Hibernate的回調與攔截機制有三種實現方法：
1、實體對象implements Lifecycle接口，Lifecycle接口代碼：
public?interface?Lifecycle?{
????/**
?????*?在實體對象Save/Insert操作之前觸發.
?????*/
????public?boolean?onSave(Session?s)?throws?CallbackException;
????
????/**
?????*?在Session.update()操作之前觸發.
?????*/
????public?boolean?onUpdate(Session?s)?throws?CallbackException;
????/**
?????*?在實體對象刪除之前觸發.
?????*/
????public?boolean?onDelete(Session?s)?throws?CallbackException;
????/**
???? *?在實體對象加載之后觸發.
?????*/
????public?void?onLoad(Session?s,?Serializable?id);
}
實體對象通過實現Lifecycle接口，即可以在特定的持久化階段，觸發特定的處理過程。比如在實體對象Tuser實現了Lifecycle接口的onSave方法，則在實體對象Tuser保存之前將先執行onSave方法。
2、實體對象implements Validatable接口，Validatable接口代碼：
public?interface?Validatable?{
????public?void?validate()?throws ValidationFailure;
}
?? Validatable接口定義了數據驗證實現方式。實體對象實現Validatable接口，并在validate方法中對當前
待保存的數據進行驗證，以保證數據的邏輯合法性(由于該方法在實體對象生命周期內，可能被多次調用，所以此方法最好只用于數據本身的邏輯合法性驗證，而不要試圖去實現數據業務邏輯的驗證)。
以上2種方法都要求實現Hibernate中的Lifecycle或Validatable接口，具有很大的侵入性，使得實體對象的移植很不方便。Hibernate又提供了一種攔截機制，為對象持久化事件的捕獲和處理提供了一個非侵入性的實現。
3、實現Interceptor接口，在創建session時，指定加載Interceptor相應的實現類，此session 的持久化操作都將首先經由此攔截器捕獲處理。Interceptor(Hibernate3)接口代碼：
package?org.hibernate;
import?java.io.Serializable;
import?java.util.Iterator;
import?org.hibernate.type.Type;
public?interface?Interceptor?{
?
??? //對象初始化之前加載,這里的entity處于剛被創建的狀態(即屬性均未賦值).
????public?boolean?onLoad(Object?entity,?Serializable?id,?Object[]?state,?String[]?propertyNames,
??????????? Type[]?types)?throws?CallbackException;
???
??? //Session.flush()方法進行臟數據檢查時,如果發現PO狀態改變,則調用此方法(即實體對象更新之前調用).
????public?boolean?onFlushDirty(Object?entity,?Serializable?id,?Object[]?currentState,
?????????? Object[]?previousState,?String[]?propertyNames,?Type[]?types)?throws?CallbackException;
???
??? //在實體對象被保存之前調用.
????public?boolean?onSave(Object?entity,?Serializable?id,?Object[]?state,?String[]?propertyNames,
?????????? Type[]?types)?throws?CallbackException;
???
??? //在對象被刪除之前調用.
????public?void?onDelete(Object?entity,?Serializable?id,?Object[]?state,?String[]?propertyNames,
?????????? Type[]?types)?throws?CallbackException;
????/**
?????*?Called?before?a?collection?is?(re)created.
?????*/
????public?void?onCollectionRecreate(Object?collection,?Serializable?key)?throws?CallbackException;
????/**
?????*?Called?before?a?collection?is?deleted.
?????*/
????public?void?onCollectionRemove(Object?collection,?Serializable?key)?throws?CallbackException;
????/**
?????*?Called?before?a?collection?is?updated.
?????*/
????public?void?onCollectionUpdate(Object?collection,?Serializable?key)?throws?CallbackException;
???
??? //Session執行flush方法之前調用.
????public?void?preFlush(Iterator?entities)?throws?CallbackException;
??
??? //Session執行flush方法之后調用.
