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Thorntail is the new name of WildFly Swarm. This documentation applies to the proof of concept for v4.x of the project.

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1. Lessons Learned

We’ve spent a couple of years building and living with the current Thorntail (née WildFly Swarm) codebase. Over this time, we’ve learned a few things from our own experiences and those of our community. These are their stories.

Mangling artifacts is dangerous

When you mangle and repackage a user’s artifacts and dependencies, it can many times go awry.

Don’t replace Maven

Let Maven (or Gradle) handle the entirety of pulling dependencies. We cannot predict the topology of someone’s repository managers, proxies and network.

Don’t get complicated with uberjars

The more complex our uberjar layout is, the harder it is to support Gradle or other non-Maven build systems.

Classpaths are tricky

If different codepaths are required for executing from Maven, an IDE, a unit-test, and during production, you will have a bad time.

Don’t insist on uberjars

For Linux containers, people want layers that cleanly separate application code from runtime support code.

Testability is important

A slow test is a test that is never willingly executed. PRs take forever to validate. Users like to be able to test their own code quickly and iteratively.

Easily extensible means ecosystem

If it’s entirely too difficult to extend the platform, the ecosystem will not grow. New integrations should be simple.

Related: Core things should not be any more first-class than community contributions

For instance, auto-detection in WildFly Swarm only worked with core fractions; user-provided wouldn’t auto-detect.

Ensure the public-vs-private API guarantees are clear.

Intertwingly code (and javadocs) make finding the delineation between public API and private implementations difficult.

Allow BYO components

We don’t want to decide all of the implementations, and certainly not versions, of random components we support.

Be a framework, not a platform

Frameworks are easier to integrate into an existing app; a platform becomes the target with (generally too many) constraints.

Maintain tests & documentation

Ensure the definition of "done" includes both tests and documentation.

Productization complexity

The greater divergence between community and product, the more effort is required for productization. Complicating any process to automate productization from community.

BOM complexity

Related to productization as well, but of itself having a handful of BOMs made life confusing for us and for users. There were often times where fractions would be "Unstable" or "Experimental" for months with no real reason other than we forgot to update it.

2. Architecture

Previous versions of Thorntail had a lot of architecture. And a lot of complexity.

2.1. Basics

Just CDI Bean Archives

Instead of magic fractions with a lot of ceremony and boiler-plate, a Thorntail component is usually just a plain CDI bean archive. These archives may include CDI beans, extensions, and optional default configuration (provided through MicroProfile Config mechanisms).

Application & Runtimes Mix

There is no distinction between application code and runtime code, other than the archives that provide the classes and components.

2.2. Details

Any given component may provide CDI beans, extensions, both or neither. A CDI portable extension may be used to convert non-CDI components, such as Servlets or JAX-RS resources, into CDI-aware components. For instance, thorntail-servlet contains a CDI extension that scans for all Servlet implementations and creates relevant meta-data to allow deployment of them.

void createServletMetaData(@Observes AfterBeanDiscovery event, BeanManager beanManager) {
    beanManager.getBeans(Servlet.class).forEach(e -> {
        createServletMetaData((Bean<Servlet>) e, event, beanManager);

Similar extensions exist to discover things such as @MessageDriven implementations.

Optional Dependency-enabled Functionality

For functionality such as OpenTracing, the ability to detect the presence of implementations is baked into the kernel. When a particular dependency is available (such as Jaeger), additional capability is enabled. Through the usage of @RequiredClassPresent, entire CDI beans and producers may be automatically vetoed (disabled) if particular classes are not present.

public class JaegerTracerProvider implements TracerProvider {
    public Tracer get() {
        return this.configuration.getTracer();

    Configuration configuration;

In the above situation, if Jaeger’s Configuration class is not available on the classpath through dependencies, then the Jaeger-based Tracer will not be produced.

Multiple instances of @RequiredClassPresent and its inverse, @RequiredClassNotPresent, may be applied. If either annotation is supplied, then all annotations must be true to prevent the automatic disabling of that component.

3. Concepts

3.1. Microservice

A microservice is small application with a bounded domain. A microservice is intended to solve a semantically constrained problem related to a larger system. In a microservice-based architecture, an application is made from a collection of many microservices.

3.2. CDI-native

Thorntail is built from the from ground-up to be CDI-native. Building applications of any notable size benefit from the usage of a dependency-injection framework.

3.3. MicroProfile-native

Thorntail is built from the from ground-up to be MicroProfile-native. MicroProfile addresses many of the needs and requirements of microservices-centric applications. Instead of bolting MicroProfile facilities on, Thorntail natively supports the various MicroProfile specifications directly.

