[SPARK-16122][CORE] Add rest api for job environment

## What changes were proposed in this pull request?

add rest api for job environment.

## How was this patch tested?

existing ut.

Author: uncleGen <hustyugm@gmail.com>

Closes #16949 from uncleGen/SPARK-16122.

core/src/main/scala/org/apache/spark/status/api/v1/ApiRootResource.scala

@@ -199,6 +199,21 @@ private[v1] class ApiRootResource extends ApiRequestContext {
     new VersionResource(uiRoot)
   }
 
+  @Path("applications/{appId}/environment")
+  def getEnvironment(@PathParam("appId") appId: String): ApplicationEnvironmentResource = {
+    withSparkUI(appId, None) { ui =>
+      new ApplicationEnvironmentResource(ui)
+    }
+  }
+
+  @Path("applications/{appId}/{attemptId}/environment")
+  def getEnvironment(
+      @PathParam("appId") appId: String,
+      @PathParam("attemptId") attemptId: String): ApplicationEnvironmentResource = {
+    withSparkUI(appId, Some(attemptId)) { ui =>
+      new ApplicationEnvironmentResource(ui)
+    }
+  }
 }
 
 private[spark] object ApiRootResource {

core/src/main/scala/org/apache/spark/status/api/v1/ApplicationEnvironmentResource.scala

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF 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.apache.spark.status.api.v1
+
+import javax.ws.rs._
+import javax.ws.rs.core.MediaType
+
+import org.apache.spark.ui.SparkUI
+
+@Produces(Array(MediaType.APPLICATION_JSON))
+private[v1] class ApplicationEnvironmentResource(ui: SparkUI) {
+
+  @GET
+  def getEnvironmentInfo(): ApplicationEnvironmentInfo = {
+    val listener = ui.environmentListener
+    listener.synchronized {
+      val jvmInfo = Map(listener.jvmInformation: _*)
+      val runtime = new RuntimeInfo(
+        jvmInfo("Java Version"),
+        jvmInfo("Java Home"),
+        jvmInfo("Scala Version"))
+
+      new ApplicationEnvironmentInfo(
+        runtime,
+        listener.sparkProperties,
+        listener.systemProperties,
+        listener.classpathEntries)
+    }
+  }
+
+}

core/src/main/scala/org/apache/spark/status/api/v1/api.scala

@@ -252,3 +252,14 @@ class AccumulableInfo private[spark](
 
 class VersionInfo private[spark](
   val spark: String)
+
+class ApplicationEnvironmentInfo private[spark] (
+    val runtime: RuntimeInfo,
+    val sparkProperties: Seq[(String, String)],
+    val systemProperties: Seq[(String, String)],
+    val classpathEntries: Seq[(String, String)])
+
+class RuntimeInfo private[spark](
+    val javaVersion: String,
+    val javaHome: String,
+    val scalaVersion: String)