Reference


Table of Contents


Installation

Cettia Java Platform requires Java 7 and is distributed through Maven Central.

  • To run application on platform

Generally speaking, having application run on the specific platform means to feed one or both of ServerHttpExchange and ServerWebSocket into the application which are produced by the specific platform or framework using the corresponding bridge module. How to varies for each platform or framework. See Platform and Platform on platform section.

  • To write application running on platform

An application running on platform is a collection of actions that consumes resources like ServerHttpExchange and ServerWebSocket. Therefore, application should expose those actions to receive them. To handle HTTP exchange and WebSocket, see HTTP and Websocket respectively.


Platform

Platform stands for lietrally platform where application runs by facilitating dealing with HTTP exchange and WebSocket like full-stack web application framework and raw web server.

To bridge application and platform, a module called bridge is required which transforms the underlying platform’s resources representing HTTP exchange and WebSocket into ServerHttpExchange and ServerWebSocket. The following bridges are available.

Platform HTTP WebSocket
Atmosphere 2
Grizzly 2
Java WebSocket API 1  
Netty 4
Play 2
Servlet 3  
Vert.x 2

Atmosphere 2

Atmosphere 2 is a platform to use Servlet 3 and Java WebSocket API 1 together in more comfortable way.

Note

  • Requires Atmosphere 2.2 and later.
  • Servlet can’t detect disconnection so that ServerHttpExchange’s onclose doesn’t work.

Example

Add the following dependency to your build or include it on your classpath manually.

<dependency>
    <groupId>io.cettia.platform</groupId>
    <artifactId>cettia-platform-bridge-atmosphere2</artifactId>
    <version>1.0.0-Alpha1</version>
</dependency>

To bridge application and Atmosphere, you should register a servlet of CettiaAtmosphereServlet. When registering servlet, you must set asyncSupported to true and set a init param, org.atmosphere.cpr.AtmosphereInterceptor.disableDefaults, to true.

@WebListener
public class Bootstrap implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent event) {
        // Your application
        Action<ServerHttpExchange> httpAction = http -> {};
        Action<ServerWebSocket> websocketAction = ws -> {};
        
        ServletContext context = event.getServletContext();
        Servlet servlet = new CettiaAtmosphereServlet().onhttp(httpAction).onwebsocket(websocketAction);
        ServletRegistration.Dynamic reg = context.addServlet(CettiaAtmosphereServlet.class.getName(), servlet);
        reg.setAsyncSupported(true);
        reg.setInitParameter(ApplicationConfig.DISABLE_ATMOSPHEREINTERCEPTOR, Boolean.TRUE.toString());
        reg.addMapping("/cettia");
    }

    @Override
    public void contextDestroyed(ServletContextEvent sce) {}
}

Grizzly 2

Grizzly 2 is a framework to help developers to take advantage of the Java™ NIO API.

Example

Add the following dependency to your build or include it on your classpath manually.

<dependency>
    <groupId>io.cettia.platform</groupId>
    <artifactId>cettia-platform-bridge-grizzly2</artifactId>
    <version>1.0.0-Alpha1</version>
</dependency>

And then, you should register an instance of CettiaHttpHandler to deal with HTTP exchange and an instance of CettiaWebSocketApplication to deal with WebSocket.

public class Bootstrap {
    public static void main(String[] args) throws Exception {
        // Your application
        Action<ServerHttpExchange> httpAction = http -> {};
        Action<ServerWebSocket> websocketAction = ws -> {};
        
        HttpServer httpServer = HttpServer.createSimpleServer();
        ServerConfiguration config = httpServer.getServerConfiguration();
        config.addHttpHandler(new CettiaHttpHandler().onhttp(httpAction), "/cettia");
        NetworkListener listener = httpServer.getListener("grizzly");
        listener.registerAddOn(new WebSocketAddOn());
        WebSocketEngine.getEngine().register("", "/cettia", new CettiaWebSocketApplication().onwebsocket(websocketAction));
        httpServer.start();
        System.in.read();
    }
}

Java WebSocket API 1

Java WebSocket API 1 (JWA) from Java EE 7.

Example

Add the following dependency to your build or include it on your classpath manually.

