Chapter 2. Understand MicroProfile

2.1. MicroProfile Config

2.1.1. MicroProfile Config in JBoss EAP

Configuration data can change dynamically and applications need to be able to access the latest configuration information without restarting the server.

MicroProfile Config provides portable externalization of configuration data. This means, you can configure applications and microservices to run in multiple environments without modification or repackaging.

MicroProfile Config functionality is implemented in JBoss EAP using the SmallRye Config component and is provided by the microprofile-config-smallrye subsystem.


MicroProfile Config is only supported in JBoss EAP XP. It is not supported in JBoss EAP.


If you are adding your own Config implementations, you need to use the methods in the latest version of the Config interface.

2.1.2. MicroProfile Config sources supported in MicroProfile Config

MicroProfile Config configuration properties can come from different locations and can be in different formats. These properties are provided by ConfigSources. ConfigSources are implementations of the org.eclipse.microprofile.config.spi.ConfigSource interface.

The MicroProfile Config specification provides the following default ConfigSource implementations for retrieving configuration values:

  • System.getProperties().
  • System.getenv().
  • All META-INF/ files on the class path.

The microprofile-config-smallrye subsystem supports additional types of ConfigSource resources for retrieving configuration values. You can also retrieve the configuration values from the following resources:

  • Properties in a microprofile-config-smallrye/config-source management resource
  • Files in a directory
  • ConfigSource class
  • ConfigSourceProvider class

2.2. MicroProfile Fault Tolerance

2.2.1. About MicroProfile Fault Tolerance specification

The MicroProfile Fault Tolerance specification defines strategies to deal with errors inherent in distributed microservices.

The MicroProfile Fault Tolerance specification defines the following strategies to handle errors:

Define the amount of time within which an execution must finish. Defining a timeout prevents waiting for an execution indefinitely.
Define the criteria for retrying a failed execution.
Provide an alternative in the case of a failed execution.
Define the number of failed execution attempts before temporarily stopping. You can define the length of the delay before resuming execution.
Isolate failures in part of the system so that the rest of the system can still function.
Execute client request in a separate thread.

2.2.2. MicroProfile Fault Tolerance in JBoss EAP

The microprofile-fault-tolerance-smallrye subsystem provides support for MicroProfile Fault Tolerance in JBoss EAP. The subsystem is available only in the JBoss EAP XP stream.

The microprofile-fault-tolerance-smallrye subsystem provides the following annotations for interceptor bindings:

  • @Timeout
  • @Retry
  • @Fallback
  • @CircuitBreaker
  • @Bulkhead
  • @Asynchronous

You can bind these annotations at the class level or at the method level. An annotation bound to a class applies to all of the business methods of that class.

The following rules apply to binding interceptors:

  • If a component class declares or inherits a class-level interceptor binding, the following restrictions apply:

    • The class must not be declared final.
    • The class must not contain any static, private, or final methods.
  • If a non-static, non-private method of a component class declares a method level interceptor binding, neither the method nor the component class may be declared final.

Fault tolerance operations have the following restrictions:

  • Fault tolerance interceptor bindings must be applied to a bean class or bean class method.
  • When invoked, the invocation must be the business method invocation as defined in the Jakarta Contexts and Dependency Injection specification.
  • An operation is not considered fault tolerant if both of the following conditions are true:

    • The method itself is not bound to any fault tolerance interceptor.
    • The class containing the method is not bound to any fault tolerance interceptor.

The microprofile-fault-tolerance-smallrye subsystem provides the following configuration options, in addition to the configuration options provided by MicroProfile Fault Tolerance:

  • io.smallrye.faulttolerance.globalThreadPoolSize
  • io.smallrye.faulttolerance.timeoutExecutorThreads

2.3. MicroProfile Health

2.3.1. MicroProfile Health in JBoss EAP

JBoss EAP includes the SmallRye Health component, which you can use to determine whether the JBoss EAP instance is responding as expected. This capability is enabled by default.

MicroProfile Health is only available when running JBoss EAP as a standalone server.

The MicroProfile Health specification defines the following health checks:

Determines whether an application is ready to process requests. The annotation @Readiness provides this health check.
Determines whether an application is running. The annotation @Liveness provides this health check.

The @Health annotation was removed in MicroProfile Health 3.0.

MicroProfile Health 3.0 has the following breaking changes:

  • Pruning of @Health qualifier
  • Renaming of the HealthCheckResponse state parameter to status to fix deserialization issues. This has also resulted in renaming of the corresponding methods.

For more information about the breaking changes in MicroProfile Health 3.0, see Release Notes for MicroProfile Health 3.0.


The :empty-readiness-checks-status and the :empty-liveness-checks-status management attributes specify the global status when no readiness or liveness probes are defined.

2.4. MicroProfile JWT

2.4.1. MicroProfile JWT integration in JBoss EAP

The subsystem microprofile-jwt-smallrye provides MicroProfile JWT integration in JBoss EAP.

The following functionalities are provided by the microprofile-jwt-smallrye subsystem:

  • Detecting deployments that use MicroProfile JWT security.
  • Activating support for MicroProfile JWT.

The subsystem contains no configurable attributes or resources.

In addition to the microprofile-jwt-smallrye subsystem, the org.eclipse.microprofile.jwt.auth.api module provides MicroProfile JWT integration in JBoss EAP.

Additional Resources

2.4.2. Differences between a traditional deployment and an MicroProfile JWT deployment

MicroProfile JWT deployments do not depend on managed SecurityDomain resources like traditional JBoss EAP deployments. Instead, a virtual SecurityDomain is created and used across the MicroProfile JWT deployment.

