的中覆盖

开始再看这个crud示例时，居然发现我没有准备数据库信息及数据也可以运行成功，后来看了实现才明白，该示例使用了Map模拟数据库存储操作数据，不过struts2的实现还是又可以观飨的地方，下面就看看它的实现。

首先，定义持久类存储接口Storage：

publicinterfaceStorageextendsSerializable...{

IdEntityget(ClassentityClass,Serializableid);

Serializablecreate(IdEntityobject)throwsCreateException;

IdEntityupdate(IdEntityobject)throwsUpdateException;

Serializablemerge(IdEntityobject)throwsStorageException;

intdelete(ClassentityClass,Serializableid)throwsCreateException;

intdelete(IdEntityobject)throwsCreateException;

CollectionfindAll(ClassentityClass);

}

很明了，定义了操作数据的几种的方法，然后实现了一种使用map存储数据的方式（当然你可以使用自己存储数据的方式实现，比如xml等等）代码如下： publicclassMemoryStorageimplementsStorage...{

privatestaticfinallongserialVersionUID=L;

privateMapmemory=newHashMap();

privateMapgetEntityMap(ClassentityClass)...{

if(entityClass!=null)...{

MaptryMap=(Map)t(entityClass);

if(tryMap==null)...{

synchronized(memory)...{

tryMap=newHashMap();

t(entityClass,tryMap);

}

}

returntryMap;

}else...{

returnnull;

}

}

privateIdEntityintStore(ClassentityClass,IdEntityobject)...{

getEntityMap(entityClass).put(tId(),object);

returnobject;

}

publicIdEntityget(ClassentityClass,Serializableid)...{

四千服以神的姿势降临 if(entityClass!=nullid!=null)...{

return(IdEntity)getEntityMap(entityClass).get(id);

}else...{

returnnull;

}

}

publicSerializablecreate(IdEntityobject)throwsCreateException...{

if(object==null)...{

thrownewCreateException(\"Eithergivenclassorobjectwasnull\");

}

if(tId()==null)...{

thrownewCreateException(\"Cannotstoreobjectwithnullid\");

}

if(get(tClass(),tId())!=null)...{

thrownewDuplicateKeyException(\"Objectwiththisidalreadyexists.\");

}

returnintStore(tClass(),object).getId();

}

publicIdEntityupdate(IdEntityobject)throwsUpdateException...{

if(object==null)...{

thrownewUpdateException(\"Cannotupdatenullobject.\");

}

if(get(tClass(),tId())==null)...{

thrownewUpdateException(\"Objecttoupdatenotfound.\");

}

returnintStore(tClass(),object);

}

publicSerializablemerge(IdEntityobject)throwsStorageException...{

if(object==null)...{

thrownewStorageException(\"Cannotmergenullobject\");

}

if(tId()==null||get(tClass(),tId())==null)...{

returncreate(object);

}else...{

returnupdate(object).getId();

}

}

publicintdelete(ClassentityClass,Serializableid)throwsCreateException...{

try...{

if(get(entityClass,id)!=null)...{

getEntityMap(entityClass).remove(id);

return1;

}else...{

return0;

}

}catch(Exceptione)...{

thrownewCreateException(e);

}

}

publicintdelete(IdEntityobject)throwsCreateException...{

if(object==null)...{

thrownewCreateException(\"Cannotdeletenullobject\");

}

returndelete(tClass(),tId());

}

publicCollectionfindAll(ClassentityClass)...{

if(entityClass!=null)...{

returngetEntityMap(entityClass).values();

}else...{

returnnewArrayList();

}

}

publicvoidreset()...{

mory=newHashMap();

}

}

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