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" />