Added support for rate limiting by Etherscan: throw RateLimitException

(cherry picked from commit 120ba0f)

Author: iSnow

src/main/java/io/api/etherscan/core/impl/BasicProvider.java

@@ -1,12 +1,16 @@
 package io.api.etherscan.core.impl;
 
 import com.google.gson.Gson;
+import com.google.gson.JsonSyntaxException;
 import io.api.etherscan.error.EtherScanException;
 import io.api.etherscan.error.ParseException;
+import io.api.etherscan.error.RateLimitException;
 import io.api.etherscan.executor.IHttpExecutor;
 import io.api.etherscan.manager.IQueueManager;
 import io.api.etherscan.util.BasicUtils;
 
+import java.util.Map;
+
 /**
  * Base provider for API Implementations
  *
@@ -42,6 +46,19 @@ <T> T convert(final String json, final Class<T> tClass) {
         try {
             return gson.fromJson(json, tClass);
         } catch (Exception e) {
+            if (e instanceof JsonSyntaxException) {
+                Map<String, Object> map = gson.fromJson(json, Map.class);
+                Object statusCode = map.get("status");
+                if ((statusCode instanceof String) && (statusCode.equals("0"))) {
+                    Object message = map.get("message");
+                    if ((message instanceof String) && (message.equals("NOTOK"))) {
+                        Object result = map.get("result");
+                        if ((result instanceof String) && (result.equals("Max rate limit reached"))) {
+                            throw new RateLimitException ("Max rate limit reached");
+                        }
+                    }
+                }
+            }
             throw new ParseException(e.getMessage(), e.getCause(), json);
         }
     }

src/main/java/io/api/etherscan/error/RateLimitException.java

@@ -0,0 +1,15 @@
+package io.api.etherscan.error;
+
+/**
+ * ! NO DESCRIPTION !
+ *
+ * @author iSnow
+ * @since 2020-10-06
+ */
+public class RateLimitException extends ApiException {
+
+    public RateLimitException(String message) {
+        super(message);
+    }
+
+}