XOAI

What is XOAI?

XOAI is the most powerful and flexible OAI-PMH Java Toolkit (initially developed by Lyncode, updated by DSpace). XOAI contains common Java classes allowing to easily implement OAI-PMH data and service providers.

Compliance with the OAI-PMH standard is checked using an included Technology Compatibility Kit, relying on https://github.com/zimeon/oaipmh-validator. Compliance checks are operated on every pull request and push to main branch.

Usage

Moving (again): as XOAI is no longer actively maintained by DSpace since 2019, this fork by the Global Dataverse Community Consortium provides an updated version for the needs of and usage with the open source repository Dataverse Software.

This library is available from Maven Central, simply rely on them in your builds:

When building a data provider, you'll add xoai-data-provider:

<dependency>
	<groupId>io.gdcc</groupId>
	<artifactId>xoai-data-provider</artifactId>
	<version>${xoai.version}</version>
</dependency>

When building a service provider, you'll add xoai-service-provider:

<dependency>
	<groupId>io.gdcc</groupId>
	<artifactId>xoai-service-provider</artifactId>
	<version>${xoai.version}</version>
</dependency>

Some minimal usage documentation has been scraped from the DSpace Wiki, mostly explaining the concepts of this library, and put into docs/README.md. It also contains some minimal explanation of this forks special changes. Feel free to extend the documentation, pull requests welcome.

Development

This project uses Spotless Maven Plugin, google-format-java and pre-commit to ensure a standardized and well-formatted codebase.

After cloning the repo, please make sure to install pre-commit, which will take care of everything for you:

pip install pre-commit
pre-commit install

If you want to run spotless directly, use Maven:

mvn spotless:apply
# - or to just check for consistency use -
mvn spotless:check

Release notes

v5.1.0

🌟 FEATURES

• Switching to Java 17 for compilation and testing, but keeping compatibility with Java 11 for JARs
• Switching to Jakarta EE 10 dependencies (For most scenarios, this is not a breaking change.)
• More updated dependencies, Maven plugins, etc

💔 BREAKING CHANGES

• (none)

🏹 BUG FIXES

• (none)

v5.0.0

This is a breaking changes release with a lot of new features, influenced by the usage of XOAI within Dataverse and other places.

💔 BREAKING CHANGES

• Compatible with Java 11+ only
• Uses java.time API instead of java.util.Date
• Data Provider:
  • Changes required to your ItemRepository, Item and ItemIdentifier implementations
  • Changes required to your SetRepository implementation
  • Changes required to your usage of DataProvider (much simplified!)
  • Renewed configuration mechanism for data provider requires adaption
• Service Provider: Changes required to your code using an OAIClient, as default implementation changed

🌟 FEATURES

• Use the new CopyElement or Metadata.copyFromStream() to skip metadata XML processing, so pregenerated or cached data can be served from your ItemRepository implementation
• Use native JDK HTTP client for OAI requests in service provider, extended with client builder and option to create unsafe SSL connections for testing
• New JDK HTTP client allows to send custom headers, useful for authentication etc
• Add total number of results (inspired by GBIF #8)
• Larger rewrite of how data provider works:
  • Enable caching requests by exposing the resumption token to the application and making the pagination of results more explicit and comprehensible using a new type ResultsPage
  • Extended, simplified and more verbose parameter validation for requests
  • until timestamps are tweaked to enable more inclusive requests (avoid spilling milk with database timestamps etc)
  • Extensible reuse of RawRequest and Request classes to create non-servlet based endpoints with in-tree verification methods now possible via RequestBuilder!
  • Simplified filtering model for XOAI: easier to setup, default conditions provided
• Special XML handling for Dataverse JSON metadata to provide backward compatibility

🏹 BUG FIXES

• Sets now are properly compared, re-enabling SetRepositoryHelper to identify available sets
• Many new try-with-resources to mitigate memory leak risks
• The StAX XML components have been configured to avoid loading external entities, mitigating potential security risks
• from and until timestamps are now correctly verified in data provider, see #25
  • Granularity "Lenient" introduced, as the OAI-PMH 2.0 spec allows request with both precisions when "Second" granularity is supported. Former implementation did not allow this - remember to configure this, default is stick with old behaviour!
  • Configurable behaviour how to deal with requests where from is not after earliestDate. Default is to allow such requests, as spec is non-prohibitive. Former implementation behaviour was to deny such requests!
• And more...

License

See LICENSE or DSpace BSD License