struts2的demo中showcase的crud示例

文章作者 100test 发表时间 2007:05:12 13:48:24
来源 100Test.Com百考试题网

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：

public interface Storage extends Serializable ...{

IdEntity get( Class entityClass, Serializable id ).

Serializable create ( IdEntity object ) throws CreateException.

IdEntity 0update ( IdEntity object ) throws UpdateException.

Serializable merge ( IdEntity object ) throws StorageException.

int 0delete( Class entityClass, Serializable id ) throws CreateException.

int 0delete( IdEntity object ) throws CreateException.

Collection findAll( Class entityClass ).
}

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：

public class MemoryStorage implements Storage ...{

private static final long serialVersionUID = 8611213748834904125L.


private Map memory = new HashMap().

private Map getEntityMap ( Class entityClass ) ...{
if (entityClass != null) ...{
Map tryMap = (Map) memory.get(entityClass).
if (tryMap == null) ...{
synchronized(memory) ...{
tryMap = new HashMap().
memory.put(entityClass, tryMap).
}
}
return tryMap.
} else ...{
return null.
}
}

private IdEntity intStore( Class entityClass, IdEntity object ) ...{
getEntityMap(entityClass).put(object.getId(), object).
return object.
}

public IdEntity get( Class entityClass, Serializable id ) ...{
if (entityClass != null &.&. id != null) ...{
return (IdEntity) getEntityMap(entityClass).get(id).
} else ...{
return null.
}
}

public Serializable create ( IdEntity object ) throws CreateException ...{
if (object == null) ...{
throw new CreateException("Either given class or object was null").
}
if (object.getId() == null) ...{
throw new CreateException("Cannot store object with null id").
}
if (get(object.getClass(), object.getId()) != null) ...{
throw new DuplicateKeyException("Object with this id already exists.").
}
return intStore(object.getClass(), object).getId().
}

public IdEntity 0update ( IdEntity object ) throws UpdateException ...{
if (object == null) ...{
throw new UpdateException("Cannot 0update null object.").
}
if ( get(object.getClass(), object.getId())==null ) ...{
throw new UpdateException("Object to 0update not found.").
}
return intStore(object.getClass(), object).
}

public Serializable merge ( IdEntity object ) throws StorageException ...{
if (object == null) ...{
throw new StorageException("Cannot merge null object").
}
if (object.getId() == null || get(object.getClass(), object.getId())==null) ...{
return create(object).
} else ...{
return 0update(object).getId().
}
}

public int 0delete( Class entityClass, Serializable id ) throws CreateException ...{
try ...{
if (get(entityClass, id) != null) ...{
getEntityMap(entityClass).remove(id).
return 1.
} else ...{
return 0.
}
} catch (Exception e) ...{
throw new CreateException(e).
}
}

public int 0delete( IdEntity object ) throws CreateException ...{
if (object == null) ...{
throw new CreateException("Cannot 0delete null object").
}
return 0delete(object.getClass(), object.getId()).
}

public Collection findAll( Class entityClass ) ...{
if (entityClass != null) ...{
return getEntityMap(entityClass).values().
} else ...{
return new ArrayList().
}
}

public void reset() ...{
this.memory = new HashMap().
}

}