Spring和Hibernate动态建表及动态加载映射文件（无需Session factory Rebuild)

Spring与Hibernate动态建表及动态加载映射文件(无需SessionFactory Rebuild)



J.Office2有一功能是工作流支持动态表单设计，设计后可以动态生成数据库表，并且支持实时查询（单表及多表均可）。



由于J.Office2版本中采用了Hibernate作为底层的ORM框架，结合Spring框架，Spring容器启动后，SessionFactory就会被注入到各个业务的Dao层中去。



动态建表功能比较容易实现，我们可以new一个SessionFactory,然后把它的配置属性hibernate.hbm2ddl.auto改为update或create，就可以达到动态修改表结构的效果。



但若要加入新的hbm或class，需要重新调用SessionFactoryBean来获取一个全新的SessionFactory，这种方案试过了，效果并不理想。重新加载，会导致大量的hbm或class文件重新加载，实在有点慢。并且严重影响现在注入SessionFactory的Dao。若Dao采用动态构建SessionFactory，性能又是一问题。而Hibernate没有提供SessionFactory动态加入hbm或Class文件。所以实在无计可施。



所以最终还是回到如何扩展Hibernate的SessionFactory类中去了，这想法已经有不少开发人员尝试过，JE也有一帖子专门讨论这个。不过仅是一Demo，不完善。我们提供了两个扩展的类（修改Hibernate中的两类，使其支持动态加入配置文件，并且能实时查询。



我们仅需要修改两个类，一个是Configuration,在其里面加一方法，如下：

public void doComplie(){
secondPassCompile();
}



修改



在SessonFactoryImpl类中加入以下方法，（有一些变量值不能修改的，请改为可修改）


Java代码 收藏代码

Java代码 收藏代码

//add by csx
public void addNewConfig(Configuration cfg){
log.info("add NewConfig.....");

Mapping mapping=this.configuration.getMapping();
this.filters.putAll( cfg.getFilterDefinitions() );
//Generators:
Iterator classes = cfg.getClassMappings();
while ( classes.hasNext() ) {
PersistentClass model = (PersistentClass) classes.next();

if ( !model.isInherited() ) {
IdentifierGenerator generator = model.getIdentifier().createIdentifierGenerator(
settings.getDialect(),
settings.getDefaultCatalogName(),
settings.getDefaultSchemaName(),
(RootClass) model
);
identifierGenerators.put( model.getEntityName(), generator );
}
}

///////////////////////////////////////////////////////////////////////
// Prepare persisters and link them up with their cache
// region/access-strategy

String cacheRegionPrefix = settings.getCacheRegionPrefix() == null ? "" : settings.getCacheRegionPrefix() + ".";

Map entityAccessStrategies = new HashMap();
Map tmpEntityPersisters=new HashMap();
Map tmpClassMetadata=new HashMap();


this.configuration.getClassMap().putAll(cfg.getClassMap());
classes = cfg.getClassMappings();

while ( classes.hasNext() ) {

PersistentClass model = (PersistentClass) classes.next();

model.prepareTemporaryTables( mapping, settings.getDialect() );
String cacheRegionName = cacheRegionPrefix + model.getRootClass().getCacheRegionName();

// cache region is defined by the root-class in the hierarchy...
EntityRegionAccessStrategy accessStrategy = ( EntityRegionAccessStrategy ) entityAccessStrategies.get( cacheRegionName );
if ( accessStrategy == null && settings.isSecondLevelCacheEnabled() ) {
AccessType accessType = AccessType.parse( model.getCacheConcurrencyStrategy() );
if ( accessType != null ) {

log.trace( "Building cache for entity data [" + model.getEntityName() + "]" );
EntityRegion entityRegion = settings.getRegionFactory().buildEntityRegion( cacheRegionName, properties, CacheDataDescriptionImpl.decode( model ) );
accessStrategy = entityRegion.buildAccessStrategy( accessType );
entityAccessStrategies.put( cacheRegionName, accessStrategy );
allCacheRegions.put( cacheRegionName, entityRegion );
}
}
EntityPersister cp = PersisterFactory.createClassPersister( model, accessStrategy, this, cfg.getMapping() );
tmpEntityPersisters.put( model.getEntityName(), cp );
tmpClassMetadata.put( model.getEntityName(), cp.getClassMetadata() );

