fix: base64 decode json error (#536)

Author: YongwuHe

arex-instrumentation/httpclient/arex-httpclient-ning/src/main/java/io/arex/inst/httpclient/ning/NingHttpClientAdapter.java

@@ -14,7 +14,6 @@
 import java.net.URI;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
-import java.util.Base64;
 import java.util.List;
 import java.util.Map;
 
@@ -37,7 +36,7 @@ public byte[] getRequestBytes() {
         }
 
         if (request.getStringData() != null) {
-            return Base64.getDecoder().decode(request.getStringData());
+            return request.getStringData().getBytes(StandardCharsets.UTF_8);
         }
 
         if (request.getCompositeByteData() != null) {

arex-instrumentation/httpclient/arex-httpclient-ning/src/test/java/io/arex/inst/httpclient/ning/NingHttpClientAdapterTest.java

@@ -52,8 +52,10 @@ void getRequestBytes() {
         assertArrayEquals("test".getBytes(), ningHttpClientAdapter.getRequestBytes());
 
         // stringData != null
-        when(request.getStringData()).thenReturn("test");
-        assertArrayEquals("test".getBytes(), ningHttpClientAdapter.getRequestBytes());
+        String json = "{\"accountId\":\"uat-account-866e34f7\"}";
+        when(request.getByteData()).thenReturn(null);
+        when(request.getStringData()).thenReturn(json);
+        assertArrayEquals(json.getBytes(StandardCharsets.UTF_8), ningHttpClientAdapter.getRequestBytes());
 
         // compositeByteData != null
         when(request.getByteData()).thenReturn(null);