fix(config): handle null config values and SonarCloud issues

- Replace null values (discovery.external.ip, trustNode) with empty
  string before ConfigBeanFactory binding for external config compat
  (system-test uses "external.ip = null" which ConfigBeanFactory cannot
  bind to String fields; recommend updating system-test to use "" instead)
- Fix floating point comparison with Double.compare (java:S1244)
- Extract duplicated string literals into constants/variables (java:S1192)

Author: vividctrlalt

common/src/main/java/org/tron/core/config/args/CommitteeConfig.java

@@ -92,22 +92,25 @@ public class CommitteeConfig {
    * uppercase letters) which causes ConfigBeanFactory key mismatch. These two fields
    * are excluded from automatic binding and handled manually after.
    */
+  private static final String PBFT_EXPIRE_NUM_KEY = "pBFTExpireNum";
+  private static final String ALLOW_PBFT_KEY = "allowPBFT";
+
   public static CommitteeConfig fromConfig(Config config) {
     Config section = config.getConfig("committee");
 
     // ConfigBeanFactory derives key names from setter methods. For setPBFTExpireNum()
     // it expects "PBFTExpireNum" (capital P), but config.conf uses "pBFTExpireNum".
-    // Similarly, getAllowPBFT() maps to "allowPBFT" which may be missing in test configs.
-    // Add uppercase aliases so ConfigBeanFactory can find them.
+    // Add uppercase alias so ConfigBeanFactory can find it.
     Config aliased = section;
-    if (section.hasPath("pBFTExpireNum") && !section.hasPath("PBFTExpireNum")) {
-      aliased = aliased.withValue("PBFTExpireNum", section.getValue("pBFTExpireNum"));
+    if (section.hasPath(PBFT_EXPIRE_NUM_KEY) && !section.hasPath("PBFTExpireNum")) {
+      aliased = aliased.withValue("PBFTExpireNum", section.getValue(PBFT_EXPIRE_NUM_KEY));
     }
 
     CommitteeConfig cc = ConfigBeanFactory.create(aliased, CommitteeConfig.class);
     // Ensure the manually-named fields get the right values from the original keys
-    cc.allowPBFT = section.hasPath("allowPBFT") ? section.getLong("allowPBFT") : 0;
-    cc.pBFTExpireNum = section.hasPath("pBFTExpireNum") ? section.getLong("pBFTExpireNum") : 20;
+    cc.allowPBFT = section.hasPath(ALLOW_PBFT_KEY) ? section.getLong(ALLOW_PBFT_KEY) : 0;
+    cc.pBFTExpireNum = section.hasPath(PBFT_EXPIRE_NUM_KEY)
+        ? section.getLong(PBFT_EXPIRE_NUM_KEY) : 20;
 
     cc.postProcess();
     return cc;

common/src/main/java/org/tron/core/config/args/EventConfig.java

@@ -81,13 +81,15 @@ public static EventConfig fromConfig(Config config) {
 
     // "native" is a Java reserved word, "topics" has optional fields per item —
     // strip both before binding, read manually
-    Config bindable = section.withoutPath("native").withoutPath("topics")
+    String nativeKey = "native";
+    String topicsKey = "topics";
+    Config bindable = section.withoutPath(nativeKey).withoutPath(topicsKey)
         .withoutPath("topicDefaults");
     EventConfig ec = ConfigBeanFactory.create(bindable, EventConfig.class);
 
     // manually bind "native" sub-section
-    Config nativeSection = section.hasPath("native")
-        ? section.getConfig("native") : ConfigFactory.empty();
+    Config nativeSection = section.hasPath(nativeKey)
+        ? section.getConfig(nativeKey) : ConfigFactory.empty();
     ec.nativeQueue = new NativeConfig();
     if (nativeSection.hasPath("useNativeQueue")) {
       ec.nativeQueue.useNativeQueue = nativeSection.getBoolean("useNativeQueue");
@@ -100,9 +102,9 @@ public static EventConfig fromConfig(Config config) {
     }
 
     // manually bind topics — each item may have optional fields
-    if (section.hasPath("topics")) {
+    if (section.hasPath(topicsKey)) {
       ec.topics = new ArrayList<>();
-      for (com.typesafe.config.ConfigObject obj : section.getObjectList("topics")) {
+      for (com.typesafe.config.ConfigObject obj : section.getObjectList(topicsKey)) {
         Config tc = obj.toConfig();
         TopicConfig topic = new TopicConfig();
         if (tc.hasPath("triggerName")) {

common/src/main/java/org/tron/core/config/args/MiscConfig.java

@@ -43,9 +43,10 @@ public static MiscConfig fromConfig(Config config) {
     // trx
     mc.trxReferenceBlock = config.hasPath("trx.reference.block")
         ? config.getString("trx.reference.block") : "solid";
-    if (config.hasPath("trx.expiration.timeInMilliseconds")
-        && config.getLong("trx.expiration.timeInMilliseconds") > 0) {
-      mc.trxExpirationTimeInMilliseconds = config.getLong("trx.expiration.timeInMilliseconds");
+    String trxExpirationKey = "trx.expiration.timeInMilliseconds";
+    if (config.hasPath(trxExpirationKey)
+        && config.getLong(trxExpirationKey) > 0) {
+      mc.trxExpirationTimeInMilliseconds = config.getLong(trxExpirationKey);
     }
 
     // energy (note: config key has typo "enery" — preserved for backward compat)

common/src/main/java/org/tron/core/config/args/NodeConfig.java

@@ -360,6 +360,13 @@ public static class DnsConfig {
   public static NodeConfig fromConfig(Config config) {
     Config section = config.getConfig("node");
 
+    // Replace null values with empty strings before bean binding.
+    // Some external configs (e.g. system-test) set "discovery.external.ip = null"
+    // which ConfigBeanFactory cannot bind to a String field.
+    // Note: hasPath() returns false for null values, use hasPathOrNull() instead.
+    section = replaceNullWithEmpty(section, "discovery.external.ip");
+    section = replaceNullWithEmpty(section, "trustNode");
+
     // Auto-bind all fields and sub-beans
     NodeConfig nc = ConfigBeanFactory.create(section, NodeConfig.class);
 
@@ -474,4 +481,14 @@ private static String getString(Config config, String path, String defaultValue)
     return config.hasPath(path) ? config.getString(path) : defaultValue;
   }
 
+  // Replace a null config value with empty string so ConfigBeanFactory can bind it.
+  // hasPath() returns false for null values; hasPathOrNull() returns true.
+  private static Config replaceNullWithEmpty(Config config, String path) {
+    if (config.hasPathOrNull(path) && config.getIsNull(path)) {
+      return config.withValue(path,
+          com.typesafe.config.ConfigValueFactory.fromAnyRef(""));
+    }
+    return config;
+  }
+
 }

framework/src/main/java/org/tron/core/config/args/Args.java

@@ -1075,7 +1075,7 @@ private static void loadDnsPublishParameters(NodeConfig.DnsConfig dns,
 
       if (dns.getChangeThreshold() > 0) {
         publishConfig.setChangeThreshold(dns.getChangeThreshold());
-      } else if (dns.getChangeThreshold() != 0.0) {
+      } else if (Double.compare(dns.getChangeThreshold(), 0.0) != 0) {
         logger.error("Check node.dns.changeThreshold, should be bigger than 0, default 0.1");
       }