DSpace 7 REST: Coding DSpace Objects

Code Branch

The code of the DSapce 7 REST API have been merged in the master branch: https://github.com/DSpace/DSpace/tree/master/dspace-spring-rest

Code Representation of a DSpace Object

DSpace API Object (hibernate): org.dspace.content.DSpaceObject

This is the representation of an object from the DSpace database. Since DSpace 6, this object is populated with hibernate.

Rest Object: org.dspace.app.rest.model.DSpaceObject

This is a plain old java object (pojo) representation of a DSpace object.

Coding the REST object

• Add private properties
  • Add a property to the class DSpaceObjectRest
• Add a get/set method
  
  • Add get and set to the class DSpaceObjectRest
• To exclude a property from JSON representation, add @JsonIgnore to the get method or to the property
  • Example of exclusion in the class DSpaceObjectRest
  • Another example of exclusion in the class DSpaceObjectRest

Hateoas Object:  org.dspace.app.rest.model.hateoas.DSpaceResource

This representation of an object allows for 

1. the embedding of other DSpace objects within the object.  Embedded objects are always linked.
   1. property returns a RestModel object
2. linking to other external DSpace objects
   1. property returns a RestModel.  Property is marked with @JsonIgnore annotation.

The base class in this package uses reflection to identify attributes that are actual links to other REST resources.

• DSpaceResource

If an attribute is of type RestModel, then the code will

1. wrap the linked REST resource inside a DSpaceResource (so to have the identifier, self link, and links to other resources). The wrapper is actually created by the Repository responsible of the specific resource (ItemRepository, BitstreamRepository, etc.) 
   1. https://github.com/DSpace/DSpace/blob/rest7/dspace-spring-rest/src/main/java/org/dspace/app/rest/model/hateoas/DSpaceResource.java#L58
      This give a chance to add custom logic for extra links in specific resource
2. put the wrapper in the embedded section 
3. clean the attribute (not sure if useful/required/right): 
   1.  https://github.com/DSpace/DSpace/blob/rest7/dspace-spring-rest/src/main/java/org/dspace/app/rest/model/hateoas/DSpaceResource.java#L64

Converter Object: org.dspace.app.rest.converter.DSpaceObjectConverter

Convert between the REST representation of an object and the hibernate representation of an object

Coding a converter object

• In the fromModel() function, map all object attributes from the persistence/hibernate model to the rest model
  • https://github.com/DSpace/DSpace/blob/rest7/dspace-spring-rest/src/main/java/org/dspace/app/rest/converter/DSpaceObjectConverter.java#L33-L50

Repository Object: org.dspace.app.rest.repository.DSpaceRestRepository

Provide repository interface functions that return REST representations of DSpace objects.

Managing Object Initialization (TODO)

• When referencing a linked object, how do we control the initialization/load of reference object?