FlatMessage没有默认构造方法json反序列化的问题

Dml类增加isDdl属性

protocol/src/main/java/com/alibaba/otter/canal/protocol/FlatMessage.java

@@ -29,6 +29,9 @@ public class FlatMessage implements Serializable {
     private List<Map<String, String>> data;
     private List<Map<String, String>> old;
 
+    public FlatMessage() {
+    }
+
     public FlatMessage(long id){
         this.id = id;
     }