com.hazelcast.jet.cdc

Interface RecordPart

@EvolvingApi
public interface RecordPart

Represents the top-level component of a ChangeRecord, such as the key or the value. Since these components are JSON expressions, this is actually a generic wrapper around a JSON expression. Contains various methods for retrieving component values or for mapping itself to data objects.

Since:

Jet 4.2

Method Summary

Modifier and Type	Method and Description
String	toJson() Returns the raw JSON string that this object wraps.
Map<String,Object>	toMap() Presents a parsed form of the underlying JSON message as a Map.
<T> T	toObject(Class<T> clazz) Maps the entire element to an instance of the specified class.

Method Detail

toObject

@Nonnull
<T> T toObject(@Nonnull
                        Class<T> clazz)
                 throws ParsingException

Maps the entire element to an instance of the specified class.

Parsing is based on Jackson jr with annotation support, so the supplied class can be annotated accordingly.

Note: there is a neat trick for converting types during object mapping. Let's say we have a birth_date column in a table of type DATE and we want to map it to a field named birthDate in our row object, of type LocalDate. We would write code like this:

  
  public LocalDate birthDate;

  public void setBirthDate(long dateInEpochDays) {
      this.birthDate = dateInEpochDays == 0 ? null : LocalDate.ofEpochDay(dateInEpochDays);
  }
  
 

The things to note here is that by specifying a setter and giving it the input parameter type of long we force the object mapping to interpret the column value as a long (as opposed to Date). Then we can take care of null handling and converting to whatever desired type ourselves.

Returns:

object of type T, obtained as the result of the mapping

Throws:

ParsingException - if the mapping fails to produce a result

toMap

@Nonnull
Map<String,Object> toMap()
                           throws ParsingException

Presents a parsed form of the underlying JSON message as a Map. The keys are the top-level fields from the JSON and the values can range from simple strings, numbers, collections and sub-maps.

Parsing is based on Jackson jr, you can refer to its documentation for more details.

Returns:

Map representation of the JSON data

Throws:

ParsingException - if the underlying JSON message fails to parse

toJson

@Nonnull
String toJson()

Returns the raw JSON string that this object wraps. You can use it if parsing is failing for some reason (for example on some untested DB-connector version combination).