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HTTP with Java 8 Philipp Schirmacher

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Building HTTP servers with Java...

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...should be awesome!

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But it’s not.

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servlet api

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servlet containers

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annotations

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@GET @Path("/my-path") public Response foo(@QueryParam("id") Integer id) { return Response.ok().build(); }

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poor HTML integration

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$ grep -ic controller RFC2616 > 0

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$ curl -i playframework.com > HTTP/1.1 200 OK

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$ curl -i -XDELETE playframework.com > HTTP/1.1 404 Not Found

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content negotiation

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conditional requests

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$ curl myresource -i > HTTP/1.1 200 OK ETag: 2 $ curl myresource -i -H’If-None-Match: 2’ > HTTP/1.1 304 Not Modified $ curl myresource -i -H’If-Match: 1’ -XPOST --data foo=bar > HTTP/1.1 412 Precondition Failed

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> async, no servlets, no containers > just plain Java > proper HTTP support

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github.com/pschirmacher/webster

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https://github.com/basho/webmachine/wiki/Diagram

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https://github.com/basho/webmachine/wiki/Diagram

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https://github.com/basho/webmachine/wiki/Diagram

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https://github.com/basho/webmachine/wiki/Diagram

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https://github.com/basho/webmachine/wiki/Diagram

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graph + resource + request = response https://github.com/basho/webmachine/wiki/Diagram

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public interface Node extends BiFunction> { }

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3

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3 .thenApply(inc)

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3 .thenApply(inc) 4

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3 .thenApply(incFuture)

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3 .thenApply(incFuture) 3 4

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3 .thenCompose(incFuture)

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3 .thenCompose(incFuture) 4

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public interface Node extends BiFunction> { }

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public class Decision implements Node { private final BiFunction> decision; private final Node onTrue; private final Node onFalse; @Override public CompletableFuture apply(Resource resource, Request request) { return decision .apply(resource, request) .thenCompose(decisionResult -> decisionResult ? onTrue.apply(resource, request) : onFalse.apply(resource, request)); } }

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public class Decision implements Node { private final BiFunction> decision; private final Node onTrue; private final Node onFalse; @Override public CompletableFuture apply(Resource resource, Request request) { return decision .apply(resource, request) .thenCompose(decisionResult -> decisionResult ? onTrue.apply(resource, request) : onFalse.apply(resource, request)); } public static interface Fn extends BiFunction> { } }

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public class Completion implements Node { private final BiFunction> completion; @Override public CompletableFuture apply(Resource resource, Request request) { // logging return completion.apply(resource, request); } public static interface Fn extends BiFunction> { } }

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public class Action implements Node { private final BiFunction> action; private final Node then; @Override public CompletableFuture apply(Resource resource, Request request) { return action.apply(resource, request) .thenCompose(ignored -> then.apply(resource, request)); } public static interface Fn extends BiFunction> { } }

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public static Decision.Fn isMethodAllowed = (r, req) -> CompletableFuture.completedFuture( r.allowedMethods().contains(req.method()));

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public static Completion.Fn methodNotAllowed = (r, req) -> { String allow = r.allowedMethods().stream().collect(Collectors.joining(", ")); Map headers = new HashMap<>(); headers.put("Allow", allow); return CompletableFuture.completedFuture(new Response(405, headers)); };

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public static Action.Fn doPost = (r, req) -> r.onPost(req);

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public static Node everythingFine = ...; public static Node decision = new Decision(isMethodAllowed, everythingFine, new Completion(methodNotAllowed));

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public static Node decisionTree = decide(isMethodAllowed) .onTrue(...) .onFalse(complete(methodNotAllowed))

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public static Node contentNegotiation = decide(acceptExists) .onTrue(decide(acceptableMediaTypeAvailable) .onTrue(existingResourceDecision) .onFalse(complete(notAcceptable))) .onFalse(existingResourceDecision);

