Hibernate详细教程

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