[GitHub] [flink-shaded] gauravmiglanid11 edited a comment on pull request #108: [FLINK-25588] Add Jackson JDK8 types to shaded jackson

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gauravmiglanid11 edited a comment on pull request #108:
URL: https://github.com/apache/flink-shaded/pull/108#issuecomment-1011939361


   hi @slinkydeveloper, ya tried building jar from your branch, it is not working. The mapper object in JsonRowSerializationSchema is instance and private field,  I have tried registering `JavaTimeModule` using reflection as well, but getting famous java.time.format.DateTimeFormatter serialization issue. https://github.com/FasterXML/jackson-databind/issues/2452. So what I did is to write a generic serialization class for flink row. The below code is working as of now
   
   ```
   import java.util.HashMap;
   import java.util.Map;
   import lombok.SneakyThrows;
   import org.apache.flink.api.common.serialization.SerializationSchema;
   import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.ObjectMapper;
   import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.SerializationFeature;
   import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
   import org.apache.flink.types.Row;
   
   public class GenericSerializationSchema implements SerializationSchema<Row> {
   
     private final String[] columnNames;
     private static final ObjectMapper objectMapper = new ObjectMapper();
   
     public GenericSerializationSchema(String[] columnNames) {
       this.columnNames = columnNames;
       objectMapper.registerModule(new JavaTimeModule());
       objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
     }
   
     @SneakyThrows
     @Override
     public byte[] serialize(Row row) {
       if (row == null) {
         return null;
       }
       Map<String, Object> map = new HashMap<>();
       for (int i = 0; i < columnNames.length; i++) {
         Object field = row.getField(i);
         if (field instanceof Row) {
           Row fieldRow = (Row) field;
           String[] rowColumnNames = fieldRow.getFieldNames(true).stream().toArray(String[]::new);
           map.put(
               columnNames[i],
               new String(new GenericSerializationSchema(rowColumnNames).serialize(fieldRow)));
         } else {
           map.put(columnNames[i], field);
         }
       }
       return objectMapper.writeValueAsBytes(map);
     }
   }
   ```
   
   If I make `objectMapper` instance field instead of static, I'm getting the same not serializable issue for java time formatter, which is the same error scenario as with class `JsonRowSerializationSchema`
   
   Jackson object mapper can be declared static as per this https://stackoverflow.com/questions/3907929/should-i-declare-jacksons-objectmapper-as-a-static-field, am I missing something?


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