3.4. Flat Classpath

While Java application servers previously have had the ability to support multiple disparate applications, when building microservices, a runtime need only support a single application, or service. With a microservices architecture, significantly fewer resources and capabilities may be required for each service. Freely mixing service and application implementations becomes significantly less problematic and certainly less cumbersome.

That being said, the Java Platform Module System (JPMS) may become beneficial in the future after further adoption by other upstream projects.


4. main(…​)

Since Thorntail is more of a library and framework than it is a platform, and everything executes within a flat classpath, you need a main(…​) to start the Java process.

Implicit main(…​)

Implicitly, Thorntail provides a main(…​) entry-point if you do not provide one. The Maven plugin will scan your application for a class that provides a main(…​) method, but if one is not found, io.thorntail.Main will be used.

From your IDE, you can usually configure a Run target specifying an arbitrary class outside of your application (but within your classpath). In this case, you may also use io.thorntail.Main.

Explicit main(…​)

In the event you desire to write and control the process startup, you must provide a main(…​) method matching the Java requirements:

  • public qualifier

  • static qualifiter

  • void return type

  • named main

  • with an array (or varargs) of String arguments.

The simplest possible main(…​):

public class MyMain {
  public static void main(String... args) throws Exception {;

If you desire to have a main(…​) within your codebase, but have do not require custom behaviour, your class my simply extend io.thorntail.Main, which provides an appropriate entry-point.

import io.thorntail.Main;

public class MyMain extends Main {
  /* nothing required */

Now you may directly execute your MyMain class directly from your IDE.

When Using Other Frameworks

One common pattern, when using a framework such as JAX-RS, is to place the main(…​) within the primary application class, instead of a specialized class. With JAX-RS, the Application is a prime candidate:

public class MyApplication extends Application {
    public static void main(String... args) throws Exception {


5. Maven Plugin

The thorntail-maven-plugin exists to make packaging your application easier.

Basic Configuration

As with any Maven plugin, configuration occurs within your project’s pom.xml

The plugin has one available goal: package. The behavior of this goal is controlled by the plugin configuration, described below.

    <!-- global configuration -->
        <!-- execution-specific configuration -->

5.1. Modes

The plugin can operate in two modes: fat and thin, with fat being the default. The mode is selected by a <mode>…​</mode> block within the plugin configuration, or by the thorntail.mode property.


Produces an executable build that includes all dependencies and your application artifact.


Produces an executable build that includes all dependencies but not your application artifact.

Mode is an independent concept from format, described below.


5.2. Formats

The plugin can produce three different types of executable distributions: jar, dir, and zip, with jar being the default. The format is selected by a <format>…​</format> block within the plugin configuration, or by the thorntail.format property. These contents of any of these formats is still defined by the mode, described above.


Produces a fat jar (or überjar) containing the cotnents defined by the mode above. The jar may be executed using normal java -jar commands.


Produces a directory containing the contents defined by the mode above, along with scripts to easily execute it. The dir layout may be best suited for container-related pipelines, where all runtime support aspects are added to a base layer, and the topmost layer contains only the vanillia application artifact. To achieve this method, mode should be configured to be thin.


Produces the same content as the dir format, but as a .zip file.


5.3. main()

The plugin will attempt to discover an existing non-ambiguous main(…​) within your application. If it finds none, a default main(…​) will be configured. If it finds a single application-provided main(…​), it will be used. If it finds multiple application-provided main(…​) methods, an error will result. To resolve an ambiguous main(…​) error, a mainClass may be configured using a <mainClass>…​</mainClass> block within the plugin configuration, or by the thorntail.mainClass property.


5.4. Other configuration


The artifact produced will include the Maven classifier of -bin. This classifier may be changed using the <classifier>…​</classifier> configuration element, or thorntail.classifier property.

The artifact will be named the same as the primary project artifact (according to ${project.finalName}), unless a plugin configuration of <finalName>…​</finalName> or a property of thorntail.finalName is provided.


If the format is jar or zip, it will be attached to the Maven project, causing it to be built or deployed to the repository. If the format is dir, it can not be attached.

To disable attaching of a jar or zip build, a configuration block of <attach>…​</attach> or property of thorntail.attach may be set to false.

5.5. Distribution Structure

Directory and Zip

When dir or zip formats are selected, the layout of the resulting tree is relatively simple:


Directory containing platform-specific scripts to execute the application.


A Unix-compatible shell script for launching the application. If the distribution was built as a thin distribution, the application archive must be provided in one of two ways:

  • As an argument to the command.

  • By placing it within the app/ directory.


A Windows-compatible batch script for launching the application. If the distribution was built as a thin distribution, the application archive must be provided in one of two ways:

  • As an argument to the run.bat command.

  • By placing it within the app/ directory.


