Filter empty string for networkTopologyScriptFileName

Descriptions of the changes in this PR:

- filter empty string for networkTopologyScriptFileName.

Reviewers: Enrico Olivelli <eolivelli@gmail.com>, Sijie Guo <sijie@apache.org>

This closes #1952 from reddycharan/ignoreemptystring

(cherry picked from commit 166be82)
Signed-off-by: Sijie Guo <sijie@apache.org>

Author: reddycharan

bookkeeper-server/src/main/java/org/apache/bookkeeper/net/AbstractDNSToSwitchMapping.java

@@ -23,6 +23,7 @@
 
 import org.apache.bookkeeper.conf.Configurable;
 import org.apache.commons.configuration.Configuration;
+import org.apache.commons.lang.StringUtils;
 
 /**
  * This is a base class for DNS to Switch mappings.
@@ -117,7 +118,8 @@ public String dumpTopology() {
     }
 
     protected boolean isSingleSwitchByScriptPolicy() {
-        return conf != null && conf.getString(CommonConfigurationKeys.NET_TOPOLOGY_SCRIPT_FILE_NAME_KEY) == null;
+        return conf != null
+                && (!StringUtils.isNotBlank(conf.getString(CommonConfigurationKeys.NET_TOPOLOGY_SCRIPT_FILE_NAME_KEY)));
     }
 
     /**

bookkeeper-server/src/main/java/org/apache/bookkeeper/net/ScriptBasedMapping.java

@@ -25,6 +25,7 @@
 
 import org.apache.bookkeeper.util.Shell.ShellCommandExecutor;
 import org.apache.commons.configuration.Configuration;
+import org.apache.commons.lang.StringUtils;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -139,8 +140,14 @@ private static final class RawScriptBasedMapping extends AbstractDNSToSwitchMapp
         public void setConf(Configuration conf) {
             super.setConf(conf);
             if (conf != null) {
-                scriptName = conf.getString(SCRIPT_FILENAME_KEY);
-                maxArgs = conf.getInt(SCRIPT_ARG_COUNT_KEY, DEFAULT_ARG_COUNT);
+                String scriptNameConfValue = conf.getString(SCRIPT_FILENAME_KEY);
+                if (StringUtils.isNotBlank(scriptNameConfValue)) {
+                    scriptName = scriptNameConfValue;
+                    maxArgs = conf.getInt(SCRIPT_ARG_COUNT_KEY, DEFAULT_ARG_COUNT);
+                } else {
+                    scriptName = null;
+                    maxArgs = 0;
+                }
             } else {
                 scriptName = null;
                 maxArgs = 0;