????public?void?postFlush(Iterator?entities)?throws?CallbackException;
????/**
?????*?Called?to?distinguish?between?transient?and?detached?entities.?The?return?value?determines?the
?????*?state?of?the?entity?with?respect?to?the?current?session.
?????*?<ul>
?????*?<li><tt>Boolean.TRUE</tt>?-?the?entity?is?transient
?????*?<li><tt>Boolean.FALSE</tt>?-?the?entity?is?detached
?????*?<li><tt>null</tt>?-?Hibernate?uses?the?<tt>unsaved-value</tt>?mapping?and?other?heuristics?to?
?????*?determine?if?the?object?is?unsaved
?????*?</ul>
?????*?@param?entity?a?transient?or?detached?entity
?????*?@return?Boolean?or?<tt>null</tt>?to?choose?default?behaviour
?????*/
????public?Boolean?isTransient(Object?entity);
????/**
?????*?Called?from?<tt>flush()</tt>.?The?return?value?determines?whether?the?entity?is?updated
?????*?<ul>
?????*?<li>an?array?of?property?indices?-?the?entity?is?dirty
?????*?<li>an?empty?array?-?the?entity?is?not?dirty
?????*?<li><tt>null</tt>?-?use?Hibernate's?default?dirty-checking?algorithm
?????*?</ul>
?????*?@param?entity?a?persistent?entity
?????*?@return?array?of?dirty?property?indices?or?<tt>null</tt>?to?choose?default?behaviour
?????*/
????public?int[]?findDirty(Object?entity,?Serializable?id,?Object[]?currentState,
???????????? Object[]?previousState, String[]?propertyNames,?Type[]?types);
????/**
?????*?Instantiate?the?entity?class.?Return?<tt>null</tt>?to?indicate?that?Hibernate?should?use
?????*?the?default?constructor?of?the?class.?The?identifier?property?of?the?returned?instance
?????*?should?be?initialized?with?the?given?identifier.
?????*
?????*?@param?entityName?the?name?of?the?entity
?????*?@param?entityMode?The?type?of?entity?instance?to?be?returned.
?????*?@param?id?the?identifier?of?the?new?instance
?????*?@return?an?instance?of?the?class,?or?<tt>null</tt>?to?choose?default?behaviour
?????*/
????public?Object?instantiate(String?entityName,?EntityMode?entityMode,
?????????? Serializable?id)?throws?CallbackException;
????/**
?????*?Get?the?entity?name?for?a?persistent?or?transient?instance
?????*?@param?object?an?entity?instance
?????*?@return?the?name?of?the?entity
?????*/
????public?String?getEntityName(Object?object)?throws?CallbackException;
????/**
?????*?Get?a?fully?loaded?entity?instance?that?is?cached?externally
?????*?@param?entityName?the?name?of?the?entity
?????*?@param?id?the?instance?identifier
?????*?@return?a?fully?initialized?entity
?????*?@throws?CallbackException
?????*/
????public?Object?getEntity(String?entityName,?Serializable?id)?throws?CallbackException;
????
????/**
?????*?Called?when?a?Hibernate?transaction?is?begun?via?the?Hibernate?<tt>Transaction</tt>?
?????*?API.?Will?not?be?called?if?transactions?are?being?controlled?via?some?other?
?????*?mechanism?(CMT,?for?example).
?????*/
????public?void?afterTransactionBegin(Transaction?tx);
????/**
?????*?Called?before?a?transaction?is?committed?(but?not?before?rollback).
?????*/
????public?void?beforeTransactionCompletion(Transaction?tx);
????/**???? *?Called?after?a?transaction?is?committed?or?rolled?back.
?????*/
????public?void?afterTransactionCompletion(Transaction?tx);
????/**
?????*?Called?when?sql?string?is?being?prepared.?
?????*?@param?sql?sql?to?be?prepared
?????*?@return?original?or?modified?sql
?????*/
????public?String?onPrepareStatement(String?sql);
}
posted on 2006-08-16 17:41
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