add SHOW_DATABASE_COMMAND_ENCODED constant

Author: shanexu

src/main/java/org/influxdb/impl/InfluxDBImpl.java

@@ -50,6 +50,9 @@
 public class InfluxDBImpl implements InfluxDB {
   static final okhttp3.MediaType MEDIA_TYPE_STRING = MediaType.parse("text/plain");
 
+  private static final String SHOW_DATABASE_COMMAND_ENCODED =
+          UrlEscapers.urlFormParameterEscaper().escape("SHOW DATABASES");
+
   private final InetAddress hostAddress;
   private final String username;
   private final String password;
@@ -362,7 +365,7 @@ public void deleteDatabase(final String name) {
   @Override
   public List<String> describeDatabases() {
     QueryResult result = execute(this.influxDBService.query(this.username,
-                                                            this.password, "SHOW+DATABASES"));
+                                                            this.password, SHOW_DATABASE_COMMAND_ENCODED));
     // {"results":[{"series":[{"name":"databases","columns":["name"],"values":[["mydb"]]}]}]}
     // Series [name=databases, columns=[name], values=[[mydb], [unittest_1433605300968]]]
     List<List<Object>> databaseNames = result.getResults().get(0).getSeries().get(0).getValues();