<dependency>
    <groupId>io.cettia.platform</groupId>
    <artifactId>cettia-platform-bridge-jwa1</artifactId>
    <version>1.0.0-Alpha1</version>
</dependency>

Then, you should register an endpoint of CettiaServerEndpoint. Note that each WebSocket session is supposed to have each endpoint instance so an instance of CettiaServerEndpoint can’t be shared among ServerEndpointConfigs.

public class Bootstrap implements ServerApplicationConfig {
    @Override
    public Set<ServerEndpointConfig> getEndpointConfigs(Set<Class<? extends Endpoint>> _) {
        // Your application
        Action<ServerWebSocket> websocketAction = ws -> {};
        
        ServerEndpointConfig config = ServerEndpointConfig.Builder.create(CettiaServerEndpoint.class, "/cettia")
        .configurator(new Configurator() {
            @Override
            public <T> T getEndpointInstance(Class<T> endpointClass) throws InstantiationException {
                return endpointClass.cast(new CettiaServerEndpoint().onwebsocket(websocketAction));
            }
        })
        .build();
        return Collections.singleton(config);
    }

    @Override
    public Set<Class<?>> getAnnotatedEndpointClasses(Set<Class<?>> scanned) {
        return null;
    }
}

With this bridge, you have no way to handle HTTP resource unless your web server implements Servlet 3 as well as Java WebSocket API 1 like Tomcat or Jetty. If you have such server, see an example demonstrating how to use Java WebSocket API 1 bridge and Servlet 3 bridge together on the same server.

Netty 4

Netty 4 is an asynchronous event-driven network application framework.

Example

Add the following dependency to your build or include it on your classpath manually.

<dependency>
    <groupId>io.cettia.platform</groupId>
    <artifactId>cettia-platform-bridge-netty4</artifactId>
    <version>1.0.0-Alpha1</version>
</dependency>

To bridge application and Netty, you should register a handler of CettiaServerCodec. When configuring handlers, you must add HttpServerCodec in front of the handler.

public class Bootstrap {
    public static void main(String[] args) throws Exception {
        // Your application
        Action<ServerHttpExchange> httpAction = http -> {};
        Action<ServerWebSocket> websocketAction = ws -> {};
        
        EventLoopGroup bossGroup = new NioEventLoopGroup();
        EventLoopGroup workerGroup = new NioEventLoopGroup();
        try {
            ServerBootstrap bootstrap = new ServerBootstrap();
            bootstrap.group(bossGroup, workerGroup)
            .channel(NioServerSocketChannel.class)
            .childHandler(new ChannelInitializer<SocketChannel>() {
                @Override
                public void initChannel(SocketChannel ch) {
                    ChannelPipeline pipeline = ch.pipeline();
                    pipeline.addLast(new HttpServerCodec())
                    .addLast(new CettiaServerCodec() {
                        @Override
                        protected boolean accept(HttpRequest req) {
                            return URI.create(req.getUri()).getPath().equals("/cettia");
                        }
                    }
                    .onhttp(httpAction)
                    .onwebsocket(websocketAction));
                }
            });
            Channel channel = bootstrap.bind(8080).sync().channel();
            channel.closeFuture().sync();
        } finally {
            workerGroup.shutdownGracefully();
            bossGroup.shutdownGracefully();
        }
    }
}

Play 2

Play framework 2 is a high velocity web framework for Java and Scala.

Note

  • With the current implementation written in Play Java API, it’s not possible to send and receive text frame and binary frame together via a WebSocket connection. It will be fixed by rewriting implementation in Play Scala API. cettia-java-platform#3

Example

Add the following dependency to your build.sbt or include it on your classpath manually.

libraryDependencies ++= Seq(
  "io.cettia.platform" % "cettia-platform-bridge-play2" % "1.0.0-Alpha1"
)

Then, write entry point for HTTP exchange and WebSocket extending Controller. A helper class will be introduced solving the above notes.

public class Bootstrap extends Controller {
    // Your application
    static Action<ServerHttpExchange> httpAction = http -> {};
    static Action<ServerWebSocket> websocketAction = ws -> {};

    @BodyParser.Of(BodyParser.Raw.class)
    public static Promise<Result> http() {
        PlayServerHttpExchange http = new PlayServerHttpExchange(request(), response());
        httpAction.on(http);
        return http.result();
    }
    
    public static WebSocket<String> websocket() {
        final Http.Request request = request();
        return new WebSocket<String>() {
            @Override
            public void onReady(WebSocket.In<String> in, WebSocket.Out<String> out) {
                websocketAction.on(new PlayServerWebSocket(request, in, out));
            }
        };
    }
}

Play doesn’t allow to share URI between HTTP and WebSocket entry points. Instead of routes, write Global.scala in the default package and override onRouteRequest. It’s not easy to do that in Java, if any. Note that this uses internal API that has broken even in patch release. I’ve confirmed the following code works in 2.2.2 and 2.3.2.

