监听者模式(Listener-Event)---hibernate
?? 今天浏览博客,偶然浏览到了hibernate中crud等,所采用的观察模式,追踪下源码,记录备忘.....
也可以看http://wuquanyin1011.iteye.com/admin/blogs/628993这篇文章(tomcat中容器周期的通知,也是采用了监听者的模式)
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以session.save(object)为例
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//追踪到这一步(SessionImpl下)public void save(String entityName, Object object, Serializable id) throws HibernateException {//这是创建一个事件,带有object(对像)fireSave( new SaveOrUpdateEvent(entityName, object, id, this) );}private Serializable fireSave(SaveOrUpdateEvent event) {errorIfClosed();checkTransactionSynchStatus(); //hibernate中提供了一系列的监听器,供调用SaveOrUpdateEventListener[] saveEventListener = listeners.getSaveEventListeners();for ( int i = 0; i < saveEventListener.length; i++ ) {saveEventListener[i].onSaveOrUpdate(event);//实行对象保存}return event.getResultId();}?
?//从以上可以看出监听者模式的运用.
以下贴出所有的监听器
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//需要操作的监听器都可以从这个类中获取public class EventListeners extends Cloneable implements Serializable {private LoadEventListener[] loadEventListeners = { new DefaultLoadEventListener() };private SaveOrUpdateEventListener[] saveOrUpdateEventListeners = { new DefaultSaveOrUpdateEventListener() };private MergeEventListener[] mergeEventListeners = { new DefaultMergeEventListener() };private PersistEventListener[] persistEventListeners = { new DefaultPersistEventListener() };private PersistEventListener[] persistOnFlushEventListeners = { new DefaultPersistOnFlushEventListener() };private ReplicateEventListener[] replicateEventListeners = { new DefaultReplicateEventListener() };private DeleteEventListener[] deleteEventListeners = { new DefaultDeleteEventListener() };private AutoFlushEventListener[] autoFlushEventListeners = { new DefaultAutoFlushEventListener() };private DirtyCheckEventListener[] dirtyCheckEventListeners = { new DefaultDirtyCheckEventListener() };private FlushEventListener[] flushEventListeners = { new DefaultFlushEventListener() };private EvictEventListener[] evictEventListeners = { new DefaultEvictEventListener() };private LockEventListener[] lockEventListeners = { new DefaultLockEventListener() };private RefreshEventListener[] refreshEventListeners = { new DefaultRefreshEventListener() };private FlushEntityEventListener[] flushEntityEventListeners = { new DefaultFlushEntityEventListener() };private InitializeCollectionEventListener[] initializeCollectionEventListeners = { new DefaultInitializeCollectionEventListener() };private PostLoadEventListener[] postLoadEventListeners = { new DefaultPostLoadEventListener() };private PreLoadEventListener[] preLoadEventListeners = { new DefaultPreLoadEventListener() };private PreDeleteEventListener[] preDeleteEventListeners = {};private PreUpdateEventListener[] preUpdateEventListeners = {};private PreInsertEventListener[] preInsertEventListeners = {};private PostDeleteEventListener[] postDeleteEventListeners = {};private PostUpdateEventListener[] postUpdateEventListeners = {};private PostInsertEventListener[] postInsertEventListeners = {};private PostDeleteEventListener[] postCommitDeleteEventListeners = {};private PostUpdateEventListener[] postCommitUpdateEventListeners = {};private PostInsertEventListener[] postCommitInsertEventListeners = {};private SaveOrUpdateEventListener[] saveEventListeners = { new DefaultSaveEventListener() };private SaveOrUpdateEventListener[] updateEventListeners = { new DefaultUpdateEventListener() };private MergeEventListener[] saveOrUpdateCopyEventListeners = { new DefaultSaveOrUpdateCopyEventListener() };//saveOrUpdateCopy() is deprecated!private static Map eventInterfaceFromType;static {eventInterfaceFromType = new HashMap();eventInterfaceFromType.put("auto-flush", AutoFlushEventListener.class);eventInterfaceFromType.put("merge", MergeEventListener.class);eventInterfaceFromType.put("create", PersistEventListener.class);eventInterfaceFromType.put("create-onflush", PersistEventListener.class);eventInterfaceFromType.put("delete", DeleteEventListener.class);eventInterfaceFromType.put("dirty-check", DirtyCheckEventListener.class);eventInterfaceFromType.put("evict", EvictEventListener.class);eventInterfaceFromType.put("flush", FlushEventListener.class);eventInterfaceFromType.put("flush-entity", FlushEntityEventListener.class);eventInterfaceFromType.put("load", LoadEventListener.class);eventInterfaceFromType.put("load-collection", InitializeCollectionEventListener.class);eventInterfaceFromType.put("lock", LockEventListener.class);eventInterfaceFromType.put("refresh", RefreshEventListener.class);eventInterfaceFromType.put("replicate", ReplicateEventListener.class);eventInterfaceFromType.put("save-update", SaveOrUpdateEventListener.class);eventInterfaceFromType.put("save", SaveOrUpdateEventListener.class);eventInterfaceFromType.put("update", SaveOrUpdateEventListener.class);eventInterfaceFromType.put("pre-load", PreLoadEventListener.class);eventInterfaceFromType.put("pre-update", PreUpdateEventListener.class);eventInterfaceFromType.put("pre-delete", PreDeleteEventListener.class);eventInterfaceFromType.put("pre-insert", PreInsertEventListener.class);eventInterfaceFromType.put("post-load", PostLoadEventListener.class);eventInterfaceFromType.put("post-update", PostUpdateEventListener.class);eventInterfaceFromType.put("post-delete", PostDeleteEventListener.class);eventInterfaceFromType.put("post-insert", PostInsertEventListener.class);eventInterfaceFromType.put("post-commit-update", PostUpdateEventListener.class);eventInterfaceFromType.put("post-commit-delete", PostDeleteEventListener.class);eventInterfaceFromType.put("post-commit-insert", PostInsertEventListener.class);eventInterfaceFromType = Collections.unmodifiableMap( eventInterfaceFromType );}//....略}?
