Add j2cl demo

.docker/Dockerfile

@@ -7,6 +7,16 @@ RUN npm install jsvu wasm-opt wasm-pack -g \
  && dpkg -i tinygo_0.23.0_amd64.deb \
  && rm tinygo_0.23.0_amd64.deb
 
+RUN apt-get update && export DEBIAN_FRONTEND=noninteractive \
+    && curl -fsSL https://storage.googleapis.com/www.bazel.build/bazel-release.pub.gpg | gpg --dearmor > bazel-archive-keyring.gpg \
+    && mv bazel-archive-keyring.gpg /usr/share/keyrings/ \
+    && echo "deb [arch=amd64 signed-by=/usr/share/keyrings/bazel-archive-keyring.gpg] https://storage.googleapis.com/bazel-apt stable jdk1.8" > /etc/apt/sources.list.d/bazel.list
+
+RUN apt-get update && apt-get install bazel-5.1.0 && ln -s /usr/bin/bazel-5.1.0 /usr/bin/bazel
+
+RUN curl -fsSL https://github.com/WebAssembly/binaryen/releases/download/version_108/binaryen-version_108-x86_64-linux.tar.gz | tar -xzf - \
+    && (cd binaryen-version_108; cp -rf * /usr) && rm -rf binaryen*
+
 USER gitpod
 
 RUN rustup target add wasm32-wasi wasm32-unknown-unknown \

java/browser-hello-world/.gitignore

@@ -0,0 +1 @@
+bazel-*

java/browser-hello-world/README.md

@@ -0,0 +1,9 @@
+# Java Implementation of WASM using J2CL
+
+This sample demonstrates how to use [j2cl](https://github.com/google/j2cl) to implement a WASM function in Java and call it from the browser on port 8000.
+
+To launch the browser (you need Chrome unstable):
+
+```
+$ google-chrome-unstable --js-flags="--experimental-wasm-typed-funcref  --experimental-wasm-gc --experimental-wasm-eh"
+```

java/browser-hello-world/WORKSPACE

@@ -0,0 +1,27 @@
+workspace(name = "com_google_j2cl_samples_helloworld")
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+    name = "com_google_elemental2",
+    strip_prefix = "elemental2-1.1.0",
+    url = "https://github.com/google/elemental2/archive/1.1.0.zip",
+)
+
+load("@com_google_elemental2//build_defs:repository.bzl", "load_elemental2_repo_deps")
+load_elemental2_repo_deps()
+
+load("@com_google_elemental2//build_defs:workspace.bzl", "setup_elemental2_workspace")
+setup_elemental2_workspace()
+
+# Load j2cl repository
+http_archive(
+    name = "com_google_j2cl",
+    strip_prefix = "j2cl-master",
+    urls = ["https://github.com/google/j2cl/archive/refs/heads/master.zip"],
+)
+
+load("@com_google_j2cl//build_defs:repository.bzl", "load_j2cl_repo_deps")
+load_j2cl_repo_deps()
+
+load("@com_google_j2cl//build_defs:rules.bzl", "setup_j2cl_workspace")
+setup_j2cl_workspace()

java/browser-hello-world/run.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+
+set -ex
+
+bazel run src/main/java/com/google/j2cl/samples/wasm:jsapp_dev_server

java/browser-hello-world/src/main/java/com/google/j2cl/samples/wasm/BUILD

@@ -0,0 +1,70 @@
+# Sample for J2WASM copied from https://github.com/google/j2cl.
+#
+# Note that J2WASM is experimental and it is NOT production ready.
+#
+# It is mostly developed to help with the evolution of WASM GC specification and
+# what is released externally here is minimal working version to provide .wat files
+# for community experimentation and it doesn't reflect final workings of the product
+# nor the WASM spec.
+
+load("@io_bazel_rules_closure//closure:defs.bzl", "closure_js_library")
+load(
+    "@com_google_j2cl//build_defs:rules.bzl",
+    "j2cl_application",
+    "j2wasm_application",
+    "j2wasm_library",
+)
+
+package(licenses = ["notice"])
+
+# This is the bazel target that compiles our J2WASM library.
+# Since J2WASM currently does global compilation this only serves as a way
+# to collect sources and byte code required for j2wasm_application compilation.
+j2wasm_library(
+    name = "helloworld",
+    srcs = glob(["*.java"]),
+)
+
+# This is the bazel target that compiles and optimizes whole J2WASM app.
+# It provides couple of convenient targets:
+#  :app produces the app.wat and app.wasm that could be used for production.
+#  :app_dev produces app_dev.wat and app_dev.wasm as development version
+#
+# e.g.:
+#   $ (cd j2cl; bazel build src/main/java/com/google/j2cl/samples/wasm:app)
+#
+# Note that for .wat files (wasm binary output) to be available, you would
+# need to have a recent version of binaryen available in your path.
+j2wasm_application(
+    name = "app",
+    entry_points = [r"com\.google\.j2cl\.samples\.wasm\.HelloWorld\.getHelloWorld"],
+    deps = [":helloworld"],
+)
+
+# Below is an example of the JS wiring of the wasm app
+
+closure_js_library(
+    name = "hellojs",
+    srcs = glob(["*.js"]),
+    lenient = True,
+    deps = ["@com_google_j2cl//:j2wasm_js"],
+)
+
+# This is the bazel target that serves your J2WASM app.
+#
+# Give it a try:
+#   $ (cd j2cl; bazel run src/main/java/com/google/j2cl/samples/wasm:jsapp_dev_server)
+#
+# To launch the browser (use unstable):
+#
+# $ google-chrome-unstable --js-flags="--experimental-wasm-typed-funcref  --experimental-wasm-gc --experimental-wasm-eh"
+#
+j2cl_application(
+    name = "jsapp",
+    entry_points = ["entry"],
+    extra_dev_resources = [
+        ":app.wasm",
+    ],
+    deps = [":hellojs"],
+    dev_server_port = "8000",
+)

java/browser-hello-world/src/main/java/com/google/j2cl/samples/wasm/HelloWorld.java

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2021 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package com.google.j2cl.samples.wasm;
+
+import javaemul.internal.WasmExtern;
+
+/** A simple hello world example. */
+public class HelloWorld {
+  public static WasmExtern getHelloWorld() {
+    return "Hello from Java!".toJsString();
+  }
+}

java/browser-hello-world/src/main/java/com/google/j2cl/samples/wasm/hello.js

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2021 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+goog.module('entry');
+
+const j2wasm = goog.require('j2wasm');
+
+j2wasm.instantiateStreaming('app.wasm').then((instance) => {
+  document.body.innerText = instance.exports.getHelloWorld();
+}, (err) => {
+  document.body.style.color = 'red';
+  document.body.innerText = `Failed to load wasm: ${err}`;
+  // rethrow so it also bubbles up to the console.
+  throw err;
+});