====== Custom object persistence ======

GroIMP require Nodes, Node's attributes, and SCOs to be manageable by the persistence manager, to process the save/ load/ query operations.

GroIMP define its own [[:groimp-platform:persistence|persistence management]]. To be managed by the GroIMP persistence management, an object need to implements either [[https://javadoc.grogra.de/graph/de/grogra/persistence/PersistenceCapable.html|PersistenceCapable]] (GroIMP interface), or [[https://docs.oracle.com/javase/8/docs/api/java/io/Serializable.html|Serializable]] (java interface).
 
Usually the persistence is handled in memory (except when the project is saved), but GroIMP provides a way to integrate it with file persistence (the object is written/loaded from the file). This rely on EmbeddedSharedObject and EmbeddedFileObject.

===== Embedded objects ===== 

In GroIMP embedded objects are objects whose persistence is pushed in a file. 

EmbeddedSharedObject (ESO) is a class, thus the object needs to extends it. 
The ESO create on the fly and manage an EmbeddedFileObject (EFO). 

The object that extends ESO need to implements the following methods:
  * ''public MimeType getMimeType()'': to provide the mimetype to use when writing and loading the object (see GroIMP [[:groimp-platform:input-and-output-in-groimp:mimetype|mimetype]]).
  * ''public String getExtension()'': to provide the file extension (can be an empty string. File extensions are used to make it easier read files but are usually not required).
  * ''public String getResourceDirectoryName()'': Name of the directory in which the file will be stored when the project is saved.
  * ''public String getObjectType()'': java name of the object type (e.g. MyObject.class.getName()).
  * ''public boolean hasContent()'': custom way to check if the object actually needs to be disposed. Can be set to true if it is always the case.


Check [[:tutorials:create-parameternode-eso|this tutorial]] for an example.