?事件的生成...
hibernate中抽取了AbstractEvent的抽象类,如下
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public abstract class AbstractEvent implements Serializable { //存放SessionImpl,该类实现了以下的接口private final EventSource session; /** * Constructs an event from the given event session. * * @param source The session event source. */public AbstractEvent(EventSource source) {this.session = source;} /** * Returns the session event source for this event. This is the underlying * session from which this event was generated. * * @return The session event source. */public final EventSource getSession() {return session;}}?
??SaveEvent,hibernate就是根据以下的模式抽象出一系列的操作(LoadEvent等)
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//进行一些参数赋值public class SaveOrUpdateEvent extends AbstractEvent {private Object object;private Serializable requestedId;private String entityName;private Object entity;private EntityEntry entry;private Serializable resultId;public SaveOrUpdateEvent(String entityName, Object original, EventSource source) {this(original, source);this.entityName = entityName;}public SaveOrUpdateEvent(String entityName, Object original, Serializable id, EventSource source) {this(entityName, original, source);this.requestedId = id;if ( requestedId == null ) {throw new IllegalArgumentException("attempt to create saveOrUpdate event with null identifier");}}public SaveOrUpdateEvent(Object object, EventSource source) {super(source);if ( object == null ) {throw new IllegalArgumentException("attempt to create saveOrUpdate event with null entity");}this.object = object;}public Object getObject() {return object;}public void setObject(Object object) {this.object = object;}public Serializable getRequestedId() {return requestedId;}public void setRequestedId(Serializable requestedId) {this.requestedId = requestedId;}public String getEntityName() {return entityName;}public void setEntityName(String entityName) {this.entityName = entityName;}public Object getEntity() {return entity;}public void setEntity(Object entity) {this.entity = entity;}public EntityEntry getEntry() {return entry;}public void setEntry(EntityEntry entry) {this.entry = entry;}public Serializable getResultId() {return resultId;}public void setResultId(Serializable resultId) {this.resultId = resultId;}}??现在查看下,hibernate是如何利用Listener对Event进行操作
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这一步的操作如下.
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saveEventListener[i].onSaveOrUpdate(event);//实行对象保存
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public class DefaultSaveOrUpdateEventListener extends AbstractSaveEventListener implements SaveOrUpdateEventListener {private static final Log log = LogFactory.getLog(DefaultSaveOrUpdateEventListener.class);/** * Handle the given update event. * * @param event The update event to be handled. * @throws HibernateException */ //进行对象的保存操作public void onSaveOrUpdate(SaveOrUpdateEvent event) throws HibernateException {final SessionImplementor source = event.getSession();final Object object = event.getObject();final Serializable requestedId = event.getRequestedId();if ( requestedId!=null ) {//assign the requested id to the proxy, *before* //reassociating the proxyif ( object instanceof HibernateProxy ) {( (HibernateProxy) object ).getHibernateLazyInitializer().setIdentifier(requestedId);}}if ( reassociateIfUninitializedProxy(object, source) ) {log.trace("reassociated uninitialized proxy");// an uninitialized proxy, noop, don't even need to // return an id, since it is never a save()}else {//initialize properties of the event:final Object entity = source.getPersistenceContext().unproxyAndReassociate(object);event.setEntity(entity);event.setEntry( source.getPersistenceContext().getEntry(entity) );//return the id in the event objectevent.setResultId( performSaveOrUpdate(event) );}}//...略}以上为hibernate的一个命令模式的操作过程.
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1 楼 wgx198302 2010-05-24 正在学习command模式 2 楼 weilingfeng98 2011-01-12 到底是command 还是观察者模式 3 楼 Caedmon 2011-03-03 监听模式就是观察者模式吧 4 楼 spawnyy 2011-03-15 我认为观察者模式+命令模式的一种变体，因为事件监听模式是J2EE设计模式中模式之一。