverse=true的另一方直接删除会出错，这个时候可以用casecade完成级联删除
3.inverse=false只用于set等集合属性，在one to one关系中可以用casecade完成级联删除
五、使用C3P0连接池
1.需要额外导入3个jar包
2.在hibernate.cfg.xml中加入C3P0配置信息
<!-- C3P0连接池设定--> <!-- 使用c3p0连接池 配置连接池提供的供应商--> <property name="connection.provider_class">org.hibernate.connection.C3P0ConnectionProvider</property> <!--在连接池中可用的数据库连接的最少数目 --> <property name="c3p0.min_size">5</property> <!--在连接池中所有数据库连接的最大数目 --> <property name="c3p0.max_size">20</property> <!--设定数据库连接的过期时间,以秒为单位, 如果连接池中的某个数据库连接处于空闲状态的时间超过了timeout时间,就会从连接池中清除 --> <property name="c3p0.timeout">120</property> <!--每3000秒检查所有连接池中的空闲连接 以秒为单位--> <property name="c3p0.idle_test_period">3000</property>
六、HQL语句
@Test public void HQLSearch(){ Session session = SessionFactory.getSession(); Transaction tr = session.beginTransaction(); //----------------------------------------- //common search with where// String hql= "select e.id,e.name from User e where e.id>=5 and e.id<=9";// Query query = session.createQuery(hql);// List list = query.list(); // for(Object o : list){ // System.out.println(Arrays.toString((Object[])o));// } //paging search// String hql= "select e.id,e.name from User e";// Query query = session.createQuery(hql);// query.setFirstResult(0);// query.setMaxResults(10);// List list = query.list(); // for(Object o : list){ // System.out.println(Arrays.toString((Object[])o));// } //search with parameters// String hql= "select e.id,e.name from User e where id>=? and id<=?";// Query query = session.createQuery(hql)// .setParameter(0, 1)// .setParameter(1, 3);// List list = query.list(); // for(Object o : list){ // System.out.println(Arrays.toString((Object[])o));// } //search with parameters whose type is collection// String hql= "select e.id,e.name from User e where id in (:ids)";// Query query = session.createQuery(hql)// .setParameterList("ids",new Object[]{1,2,3,8} );// List list = query.list(); // for(Object o : list){ // System.out.println(Arrays.toString((Object[])o));// } //----------------------------------------- tr.commit(); SessionFactory.closeSession(); }
七、DML语句
@Test public void DML(){ Session session = SessionFactory.getSession(); Transaction tr = session.beginTransaction(); //----------------------------------------- User u = (User)session.get(User.class, 11); String sql = "update User set name=? where id>?"; int result = session.createQuery(sql) .setParameter(0, "updated") .setParameter(1, 10) .executeUpdate(); System.out.println("count of update:"+result); //the object's status in session was not updated when the object in database have been changed,so if you want //to get the updated object in session,you should use method "refresh". session.refresh(u); System.out.println(u); //----------------------------------------- tr.commit(); SessionFactory.closeSession(); }
八、开启二级缓存
1. 需要导入以下jar包
2.在hibernate.cfg.xml中加入以下配置
<!-- 使用二级缓存，默认是未打开的。 --> <!-- 指定要使用的缓存的提供商，这也就打开了二级缓存--> <property name="hibernate.cache.use_second_level_cache">true</property> <property name="hibernate.cache.region.factory_class">org.hibernate.cache.ehcache.EhCacheRegionFactory</property> <!-- 开启使用查询缓存 --> <property name="cache.use_query_cache">true</property> <!-- 指定要使用二级缓存的实体类 --> <class-cache usage="read-write" class="test.Hibernate.model.Person" />
九、Hibernate对象状态及转化
- 1楼DNMCM
- 这玩意还那么多人用么
- Re: Sunnier
- @DNMCM，不知道。JPA、MyBatis也用得挺多吧。毕竟Hibernate那么强大。