Further development
This is the page describing GSoC 2010 project ended officially in August 2010. The REST API project is continued after official GSoC date. The new address of wiki page is located at https://wiki.duraspace.org/display/DSPACE/REST+API. Please bookmark this page as all further development will be described there. Current GSoC page stays here for historical/documentation purposes.
DSpace REST API - Bojan Suzic
Integration, testing, documentation and further development of DSpace REST services for 1.x and 2.0 versions. - Bojan Suzic
Details
Project Title: |
DSpace REST API |
Student: |
Bojan Suzic, University of Technology Graz |
Mentors: |
Aaron Zeckoski, Mark Diggory |
Contacting author: |
bojan.suzic AT gmail _DOT _com - using subject line DSpace |
SCM Location for Project: |
Project description
The REST approach promotes simplification and decoupling of software architecture, enabling further scalability, portability, granularity and simplified interaction of software systems and components.
The aim of this project is to provide DSpace with REST capable API and underlying component, which will enable developers and end-users to exploit the advantages of such approach.
Some of uses this module is intended to provide could be, for instance:
- interaction between DSpace systems and/or other repositories
- automation of different activities, e.g. submission of packages
- integrating repositories in process workflows of other applications or systems
- interaction with many kinds of systems or web applications, such as CMS, LMS, LCMS, VLS, AMS etc
- providing of other approaches to UI, such as client based/run UI
- crawling of repositories, exposing information in structural way
This project is continuation of last year's activities, supported by Google as part of GSoC 2009. In the first stage the basic support for REST for DSpace is provided, exposing many parts of DSpace functionality to the clients.
In this year's GSoC the following activities should be primarily addressed:
- integration of existing code in the system
- alignment of REST API with currently available DSpace features/functionality, e.g. adding of new features
- extending of existing code, in order to provide better handling of management and injection functions
- providing more detailed documentation and examples for end users
- testing activities, e.g. cooperation/coordination with other GSoC 10 project Unit testing
- promotion of DSpace REST interaction (by taking part in integration with other systems)
Detailed activities
In the following sections main activities are elaborated in detail.
REST API Endpoints
In the following section listed are supported endpoints on the application level. The items marked with dot (in C column) are in phase of implementation, while other items are considered already working.
Please note that additional tests should be made in order to ensure proper stability of the whole application.
The sorting of the fields / output results is currently partially supported. This part of the application is implemented independently of the endpoints and will be worked on after the most of endpoints are completed.
Naming convention for endpoints
DSpace 1.x and 2.x are treating the resources on different way. 2.x is more generalized, suggesting the use of RDF-like interrelation notations.
Repository browsing
Earlier Implementation Description - GSoC09
C |
Verb |
URL |
Description |
Mandatory parameters |
Optional parameters |
Sorting fields |
Response Data |
Formats |
Response codes |
---|---|---|---|---|---|---|---|---|---|
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Returns a list of all communities on the system or return just top level communities. |
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The list of communities containing DSPACE:respective fields . |
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Return detailed information about |
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DSPACE:Fields describing community. |
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Return a particular data field found in the community |
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Respective field info |
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Return a community logo |
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- |
- |
Contains community logo (bitstream) |
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Return a list of all collections in the system. |
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The list of the collections containing DSPACE:respective fields. |
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Return detailed information about |
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DSPACE:Fields of the collection entity. |
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Return a particular data field found in the collection |
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Respective field info |
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Return a list of the items in the system |
- |
- |
- |
The list of the items containing DSPACE:related fields . |
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Return detailed information about an item. |
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- |
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DSPACE:Fields of the item entity. |
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200, 204, 400, 500 |
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Return a particular data field fould in the item |
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- |
- |
Respective field info |
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200, 204, 400, 500 |
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Return bitstream object - usually the library item file. |
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- |
- |
DSPACE:Fields of the bitstream entity. |
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200, 400, 401, 403, 404, 500 |
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Return a particular data field found in bitstream |
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- |
- |
Respective field info |
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200, 400, 401, 403, 404, 500 |
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Return bitstream |
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- |
- |
Return bitstream |
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200, 400, 401, 403, 404, 500 |
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Return a list of the groups in the system |
- |
- |
- |
The list of the groups containing related DSPACE:fields . |
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200, 204, 400, 500 |
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Return a group object |
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- |
- |
DSPACE:Fields of the group entity. |
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200, 204, 400, 500 |
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Return a particular data field found in the group entity |
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- |
- |
Respective field info |
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200, 204, 400, 500 |
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Return a list of the users in the system |
- |
- |
- |
The list of the users containing related DSPACE:fields . |
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200,204,400,500 |
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Return a user info |
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- |
- |
DSPACE:Fields of the user entity. |
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200,204,400,500 |
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Return a particular data field found in the user |
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- |
- |
Respective field info |
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200,204,400,500 |
Note: modifier idOnly
is referred only to first layer of the results. For all other layers (e.g. nested results) only ids are returned in some cases, due to possible loops. Example: for community containing collections, on second level the response contains only ids for some elements where multiple loops may be created (community->has_collection->has_community....). Other data is modified according to idOnly
flag.