A directory to contain the application archive. If the distribution was built as a thin distribution, this directory will be empty. When using containers, the top-most layer may be responsible for placing the application archive in this location, or may mount the archive into this directory when run.


Contains all dependencies for the application. Care is taken to ensure last-modified timestamps of the contents of this directly do not change needlessly.


When the jar format is selected, the contents of the jar are also relatively simple:


All .jar archives are placed within the root of the resulting -bin.jar.


A bootstrapping class is provided which can set up the classpath given the contents at the root of the jar. The bootstrap class will extract all of the .jar artifacts from the root to a cache directory at $HOME/.thorntail-cache. The extracted jars will have a SHA-1 hash added to their names in order to disambiguate any identically named jars from this or other applications, as the cache is shared.


The Jar manifest is configured to run the bin.Run main bootstrapping class when java -jar is used.

6. Maven Archetypes

Maven archetypes are provided to make it quick to get started with new Thorntail projects.

6.1. JAX-RS

Maven Coordinates
Create a new project
mvn archetype:generate \
    -DarchetypeGroupId=io.thorntail.archetypes \
    -DarchetypeArtifactId=thorntail-jaxrs-archetype \
    -DarchetypeVersion=4.0.0-SNAPSHOT \
    -DgroupId=com.mycorp \
    -DartifactId=my-app \

Your project will be created in the my-app/ directory, and contain stubs to get your started. These stubs include a JUnit-based test, along with appropriate configuration of your pom.xml.

7. Testing with JUnit

Thorntail provides a JUnit TestRunner implementation which allows your JUnit tests to execute within the context of your full application. To use the TestRunner, you must include the testing artifact with <scope>test</scope>.

Maven Coordinates
Use the ThorntailRunner`

Write your JUnit test as usual, but include a class-level annotation of @RunWith(ThorntailRunner.class)

public class MyTest {
  // tests go here
Participate in CDI

Your test class will be instantiated and injected for each test method. You may use @Inject to inject any component available to your application. The entirety of your application will be booted and available.

public class MyTest {

  public void testSomething() throws Exception {

  private Lunch myLunch;
Use @EphemeralPorts

If the annotation @EphemeralPorts is applied at the class level, and your application uses a servlet container, then arbitrary emphemeral ports will be selected and used. This may be useful when running tests on a CI machine or if you wish to parallelize your tests.

In order to know what port are actually selected and in-use, you may @Inject either a @Primary or @Management URL or InetSocketAddress component. These instances are made available throw the Servlet component.


The testing artifact transitively brings in assertj for making fluent assertions in your tests.


The testing artifact transitively brings in RestAssured to enable easily testing of HTTP endpoints. Additionally, it preconfigures the RestAssured.baseURI to the URL for the primary web endpoint, if available. The preconfiguration of the baseURI is especially useful when you use @EphemeralPorts.

Related Information

Testing with Arquillian

8. Testing with Arquillian

Arquillian is a framework which assists with both blackbox and in-container testing of your components. The MicroProfile TCKs use the Arquillian framework in order to verify compliance with the specifications.

Maven Coordinates

To use the Arquillian integration, include the testing-arquillian artifact in your project with a <scope>test</scope> block.

Arquilian Deployable Container

Thorntail provides an Arquillian-compatible deployable container which allows a developer to deploy only the components they wish to test. Additionally, the tests themselves may either be blackbox (@RunAsClient) or in-container where they can directly interact with the components under test.

Writing an in-container Test

Using JUnit, write a test as you normally would, but include a class-level annotation of @RunWith(Arquillian.class).

Additionally, to specify the components you wish to be tested, you must provide a method marked @Deployment which produces a ShrinkWrap archive to be consider as the application.

public class MyTest {

  public static JavaArchive myDeployment() {
    JavaArchive archive = ShrinkWrap.create(JavaArchive.class);
    // set up archive
    return archive;


For in-container tests, the test class itself (MyTest in this case) is considered an injectable CDI bean. Any components your application creates, or which are normally available from Thorntail may be injected.

public class MyTest {

  public static JavaArchive() {
    JavaArchive archive = ShrinkWrap.create(JavaArchive.class);
    // set up archive
    return archive;

  public void testSomething() throws Exception {

  private Lunch myLunch;

Related Information

Testing with JUnit

9. Developer Tools

Thorntail provides a set of developer tools to allow for restarting or reloading classes when developing a Thorntail-based application. The simple ability to restart a running process when compiled .class files or packaged .jar files are changed is built in to the core. To gain the ability to hot reload classes into an running executable, an additional dependency is required.

Maven Coordinates

To enable either the restarting of processes or hot-reloading of classes, the environment variable THORNTAIL_DEV_MODE must be set.