}

//Named Queries:
namedQueries.putAll(cfg.getNamedQueries());
namedSqlQueries.putAll( cfg.getNamedSQLQueries() );
sqlResultSetMappings.putAll(cfg.getSqlResultSetMappings());
imports.putAll(cfg.getImports());

entityPersisters.putAll(tmpEntityPersisters);

classMetadata.putAll(tmpClassMetadata);

Map tmpEntityToCollectionRoleMap = new HashMap();
Map tempCollectionPersisters=new HashMap();

this.configuration.getCollectionMap().putAll(cfg.getCollectionMap());
Iterator collections = cfg.getCollectionMappings();

while ( collections.hasNext() ) {
Collection model = (Collection) collections.next();
final String cacheRegionName = cacheRegionPrefix + model.getCacheRegionName();
final AccessType accessType = AccessType.parse( model.getCacheConcurrencyStrategy() );
CollectionRegionAccessStrategy accessStrategy = null;
if ( accessType != null && settings.isSecondLevelCacheEnabled() ) {
log.trace( "Building cache for collection data [" + model.getRole() + "]" );
CollectionRegion collectionRegion = settings.getRegionFactory().buildCollectionRegion( cacheRegionName, properties, CacheDataDescriptionImpl.decode( model ) );
accessStrategy = collectionRegion.buildAccessStrategy( accessType );
entityAccessStrategies.put( cacheRegionName, accessStrategy );
allCacheRegions.put( cacheRegionName, collectionRegion );
}
CollectionPersister persister = PersisterFactory.createCollectionPersister(this.getConfiguration(), model, accessStrategy, this) ;
tempCollectionPersisters.put( model.getRole(), persister.getCollectionMetadata() );
Type indexType = persister.getIndexType();
if ( indexType != null && indexType.isAssociationType() && !indexType.isAnyType() ) {
String entityName = ( ( AssociationType ) indexType ).getAssociatedEntityName( this );
Set roles = ( Set ) tmpEntityToCollectionRoleMap.get( entityName );
if ( roles == null ) {
roles = new HashSet();
tmpEntityToCollectionRoleMap.put( entityName, roles );
}
roles.add( persister.getRole() );
}
Type elementType = persister.getElementType();
if ( elementType.isAssociationType() && !elementType.isAnyType() ) {
String entityName = ( ( AssociationType ) elementType ).getAssociatedEntityName( this );
Set roles = ( Set ) tmpEntityToCollectionRoleMap.get( entityName );
if ( roles == null ) {
roles = new HashSet();
tmpEntityToCollectionRoleMap.put( entityName, roles );
}
roles.add( persister.getRole() );
}

}
//加入新的
collectionPersisters.putAll(tempCollectionPersisters);

Iterator itr = tmpEntityToCollectionRoleMap.entrySet().iterator();
while ( itr.hasNext() ) {
final Map.Entry entry = ( Map.Entry ) itr.next();
entry.setValue( Collections.unmodifiableSet( ( Set ) entry.getValue() ) );
}

collectionRolesByEntityParticipant.putAll( tmpEntityToCollectionRoleMap);

// after *all* persisters and named queries are registered
Iterator iter = tmpEntityPersisters.values().iterator();
while ( iter.hasNext() ) {
( (EntityPersister) iter.next() ).postInstantiate();
}
iter = tempCollectionPersisters.values().iterator();
while ( iter.hasNext() ) {
( (CollectionPersister) iter.next() ).postInstantiate();
}

queryPlanCache=new QueryPlanCache(this);


