Here’s the latest WebSphere Liberty beta and WebSphere Developer Tools (WDT). Thanks to your support for our regular beta programme, we are able to release new Liberty features every few months. Most recently, in June. Look out for more betas over the coming months.

Get it now! Ask a question about the beta

What’s new in this release?

The OpenAPI feature and the MicroProfile Fault Tolerance and Configuration API features have all been updated since the last beta release of Liberty. The OpenAPI feature also has updated support in the WebSphere Developer Tools beta.

OpenAPI v3

The OpenAPI v3 updates include additions to the Liberty OpenAPI feature and changes in WebSphere Developer Tools to support the OpenAPI feature.

Liberty Runtime updates

This is a new feature (introduced in the June beta) to implement the official OpenAPI 3.0 specification, which is now final.

New additions to the August Beta include:

  • A new OpenAPI User Interface! Similar to apiDiscovery-1.0, the public UI for openapi-3.0 is available at /api/explorer, and if the private endpoint is enabled (<openapi enablePrivateURL="true />), you can reach the private UI at /ibm/api/explorer. This UI builds upon the Swagger UI through our collaboration with the open source community. Check out the UI by using our sample OpenAPI v3 application today! (Note that there are some limitations with the UI at the moment; for example, it’s not currently possible to edit the request body when trying out a particular operation.)

  • New validation support. Each OpenAPI v3 document provided by the application is validated against the validation constraints declared in the OpenAPI v3 specification. If an OpenAPI document processed by the openapi-3.0 feature is invalid, an error is reported in the logs for each constraint that has been violated. In this Beta, a subset of the OpenAPI v3 specification was chosen, therefore Callback, Encoding, Link and Schema objects are not yet being validated.
  • Updates to the converter. The openapi-3.0 feature supports Swagger 2.0 format API descriptions in the META-INF directory of an application and automatically converts them to Swagger 3.0 format. Previously only simple descriptions were accepted but in this beta many useful features are added:
    • array and object types in parameter schemas and in component descriptions and including nested arrays and objects
    • parameters which are $ref objects referring to in: body parameters
    • example objects in schemas, properties and responses
    • default values specified for parameters
    • tags in the top level of the document and in endpoint operations

    Some Swagger 2.0 features are also known as limitations:

    • collectionFormat in parameter object
    • definitions including allof
    • external documentation object
    • basePath object
  • Updated programming interface (API). Application developers now have an interface to configure and customize the auto-generation of OpenAPI documents, including the ability to provide programmatic OpenAPI models to augment or replace annotation scanning. Here are the updated interfaces:
    • The io.swagger.oas.web.OpenAPIConfigBuilder interface is the main service that allows for the customization of the OpenAPI v3 processing in Liberty. It allows the application developer to receive framework-dependent environment variables to process during the build of a new OpenAPIConfig object.
      public interface OpenAPIConfigBuilder {
      OpenAPIConfig build(Map<String, Object> environment);
    • The io.swagger.oas.web.OpenAPIConfig interface is a container for all configuration parameters pertaining to OpenAPI v3 processing. With this interface you can provide a complete OpenAPI model, control aspects of annotation scanning (including the ability to disable it), and provide other helper services such as a custom filter, reader and scanner.
      [Beta] For the current Beta, only the getOpenAPI() method from OpenAPIConfig is processed.

      public interface OpenAPIConfig {
      OpenAPI getOpenAPI();
      String getFilterClass();
      String getReaderClass();
      String getScannerClass();
      Set<String> getIgnoredClasses();
      Map<String, Object> getOptions();
      Set<String> getResourceClasses();
      Set<String> getResourcePackages();
      boolean isScanDisabled();
    • The io.swagger.oas.web.OpenAPIScanner interface allows an application developer to provide a custom scanner. Essentially this overrides Liberty’s annotation scanning.
      [Beta] This service is not currently enabled in the Beta, but its interface is exposed to provide an illustration of the complete programming model.

      public interface OpenAPIScanner {
      Set<Class<?>> classes();
      Map<String, Object> resources()
    • The io.swagger.oas.web.OpenAPIReader interface allows an application developer to provide a custom reader. Essentially this overrides Liberty’s annotation and document processing.
      [Beta] This service is not currently enabled in the Beta, but its interface is exposed to provide an illustration of the complete programming model.

      public interface OpenAPIReader {
      OpenAPI read(OpenAPIConfig configuration, OpenAPIScanner scanner)
  • New SPI for OSGi bundles! Liberty’s openapi-3.0 feature introduces an interface for OSGi bundles (user or product extensions) running in Liberty to provide OpenAPI v3 documentation for their APIs. These SPIs can be found inside /wlp/dev/spi/spec. Simply register an implementation of the interface into the OSGi framework to contribute the documentation.

    Here’s a snippet of these interfaces:

    • This interface is the main service that SPI users must implement in order to contribute documentation into the overall OpenAPI v3 feature. You must register one OASProvider per context root that you wish to document. The different set of results means that you can support different document variations, such as for different languages.
      public interface OASProvider {
          List<OASProviderResult> getResults();
          String getContextRoot();
          default boolean isPublic() {
              return false;
    • This interface encapsulates a single OpenAPI v3 document, either using the OpenAPI model or a YAML/JSON text formatted as a Java String. It has a configuration attached to it, which provides metadata about the document.
      public interface OASProviderResult {
          OpenAPI getOpenAPI();
          String getDocument();
          default OASProviderConfig getOASProviderConfig() {
              return OASProviderConfig.defaultConfig();
    • This helper class encapsulates a set of support options that can be linked to a particular OpenAPI v3 document.
      [Beta] For the Beta, we do not take different languages into account. However, the method is there as a preview of upcoming capability.

      public final class OASProviderConfig {
          private String language;
          public String getLanguage() {
              return this.language;
          public void setLanguage(String language) {
              this.language = language;
          public boolean equals(Object o) {
              if (o == null || getClass() != o.getClass()) {
                  return false;
              OASProviderConfig config = (OASProviderConfig) o;
              return Objects.equals(this.language, config.language);
          public int hashCode() {
              return Objects.hash(this.language);
          public static OASProviderConfig defaultConfig() {
              return new OASProviderConfig();

For more information, see the Knowledge Center.

