hibernate 中的拦截器EmptyInterceptor接口功能

Interceptor接口提供了从会话(session)回调(callback)应用程序(application)的机制， 这种回调机制可以允许应用程序在持久化对象被保存、更新、删除或是加载之前，检查并（或）修改其 属性。一个可能的用途，就是用来跟踪审核(auditing)信息。例如：下面的这个拦截器，会在一个实现了 Auditable接口的对象被创建时自动地设置createTimestamp属性，并在实现了 Auditable接口的对象被更新时，同步更新lastUpdateTimestamp属性。

你可以直接实现Interceptor接口，也可以（最好）继承自EmptyInterceptor。

package org.hibernate.test;

import java.io.Serializable;
import java.util.Date;
import java.util.Iterator;

import org.hibernate.EmptyInterceptor;
import org.hibernate.Transaction;
import org.hibernate.type.Type;

public class AuditInterceptor extends EmptyInterceptor {

    private int updates;
    private int creates;
    private int loads;

    public void onDelete(Object entity,
                         Serializable id,
                         Object[] state,
                         String[] propertyNames,
                         Type[] types) {
        // do nothing
    }

    public boolean onFlushDirty(Object entity,
                                Serializable id,
                                Object[] currentState,
                                Object[] previousState,
                                String[] propertyNames,
                                Type[] types) {

        if ( entity instanceof Auditable ) {
            updates++;
            for ( int i=0; i < propertyNames.length; i++ ) {
                if ( "lastUpdateTimestamp".equals( propertyNames[i] ) ) {
                    currentState[i] = new Date();
                    return true;
                }
            }
        }
        return false;
    }

    public boolean onLoad(Object entity,
                          Serializable id,
                          Object[] state,
                          String[] propertyNames,
                          Type[] types) {
        if ( entity instanceof Auditable ) {
            loads++;
        }
        return false;
    }

    public boolean onSave(Object entity,
                          Serializable id,
                          Object[] state,
                          String[] propertyNames,
                          Type[] types) {
        if ( entity instanceof Auditable ) {
            creates++;
            for ( int i=0; i<propertyNames.length; i++ ) {
                if ( "createTimestamp".equals( propertyNames[i] ) ) {
                    state[i] = new Date();
                    return true;
                }
            }
        }
        return false;
    }

    public void afterTransactionCompletion(Transaction tx) {
        if ( tx.wasCommitted() ) {
            System.out.println("Creations: " + creates + ", Updates: " + updates, "Loads: " + loads);
        }
        updates=0;
        creates=0;
        loads=0;
    }
}

拦截器可以有两种:Session范围内的，和SessionFactory范围内的。

当使用某个重载的SessionFactory.openSession()使用Interceptor作为参数调用打开一个session的时候，就指定了Session范围内的拦截器。

Session session = sf.openSession( new AuditInterceptor() );

或在配置文件中加:

<bean id="sessionFactory" class="cn.sh.cares.framework.spring.annotationSessionFactoryBean">
    <property name="dataSource" ref="ppcDataSource"/>
    <!--<property name="lobHandler" ref="lobHandler"/>-->
    <property name="annotatedClassesLocations">
        <list>
            <value>classpath*:</value>
        </list>
    </property>
    <property name="hbmLocations">
        <list>
            <value>classpath*:</value>
        </list>
    </property>

    <property name="hibernateProperties">
        <props>
            <prop key="hibernate.dialect">cn.sh.cares.framework.dao.hibernate.OracleDialect</prop>
            <prop key="hibernate.format_sql">true</prop>
            <prop key="hibernate.show_sql">true</prop>
            <prop key="hibernate.use_sql_comments">false</prop>
            <prop key="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</prop>
            <prop key="hibernate.cache.use_query_cache">true</prop>
            <prop key="hibernate.cache.use_second_level_cache">true</prop>
            <prop key="hibernate.jdbc.batch_size">20</prop>
            <prop key="hibernate.jdbc.fetch_size">20</prop>
        </props>
    </property>

    <property name="entityInterceptor">
        <bean id ="auditInterceptor" class="cn.sh.cares.framework.dao.hibernate.AuditInterceptor" />
    </property>

本文转自：http://blog.csdn.net/pengchua/article/details/5013889