spring + hibernate 设置更新指定字段

spring + hibernate 设置更新指定字段
hibernate的update方式默认的是更新所有字段的，这导致一个很大的问题，当想更新部分字段时必须要把整个entity先load一遍，然后set相应的更新字段再保存
这一步load数据势必将数据库的操作增加一倍，而且基本上是多余的，最近看了下hibernate源码，发现hibernate有设置指定更新的方式，具体方式如下

org.hibernate.persister.entity.AbstractEntityPersister中定义了基类的更新方法
public void update(
			final Serializable id,
	        final Object[] fields,
	        final int[] dirtyFields,
	        final boolean hasDirtyCollection,
	        final Object[] oldFields,
	        final Object oldVersion,
	        final Object object,
	        final Object rowId,
	        final SessionImplementor session) throws HibernateException {

其中的一段代码：

if ( ( entityMetamodel.isDynamicUpdate() && dirtyFields != null ) ) {
			// We need to generate the UPDATE SQL when dynamic-update="true"
			propsToUpdate = getPropertiesToUpdate( dirtyFields, hasDirtyCollection );
			// don't need to check laziness (dirty checking algorithm handles that)
			updateStrings = new String[span];
			for ( int j = 0; j < span; j++ ) {
				updateStrings[j] = tableUpdateNeeded[j] ?
						generateUpdateString( propsToUpdate, j, oldFields, j == 0 && rowId != null ) :
						null;
			}
		}
		else if ( ! isModifiableEntity( entry ) ) {
			// We need to generate UPDATE SQL when a non-modifiable entity (e.g., read-only or immutable)
			// needs:
			// - to have references to transient entities set to null before being deleted
			// - to have version incremented do to a "dirty" association
			// If dirtyFields == null, then that means that there are no dirty properties to
			// to be updated; an empty array for the dirty fields needs to be passed to
			// getPropertiesToUpdate() instead of null.
			propsToUpdate = getPropertiesToUpdate(
					( dirtyFields == null ? ArrayHelper.EMPTY_INT_ARRAY : dirtyFields ),
					hasDirtyCollection
			);
			// don't need to check laziness (dirty checking algorithm handles that)
			updateStrings = new String[span];
			for ( int j = 0; j < span; j++ ) {
				updateStrings[j] = tableUpdateNeeded[j] ?
						generateUpdateString( propsToUpdate, j, oldFields, j == 0 && rowId != null ) :
						null;
			}
		}
		else {
			// For the case of dynamic-update="false", or no snapshot, we use the static SQL
			updateStrings = getUpdateStrings(
					rowId != null,
					hasUninitializedLazyProperties( object )
			);
			propsToUpdate = getPropertyUpdateability( object );
		}

可以看到hibernate提供了3种的获得更新字段方式，默认情况下会进入最后的else中获得所有的字段，中间else if 的方式可以看到注解里的说明，应该是为read-only的对象准备，此处没有详细深入，而我们需要的是第一种方式
当对象的mapping文件配置了dynamic-update="true" 且dirtyFields存在时hibernate便会根据dirtyFields获得需要更新的字段
propsToUpdate = getPropertiesToUpdate( dirtyFields, hasDirtyCollection );
这里的dirtyFields便是entity对应的字段下标
一直向前追溯dirtyFields的来源可以在org.hibernate.event.internal.DefaultFlushEntityEventListener中找到protected void dirtyCheck(final FlushEntityEvent event) throws HibernateException函数
关键代码：

int[] dirtyProperties = session.getInterceptor().findDirty(
				entity,
				id,
				values,
				loadedState,
				persister.getPropertyNames(),
				persister.getPropertyTypes()
		);

hibernate在session中做了一个拦截器，可以在操作前做一些处理。
session由sessionFactory创建，而interceptor则由从Configuration注入
这样就很清楚了，我们要做的操作只要在Configuration中注入我们自定义的interceptor就行了

先写一个interceptor继承与emtpyInterceptor

package net.esj.basic.dao.hibernate.sessioninterceptor;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

import net.esj.basic.pojo.AbstractPojo;
import net.esj.basic.pojo.UpdateType;
import net.esj.basic.pojo.Updater;
import net.esj.basic.utils.JavaProtoTypeHelper;

import org.hibernate.EmptyInterceptor;
import org.hibernate.type.Type;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Component;

@Component("dirtyFindInterceptor")
@Scope("prototype")
public class DirtyFindInterceptor extends EmptyInterceptor {

