Add Bzlmod support

MODULE.bazel

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+JDK_VERSIONS = ["11", "15", "16", "17"]
+PLATFORMS = ["linux", "macos", "macos_aarch64", "win"]
+
+# Remote JDK repos for those Linux platforms are only defined for JDK 11.
+EXTRA_REMOTE_JDK11_REPOS = [
+    "remotejdk11_linux_aarch64",
+    "remotejdk11_linux_ppc64le",
+    "remotejdk11_linux_s390x",
+]
+
+REMOTE_JDK_REPOS = [("remotejdk" + version + "_" + platform) for version in JDK_VERSIONS for platform in PLATFORMS] + EXTRA_REMOTE_JDK11_REPOS
+
+REMOTE_JAVA_TOOLCHAINS = [("@" + name + "_toolchain_config_repo//:toolchain") for name in REMOTE_JDK_REPOS]
+
+module(
+    name = "rules_java",
+    version = "4.0.0",
+    compatibility_level = 1,
+    toolchains_to_register = [
+        "//toolchains:all",
+        "@local_jdk//:runtime_toolchain_definition",
+    ] + REMOTE_JAVA_TOOLCHAINS,
+)
+
+bazel_dep(name = "bazel_skylib", version = "1.0.3")
+bazel_dep(name = "platforms", version = "0.0.4")
+bazel_dep(name = "rules_cc", version = "0.0.1")
+bazel_dep(name = "rules_proto", version = "4.0.0")
+bazel_dep(name = "rules_python", version = "0.4.0")
+
+toolchains = use_extension("//java:extensions.bzl", "toolchains")
+
+# Declare remote java tools repos
+use_repo(toolchains, "remote_java_tools")
+use_repo(toolchains, "remote_java_tools_linux")
+use_repo(toolchains, "remote_java_tools_windows")
+use_repo(toolchains, "remote_java_tools_darwin")
+
+# Declare local jdk repo
+use_repo(toolchains, "local_jdk")
+
+# Declare all remote jdk toolchain config repos
+[use_repo(toolchains, repo + "_toolchain_config_repo") for repo in REMOTE_JDK_REPOS]
+
+# Dev dependencies
+bazel_dep(name = "rules_pkg", version = "0.5.1", dev_dependency = True)

WORKSPACE.bzlmod

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+# A completely empty WORKSPACE file to replace the original WORKSPACE content

java/extensions.bzl

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+# Copyright 2021 The Bazel Authors. All rights reserved.
+#
+# 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.
+"""Module extensions for rules_java."""
+
+load("//java:repositories.bzl", "java_tools_javac11_repos", "local_jdk_repo", "remote_jdk11_repos", "remote_jdk15_repos", "remote_jdk16_repos", "remote_jdk17_repos")
+
+def _toolchains_impl(ctx):
+    local_jdk_repo()
+    java_tools_javac11_repos()
+    remote_jdk11_repos()
+    remote_jdk15_repos()
+    remote_jdk16_repos()
+    remote_jdk17_repos()
+
+toolchains = module_extension(implementation = _toolchains_impl)