Capability always included in the core, which will watch the contents of the classpath. Upon noticing changes, the process will be terminated and restarted, causing the JVM to load new versions of all classes.


Capbility only available if the above thorntail-devtools dependency is added to the project. It will watch for changes to the contents of the classpath (only .class files, not packaged .jar files) and attempt to load and redefine the classes within the running process.


Capbility always included in the core, which only enables remote debug mode for the JVM.

Using restart mode

Restart works primarily with directory layouts. The provided bin/ will use either the application’s own packaged .jar if built using <mode>fat</mode> or will attempt to use target/classes/ if built with <mode>thin</mode>. Start the process with the environment variable set to restart

$ THORNTAIL_DEV_MODE=restart ./target/myapp-bin/bin/

Then rebuild your project as appropriate

$ mvn compile

Within the console of the running process, you should see, within a few seconds, the process stop and restart automatically.

Using reload mode

Add the above Maven <dependency> block to your project.

Then follow the same steps as for restart, but setting the mode to reload.

$ THORNTAIL_DEV_MODE=reload ./target/myapp-bin/bin/

The rebuilt your project as appropriate

$ mvn compile

Additionally, the same behavior is available if you execute your main() directly from your IDE with the environment variable set appropriately. Triggering a recompilation from within your IDE should also cause hot reloading of your classes within the running process.

Using debug mode

This mode simply enables the remote JVM debug protocol on port 8000.

$ THORNTAIL_DEV_MODE=debug ./target/myapp-bin/bin/


10. Using the BOM with Maven

Use the BOM

All components and dependencies of Thorntail are version-managed in a Bill of Materials (BOM). Within your pom.xml you would import this BOM within a <dependencyManagement> stanza. This allows you to reference any Thorntail component or verified version of a dependency without having to specify the <version> of each.


11. Kernel

Maven Coordinates

The core of Thorntail is usually brought in transitively through other dependencies. It’s Maven coordinates are:

CDI Components

A @Dependent-scoped ThreadFactory for utilizing Thread instances.


An ExecutorService for executing tasks.


An @Application-scoped IndexView representing the jandex’d files of the Deployment, read from META-INF/thorntail.idx which is created by the plugin. If not found, it produces an empty IndexView instance.

11.1. Configuration

Configuration of applications built on Thorntail is performed using MicroProfile-config mechanisms. The default file located within the META-INF/ directory of the application can be used to set or override default configuration values. The same file may be used to provide application-specific configuration which does not directly affect the Thorntail behavior.

Additionally, other files, both within META-INF/ and on the filesystem may contribute to the final configuration, with various degrees of priority. The priority may be controlled on a file-by-file basis using the MicroProfile-config config_ordinal property within each file. Files with larger priorities will override values set in files with lower priorities.


Configuration files may be conditionally activated using profiles. Profiles are activated by setting the Java system property of thorntail.profiles or the system environment variable of THORNTAIL_PROFILES to a comma-separated list of names.

Search Paths & Explicit Configuration Files

To externalize configuration, the Java system property of thorntail.config.location or the system environment variable of THORNTAIL_CONFIG_LOCATION may be set to a system-dependent delimited set of paths. Each path is considered in turn, withi increasing priority. If a path is a directory, it will be searched for appropriate configuration files matching any activated profiles. If a path is a regular file, it will be loaded, regardless of name or activated profiles.


If the application includes a dependency on snakeyaml, then YAML-based configuration files will also be located and loaded.

Environment Variables

All configuration items may be set through environment variables. As the format used for many configuration keys may include characters not allowed as environment variable names, a mechanical translation is performed. A requested configuration key is converted to uppercase, and each dot is replaced with an underscore. For example, a configuration key of web.primary.port may be configured through an environment variable named WEB_PRIMARY_PORT.

Framework Defaults

Each framework component may include default values for any required configuration item. These defaults have a priority of -1000 to allow easy overriding of them.

Table 1. Configuration Sources
Path Priority Notes



Located via classloader and provided by framework components.



Located via classloader.



Located via classloader.



Located via classloader, if SnakeYAML is available



Located via classloader, in order specified, with increasing priority.



Located via classloader, in order specified, with increasing priority.


Located via filesystem from specified search paths, in order, with increasing priority.



Located via filesystem from specified search paths, in order, with increasing priority.



Located via filesystem, through explicit property or environment variable.

environment variables


Converted from all available system environment variables.

system properties


All available system properties.


Configuration values may be interpreted and assembled from other values. Interpolation expressions are wrapped within delimeters of `${' and `}'. Additionally, expressions may provide a default value, which may in turn be another expression or a literal. All interpolation is performed before using the value converters to convert to the desired type.

As with normal usage of Config, if an interpolation expression references a configuration key and provides no default, if that key does not exist, a NoSuchElementException will be thrown.

