[improve]Optimize the code for creating ObjectMapper in GeoUtils (#50)

src/main/java/org/apache/doris/kafka/connector/converter/type/util/GeoUtils.java

diff --git a/src/main/java/org/apache/doris/kafka/connector/converter/type/util/GeoUtils.java b/src/main/java/org/apache/doris/kafka/connector/converter/type/util/GeoUtils.java
index 9c0fc65..dec8439 100644
--- a/src/main/java/org/apache/doris/kafka/connector/converter/type/util/GeoUtils.java
+++ b/src/main/java/org/apache/doris/kafka/connector/converter/type/util/GeoUtils.java
@@ -32,13 +32,13 @@
 
 public class GeoUtils {
     private static final Logger LOGGER = LoggerFactory.getLogger(GeoUtils.class);
+    private static final ObjectMapper objectMapper = new ObjectMapper();
 
     private GeoUtils() {}
 
     public static Object handleGeoStructData(Object sourceValue) {
         // the Geometry datatype in MySQL will be converted to
         // a String with Json format
-        final ObjectMapper objectMapper = new ObjectMapper();
         Struct geometryStruct = (Struct) sourceValue;
 
         try {