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HTTP/2 Java Server using Embedded Jetty - Part 1

Have you ever wanted to configure internal Java servers using HTTP/2 (or H2 in short), because of the following advantages?
  • Internal clients making concurrent calls, can now use a single connection by utilizing the multiplexing nature of HTTP/2.
  • Server will/can use less threads as there are less connections overall.
  • Servers can also push resources/data and can communicate using websockets
But what if you don’t want to go through tedious process of setting up SSL/TLS certificates? HTTP/2 insists on SSL/TLS as no browser supports HTTP/2 on insecure mode.

Or what if you want to save every bit of CPU and time by skipping encryption and decryption?

You are at the right place. Since everyone nowadays is moving towards (or talking about) micro services, we will also configure Jetty HTTP/2 server in embedded mode.

What more? We are also going to configure our server to use Asynchronous Servlets and Asynchronous IO (aka non-blocking IO or NIO) in Part-2 of this article.

Read more on how to produce a native executable of this setup in Part-3 of this article.

Software used

  • Java 11
  • Jetty 9.4.28 
  • NetBeans IDE 11.3
Let’s configure HTTP/1.1 and HTTP/2 over plain text (aka H2C) on same port. This has the advantage that the interested clients can speak directly HTTP/2 over plain text, without upgrading from HTTP/1.1 to HTTP/2.

Note: At present, only Jetty client supports H2C.

Server configuration

import org.eclipse.jetty.http2.server.HTTP2CServerConnectionFactory;
import org.eclipse.jetty.server.HttpConfiguration;
import org.eclipse.jetty.server.HttpConnectionFactory;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.server.ServerConnector;
import org.eclipse.jetty.servlet.ServletContextHandler;
import org.eclipse.jetty.servlet.ServletHolder;

public class Main {

    private static final int PORT = 8080;
    private static final String HOST = "localhost";

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

        // HTTP connector
        HttpConfiguration http2Config = new HttpConfiguration();
        ServerConnector http = new ServerConnector(server, new HttpConnectionFactory(), new HTTP2CServerConnectionFactory(http2Config));
        http.setHost(HOST);
        http.setPort(PORT);
        http.setIdleTimeout(30_000);
        // Set the connector
        server.addConnector(http);

        // set servlet handler
        ServletContextHandler context = new ServletContextHandler();
        context.setContextPath("/");
        ServletHolder asyncHolder = context.addServlet(HelloServlet.class, "/hello-servlet");
        server.setHandler(context);

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

Servlet content

import java.io.IOException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@SuppressWarnings("serial")
public class HelloServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws IOException {
        response.setStatus(HttpServletResponse.SC_OK);
        response.setContentType("text/html");
        response.setCharacterEncoding("utf-8");
        response.getWriter().println("<h1>Hello from HelloServlet</h1>");
    }
}

POM file

<?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>com.pb</groupId>
   <artifactId>jetty-http2-server</artifactId>
   <version>1.0</version>
   <packaging>jar</packaging>
   <properties>
       <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
       <maven.compiler.source>11</maven.compiler.source>
       <maven.compiler.target>11</maven.compiler.target>
       <jetty.version>9.4.28.v20200408</jetty.version>
   </properties>
    
   <dependencies>
       <dependency>
           <groupId>org.eclipse.jetty</groupId>
           <artifactId>jetty-server</artifactId>
           <version>${jetty.version}</version>
       </dependency>
       <dependency>
           <groupId>org.eclipse.jetty.http2</groupId>
           <artifactId>http2-server</artifactId>
           <version>${jetty.version}</version>
       </dependency>
       <dependency>
           <groupId>org.eclipse.jetty</groupId>
           <artifactId>jetty-servlet</artifactId>
           <version>${jetty.version}</version>
       </dependency>
       <dependency>
           <groupId>org.eclipse.jetty.http2</groupId>
           <artifactId>http2-http-client-transport</artifactId>
           <version>${jetty.version}</version>
       </dependency>
       <dependency>
           <groupId>org.slf4j</groupId>
           <artifactId>slf4j-api</artifactId>
           <version>1.7.30</version>
       </dependency>
       <dependency>
           <groupId>org.slf4j</groupId>
           <artifactId>slf4j-simple</artifactId>
           <version>1.7.30</version>
       </dependency>
       <dependency>
           <groupId>org.projectlombok</groupId>
           <artifactId>lombok</artifactId>
           <version>1.18.12</version>
           <scope>provided</scope>
       </dependency>
   </dependencies>

   <build>
       <plugins>
           <plugin>
               <groupId>org.apache.maven.plugins</groupId>
               <artifactId>maven-jar-plugin</artifactId>
               <configuration>
                   <archive>
                       <manifest>
                           <mainClass>com.pb.jetty.http2.server.Main</mainClass>
                           <addClasspath>true</addClasspath>
                       </manifest>
                   </archive>
               </configuration>
           </plugin>
       </plugins>
   </build>
</project>

Now run the program using NetBeans or maven-command line and hit the url http://localhost:8080/hello-servlet in browser.
You can get source for this project from here. You can directly open the project in NetBeans and run or run it from command line using maven.

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