Question

Suppose I have the following example of an embedded Java servlet in Jetty libraries – is it possible to do an equivalent using the Tomcat API libraries?

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.eclipse.jetty.server.Request;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.handler.AbstractHandler;

public class HelloHandler extends AbstractHandler
{
    public void handle(String target,Request baseRequest,HttpServletRequest     request,HttpServletResponse response) 
        throws IOException, ServletException
    {
        response.setContentType("text/html;charset=utf-8");
        response.setStatus(HttpServletResponse.SC_OK);
        baseRequest.setHandled(true);
        response.getWriter().println("<h1>Hello World</h1>");
    }

    public static void main(String[] args) throws Exception
    {
        Server server = new Server(8080);
        server.setHandler(new HelloHandler());

        server.start();
        server.join();
    }
}

Answer 1

A Tomcat7 embedded equivalent would look like this:

public class TinyTomcat7Embedded {

    public static void main(String[] args) {
        Tomcat tomcat = new Tomcat();
        tomcat.setPort(8080);

        File baseDir = new File("tomcat");
        tomcat.setBaseDir(baseDir.getAbsolutePath());

        File applicationDir = new File(baseDir + "/webapps", "/ROOT");
        if (!applicationDir.exists()) {
            applicationDir.mkdirs();
        }

        try {
            Context appContext = tomcat.addWebapp("/", "ROOT");

            // A Jetty AbstractHandler is an HttpServlet here:
            Tomcat.addServlet(appContext, "helloWorldServlet", new HttpServlet() {

                @Override
                protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
                    response.setContentType("text/html;charset=utf-8");
                    response.setStatus(HttpServletResponse.SC_OK);
                    response.getWriter().println("<h1>Hello World</h1>");
                }
            });
            appContext.addServletMapping("/helloworld", "helloWorldServlet");

            tomcat.start();
            System.out.println("Tomcat server: http://" + tomcat.getHost().getName() + ":" + 8080 + "/");
            tomcat.getServer().await();
        } catch (ServletException e) {
            e.printStackTrace();
        } catch (LifecycleException e) {
            e.printStackTrace();
        }
    }
}

Add these dependencies to your pom.xml:

    <!-- Eclipse Java Compiler -->
    <dependency>
        <groupId>org.eclipse.jdt.core.compiler</groupId>
        <artifactId>ecj</artifactId>
        <version>3.7.1</version>
    </dependency>

    <!-- Tomcat Embedded -->
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-core</artifactId>
        <version>7.0.26</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-logging-juli</artifactId>
        <version>7.0.26</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-logging-log4j</artifactId>
        <version>7.0.26</version>
    </dependency>
    <dependency>
        <groupId>org.apache.tomcat.embed</groupId>
        <artifactId>tomcat-embed-jasper</artifactId>
        <version>7.0.26</version>
    </dependency>