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[Java教程]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.配置文件

PS:文件的名字不能改!

<??><!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.

<??><!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.

<mapping resource="test/Hibernate/model/Person.hbm. />

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.*/  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

<??><!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>

<??><!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)

<??><!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>

<??><!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)

<??><!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>

<??><!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.

    <!-- 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.

    <!-- 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