Difference between revisions of "Persistence code samples"
(→Simplified BON diagram) |
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feature -- Basic operations | feature -- Basic operations | ||
+ | |||
+ | serialized_form: SERIALIZED_FORM | ||
+ | |||
+ | set_serialized_form (custom_ser: SERIALIZED_FORM) | ||
+ | -- Set desired custom serialized form. This is what will be serialized. | ||
+ | require | ||
+ | object_exists: custom_ser /= Void | ||
+ | do | ||
+ | serialized_form := custom_ser | ||
+ | ensure | ||
+ | object_set: custom_ser = serialized_form | ||
+ | end | ||
store (object:ANY; medium:PERSISTENCE_MEDIUM) | store (object:ANY; medium:PERSISTENCE_MEDIUM) |
Revision as of 11:54, 23 April 2009
Below are sketches of essential classes of the PERSIST framework.
For an open discussion on the design choices please have a look at the persistence framework design discussion.
You can download the source code here (TODO: provide a link to the sources)
An example of an actually implemented library built according to the PERSIST framework is dadle.
You can also go back to the persistence unified page.
Contents
Simplified BON diagram
PERSISTENCE_MANAGER
class PERSISTENCE_MANAGER feature -- Access medium: PERSISTENCE_MEDIUM -- the chosen medium format: PERSISTENCE_FORMAT -- the chosen format feature -- Basic operations store (an_object:ANY) -- persists an_object using the format and medium stored by current object require an_object_exists:an_object /= Void medium_exists: medium /= Void do format.store(an_object,medium) end retrieve: ANY -- retrieves an_object using the medium and format stored by current object require medium_exists: medium /= Void do Result:=format.retrieve(medium) end end
BINARY_SERIALIZATION_MANAGER
class BINARY_SERIALIZATION_MANAGER inherit PERSISTENCE_MANAGER create make feature -- Initialization make (file_name: STRING) -- Initialization procedure require file_name_exists: file_name /= Void do create {FILE_MEDIUM} medium.make (file_name) create {INDEPENDENT_BINARY_FORMAT} format ensure medium_exists: medium /= Void format_exists: format /= Void end end
PERSISTENCE_FORMAT
deferred class PERSISTENCE_FORMAT feature -- Basic operations serialized_form: SERIALIZED_FORM set_serialized_form (custom_ser: SERIALIZED_FORM) -- Set desired custom serialized form. This is what will be serialized. require object_exists: custom_ser /= Void do serialized_form := custom_ser ensure object_set: custom_ser = serialized_form end store (object:ANY; medium:PERSISTENCE_MEDIUM) -- stores object using medium require object_exists: object /= Void medium_exists: medium /= Void deferred end retrieve (medium: PERSISTENCE_MEDIUM):ANY require medium_exists: medium /= Void deferred end end
BINARY_FORMAT
deferred class BINARY_FORMAT inherit PERSISTENCE_FORMAT redefine store, retrieve end feature -- Access store_handler:SED_STORABLE_FACILITIES serializer:SED_MEDIUM_READER_WRITER feature -- Basic operations store (object:ANY; data_file:FILE_MEDIUM) -- stores object using a FILE_MEDIUM do create store_handler create serializer.make (data_file.raw_file) if data_file.exists then data_file.reopen_write (data_file.file_name) else data_file.open_write end serializer.set_for_writing store_now (object) end store_now (object_to_store:ANY) --proper store operation depends on specific descendant require object_to_store_exists:object_to_store/=Void deferred end retrieve (data_file:FILE_MEDIUM):ANY -- retrieves object using a FILE_MEDIUM do create store_handler create serializer.make (data_file.raw_file) if data_file.exists then data_file.open_read serializer.set_for_reading Result:= store_handler.retrieved (serializer,true) else print ("%NData file does not exist! ") end end end
INDEPENDENT_BINARY_FORMAT
class INDEPENDENT_BINARY_FORMAT inherit BINARY_FORMAT feature -- Access optimized_for_retrieval: BOOLEAN feature -- Status setting set_optimized_for_retrieval (is_optimized_for_retrieval:BOOLEAN) do optimized_for_retrieval:= is_optimized_for_retrieval ensure optimized_for_retrieval_set:optimized_for_retrieval = is_optimized_for_retrieval end feature -- Basic operations store_now (object_to_store:ANY) do store_handler.independent_store(object_to_store,serializer,optimized_for_retrieval) end end
FILE_MEDIUM
class FILE_MEDIUM inherit PERSISTENCE_MEDIUM create make feature -- Initialization make (a_file_name:STRING) require a_file_name_exists:a_file_name /= Void do create raw_file.make (a_file_name) file_name:=a_file_name ensure raw_file_exists: raw_file /=Void file_name_set: file_name = a_file_name end feature -- Access raw_file: RAW_FILE file_name: STRING feature -- Status report exists: BOOLEAN do Result:= raw_file.exists end feature -- Basic operations reopen_write (a_file_name:STRING) -- reopens the file named 'a_file_name' for writing require a_file_name_exists:a_file_name /= Void do raw_file.reopen_write (a_file_name) end open_write -- opens the current file for writing require a_file_to_open_exists:raw_file /= Void do raw_file.open_write end open_read -- opens the current file for reading do raw_file.open_read end end