In the event that a literal ${ is desired within a value, without interpolation, a \ character may be used to escape it.

All other \ which appear before any other character will be included literally in the value, not as an escape.


Will be replaced with the current value of the configuration item web.primary.port if it exists. If no such value exists, an exception will be thrown.


Will be replaced with the current value of the configuration item web.primary.port if it exists. If no such value exists, the value of 8080 will be provided, and converted as appropriate.


Will be replaced with the current value of the configuration item if it exists. If not such value exists, will be replaced by the current value of the configuration item web.primary.port if it exists. If no such value exists, the value of 8080 will be provided, and converted as appropriate.


Will be a combination of the literal thing- text, the value of thing.type configuration item` if present, using the word 'default' if not, with a suffix of -impl.


Will result in a string literal of %40-$


Will result in a string literal of ${foo} without interpolation, removing the escape character.


Will result in a string literal of foo\,bar without removal of the escape character.

Related Information

12. Java EE

12.1. Bean Validation

The Bean Validation component provides for using bean validation according to JSR 380.

Maven Coordinates
CDI Components

Injectable components are defined by the Bean Validation specification.

Related Information

12.2. Servlet

The Servlet component of Thorntail enables basic Java Web Servlet processing and serving.

Maven Coordinates

To include the servlet component, add a dependency:

Implicit Deployment

An application archive will be scanned for all Servlet implementations and added to a default deployment. The @WebServlet annotation should be used to configure the servlet as desired.

Explicit Deployments

To have more control over the deployment, the application may use normal CDI facilities to produce instances of DeploymentMetaData. Each instance of DeploymentMetaData will be individually deployed to the underlying servlet container.

Management Deployments

Various other components, such as Metrics and Health produce additional web endpoints. Each of these are marked as management deployments. By default, these management deployments will be automatically deployed alongside the application deployment. The servlet component may be configured (see below) to separate application endpoints from management endpoints.

Static Content

Your application may provide static resources through its classpath, under static/, public/ or META-INF/resources/ within your jar. In a Maven-based project, that would be represented by paths such as:

  • src/main/resources/static/

  • src/main/resources/public/

  • src/main/resources/META-INF/resources/

Any file in the root of those directories would be served at the root of your application’s context path. The static or public prefix is not included in the resulting URL.

For instance:

src/main/resources/static/index.html would be served by default at /index.html.

Configuration of Primary Endpoints

If the management endpoints (see below) are not configured separately, then the primary configuration applies to all endpoints.

Sets the host or interface to bind the primary endpoint connection listener.


Sets the port to bind the primary endpoint connection listener. If this value is set to 0, a random available port will be used.

Configuration of Management Endpoints

Two configuration properties control which host and port management endpoints are served from. By default, they match the primary host and port, and serve from the same connection.

To change the management host or port, use the following configuration properties:

Sets the host or interface to bind the management endpoint connection listener.

Sets the port to bind the management endpoint connection listener. If this value is set to 0, a random available port will be used.

Configuration of Undertow

The servlet componet includes a variety of configuration options related to the default Undertow-based implementation.

The number of I/O threads to use by the web server. By default it is calculated as the maximum of 2 or the number of available CPUs.


The number of worker threads used by the web server. By default it is calculated as 8 times the number of I/O threads.


The high water mark for a server’s connections. Once this number of connections have been accepted, accepts will be suspended for that server.


The low water mark for a server’s connections. Once the number of active connections have dropped below this number, accepts can be resumed for that server.


Configure a TCP socket to disable Nagle’s algorithm.


Specify that output should be buffered. The exact behavior of the buffering is not specified; it may flush based on buffered size or time.

CDI Components

To enable creation of well-integrated applications, the Servlet component provides access to several CDI components.

@Primary URL

A URI with the qualifier of @Primary is available for injection. It specifies the URL of the primary endpoint.

@Primary InetSocketAddress

An InetSocketAddress with the qualifier of @Primary is available for injection. It specifies the address and port of the primary endpoint.

@Management URL

A URI with the qualifier of @Primary is available for injection. It specifies the URL of the management endpoint. This may be the same as the URL with the @Primary qualifier if the management endpoint has not been separately configured.

@Management InetSocketAddress

An InetSocketAddress with the qualifier of @Primary is available for injection. It specifies the address and port of the management endpoint. This may be the same as the InetSocketAddress with the @Primary qualifier if the management endpoint has not been separately configured.

Supported Metrics

A variety of metrics are automatically provided if Metrics is configured.

Total number of requests serviced by the named deployment.

Total number of requests which responded with an HTTP response code between 100 and 199.

Total number of requests which responded with an HTTP response code between 200 and 299.

