[SPARK-32467][UI] Avoid encoding URL twice on https redirect

### What changes were proposed in this pull request?

When https is enabled for Spark UI, an HTTP request will be redirected as an encoded HTTPS URL: https://github.com/apache/spark/pull/10238/files#diff-f79a5ead735b3d0b34b6b94486918e1cR312

When we create the redirect url, we will call getRequestURI and getQueryString. Both two methods may return an encoded string. However, we pass them directly to the following URI constructor
```
URI(String scheme, String authority, String path, String query, String fragment)
```
As this URI constructor assumes both path and query parameters are decoded strings, it will encode them again. This makes the redirect URL encoded twice.

This problem is on stage page with HTTPS enabled. The URL of "/taskTable" contains query parameter `order%5B0%5D%5Bcolumn%5D`. After encoded it becomes  `order%255B0%255D%255Bcolumn%255D` and it will be decoded as `order%5B0%5D%5Bcolumn%5D` instead of `order[0][dir]`.  When the parameter `order[0][dir]` is missing, there will be an excetpion from:
https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/status/api/v1/StagesResource.scala#L176
and the stage page fail to load.

To fix the problem, we can try decoding the query parameters before encoding it. This is to make sure we encode the URL

### Why are the changes needed?

Fix a UI issue when HTTPS is enabled

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

A new Unit test + manually test on a cluster

Closes #29271 from gengliangwang/urlEncode.

Authored-by: Gengliang Wang <gengliang.wang@databricks.com>
Signed-off-by: Gengliang Wang <gengliang.wang@databricks.com>

core/src/main/scala/org/apache/spark/ui/JettyUtils.scala

@@ -17,7 +17,7 @@
 
 package org.apache.spark.ui
 
-import java.net.{URI, URL}
+import java.net.{URI, URL, URLDecoder}
 import java.util.EnumSet
 import javax.servlet.DispatcherType
 import javax.servlet.http._
@@ -377,8 +377,7 @@ private[spark] object JettyUtils extends Logging {
         if (baseRequest.isSecure) {
           return
         }
-        val httpsURI = createRedirectURI(scheme, baseRequest.getServerName, securePort,
-          baseRequest.getRequestURI, baseRequest.getQueryString)
+        val httpsURI = createRedirectURI(scheme, securePort, baseRequest)
         response.setContentLength(0)
         response.sendRedirect(response.encodeRedirectURL(httpsURI))
         baseRequest.setHandled(true)
@@ -440,16 +439,34 @@ private[spark] object JettyUtils extends Logging {
     handler.addFilter(holder, "/*", EnumSet.allOf(classOf[DispatcherType]))
   }
 
+  private def decodeURL(url: String, encoding: String): String = {
+    if (url == null) {
+      null
+    } else {
+      URLDecoder.decode(url, encoding)
+    }
+  }
+
   // Create a new URI from the arguments, handling IPv6 host encoding and default ports.
-  private def createRedirectURI(
-      scheme: String, server: String, port: Int, path: String, query: String) = {
+  private def createRedirectURI(scheme: String, port: Int, request: Request): String = {
+    val server = request.getServerName
     val redirectServer = if (server.contains(":") && !server.startsWith("[")) {
       s"[${server}]"
     } else {
       server
     }
     val authority = s"$redirectServer:$port"
-    new URI(scheme, authority, path, query, null).toString
+    val queryEncoding = if (request.getQueryEncoding != null) {
+      request.getQueryEncoding
+    } else {
+      // By default decoding the URI as "UTF-8" should be enough for SparkUI
+      "UTF-8"
+    }
+    // The request URL can be raw or encoded here. To avoid the request URL being
+    // encoded twice, let's decode it here.
+    val requestURI = decodeURL(request.getRequestURI, queryEncoding)
+    val queryString = decodeURL(request.getQueryString, queryEncoding)
+    new URI(scheme, authority, requestURI, queryString, null).toString
   }
 
   def toVirtualHosts(connectors: String*): Array[String] = connectors.map("@" + _).toArray

core/src/test/scala/org/apache/spark/ui/UISuite.scala

@@ -262,6 +262,27 @@ class UISuite extends SparkFunSuite {
     }
   }
 
+  test("SPARK-32467: Avoid encoding URL twice on https redirect") {
+    val (conf, securityMgr, sslOptions) = sslEnabledConf()
+    val serverInfo = JettyUtils.startJettyServer("0.0.0.0", 0, sslOptions, conf)
+    try {
+      val serverAddr = s"http://localhost:${serverInfo.boundPort}"
+
+      val (_, ctx) = newContext("/ctx1")
+      serverInfo.addHandler(ctx, securityMgr)
+
+      TestUtils.withHttpConnection(new URL(s"$serverAddr/ctx%281%29?a%5B0%5D=b")) { conn =>
+        assert(conn.getResponseCode() === HttpServletResponse.SC_FOUND)
+        val location = Option(conn.getHeaderFields().get("Location"))
+          .map(_.get(0)).orNull
+        val expectedLocation = s"https://localhost:${serverInfo.securePort.get}/ctx(1)?a[0]=b"
+        assert(location == expectedLocation)
+      }
+    } finally {
+      stopServer(serverInfo)
+    }
+  }
+
   test("http -> https redirect applies to all URIs") {
     val (conf, securityMgr, sslOptions) = sslEnabledConf()
     val serverInfo = JettyUtils.startJettyServer("0.0.0.0", 0, sslOptions, conf)