Jasper Studio: JSON-Datasource with Sub-Arrays - json

Question

I am using Jasper Studio 5.5 and try to create a report using a JSON-Datasource. My example json-file looks as followed:
{
"dto": [
{
"item": {
"active": 1
},
"itemProjects": [
{"id": 1},
{"id": 2}
]
},
{
"item": {
"active": 1
},
"itemProjects": [
{"id": 3},
{"id": 4}
]
}
]}
To summarize it: I have an array of "dto"-objects. Each dto contains an object "item" and an array of "itemProjects".
Using the Select-Query "dto" and the Fields "item.active" allows me to read the property "acttive". However I have yet to find a way to read the properties from the sub-arrays. I tried it with different Select-Strings and Fieldnames, but had no success. I also tried passing the array as parameter to a subreport, but this also didnt worked (the generated report showed empty fields).
Does anyone know, how to correctly read data from an array inside an array in JSON ?
best regards.

Answer 1

I take care my object structure in json, fits the report. Logically you receieve the complete json in the main report.
Then I make a sub-report and tell the subreport to select a part of the JSon only. As an example, my main report calls the subreport by using a Data Source Expression:
((net.sf.jasperreports.engine.data.JsonDataSource)$P{REPORT_DATA_SOURCE}).subDataSource("data.bezirkResultatAbstimmungVorlage")
data.bezirkResultatAbstimmungVorlage then looks like this in the json:
"data":
{
"bezirkResultatAbstimmungVorlage":
[
{
"vorlageNummer": "4",
"offiziellerAbstimmungBezeichnung": "Ja für Mundart im Kindergarten", ... ... ...
Then I select the fields of this part of the json in the subreport. If you then put these fields in the detail-band jasper will loop automatically over all elements of your json-array.
The way you described should actually work. Please make sure you include the json as a datasource in the "Dataset and Query Dialog"

Answer 2

I would tackle this by creating subDatasets as you have two arrays that you want to iterate over.
In the detail band of the main report, add a list element with a new DataSet and give it JRDatasource Expression:
((net.sf.jasperreports.engine.data.JsonDataSource)$P{REPORT_DATA_SOURCE}).subDataSource("dto")
Create the field: active, which points to item.active,
Add a second list element to the detail band to the right of the first one with a new DataSet, and give it this JRDatasource Expression:
((net.sf.jasperreports.engine.data.JsonDataSource)$P{REPORT_DATA_SOURCE}).subDataSource("itemProjects")
Create the id field which points to id.
Now you should be able to get the item and item project list for each object.