Total number of requests which responded with an HTTP response code between 300 and 399.

Total number of requests which responded with an HTTP response code between 400 and 499.

Total number of requests which responded with an HTTP response code between 500 and 599.

Average response time for all responses.

12.3. JAX-RS

The JAX-RS component provides support for the JAX-RS specification. The application will be scanned for an Application component annotated with @ApplicationPath. If the discovered application does not provide a list of resources, they will be automatically scanned and added to the application.

JSON-P and the POJO-to-JSON Jackson provider are implicitly available to JAX-RS applications.

Maven Coordinates

12.4. WebSockets

The WebSockets components brings in support for JSR-356 websocket client and server endpoints.

Maven Coordinates

12.5. JSON-P

The JSON-P component provides access to the JSON-P API.

Maven Coordinates

12.6. JNDI

The JNDI component provides support for the Java Naming and Directory Interface.

Maven Coordinates
CDI Components

The JNDI initial context may be injected.

12.7. JDBC

The JDBC component helps with auto-detecting and registering JDBC drivers.

Maven Coordinates
Table 2. Detected Drivers
Driver Identifier





The identifier of each detected driver may be used when configuring a DataSource.

Related Information

12.8. DataSources

The DataSources component provides access to managed JDBC datasources.

Maven Coordinates

DataSources may be configured by providing a set of configuration properties for each datasource. Each configuration property has the prefix of datasource.MyDS.


The username for connecting to the datasource.


The password for connecting to the datasource.


The JDBC connection URL for the datasource.


The simple identifier of the JDBC driver for the datasource.


Enable tracing if OpenTracing is available. Acceptable values are OFF, ALWAYS, and ACTIVE. By setting to ACTIVE, only usage of the datasource when there is already an active parent context will be traced.

Related Information

12.9. JPA

The JPA component provides support for JPA EntityManager and @PersistenceContext resources.

Maven Coordinates

Enable tracing if OpenTracing is available. Acceptable values are OFF, ALWAYS, and ACTIVE. By setting to ACTIVE, only usage of the EntityManager when there is already an active parent context will be traced.

Related Information

12.10. JPA Support

The JPA Support component provides support for JPA EntityManager and @PersistenceContext resources inside of a CDI container.

public class EmployeeDao {
        EntityManager em;

        EntityManagerFactory emf;

        public Employee getEmployeeById(Long employeeId){
                return em.find(Employee.class, employeeId);

12.11. JTA

The JTA component provides access to a TransactionManager and the JTA API.

Maven Coordinates

12.12. JCA

The JCA component provides for using resource adapters.

Maven Coordinates
Implicit Deployment

If the configuration property of jca.resource-adapters is set to a string or array of strings, each name is attempted to be loaded and deployed as a resource adapter. For each name, a path is constructed, using the format of META-INF/name-ra.xml. The classpath is searched for a resource under that path, and if found, deployed as a resource adapter. For instance, if jca.resource-adapters is set to artemis,xadisk, then both META-INF/artemis-ra.xml and META-INF/xadisk-ra.xml are considered as deployable resource adapters. All classes related to the resource adapter should be in the normal classpath, usually as a .jar artifact, not a .rar artifact.

Explicit Deployment

In the event your application requires location of an ra.xml using different rules than the implicit deployment supports, your components may inject both the ResourceAdapterFactory and ResourceAdapterDeployments.

The factory may be used to parse an arbitrary resource from the classpath as an ra.xml type of file. Once parsed, the result should be added to the ResourceAdapterDeployments collection.


An array of strings of resource-adapter XML deployment descriptors to locate and deploy.

@MessageDriven Components

While the @MessageDriven annotation is actually part of the EJB3 specification, since it relates to resource adapters, it is supported through the JCA component.

Any normal POJO marked as @MessageDriven and implementing the appropriate interface (such as javax.jms.MessageListener for JMS resource adapters) will be deployed as a message-driven component.

These components exist within the normal CDI container, and will be injected as appropriate. These components are generally short-lived and managed by the appropriate resource-adapter, and therefore may not be injected directly into other CDI components.

If OpenTracing is available, these components may be marked with @Traced to trace their invocations.

CDI Components

A factory capable of locating an XML file within the classpath and parsing it into a ResourceAdapterDeployment.


A collection which accepts ResourceAdapterDeployment instances for deployment.

Related Information

12.13. JMS

The JMS component provides for easily connecting to remote message brokers. By itself, the JMS component provides no particular JMS client. See jms-artemis.

Maven Coordinates
CDI Components

Injectable JMS context which may be used to create queues & topics, consumers & producers.

JNDI bindings

The default JMS connection factory.

Integrating a JMS Client

See JCA for deploying a resource adapter for the JMS client.

