Create the Maven POM file

Create an empty directory to store your Maven project. Inside of that directory create the pom.xml file with the content as below.

<?xml version="1.0" encoding="UTF-8"?>

<project
    xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>cloud.piranha.guides.crac</groupId>
    <artifactId>crac</artifactId>
    <version>24.10.0-SNAPSHOT</version>
    <packaging>war</packaging>
    <name>Piranha Core Profile on Project CRaC</name>
    <properties>
        <!-- dependencies -->
        <jakartaee.version>10.0.0</jakartaee.version>
        <junit.version>5.11.0-M2</junit.version>
        <piranha.version>24.7.0</piranha.version>
        <!-- other -->
        <java.version>21</java.version>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <!-- plugins -->
        <maven-compiler-plugin.version>3.13.0</maven-compiler-plugin.version>
        <maven-failsafe-plugin.version>3.3.1</maven-failsafe-plugin.version>
        <maven-war-plugin.version>3.4.0</maven-war-plugin.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>jakarta.platform</groupId>
            <artifactId>jakarta.jakartaee-core-api</artifactId>
            <version>${jakartaee.version}</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-engine</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-params</artifactId>
            <version>${junit.version}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <finalName>crac</finalName>
        <plugins>
            <plugin>
                <groupId>cloud.piranha.maven.plugins</groupId>
                <artifactId>piranha-maven-plugin</artifactId>
                <version>${piranha.version}</version>
                <executions>
                    <execution>
                        <id>pre-integration-test</id>
                        <phase>pre-integration-test</phase>
                        <goals>
                            <goal>start</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>post-integration-test</id>
                        <phase>post-integration-test</phase>
                        <goals>
                            <goal>stop</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>${maven-compiler-plugin.version}</version>
                <configuration>
                    <release>${java.version}</release>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-failsafe-plugin</artifactId>
                <version>${maven-failsafe-plugin.version}</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>integration-test</goal>
                            <goal>verify</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>${maven-war-plugin.version}</version>
                <configuration>
                    <failOnMissingWebXml>false</failOnMissingWebXml>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Add the application class

Add the Application class in the src/main/java directory, which allows you to set the application path using the @ApplicationPath annotation.

package rest;

import jakarta.ws.rs.ApplicationPath;
import jakarta.ws.rs.core.Application;

@ApplicationPath("")
public class RestApplication extends Application {
}

Add the endpoint

And we are adding a simple ‘Hello World’ endpoint that is listening on the /helloworld path.

package rest;

import jakarta.enterprise.context.RequestScoped;
import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;

@Path("/helloworld")
@RequestScoped
public class HelloWorldBean {

    @GET
    public String helloWorld() {
        return "Hello World!";
    }
}

Add an integration test

As we want to make sure the application gets tested before we release an integration test is added which will be executed as part of the build.

We'll add the integration test to the src/test/java directory.

package rest;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.net.http.HttpResponse.BodyHandlers;
import static org.junit.jupiter.api.Assertions.assertTrue;
import org.junit.jupiter.api.Test;

class HelloWorldIT {
 
    @Test
    void testHelloWorld() throws Exception {
        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest
                .newBuilder(new URI("http://localhost:8080/crac/helloworld"))
                .build();
        HttpResponse<String> response = client.send(request, BodyHandlers.ofString());
        assertTrue(response.body().contains("Hello World!"));
    }
}

Test the application

The application is setup to use JUnit to do integration testing using the Piranha Maven plugin so when you are building the application it will also execute an integration test validating the endpoint works.

To build and test the application execute the following command:

  mvn install

Deploy the application

To deploy your application you will need 2 pieces.

1. The Piranha Core Profile runtime JAR.
2. The WAR file you just produced.

For the WAR file see the target directory. For the Piranha Core Profile distribution go to Maven Central. And then the following command line will deploy your application:

  java -XX:CRaCCheckpointTo=cr -jar piranha-dist-coreprofile.jar --enable-crac --write-pid --war-file crac.war &

Create the checkpoint

You have your application currently running so now it is time to create a checkpoint.

To ask the JVM to create a checkpoint use the command line below:

  jcmd piranha-dist-coreprofile.jar JDK.checkpoint

The application will exit and the chechkpoint files are in the cr directory.

Restart the application

To restart the application for the checkpoint you can use the following command line:

  java -XX:CRaCRestoreFrom=cr

Conclusion

As you can see using CRaC with Piranha Core Profile is matter of the right JDK and the right command line switch.

References

1. CRaC Project