Spring和Hibernate動態建表及動態加載映射文件（無需Session factory...

時間 2019-11-08

標籤 spring hibernate 動態加載映射文件無需 session factory 欄目 Spring 简体版

原文原文鏈接

J.Office2有一功能是工做流支持動態表單設計，設計後能夠動態生成數據庫表，而且支持實時查詢（單表及多表都可）。java

因爲J.Office2版本中採用了Hibernate做爲底層的ORM框架，結合Spring框架，Spring容器啓動後，SessionFactory就會被注入到各個業務的Dao層中去。sql

動態建表功能比較容易實現，咱們能夠new一個SessionFactory,而後把它的配置屬性hibernate.hbm2ddl.auto改成update或create，就能夠達到動態修改表結構的效果。數據庫

但若要加入新的hbm或class，須要從新調用SessionFactoryBean來獲取一個全新的SessionFactory，這種方案試過了，效果並不理想。從新加載，會致使大量的hbm或class文件從新加載，實在有點慢。而且嚴重影響如今注入SessionFactory的Dao。若 Dao採用動態構建SessionFactory，性能又是一問題。而Hibernate沒有提供SessionFactory動態加入hbm或 Class文件。因此實在機關用盡。session

因此最終仍是回到如何擴展Hibernate的SessionFactory類中去了，這想法已經有很多開發人員嘗試過，JE也有一帖子專門討論這個。不過僅是一Demo，不完善。咱們提供了兩個擴展的類（修改Hibernate中的兩類，使其支持動態加入配置文件，而且能實時查詢。app

咱們僅須要修改兩個類，一個是Configuration,在其裏面加一方法，以下：框架

     public void doComplie(){
        secondPassCompile();
    }eclipse

修改ide

在SessonFactoryImpl類中加入如下方法，（有一些變量值不能修改的，請改成可修改）post

Java代碼

//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);
}

咱們動態加入實體，動態可進行查詢，Hibernate提供幾種實體的查詢策略，其中一個是咱們經常使用的pojo，若採用該方法，咱們得加上hbm與 class類或僅是含註解的class至hibernate的SessionFactory,這種方案而且沒有問題，但會遇到當咱們修改表單字段，從新生成對應的實體時，咱們就會遇到原有的實體class不能在ClassLoader裏卸載。使用的仍是舊的Class,達不到動態查詢的效果。若使用動態的 ClassLoader，代碼將變得很複雜。（嘗試過，代碼相對比較繁雜）性能

還好Hibernate提供了另外一種實體查詢策略，基於Map的動態實體。基於這種方式，咱們配置一個一對多的表，其示例代碼以下：

MainEntity.hbm.xml

Java代碼

<?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代碼

<?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>

爲兩實體插入數據後，可動態測試以下：

Java代碼

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 );
}
}
}