Create JSON from List of HistoricProcessInstances

Camunda 7 Topics Discussion & Questions
1

I try to create a JSON for my List of HistoricProcessInstances.
How is the proper way of doing this?

My code:

List<HistoricProcessInstance> hpi = camunda.getHistoryService()
                .createHistoricProcessInstanceQuery()
                .variableValueEquals(name, value)
                .list();
				
Stream<HistoricProcessInstance> stream = hpi.stream();
List<HistoricProcessInstance> streamData = stream.collect(Collectors.toList());
// create json
ObjectMapper mapper = new ObjectMapper();
Object json = mapper.readValue(streamData.toString(), HistoricProcessInstance.class);
String jsonCase = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(json);
2

You already have List<HistoricProcessInstance> queried using .createHistoricProcessInstanceQuery() in the first line. Then why are you’re iterating the same result data using streams and again collecting same result set?

hpi.stream();

Don’t Repeat Yourself (DRY)

This block of code will raise below error:

com.fasterxml.jackson.databind.JsonMappingException:
No suitable constructor found for type

To convert to json string:

List<HistoricProcessInstance> historicProcessInstanceList = historicProcessInstanceQuery.list();

List<HistoricProcessInstanceDto> historicProcessInstanceDtoList = new ArrayList<>();

if (CollectionUtils.isNotEmpty(historicProcessInstanceList)) {
	historicProcessInstanceList.forEach(historicProcessInstance -> {
        HistoricProcessInstanceDto historicProcessInstanceDto = HistoricProcessInstanceDto
					.fromHistoricProcessInstance(historicProcessInstance);
			historicProcessInstanceDtoList.add(historicProcessInstanceDto);
      });

  ObjectMapper mapper = new ObjectMapper();
  String jsonCase = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(historicProcessInstanceDtoList);
}
3

Thanks,

I tried to do this without a loop but instead seems like I went in one…