The integration should also ensure it @Produces a ConnectionFactory which the JMS component will use to produce JMSContext instances.

Related Information


12.14. JMS-Artemis

The JMS-Artemis component provides for easily connecting to an external ActiveMQ Artemis message broker.

Maven Coordinates

By default, ActiveMQ-Artemis client is provided, and respects the following configuration options:


The username for the remote connection>


The password for the remote connection.


The remote connection URL, which must be set unless less and artemis.port are used.

The remote connection host, if not using artemis.url. Defaults to localhost.


The remote connection port, if not using artemis.url. Defaults to 61616.

13. MicroProfile

13.1. Config

Configuration is a in-built component of the core component, and requires no additional Maven dependency.

13.2. Fault Tolerance

The Fault Tolerance component supports the MicroProfile Fault Tolerance specification.

Maven Coordinates

13.3. Health

The Health component provides support for the MicroProfile Health API.

Maven Coordinates
Related Information

13.4. Metrics

The Metrics component supports the collection and reporting of metrics using the MicroProfile Metrics spec. This includes providing a Prometheus-compliant endpoint.

Maven Coordinates
Built-in Metrics

Depending on which other components your application uses, some metrics will be automatically provided. Please refer to each component’s documentation for details.

Related Information

13.5. OpenAPI

The OpenAPI component supports the generation of an OpenAPI document representing the JAX-RS Resources using the MicroProfile OpenAPI spec.

Maven Coordinates
Management Deployment

The OpenAPI component will deploy a servlet to the /openapi endpoint which returns the OpenAPI document for the application. The /openapi endpoint is accessible under the management host and port.

Related Information

13.6. OpenTracing

The OpenTracing component supports the MicroProfile OpenTracing specification.

Maven Coordinates

This component uses the OpenTracing TracerResolver to locate an appropriately-configured Tracer instance. Additionally, applications may provide instances of TracerProvider which may also be used to discovered a fully-configured Tracer implementation. The discovered Tracer will be registered with the GlobalTracer which allows for easy access in arbitrary code.


If the OpenTracing MockResolver is available on the classpath (usually through a <scope>test</scope> dependency), it is given the highest priority for resolution.

CDI Components

An injectable OpenTracing Tracer.


An interface which application components may implement in order to assist in resolving the current Tracer implementation.

Related Information

13.6.1. OpenTracing with Jaeger

The OpenTracing component can detect the presence of Jaeger and enable its tracer.


By setting jaeger.endpoint the HTTP sender will be used to send sampling information. Otherwise, the UDP sender will be used and configured via and jaeger.agent.port.


Required service name for the application.


The sampler type.


The sampler parameter.

The sampler remote manager host/port combination.

The UDP agent host.


The UDP agent port.


The endpoint for the HTTP sender.

CDI Components

Qualifier for direct access to the Jaeger UDP Sender


Qualifier for direct access to the Jaeger HTTP Sender

Related Information

14. Other

14.1. Vert.x

The Vert.x component provides access to the Vert.x event-bus and message-driven consumers.

Maven Coordinates

The host for clustering Vert.x. Defaults to localhost.


The port for clustering Vert.x. Defaults to 0.

@MessageDriven Components

Any implementation of the VertxListener with the appropriate @MessageDriven annotation will be registered with the Vert.x resource adapter to consume inbound messages. These components are short-lived and may not be injected into other components. They are managed by the CDI container, though, and may have other components inject into them.

package com.mycorp;

import javax.ejb.ActivationConfigProperty;
import javax.ejb.MessageDriven;
import javax.inject.Inject;

import io.vertx.core.eventbus.Message;
import io.vertx.resourceadapter.inflow.VertxListener;

    activationConfig = {
          propertyName = "address",
          propertyValue = "driven.event.address"
public class Receiver implements VertxListener {

    public <T> void onMessage(Message<T> message) {
      // handle inbound message here.

    private MyOtherComponent component;
CDI Components

The Vert.x event bus.


The Vert.x connection factory.

JNDI Bindings

The VertxConnectionFactory.

Related Information

14.2. OGM

Provides support for Hibernate OGM EntityManager and @PersistenceContext resources and allows for the use of NoSQL datastores with JPA.

Supported Datastores
  • Infinispan

  • MongoDB

  • Neo4j

  • Cassandra

  • CouchDB

  • EhCache

  • Apache Ignite

  • Redis

Maven Coordinates

Version of Hibernate Search is managed by the Thorntail bom to ensure compatibility with OGM. Add the following to pom.xml if required by the NoSQL driver in use with OGM.



15. Build Thorntail from Source

The source of Thorntail is available on GitHub.

