Use Piranha Nano as a light-weight Servlet runner

Running a Servlet using Piranha is very easy and fun! For this blog entry we will show you how you can use Piranha Nano, couple with the DefaultHttpServer to run a HelloWorldServlet.

Follow steps mentioned below.

1. Write HelloWorldServlet
2. Create HttpServerProcessor
3. Create Appplication
4. Build JLink image

Write HelloWorldServlet

The code for the HelloWorldServlet will be similar to the snippet below.

public class HelloWorldServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, 
            HttpServletResponse response) throws IOException, ServletException {
        PrintWriter writer = response.getWriter();
        writer.println("Hello World");
    }
}
        

Create HttpServerProcessor

The code for the HttpServerProcessor will be similar to the snippet below.

public class HelloWorldProcessor implements HttpServerProcessor {

    private final NanoPiranha piranha;

    public HelloWorldProcessor(NanoPiranha piranha) {
        this.piranha = piranha;
    }

    @Override
    public boolean process(HttpServerRequest request, HttpServerResponse response) {
        try {
            HttpWebApplicationRequest servletRequest = new HttpWebApplicationRequest(request);
            HttpWebApplicationResponse servletResponse = new HttpWebApplicationResponse(response);
            piranha.service(servletRequest, servletResponse);
            servletResponse.flush();
        } catch (IOException | ServletException e) {
            e.printStackTrace(System.err);
        }
        return false;
    }
}

        

Create Application

The code for the Application class will be similar to the snippet below.

public class HelloWorldApplication {

    public void run() {
        NanoPiranha piranha = new NanoPiranhaBuilder()
                .servlet("HelloWorld", new HelloWorldServlet())
                .build();
        DefaultHttpServer server = new DefaultHttpServer(8080, 
                new HelloWorldProcessor(piranha), false);
        server.start();
    }

    public static void main(String[] arguments) throws Exception {
        HelloWorldApplication application = new HelloWorldApplication();
        application.run();
    }
}
     
        

Note you can swap out DefaultHttpServer with Grizzly, JDK HTTP server, Undertow or Netty. All it takes is using the appropriate module and adjusting the class name.

Build JLink image

The project zip is also setup to build the JLink native image, see the jlink/pom.xml file. If you want to build the project download the zip file and execute the command line below.

            
mvn clean verify
        

And voila the jlink/target/jlink directory will contain the JLink native image. You now have a quick recipe to write Servlets using Piranha Nano.

Enjoy!

Posted November 23rd, 2020

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