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cmt: Container Managed Transactions (CMT)

The cmt quickstart demonstrates Container-Managed Transactions (CMT), showing how to use transactions managed by the container.

What is it?

The cmt quickstart demonstrates how to use container-managed transactions (CMT), which are transactions managed by the container in Red Hat JBoss Enterprise Application Platform. It is a fairly typical scenario of updating a database and sending a JMS message in the same transaction. A simple MDB is provided that prints out the message sent but this is not a transactional MDB and is purely provided for debugging purposes.

Aspects touched upon in the code:

  • XA transaction control using the container managed transaction annotations

  • XA access to the standard default datasource using the JPA API

  • XA access to a JMS queue

What are Container Managed Transactions?

Prior to EJB, getting the right incantation to ensure sound transactional operation of the business logic was a highly specialized skill. Although this still holds true to a great extent, EJB has provided a series of improvements to allow simplified transaction demarcation notation that is therefore easier to read and test.

With CMT, the EJB container sets the boundaries of a transaction. This differs from BMT (bean-managed transactions), where the developer is responsible for initiating and completing a transaction using the begin, commit, and rollback methods on a jakarta.transaction.UserTransaction.

What Makes This an Example of Container Managed Transactions?

Take a look at org.jboss.as.quickstarts.cmt.ejb.CustomerManagerEJB. You can see that this stateless session bean has been marked up with the @jakarta.ejb.TransactionAttribute annotation.

The following options are available for this annotation.

Required

As demonstrated in the quickstart. If a transaction does not already exist, this will initiate a transaction and complete it for you, otherwise the business logic will be integrated into the existing transaction.

RequiresNew

If there is already a transaction running, it will be suspended, the work performed within a new transaction which is completed at exit of the method and then the original transaction resumed.

Mandatory

If there is no transaction running, calling a business method with this annotation will result in an error.

NotSupported

If there is a transaction running, it will be suspended and no transaction will be initiated for this business method.

Supports

This will run the method within a transaction if a transaction exists, alternatively, if there is no transaction running, the method will not be executed within the scope of a transaction.

Never

If the client has a transaction running and does not suspend it but calls a method annotated with Never then an EJB exception will be raised.

Considerations for Use in a Production Environment

H2 Database

This quickstart uses the H2 database included with Red Hat JBoss Enterprise Application Platform 8.0. It is a lightweight, relational example datasource that is used for examples only. It is not robust or scalable, is not supported, and should NOT be used in a production environment.

System Requirements

The application this project produces is designed to be run on Red Hat JBoss Enterprise Application Platform 8.0 or later.

All you need to build this project is Java 11.0 (Java SDK 11) or later and Maven 3.6.0 or later. See Configure Maven to Build and Deploy the Quickstarts to make sure you are configured correctly for testing the quickstarts.

Use of the EAP_HOME and QUICKSTART_HOME Variables

In the following instructions, replace EAP_HOME with the actual path to your JBoss EAP installation. The installation path is described in detail here: Use of EAP_HOME and JBOSS_HOME Variables.

When you see the replaceable variable QUICKSTART_HOME, replace it with the path to the root directory of all of the quickstarts.

Building and running the quickstart application with a JBoss EAP server distribution

Start the JBoss EAP Standalone Server

  1. Open a terminal and navigate to the root of the JBoss EAP directory.

  2. Start the JBoss EAP server with the full profile by typing the following command.

    $ EAP_HOME/bin/standalone.sh -c standalone-full.xml
    Note
    		 For Windows, use the EAP_HOME\bin\standalone.bat script.

Build and Deploy the Quickstart

  1. Make sure you start the JBoss EAP server as described above.

  2. Open a terminal and navigate to the root directory of this quickstart.

  3. Type the following command to build the quickstart.

    $ mvn clean package

  4. Type the following command to deploy the quickstart.

    $ mvn wildfly:deploy

This deploys the cmt/target/cmt.war to the running instance of the server.

You should see a message in the server log indicating that the archive deployed successfully.

Access the Application

The application will be running at the following URL: http://localhost:8080/cmt/

You are presented with a simple form for adding customers to a database.

After a customer is successfully added to the database, a message is produced containing the details of the customer. An example MDB dequeues this message and print the following contents.

Received Message: Created invoice for customer named:  Jack

If an existing customer name is provided, no JMS message is sent. Instead of the above message, a duplicate warning is displayed.

The customer name should match: letter & '-', otherwise an error is given. This is to show that a LogMessage entity is still stored in the database. That is because the logCreateCustomer method in the LogMessageManagerEJB EJB is decorated with the @TransactionAttribute(TransactionAttributeType.REQUIRES_NEW) annotation.

Run the Arquillian Integration Tests

This quickstart includes Arquillian integration tests. They are located under the src/test/ directory. The integration tests verify that the quickstart runs correctly when deployed on the server.

Follow these steps to run the integration tests.

  1. Make sure you start the JBoss EAP server, as previously described.

  2. Make sure you build and deploy the quickstart, as previously described.

  3. Type the following command to run the verify goal with the arq-remote profile activated.

    $ mvn verify -Parq-remote
Note

You may also use the environment variable SERVER_HOST or the system property server.host to define the target host of the tests.