import io.cettia.example.platform.play2.{Bootstrap => T}

import play.api.GlobalSettings
import play.api.mvc._
import play.core.j._

object Global extends GlobalSettings {
  override def onRouteRequest(req: RequestHeader): Option[Handler] = {
    if (req.path == "/cettia") {
      if (req.method == "GET" && req.headers.get("Upgrade").exists(_.equalsIgnoreCase("websocket"))) {
        Some(JavaWebSocket.ofString(T.websocket))
      } else {
        Some(new JavaAction {
          val annotations = new JavaActionAnnotations(classOf[T], classOf[T].getMethod("http"))
          val parser = annotations.parser
          def invocation = T.http
        })
      }
    } else {
      super.onRouteRequest(req)
    }
  }
}

Servlet 3

Servlet 3.0 from Java EE 6 and Servlet 3.1 from Java EE 7.

Note

  • Servlet can’t detect disconnection so that ServerHttpExchange’s onclose doesn’t work.

Example

Add the following dependency to your build or include it on your classpath manually.

<dependency>
    <groupId>io.cettia.platform</groupId>
    <artifactId>cettia-platform-bridge-servlet3</artifactId>
    <version>1.0.0-Alpha1</version>
</dependency>

To bridge application and Servlet, you should register a servlet of CettiaServlet. When registering servlet, you must set asyncSupported to true.

@WebListener
public class Bootstrap implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent event) {
        // Your application
        Action<ServerHttpExchange> httpAction = http -> {};
        
        ServletContext context = event.getServletContext();
        Servlet servlet = new CettiaServlet().onhttp(httpAction);
        ServletRegistration.Dynamic reg = context.addServlet(CettiaServlet.class.getName(), servlet);
        reg.setAsyncSupported(true);
        reg.addMapping("/cettia");
    }
    
    @Override
    public void contextDestroyed(ServletContextEvent sce) {}
}

With this bridge, you have no way to handle WebSocket resource unless your web server implements Java WebSocket API 1 as well as Servlet 3 like Tomcat or Jetty. If you have such server, see an example demonstrating how to use Servlet 3 bridge and Java WebSocket API 1 bridge together on the same server.

Vert.x 2

Vert.x 2 is a lightweight, high performance application platform for the JVM

Example

Add the following dependency to your build or include it on your classpath manually.

<dependency>
    <groupId>io.cettia.platform</groupId>
    <artifactId>cettia-platform-bridge-vertx2</artifactId>
    <version>1.0.0-Alpha1</version>
</dependency>

You should register a handler of CettiaRequestHandler to handle HTTP exchange and CettiaWebSocketHandler to handle WebSocket.

public class Bootstrap extends Verticle {
    @Override
    public void start() {
        // Your application
        Action<ServerHttpExchange> httpAction = http -> {};
        Action<ServerWebSocket> websocketAction = ws -> {};
        
        HttpServer httpServer = vertx.createHttpServer();
        RouteMatcher httpMatcher = new RouteMatcher();
        httpMatcher.all("/cettia", new CettiaRequestHandler().onhttp(httpAction));
        httpServer.requestHandler(httpMatcher);
        final CettiaWebSocketHandler websocketHandler = new CettiaWebSocketHandler().onwebsocket(websocketAction);
        httpServer.websocketHandler(new Handler<org.vertx.java.core.http.ServerWebSocket>() {
            @Override
            public void handle(org.vertx.java.core.http.ServerWebSocket socket) {
                if (socket.path().equals("/cettia")) {
                    websocketHandler.handle(socket);
                }
            }
        });
        httpServer.listen(8080);
    }
}

Platform on platform

Some platform, A, is based on the other platform, B, and allows to deal with the underlying platform, B, so that if a bridge for B is available, without creating an additional bridge for A, it’s possible to run application on A through B.

The general pattern is to share an application instance between the platform and the underlying platform using static keyword, sharing application holder or adopting dependency injection.

JAX-RS 2

JAX-RS 2 from Java EE 7. JAX-RS allows to deploy JAX-RS resources to several servers, and one of them is Servlet. That means, you can run application written in JAX-RS through Servlet. The same approach may be applied to JAX-RS 1. Example.


HTTP

To write HTTP application, add the following dependency to your build or include it on your classpath manually.

<dependency>
    <groupId>io.cettia.platform</groupId>
    <artifactId>cettia-platform-http</artifactId>
    <version>1.0.0-Alpha1</version>
</dependency>

ServerHttpExchange

It represents a server-side HTTP request-response exchange and is given when request headers is read. Note that is is not thread safe.

Request properties

These are read only and might not be available in some platforms after onend or onclose.

URI

A request URI used to connect. To work with URI parts, use java.net.URI or something like that.