Clone from GitHub
git clone

The default build assumes docker is available on your system.

mvn install
Build without Docker

To skip any tests that assume docker is available, use the -DskipDocker option.

mvn install -DskipDocker
Build and run the MicroProfile TCKs

Since the MicroProfile TCKs take a fair amount of time to execute, they are excluded by default. To enable them, use the -Ptck option to enable the TCK profile.

mvn install -Ptck
Source Repository Layout

From the root of the repository, the code is grouped into a few large categories:


Contains the core kernel and other components consumed by user applications.


The Bill of Materials pom.xml use for version management by both Thorntail itself and user applications.


Maven (and in the future, Gradle) plugins which assist in packaging of Thorntail-based projects.


Tests (both those that use docker and simple ones that do not) and MicroProfile TCKs.


Maven archetype projects to assist in the creation of new user applications.


AsciiDoc-based documentation.

16. How to build Linux Containers as Layers

Your application can be packaged as a multi-layered Linux Container using the Fabric8 docker-maven-plugin.

Configure the Base Distribution

Depending on your build process, you may wish to create the base layer (with all of your dependencies) in one Maven project, and create the top-most layer with your application artifact in another one.

The base layer will include the Thorntail dependencies, along with your application’s dependencies using normal <dependency> blocks.

Configure the thorntail-maven-plugin to create a dir format thin mode distribution:

Configure the Base Container Image

Next, configure the fabric8-maven-plugin to package the base distribution:


This image builds upon a base JDK8 image theoretically named myapp/base-jdk8 within the <from> line. The only requirement of this image is the ability to execute a JDK8-compatible JVM.

This configuration will ensure that within the image, the /$thorntail directory will contain your application’s run-time components.

Additionally, the <cmd> configuration ensures the distribution’s will be used to launch the application.

We configure <skip> under <run> to true since this image is not directly executable, since it lacks application logic.

Set up the assembly

This image gets its content from an assembly descriptor, in this case named base.xml. You will need to create this file under src/main/docker. It will copy the contents from target/myapp-1.0.0-bin/ into /thorntail within the container. Ultimately, it will populate the /thorntail/bin and /thorntail/lib contents.

base.xml Assembly Descriptor
Build the base

From within this project directory, build the base image using Maven

mvn package docker:build
Set up Application Dependencies

Assuming the previous pom.xml had a groupId of com.mycorp.myapp and an artifactId of app-base, we add it as the only compile <dependency> of your application layer.

Configure the Distribution (optional)

You may configure the thorntail-maven-plugin in any fashion (or not at all) within this project.

Configure the Application Container Image

Once again, use the Fabric8 docker-maven-plugin to create another image, this time based upon the previously-created image:


The will create an push an image named myapp/base. It uses the built-in <descriptorRef> of artifact to install the application artifact under thorntail/app.

Additionally, it configures a <wait> element looking for the boot completion message, which may help if you use this image in integration tests.

Build the Application Container Image

Build using Maven:

mvn package docker:build
Related Information

17. How to build Linux Containers using Fabric8 Maven Plugin

The Fabric8 docker-maven-plugin is a Maven plugin which makes it easy to create, push and run Linux container images.

Plugin Configuration

Regardless of the mode and format used with the thorntail-maven-plugin, the docker-maven-plugin can build a suitable image for your application. As with other Maven plugins, it is configured within a typical <plugin> block within your pom.xml. A single <image> block will be necessary.


In the above example, we use fabrci8/java-jboss-openjdk8-jdk as the base image. This image includes OpenJDK on CentOS. Additionally, it provides a script which intelligently and configurably can execute your application.

The image uses the descriptorRef of the build-in artifact-with-dependencies descriptor. This causes both your project artifact and all transitive dependencies to be copied into the /maven directory of the resulting image.

The script is the default command of this image, and is configured using environment variables.

The JAVA_APP_DIR environment variable simply points to the /maven directory within the image, to define where the application’s .jar files were installed.

The JAVA_MAIN_CLASS environment variable should be defined either to your own main(…​) class, or the default io.thorntail.Thorntail class.

Building the Image

Using normal Maven build command will produce and push the image to your container repository:

mvn package docker:build
Running the image

Normal docker commands may now be used to execute the image with any additional arguments or configuration.

docker run myapp/app-fabric8

18. Using log4j


While Thorntail does not use log4j directly, some of the libraries in your application may use it. If you do not configure log4j in your application, all logging output, including output from Thorntail will get swallowed, preventing you from seeing your logs.


The recommended solution is to specify the path to your file as a log4j.configuration system property. In your parameters to your JVM you would specify it like this:


Please note, when using this method you can use any name you want for your properties file.

The other solution is to place a file name log in the default path for your classloader. In a Thorntail application you can just place this file in the root of your source directory; typically /src/main/java.


19. License

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