}



我们动态加入实体，动态可进行查询，Hibernate提供几种实体的查询策略，其中一个是我们常用的pojo，若采用该方法，我们得加上hbm与 class类或仅是含注解的class至hibernate的SessionFactory,这种方案并且没有问题，但会遇到当我们修改表单字段，重新生 成对应的实体时，我们就会遇到原有的实体class不能在ClassLoader里卸载。使用的还是旧的Class,达不到动态查询的效果。若使用动态的 ClassLoader，代码将变得很复杂。（尝试过，代码相对比较繁杂）



还好Hibernate提供了另一种实体查询策略，基于Map的动态实体。基于这种方式，我们配置一个一对多的表，其示例代码如下：



MainEntity.hbm.xml
Java代码 收藏代码

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class table="main_entity" entity-name="MainEntity">
<id name="mainId" column="mainId" type="java.lang.Long">
<generator class="native"/>
</id>
<property name="itemSubject" type="java.lang.String" length="128"/>
<property name="itemDescp" type="java.lang.String" />
<property name="createtime" type="java.util.Date" />
<bag name="subEntitys"
table="sub_entity"
lazy="false"
inverse="true"
cascade="save-update,delete-orphan"
>
<key>
<column name="mainId"/>
</key>
<one-to-many entity-name="SubEntity"/>
</bag>
</class>
</hibernate-mapping>

SubEntity.hbm.xml




Java代码 收藏代码

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class table="sub_entity" entity-name="SubEntity">
<id name="subId" column="subId" type="java.lang.Long">
<generator class="native"/>
</id>
<property name="subject" type="java.lang.String" length="128"/>
<property name="createtime" type="java.util.Date"/>
<many-to-one name="mainEntity" entity-name="MainEntity" not-null="false" fetch="select">
<column name="mainId"></column>
</many-to-one>
</class>
</hibernate-mapping>



为两实体插入数据后，可动态测试如下：




Java代码 收藏代码

public static void main(String[]args){
ClassPathXmlApplicationContext ctx=new ClassPathXmlApplicationContext("classpath:app-context.xml");

MyAnnotationSessionFactoryBean sessionFactoryBean=(MyAnnotationSessionFactoryBean)ctx.getBean("&sessionFactory");

SessionFactoryImpl sessionFactoryImpl=(SessionFactoryImpl)sessionFactoryBean.getObject();

Configuration cfg=new Configuration();
//cfg.configure();

cfg.addFile("D:/download/eclipse/workspace2/SpringHibernate/src/com/hotent/entity/MainEntity.hbm.xml");
cfg.addFile("D:/download/eclipse/workspace2/SpringHibernate/src/com/hotent/entity/SubEntity.hbm.xml");
cfg.doComplie();

sessionFactoryImpl.addNewConfig(cfg);

MainEntityDao dao=(MainEntityDao)ctx.getBean("mainEntityDao");

List list=dao.query();

for(int i=0;i<list.size();i++){
Map map=(Map)list.get(i);
Iterator it=map.keySet().iterator();
while(it.hasNext()){
//String key=(String)it.next();
Object key=it.next();
Object val=map.get(key);
System.out.println("--------------->key:"+key );
}
}

Configuration cfg2=new Configuration();
cfg2.addFile("D:/dev/product/SpringHibernate/src/com/hotent/entity/MainEntity2.hbm.xml");
cfg2.addFile("D:/dev/product/SpringHibernate/src/com/hotent/entity/SubEntity2.hbm.xml");
cfg2.doComplie();
sessionFactoryImpl.addNewConfig(cfg2);

List list2=dao.query();

for(int i=0;i<list2.size();i++){
Map map=(Map)list2.get(i);
Iterator it=map.keySet().iterator();
while(it.hasNext()){
//String key=(String)it.next();
Object key=it.next();
Object val=map.get(key);
System.out.println("key:"+key );
}
}

}


Java代码 收藏代码

MainEntity2.hbm.xml与SubEntity2.hbm.xml文件相对原来的文件增加了一些列或删除了一些列



执行后，可以实时看到不同的结果，并且不会影响现有的dao。