Chapter 2. Understand MicroProfile

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 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:

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:

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:

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:

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:

Fault tolerance operations have the following restrictions:

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

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:

The @Health annotation was removed in MicroProfile Health 3.0.

MicroProfile Health 3.1 includes a new Startup health check probe.

For more information about the changes in MicroProfile Health 3.1, see Release Notes for MicroProfile Health 3.1.

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

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

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.

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.

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:

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

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.

The MicroProfile JWT implementation in JBoss EAP has certain limitations.

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

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

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.

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.

MicroProfile Telemetry provides tracing functionality for applications based on OpenTelemetry. 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.

MicroProfile Telemetry expands on the OpenTelemetry subsystem and adds support for MicroProfile Config. This allows users to configure OpenTelemetry using MicroProfile Config.

JBoss EAP XP 5.0.0 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:

MicroProfile Config is the name of a specification that developers can use to configure applications and microservices to run in multiple environments without having to modify or repackage those apps. Previously, MicroProfile Config was available for JBoss EAP as a technology preview, but it has since been removed. MicroProfile Config is now available only on JBoss EAP XP.

Defining the resteasy.original.webapplicationexception.behavior MicroProfile Config property

You can set the resteasy.original.webapplicationexception.behavior parameter as either a web.xml servlet property or a system property. Here’s an example of one such servlet property in web.xml:

<context-param>
    <param-name>resteasy.original.webapplicationexception.behavior</param-name>
    <param-value>true</param-value>
</context-param>

You can also use MicroProfile Config to configure any other RESTEasy property.

When you upgrade to JBoss EAP XP 5.0.0, you can enable the newest version of MicroProfile Reactive Messaging, which includes reactive messaging extensions and subsystems.

A "reactive stream" is a succession of event data, along with processing protocols and standards, that is pushed across an asynchronous boundary (like a scheduler) without any buffering. An "event" might be a scheduled and repeating temperature check in a weather app, for example. The primary benefit of reactive streams is the seamless interoperability of your various applications and implementations.

Reactive messaging provides a framework for building event-driven, data-streaming, and event-sourcing applications. Reactive messaging results in the constant and smooth exchange of event data, the reactive stream, from one app to another. You can use MicroProfile Reactive Messaging for asynchronous messaging through reactive streams so that your application can interact with others, like Apache Kafka, for example.

After you upgrade your instance of MicroProfile Reactive Messaging to the latest version, you can do the following:

You can use connectors to integrate MicroProfile Reactive Messaging with a number of external messaging systems. MicroProfile for JBoss EAP comes with an Apache Kafka connector, and an Advanced Message Queuing Protocol (AMQP) connector. Use the Eclipse MicroProfile Config specification to configure your connectors.

MicroProfile Reactive Messaging connectors and incorporated layers

MicroProfile Reactive Messaging includes the following connectors:

Both the connector layers include the microprofile-reactive-messaging Galleon layer. The microprofile-reactive-messaging layer provides the core MicroProfile Reactive Messaging functionality.

Apache Kafka is an open source distributed event (data) streaming platform that can publish, subscribe to, store, and process streams of records in real time. It handles event streams from multiple sources and delivers them to multiple consumers, moving large amounts of data from points A to Z and everywhere else, all at the same time. MicroProfile Reactive Messaging uses Apache Kafka to deliver these event records in as few as two microseconds, store them safely in distributed, fault-tolerant clusters, all while making them available across any team-defined zones or geographic regions.