Undeploy the Quickstart

When you are finished testing the quickstart, follow these steps to undeploy the archive.

  1. Make sure you start the JBoss EAP server as described above.

  2. Open a terminal and navigate to the root directory of this quickstart.

  3. Type this command to undeploy the archive:

    $ mvn wildfly:undeploy

Building and running the quickstart application with OpenShift

Build the JBoss EAP Source-to-Image (S2I) Quickstart to OpenShift with Helm Charts

On OpenShift, the S2I build with Apache Maven will use an openshift profile used to provision a JBoss EAP server to deploy and run the quickstart in OpenShift environment. You can activate the Maven profile named openshift when building the quickstart:

$ mvn clean package -Popenshift

The provisioned JBoss EAP server for OpenShift, with the quickstart deployed, can then be found in the target/server directory, and its usage is similar to a standard server distribution. You may note that it uses the cloud feature pack which enables a configuration tuned for OpenShift environment.

The server provisioning functionality is provided by the EAP Maven Plugin, and you may find its configuration in the quickstart pom.xml:

        <profile>
            <id>openshift</id>
            <build>
                <plugins>
                    <plugin>
                        <groupId>org.jboss.eap.plugins</groupId>
                        <artifactId>eap-maven-plugin</artifactId>
                        <version>${version.eap.maven.plugin}</version>
                        <configuration>
                            <feature-packs>
                                <feature-pack>
                                    <location>org.jboss.eap:wildfly-ee-galleon-pack</location>
                                </feature-pack>
                                <feature-pack>
                                    <location>org.jboss.eap.cloud:eap-cloud-galleon-pack</location>
                                </feature-pack>
                            </feature-packs>
                            <layers>
                                <layer>cloud-server</layer>
                            </layers>
                            <filename>ROOT.war</filename>
                        </configuration>
                        <executions>
                            <execution>
                                <goals>
                                    <goal>package</goal>
                                </goals>
                            </execution>
                        </executions>
                    </plugin>
                </plugins>
            </build>
        </profile>
Note

Since the plugin configuration above deploys quickstart on root web context of the provisioned server, the URL to access the application should not have the /cmt path segment after HOST:PORT.

Getting Started with JBoss EAP for OpenShift and Helm Charts

This section contains the basic instructions to build and deploy this quickstart to JBoss EAP for OpenShift or JBoss EAP for OpenShift Online using Helm Charts.

Prerequisites

  • You must be logged in OpenShift and have an oc client to connect to OpenShift

  • Helm must be installed to deploy the backend on OpenShift.

Once you have installed Helm, you need to add the repository that provides Helm Charts for JBoss EAP.

$ helm repo add jboss-eap https://jbossas.github.io/eap-charts/
"jboss-eap" has been added to your repositories
$ helm search repo jboss-eap
NAME                    CHART VERSION   APP VERSION     DESCRIPTION
jboss-eap/eap8         ...             ...             A Helm chart to build and deploy EAP 8.0 applications

Deploy the JBoss EAP Source-to-Image (S2I) Quickstart to OpenShift with Helm Charts

Log in to your OpenShift instance using the oc login command. The backend will be built and deployed on OpenShift with a Helm Chart for JBoss EAP.

Navigate to the root directory of this quickstart and run the following command:

$ helm install cmt -f charts/helm.yaml jboss-eap/eap8
NAME: cmt
...
STATUS: deployed
REVISION: 1

The Helm Chart for this quickstart contains all the information to build an image from the source code using S2I on Java 17:

build:
  uri: https://github.com/jboss-developer/jboss-eap-quickstarts.git
  ref: 8.0.x
  contextDir: cmt
deploy:
  replicas: 1

This will create a new deployment on OpenShift and deploy the application.

If you want to see all the configuration elements to customize your deployment you can use the following command:

$ helm show readme jboss-eap/eap8

Let’s wait for the application to be built and deployed:

$ oc get deployment cmt -w
NAME         DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
cmt   1         1         1            0           12s
...
cmt   1         1         1            1           2m

Get the URL of the route to the deployment.

$ oc get route cmt -o jsonpath="{.spec.host}"

Access the application in your web browser using the displayed URL.

Note

The Maven profile named openshift is used by the Helm chart to provision the server with the quickstart deployed on the root web context, and thus the application should be accessed with the URL without the /cmt path segment after HOST:PORT.

Undeploy the JBoss EAP Source-to-Image (S2I) Quickstart from OpenShift with Helm Charts

$ helm uninstall cmt

Run the Arquillian Integration Tests with OpenShift

This quickstart includes Arquillian integration tests. They are located under the src/test/ directory. The integration tests verify that the quickstart runs correctly when deployed on the server.

Note

The Arquillian integration tests expect a deployed application, so make sure you have deployed the quickstart on OpenShift before you begin.

Run the integration tests using the following command to run the verify goal with the arq-remote profile activated and the proper URL:

$ mvn clean verify -Parq-remote -Dserver.host=https://$(oc get route cmt --template='{{ .spec.host }}')
Note

The tests are using SSL to connect to the quickstart running on OpenShift. So you need the certificates to be trusted by the machine the tests are run from.