URI.create(http.uri()).getQuery();
Method

A name of the request method.

switch (http.method()) {
    case "GET":
    case "POST":
        // GET or POST
        break;
}
Headers

Request headers.

for (String name : http.headerNames()) {
    String value = http.header(name);
}

Reading request

read initiates reading the request body and a read chunk is passed to onchunk. Whether to read as text or binary is determined by the content-type request header in conformance with RFC 2616. If the header starts with text/, chunk will be read as text following the specified charset in the header (ISO-8859-1 if not specified) and passed as String. If not, chunk will be read as binary and passed as ByteBuffer. But you can force the request to how to read the body using readAsText and readAsBinary. Finally, the request is fully read. Then, onend is fired which is the end of the request.

Stringbuilder bodyBuilder = new Stringbuilder();
http.onchunk(new Action<String>() {
    @Override
    public void on(String chunk) {
        bodyBuilder.append(chunk);
    }
})
.onend(new VoidAction() {
    @Override
    public void on() {
        String body = bodyBuilder.toString();
        // Your logic here
    }
})
.read();

For convenience, onbody is provided which allows to receive the whole request body. However, note that if body is quite big it will drain memory in an instant.

http.onbody(new Action<String>() {
    @Override
    public void on(String body) {
        // Your logic here
    }
})
.read();

read and its variant methods should be called after adding chunk and body event handlers. In case where the underlying platform can’t read body asynchronously, it emulates non-blocking IO by spwaning a separate thread to read it.

Response properties

These are write only and not modifiable after the write of first chunk.

Status

A HTTP Status code for response.

http.setStatus(HttpStatus.NOT_IMPLEMENTED);
Headers

Response headers.

http.setHeader("content-type", "text/javascript; charset=utf-8");

Writing response

write accepts a text chunk as String and a binary chunk as ByteBuffer and writes it to the response body. Each response must be completed by end after writing all properties and chunks or even if there is nothing to write. It’s the end of the response. In case of text chunk, if there is no specified charset parameter in the content-type response header or write, then ISO-8859-1 is used.

http.write("chunk").end();

For convenience, end accepts chunk like write. The below code is the same with the above one.

http.end("chunk");

And, on the end of the response, onfinish is fired.

http.onfinish(new VoidAction() {
    @Override
    public void on() {
        // Your logic here
    }
})

Error handling

Any error happening in request-response exchange is propagated to actions added via onerror with Throwable in question. Now Throwable thrown by the underlying platform are provided directly.

http.onerror(new Action<Throwable>() {
    @Override
    public void on(Throwable error) {
        // Your logic here
    }
});

When the underlying connection is terminated for some reason like network or protocol error, actions added via onclose are executed. After this event, exchange should be not used.

http.onclose(new VoidAction() {
    @Override
    public void on() {
        // Your logic here
    }
});

WebSocket

To write WebSocket application, add the following dependency to your build or include it on your classpath manually.

<dependency>
    <groupId>io.cettia.platform</groupId>
    <artifactId>cettia-platform-websocket</artifactId>
    <version>1.0.0-Alpha1</version>
</dependency>

ServerWebSocket

It represents a server-side WebSocket connection and is given when WebSocket is opened. Note that is is not thread safe.

Properties

These are read only and might not be available in some platforms after onclose.

URI

A request URI used to connect. It comes from handshake request so doesn’t start with ws or wss protocol. To work with URI parts, use java.net.URI or something like that.

URI.create(ws.uri()).getQuery();

Receiving frame

Text frame is passed to ontext as String and binary frame is passed to onbinary as ByteBuffer. It’s possible to receive both type of message through a single connection.

ws.ontext(new Action<String>() {
    @Override
    public void on(String data) {
        // Your logic here
    }
})
.onbinary(new Action<ByteBuffer>() {
    @Override
    public void on(ByteBuffer data) {
        // Your logic here
    }
});

Sending frame

send accepts a text frame as String and a binary frame as ByteBuffer and sends it through the connection. It’s possible to send both type of message through a single connection.

ws.send("message");

Closing connection

close closes the connection.

ws.close();

When the connection has been closed for any reason, normally or abnormally, close event handlers added via onclose are executed. It’s the end of WebSocket. After this event, WebSocket should be not used.

ws.onclose(new VoidAction() {
    @Override
    public void on() {
        // Your logic here
    }
});

Error handling

Any error happening in this connection is propagated to actions added via onerror with Throwable in question. Now Throwable thrown by the underlying platform are provided directly.

ws.onerror(new Action<Throwable>() {
    @Override
    public void on(Throwable error) {
        // Your logic here
    }
});