As the MicroProfile JWT deployment is configured entirely within the MicroProfile Config properties and the microprofile-jwt-smallrye subsystem, the virtual SecurityDomain does not need any other managed configuration for the deployment.

2.4.3. MicroProfile JWT activation in JBoss EAP

MicroProfile JWT is activated for applications based on the presence of an auth-method in the application.

The MicroProfile JWT integration is activated for an application in the following way:

  • As part of the deployment process, JBoss EAP scans the application archive for the presence of an auth-method.
  • If an auth-method is present and defined as MP-JWT, the MicroProfile JWT integration is activated.

The auth-method can be specified in either or both of the following files:

  • the file containing the class that extends, annotated with the @LoginConfig
  • the web.xml configuration file

If auth-method is defined both in a class, using annotation, and in the web.xml configuration file, the definition in web.xml configuration file is used.

2.4.4. Limitations of MicroProfile JWT in JBoss EAP

The MicroProfile JWT implementation in JBoss EAP has certain limitations.

The following limitations of MicroProfile JWT implementation exist in JBoss EAP:

  • The MicroProfile JWT implementation parses only the first key from the JSON Web Key Set (JWKS) supplied in the mp.jwt.verify.publickey property. Therefore, if a token claims to be signed by the second key or any key after the second key, the token fails verification and the request containing the token is not authorized.
  • Base64 encoding of JWKS is not supported.

In both cases, a clear text JWKS can be referenced instead of using the mp.jwt.verify.publickey.location config property.

2.5. MicroProfile Metrics

2.5.1. MicroProfile Metrics in JBoss EAP

JBoss EAP includes the SmallRye Metrics component. The SmallRye Metrics component provides the MicroProfile Metrics functionality using the microprofile-metrics-smallrye subsystem.

The microprofile-metrics-smallrye subsystem provides monitoring data for the JBoss EAP instance. The subsystem is enabled by default.


The microprofile-metrics-smallrye subsystem is only enabled in standalone configurations.

2.6. MicroProfile OpenAPI

2.6.1. MicroProfile OpenAPI in JBoss EAP

MicroProfile OpenAPI is integrated in JBoss EAP using the microprofile-openapi-smallrye subsystem.

The MicroProfile OpenAPI specification defines an HTTP endpoint that serves an OpenAPI 3.0 document. The OpenAPI 3.0 document describes the REST services for the host. The OpenAPI endpoint is registered using the configured path, for example http://localhost:8080/openapi, local to the root of the host associated with a deployment.


Currently, the OpenAPI endpoint for a virtual host can only document a single deployment. To use OpenAPI with multiple deployments registered with different context paths on the same virtual host, each deployment must use a distinct endpoint path.

The OpenAPI endpoint returns a YAML document by default. You can also request a JSON document using an Accept HTTP header, or a format query parameter.

If the Undertow server or host of a given application defines an HTTPS listener then the OpenAPI document is also available using HTTPS. For example, an endpoint for HTTPS is https://localhost:8443/openapi.

2.7. MicroProfile OpenTracing

2.7.1. MicroProfile OpenTracing

The ability to trace requests across service boundaries is important, especially in a microservices environment where a request can flow through multiple services during its life cycle.

The MicroProfile OpenTracing specification defines behaviors and an API for accessing an OpenTracing compliant Tracer interface within a CDI-bean application. The Tracer interface automatically traces JAX-RS applications.

The behaviors specify how OpenTracing Spans are created automatically for incoming and outgoing requests. The API defines how to explicitly disable or enable tracing for given endpoints.

Additional Resources

2.7.2. MicroProfile OpenTracing in JBoss EAP

You can use the microprofile-opentracing-smallrye subsystem to configure the distributed tracing of Jakarta EE applications. This subsystem uses the SmallRye OpenTracing component to provide the MicroProfile OpenTracing functionality for JBoss EAP.

MicroProfile OpenTracing 2.0 supports tracing requests for applications. You can configure the default Jaeger Java Client tracer, plus a set of instrumentation libraries for components commonly used in Jakarta EE, using JBoss EAP management API with the management CLI or the management console.


Each individual WAR deployed to the JBoss EAP server automatically has its own Tracer instance. Each WAR within an EAR is treated as an individual WAR, and each has its own Tracer instance. By default, the service name used with the Jaeger Client is derived from the deployment’s name, which is usually the WAR file name.

Within the microprofile-opentracing-smallrye subsystem, you can configure the Jaeger Java Client by setting system properties or environment variables.


Configuring the Jeager Client tracer using system properties and environment variables is provided as a Technology Preview. The system properties and environment variables affiliated with the Jeager Client tracer might change and become incompatible with each other in future releases.


By default, the probabilistic sampling strategy of the Jaeger Client for Java is set to 0.001, meaning that only approximately one in one thousand traces are sampled. To sample every request, set the system properties JAEGER_SAMPLER_TYPE to const and JAEGER_SAMPLER_PARAM to 1.

Additional Resources

2.8. MicroProfile REST Client

2.8.1. MicroProfile REST client

JBoss EAP XP 3.0.0 supports the MicroProfile REST client 2.0 that builds on Jakarta RESTful Web Services 2.1.6 client APIs to provide a type-safe approach to invoke RESTful services over HTTP. The MicroProfile Type Safe REST clients are defined as Java interfaces. With the MicroProfile REST clients, you can write client applications with executable code.

Use the MicroProfile REST client to avail the following capabilities:

  • An intuitive syntax
  • Programmatic registration of providers
  • Declarative registration of providers
  • Declarative specification of headers
  • Propagation of headers on the server
  • ResponseExceptionMapper
  • Jakarta Contexts and Dependency Injection integration
  • Access to server-sent events (SSE)