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" />