[grid] Add support for configs to be from JSON files

java/server/src/org/openqa/selenium/grid/config/BUILD.bazel

@@ -13,6 +13,7 @@ java_library(
         "//java/server/test/org/openqa/selenium:__subpackages__",
     ],
     deps = [
+        "//java/client/src/org/openqa/selenium/json",
         artifact("com.google.guava:guava"),
         artifact("io.ous:jtoml"),
     ],

java/server/src/org/openqa/selenium/grid/config/JsonConfig.java

@@ -0,0 +1,60 @@
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The SFC licenses this file
+// to you 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 org.openqa.selenium.grid.config;
+
+import org.openqa.selenium.json.Json;
+import org.openqa.selenium.json.JsonException;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+
+import static org.openqa.selenium.json.Json.MAP_TYPE;
+
+public class JsonConfig implements Config {
+
+  private static final Json JSON = new Json();
+  private final Config delegate;
+
+  public JsonConfig(Reader reader) {
+    Objects.requireNonNull(reader, "JSON source must be set.");
+
+    try {
+      delegate = new MapConfig(JSON.toType(reader, MAP_TYPE));
+    } catch (JsonException e) {
+      throw new ConfigException("Unable to parse input", e);
+    }
+  }
+
+  public static Config from(Path path) {
+    try (Reader reader = Files.newBufferedReader(path)) {
+      return new JsonConfig(reader);
+    } catch (IOException e) {
+      throw new ConfigException("Unable to read JSON.", e);
+    }
+  }
+
+  @Override
+  public Optional<List<String>> getAll(String section, String option) {
+    return delegate.getAll(section, option);
+  }
+}

java/server/test/org/openqa/selenium/grid/config/JsonConfigTest.java

@@ -0,0 +1,36 @@
+// Licensed to the Software Freedom Conservancy (SFC) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The SFC licenses this file
+// to you 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 org.openqa.selenium.grid.config;
+
+import org.junit.Test;
+
+import java.io.StringReader;
+import java.util.Optional;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class JsonConfigTest {
+
+  @Test
+  public void shouldUseATableAsASection() {
+    String raw = "{\"cheeses\": {\"selected\": \"brie\"}}";
+    Config config = new JsonConfig(new StringReader(raw));
+
+    assertThat(config.get("cheeses", "selected")).isEqualTo(Optional.of("brie"));
+  }
+}