refactor: 添加方法 getMapper()

Author: cadecode

common/core/src/main/java/top/cadecode/uniboot/common/core/util/JacksonUtil.java

@@ -27,7 +27,7 @@
 @Component
 public class JacksonUtil implements InitializingBean {
 
-    public static ObjectMapper OBJECT_MAPPER;
+    private static ObjectMapper OBJECT_MAPPER;
 
     private ObjectMapper objectMapper;
 
@@ -39,6 +39,10 @@ public void setObjectMapper(ObjectMapper objectMapper) {
         this.objectMapper = objectMapper;
     }
 
+    public static ObjectMapper getMapper() {
+        return OBJECT_MAPPER;
+    }
+
     /**
      * 转换对象到 json 串
      *