To join WebSphere OpenAPI’s external slack channel, please send an email to and you’ll receive an invitation. That’s where we talk to various members of the OpenAPI community about our Java OpenAPI v3 development.

WebSphere Developer Tools updates

The New Open API Definition Wizard allows developers of REST API to not only create Swagger 2.0 JSON definitions but also new Open API 3.0 JSON files with basic content or with sample content. This allows the API developer to get started with a basic or sample template from which to build their Open API document.

An Eclipse validation framework-based validator has been added to provide some rule-based validation of Open API 3.0-based JSON files. This allows REST API developers to validate their definitions up-front, view the errors in the Source view of the JSON Editor, and quickly fix the issue, prior to deploying to the server.

Another enhancement is the application detection logic to automatically configure Liberty with the Open API 3.0 feature. If an Open API 3.0 file exists in the META-INF folder of a Web app, then when the app is deployed to the Liberty Server, the Open API 3.0 feature is automatically added to the Liberty Server Configuration feature list, if it isn’t already added.

To try it out:

  1. Install WebSphere Application Server Developer Tools For Eclipse and create a Liberty server.
  2. From a Web project, right-click New > Open API Definition File to open the wizard. The wizard allow you to still generate Swagger 2.0 files but it defaults to Open API 3.0 files. You can choose between a skeleton template or a sample template with more Open API 3.0 elements as the initial content of the new file. The wizard only generates the Open API 3.0 file into the META-INF folder of a Web application.

By default, the validator is turned on in Web projects and it validates any Open API 3.0 JSON files in the Web project upon build. The validator can also be run directly on any workspace Open API 3.0 JSON file using the Validate option when you right-click the file.

For more information, see:

MicroProfile updates

MicroProfile Config API feature

The MicroProfile Config specification provides a single way to view and access multiple sources of configuration, such as properties files and environment variables, including, user-level properties files, registered Java classes that implement the ConfigSource API, and the Java

Building systems as collections of independent microservices increases the number of services that need to be managed. As developers of microservices, we want to be able to update configuration data in one place and for that update to affect multiple microservices. Tools such as containerisation, service meshes, and vendors’ cloud configuration services can be used help with service configuration. For our code to be portable, however, we want the applications to be insulated from vendor-specific APIs and to access different configuration data sources in a consistent way.

The well-known 12 factors for microservices refer to configuration as “everything that is likely to vary between deploys”. It is not just configuration values that vary as microservice code passes along the stages of a devOps pipeline. Different stages in the pipeline often use different configuration sources for a single piece of configuration data.

The rising proportion of code that is reused or shared across systems (eg using shared services or Docker containers) also means that components are being written to be more and more configurable. Even while a component is ‘live’ in production, the environment it is running in may be more dynamic that traditional systems and some components may require a means to update part of the configuration without restarting the application.

All this means that there is an increasing need to make fully configurable components with settings that that can be changed without requiring any change, repackaging, or restarting the component itself. There have been a number of attempts at providing such a Java configuration API including Spring Cloud Config, Apache Commons, Deltaspike and Tamaya, and Netflix Archaius but none has become a defacto standard and there is currently no official Java language API.

The Eclipse MicroProfile initiative exists for ‘Optimizing Enterprise Java for a microservices architecture’ and, after the initial base platform of existing services was defined, the Microprofile Configuration API was the first new API released by the MicroProfile community. The API allows for a consistent means to access configuration data from pluggable configuration sources. Configuration properties can be injected using Java CDI in a form that is easy to consume. Data values and sources can vary across the devOps pipeline without code change or repackaging, and dynamic and fully typed data is catered for.

For more information, see the Knowledge Center.

MicroProfile Fault Tolerance

The increasing size of ‘web-scale’ applications, newer architectures that are as likely to ‘scale out’ as to ‘scale up’, and the rising popularity of microservice architectures all contribute to the growing number of services that can be involved in a single business application. When combined with a utility model for service provision it is increasingly important to build fault tolerance into our system architecture.

Fault tolerance can be improved using a number of well tested approaches that handle failure:

  • TimeOut: Limit the amount of time we are prepared to wait for a result
  • RetryPolicy: Control how much we are prepared to re-submit a request
  • Fallback: Specify what should we do when the primary service cannot be used successfully
  • Bulkhead: If calls to a service are slow (perhaps it is overloaded or we are timing out), specify what proportion of our local resources we are prepared to get involved in the traffic jam
  • CircuitBreaker: When a service is proving unreliable, for example timing out, we can choose to ‘fail fast’ by automatically failing calls to it under control

With the Microprofile Fault Tolerance specification, we can control all these aspects with easy-to-use Java annotations at a method or class level that is independent of any particular vendor or implementation library.

For more information, see the Knowledge Center.

What’s already in there?

The July Liberty beta included the JSON Binding 1.0 and JSON Processing 1.1 features.

Take a look at the previous beta announcements for a full list of stuff added since the release in June 2017:

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1 comment on"Beta: WebSphere Liberty and tools (August 2017)"

  1. […] support this Configuration 1.0 definition should be coming shortly, with Apache Geronimo Config and WebSphere Liberty Beta leading the […]

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