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public static Node handlePost = decide(isPostForbidden) .onTrue(complete(forbidden)) .onFalse(decide(isPostValid) .onTrue(act(doPost).andThen(decide(isRedirect) .onTrue(complete(seeOther)) .onFalse(decide(isNewResource) .onTrue(complete(created)) .onFalse(entityOrNoContent)))) .onFalse(complete(badRequest)));

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HTTP logic app resources routing

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public class Route implements Function> { private final Function> handler; private final String pattern; @Override public CompletableFuture apply(Request request) { Optional routeMatch = matchFor(request); if (!routeMatch.isPresent()) { throw new IllegalArgumentException("route doesn't match"); } else { return handler.apply(requestWithPathParams(request, routeMatch.get())); } } public boolean matches(Request request) { return matchFor(request).isPresent(); } } public Route createRoute(String pattern, Resource resource, Node decisionTree) { return new Route(pattern, request -> decisionTree.apply(resource, request)); }

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public class RoutingTable implements Function> { private final List routes; public RoutingTable(List routes) { this.routes = routes; } @Override public CompletableFuture apply(Request request) { Optional route = routes.stream().filter(r -> r.matches(request)).findFirst(); return route.isPresent() ? route.get().apply(request) : CompletableFuture.completedFuture(new Response(404)); } }

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public class App { public static void main(String[] args) throws Exception { RoutingTable routingTable = routingTable() .withRoute(from("/").toResource(new Home())) .withRoute(from("/computers").toResource(new Computers())) .withRoute(from("/computer_new").toResource(new ComputerCreate())) .withRoute(from("/computer/:id").toResource(new ComputerEdit())) .withRoute(from("/assets/*").toResource(new AssetsResource())) .build(); new Server().run(routingTable); } }

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public interface Resource { default CompletableFuture> expires(Request request) { return CompletableFuture.completedFuture(Optional.empty()); } default CompletableFuture> etag(Request request) { return CompletableFuture.completedFuture(Optional.empty()); } default CompletableFuture onPost(Request request) { return CompletableFuture.completedFuture(null); } default Set supportedMediaTypes() { return Collections.singleton("text/plain"); } default Set allowedMethods() { return Collections.singleton("GET"); } ... CompletableFuture doesRequestedResourceExist(Request request); CompletableFuture entity(Request request); }

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public class HelloWorld implements Resource { @Override public CompletableFuture doesRequestedResourceExist(Request request) { return CompletableFuture.completedFuture(true); } @Override public CompletableFuture entity(Request request) { return CompletableFuture.completedFuture("hello world"); } }

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public class HelloWorld implements Resource { @Override public CompletableFuture doesRequestedResourceExist(Request request) { return CompletableFuture.completedFuture(true); } @Override public CompletableFuture entity(Request request) { return CompletableFuture.completedFuture("hello world"); } @Override public CompletableFuture> etag(Request request) { return CompletableFuture.completedFuture(Optional.of("1")); } } $ curl localhost:8080/helloworld -i -H’If-None-Match: 1’ > HTTP/1.1 304 Not Modified

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public interface Parsable { I value(); default O parse(Function parser) { return parser.apply(value()); } } public class ValueSupplier implements Parsable { private final T value; public ValueSupplier(T value) { this.value = value; } @Override public T value() { return value; } }

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public class Request { private final Map headers; private final Map> requestParams; public ValueSupplier> header(String name) { return new ValueSupplier<>(Optional.ofNullable(headers.get(name))); } public ValueSupplier> param(String name) { ... } } Optional id = request.param("id").parse(Parsers.asLong); int page = request.param("page").parse(Parsers.asInt).orElse(0); boolean hasIfMatch = request.header("If-Match").value().isPresent(); Map form = request.body().parse(Parsers.asForm); int i = request.param("id").parse(optionalString -> Integer.valueOf(optionalString.orElse("0")));

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demo

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> restrictive > proper HTTP support > async, no magic anywhere > Java 8 does make a difference

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Thanks! Questions? github.com/pschirmacher/webster

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