	@Override
	public int[] findDirty(Object entity, Serializable id,
			Object[] currentState, Object[] previousState,
			String[] propertyNames, Type[] types) {
		if(entity instanceof AbstractPojo){
			Updater updater = ((AbstractPojo)entity).getUpdater();
			UpdateType type =((AbstractPojo)entity).getUpdateType();
			if(type==UpdateType.AUTO){
				type = checkUpdateType(entity, id, currentState, previousState, propertyNames, types);
			}
			switch(type){
			case BY_DIFF:
				return findDirtyByDiff(entity, id, currentState, previousState, propertyNames, types);
			case BY_UPDATER:
				return findDirtyByUpdater(entity, id, currentState, previousState, propertyNames, types, ((AbstractPojo)entity));
			case NONE:
				return super.findDirty(entity, id, currentState, previousState, propertyNames,
						types);
			}
		}
		return super.findDirty(entity, id, currentState, previousState, propertyNames,
				types);
		
	}
	
	protected UpdateType checkUpdateType(Object entity, Serializable id,
			Object[] currentState, Object[] previousState,
			String[] propertyNames, Type[] types){
		if(! (entity instanceof AbstractPojo)){
			return UpdateType.NONE;
		}
		Updater updater = ((AbstractPojo)entity).getUpdater();
		if(updater.hasProperty()){
			return UpdateType.BY_UPDATER;
		}
		return UpdateType.NONE;
	}
 
	private int[] findDirtyByUpdater(Object entity, Serializable id,
			Object[] currentState, Object[] previousState,
			String[] propertyNames, Type[] types,AbstractPojo pojo){
		Updater updater = pojo.getUpdater();
		Set<Integer> tmp = new HashSet<Integer>(); 
		//int[] reval = new int[propertyNames.length];
		for(int i=0;i<propertyNames.length;i++){
			String propertyName = propertyNames[i];
			if(updater.getProperties().contains(propertyName)){
				tmp.add(i);
			}
		}
		int[] reval = new int[tmp.size()];
		int i=0;
		for(Integer t:tmp){
			reval[i] = t;
			i++;
		}
		return reval;
	}
	
	private int[] findDirtyByDiff(Object entity, Serializable id,
			Object[] currentState, Object[] previousState,
			String[] propertyNames, Type[] types){
		if(currentState==null
				|| previousState ==null){
			return null;
		}
		
		Set<Integer> tmp = new HashSet<Integer>(); 
		for(int i=0;i<currentState.length;i++){
			Object cur = currentState[i];
			Object pre = previousState[i];
			if(!JavaProtoTypeHelper.equal(cur, pre)){
				tmp.add(i);
			}
		}
		int[] reval = new int[tmp.size()];
		int i=0;
		for(Integer t:tmp){
			reval[i] = t;
			i++;
		}
		return reval;
	}
	
}

这里我做了3种更新方式，一种为基本的全字段更新，一种为根据程序员自定义的字段更新，一种为核查原始数据和新数据是否相等，更新不相等的字段。


基于spring的配置，我们的hibernate的Configuration是由LocalSessionFactoryBean创建的。
具体配置为：

<bean id="sessionFactory"
		class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
		<property name="dataSource">
			<ref bean="dataSource" />
		</property>
		<property name="mappingDirectoryLocations">
			<list>
				<value>classpath*:/net/esj/test/pojo/</value>
			</list>
		</property>
		<property name="hibernateProperties">
			<props>
				<prop key="hibernate.connection.release_mode">after_transaction</prop>
				<prop key="hibernate.dialect">${hibernate.dialect}</prop>
                <prop key="hibernate.show_sql">${hibernate.show_sql}</prop>
                <prop key="hibernate.format_sql">${hibernate.format_sql}</prop>
			</props>
		</property>
		<property name="entityInterceptor" ref="dirtyFindInterceptor" />
</bean>

具体的过程可以在spring的源码中找到，此处我们注入上面的dirtyFindInterceptor类。


测试：

<hibernate-mapping package="net.esj.test.pojo">
	<class
		name="Foo"
		table="test_foo" dynamic-update="true"  //dynamic-update="true"此须增加
	>
		<meta attribute="sync-DAO">true</meta>
		<id
			name="id"
			type="string"
			column="id"
		>
			<generator class="uuid"/>
		</id>

		<property
			name="name"
			column="name"
			type="string"
			not-null="false"
		/>
		<property
			name="code"
			column="code"
			type="integer"
			not-null="false"
		/>



	</class>	
</hibernate-mapping>

public void testUpdate(){
		Foo foo = new Foo();
		foo.setId("402881973aa11bb7013aa11bb8340000");
		foo.setName("asdas");
		foo.notifyUpdater("name");//只更新name字段
		baseDao.update(foo);
	}

hibernate打印的sql：
Hibernate: update test_foo set name=? where id=?
可以看到现在只更新了name字段