chore: use Joiner and copy of map when setting properties

Author: keshavdandeva

google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/jdbc/BigQueryJdbcUrlUtility.java

@@ -665,9 +665,6 @@ static String parseUriProperty(String uri, String property) {
    * @throws BigQueryJdbcRuntimeException if an unknown property is found or the URL is malformed.
    */
   static Map<String, String> parseUrl(String url) {
-    if (url == null) {
-      return Collections.emptyMap();
-    }
     return PARSE_CACHE.computeIfAbsent(url, BigQueryJdbcUrlUtility::parseUrlInternal);
   }
 

google-cloud-bigquery-jdbc/src/main/java/com/google/cloud/bigquery/jdbc/DataSource.java

@@ -17,6 +17,8 @@
 package com.google.cloud.bigquery.jdbc;
 
 import com.google.cloud.bigquery.exception.BigQueryJdbcException;
+import com.google.common.base.Joiner;
+import com.google.common.collect.ImmutableMap;
 import java.io.PrintWriter;
 import java.sql.Connection;
 import java.sql.DriverManager;
@@ -351,14 +353,7 @@ private String serializeMap(Map<String, String> map) {
     if (map == null || map.isEmpty()) {
       return "";
     }
-    StringBuilder sb = new StringBuilder();
-    for (Map.Entry<String, String> entry : map.entrySet()) {
-      if (sb.length() > 0) {
-        sb.append(",");
-      }
-      sb.append(entry.getKey()).append("=").append(entry.getValue());
-    }
-    return sb.toString();
+    return Joiner.on(",").withKeyValueSeparator("=").join(map);
   }
 
   @Override
@@ -451,7 +446,7 @@ public String getKmsKeyName() {
   }
 
   public void setQueryProperties(Map<String, String> queryProperties) {
-    this.queryProperties = queryProperties;
+    this.queryProperties = queryProperties == null ? null : ImmutableMap.copyOf(queryProperties);
   }
 
   public Map<String, String> getQueryProperties() {
@@ -711,7 +706,7 @@ public Map<String, String> getLabels() {
   }
 
   public void setLabels(Map<String, String> labels) {
-    this.labels = labels;
+    this.labels = labels == null ? null : ImmutableMap.copyOf(labels);
   }
 
   public String getRequestReason() {