Optional parameters
Parameter |
Description |
---|---|
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returns only top level communities |
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if true return only the identifiers for the record |
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return only direct parent community |
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return only collections user has permission to work on |
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return archived items for respective collection |
Sorting fields:
Not completed!
The sorting of the fields / output results is currently partially supported. This part of the application is implemented independently of the endpoints and will be worked on after the most of endpoints are completed.
Parameter |
Description |
Ordering supported |
---|---|---|
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sort results by entity id |
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sort results by entity name |
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sort results by number of items contained |
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sort results by date of last item modification |
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sort results by submitter name |
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sort results by submitter id |
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Controlling results
Parameter |
Description |
Default |
Example |
---|---|---|---|
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position of the first entity to return |
0 (first) |
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page of data to display |
0 (first) |
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number of results to show on each page |
0 (all) |
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maximum number of entities to return |
0 (all) |
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the sort order to return entities in |
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Response codes
Code |
Description |
---|---|
200 |
OK |
201 |
Created |
204 |
No content |
400 |
Bad request |
401 |
Unauthorized |
403 |
Forbidden |
404 |
Not found |
405 |
Method not allowed |
500 |
Internal server error |
503 |
Service unavailable |
Authentication/Authorization
Currently only standard authentication is supported. The authentication data is provided in the request or header body.
Example:
/rest/communities.json?user=user@email.com&pass=userpassword
The same elements user
and pass
are used for header based authentication.
Authorization is done on underlying api level; in the case of error the proper message and error code are returned to the user.
Repository manipulation
C |
Verb |
URL |
Description |
Mandatory parameters |
Optional parameters |
Response Data |
Formats |
Response codes |
---|---|---|---|---|---|---|---|---|
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Action to be done under community |
|
- |
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200, 400, 401, 403, 500 |
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/communities/{id}/{element} |
Update the field |
|
- |
Response code |
|
200, 400, 401, 403, 500 |
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Set the logo for community |
|
- |
Response code |
binary |
200, 400, 401, 403, 500 |
• |
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Delete community from the system |
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- |
Response code |
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200, 400, 401, 403, 500 |
• |
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Remove attribute/value |
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- |
Response code |
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Action to be done under collection |
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- |
Id ow newly created element |
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200, 400, 401, 403, 500 |
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Update field |
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- |
Response code |
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200, 400, 401, 403, 500 |
• |
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Delete collection from the system |
- |
- |
Response code |
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200, 400, 401, 403, 500 |
• |
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Remove attribute/value |
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Response code |
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200,400,401,403,500 |
• |
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Set the logo for collection |
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Response code |
binary |
200,400,401,403,500 |
• |
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Action to be done under item |
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Id of newly created element |
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200,400,401,403,500 |
• |
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Update field |
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- |
Response code |
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200,400,401,403,500 |
• |
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Delete item from the system |
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- |
Response code |
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200,400,401,403,500 |
• |
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Delete element/attribute |
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- |
Response code |
|
200,400,401,403,500 |
Content searching
C |
Verb |
URL |
Description |
Mandatory parameters |
Optional parameters |
Sorting fields |
Response Data |
Formats |
Response codes |
---|---|---|---|---|---|---|---|---|---|
|
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Return a list of all objects found by searching criteria. |
- |
modifiers{{query= |
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Item info with basic metadata for the search results. Additionally return only |
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200, 204, 400, 500 |
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Return a list of all objects that have been created, modified or withdrawn within specified time range. |
- |
|
- |
Contains item info including id, name, handle, metadata, bitstreams according to |
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200, 204, 400, 500 |
Statistical info
C |
Verb |
URL |
Description |
Mandatory parameters |
Optional parameters |
Sorting fields |
Response Data |
Formats |
Response codes |
---|---|---|---|---|---|---|---|---|---|
|
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Return general statistics. |
- |
- |
- |
Cummulative list of statistics data for the system currently available. |
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200, 400, 500 |
Relationships interface
Experimental feature
This is considered as a experimental feature in the phase of being considered for compability with future versions of DSpace. Consider not important section; the status of the feature for upcoming release yet to be determined.
C |
Verb |
URL |
Description |
Mandatory parameters |
Optional parameters |
Sorting fields |
Response Data |
Formats |
Response codes |
---|---|---|---|---|---|---|---|---|---|
• |
GET |
/resource/{handle}/relations |
Return entities according to relation and parameters specified |
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- |
ontains entities selected and sorted in conformance to request parameters. For more details see description of |
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Mandatory parameters
Parameter |
Description |
Values |
Example |
---|---|---|---|
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Return entities satisfying requested property relation |
Structural properties |
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restriction on type - only entity with specifed type(s) would be returned |
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rfield |
restriction on fields - return only selected fields; by default all fields are returned |
id |
rfield=id,name - return only entity id and name in response |
Note: incomplete/orientative properties, for more info check [Vocabularies|http://code.google.com/p/dspace-sandbox/source/browse/#svn/modules/dspace-rdf/tags/dspace-rdf-1.5.1/src/main/java/org/dspace/adapters/rdf/vocabularies].
Visitors' suggestions or wishes
Here the visitors and stakeholders can insert their suggestions or describe the needs for their applications in detail.
Comment: In this case it is not clear how to treat recent
part of endpoint. If we stick to semantic mapping, then it should look like /resource/id/mapping
, but recent
in this case obviously do not represent a mapping, but the property.
Comment #2: Semantic mapping presented in this case should be probably hardcoded for 1.x branch, but on abstraction level which enables easy replacement with some auto-discovery method prepared for 2.x and eventually backported to 1.x. This way we would be able to call something similar to /communities/id
or communities/id/capabilities
in order to get supported mappings (amongst other data).
Suggesting new options:
Instead of changing wiki contents visitors can enter their suggestions as a comments.
1) Kevin S. Clarke and Tim Donhue suggested adding of the new feature related to HTTP Basic Auth. Ok, I will investigate how it could be done and included here. More info comming.
Integration in the system
It is planned to consult two external subjects for cooperation and the assistance during integration process (LMS and national library internal automation process). More information coming soon - awaiting approval of other parties.
Documentation tasks
Although provided software module exposes basic documentation automatically to the end user, in order to make it easier for other developers and users the documentation in the following forms is additionaly to be provided:
- Confluence pages, current location
- integrated documentation in PDF form (manual)
- short slides containing technology overview, advocacy/facts, configuration and usage guideliens and examples
- code will be additionally commented
Example of usage
At the end of the current stage of this project as a bonus task (if time constraints allow) the examples of usage will be provided for several languages, the use-cases will be presented (example of integration in other software, e.g. LMS) and optionally simple client system demonstrating UI customization will be demonstrated (e.g. Flex or JavaFX like).
Information for developers
In this section the main sections of the software will be briefly explained in order to ease update or extension of the components.
The REST API for DSpace uses Aaron Zeckoski's EntityBus and DSpace standard libraries, as dspace-api.
There are two main packages: org.dspace.rest.providers and org.dspace.rest.entities. Providers are responsible for serving content/feeds to the users. They usually prepare entities or particular entity and/or handle update/delete/create functions. The main class there is AbstractBaseProvider, which is extended by other providers.
In the providers, at the constructor level created are mappings between particular endpoints (e.g. /rest/items/1/collections) and related functions in entities (org.dspace.entities.items.getCollections). Thus, for each GET, PUT, POST or DELETE function in the entity provider's constructor defined are such mappings between URL endpoints and functions. After the client makes specific call, the provider prepares answer and in this phase calls mapped function and prepare results for display.
So, if you want to extend currently available endpoints for already present providers and entities, it is necessary to define mapping at provider level and prepare corresponding function at the entity level (based on the template). The system then calls this function and provides necessary arguments for its successfully handling.
If you want to develop a new provider, it is usually necessary to create new provider class in org.dspace.rest.providers and then create related entity in org.dspace.rest.entities. The currently available providers are good example how to do that.