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Spring Data Mongodb Aggregation - Group by nested objects and build DTO

I have the following Employee data in MongoDB
{
"_id": {
"$oid": "625f09bb1a96bf42ff4c4006"
},
"employeeId": 1234,
"email": "jason#acme.com",
"firstName": "Jason",
"lastName": "Stuart",
"currentCTC": 1201117.61,
"department": {
"$ref": "department",
"$id": {
"$oid": "625f09bb1a96bf42ff4c4005"
}
}
}
{
"_id": {
"$oid": "625f09bb1a96bf42ff4c4006"
},
"employeeId": 1235,
"email": "jasons#acme.com",
"firstName": "Jasons",
"lastName": "Stuarts",
"currentCTC": 1201117.61,
"department": {
"$ref": "department",
"$id": {
"$oid": "625f09bb1a96bf42ff4c4005"
}
}
}
My Spring #Document looks like this:
// Employee.java
#Data
#Document
public class Employee {
#Id
private String id;
private Long employeeId;
private String email;
private String firstName;
private String middleName;
private String lastName;
private Gender gender;
private double currentCTC;
#DBRef
private Department department;
}
// Department.java
#Document
#Data
public class Department {
#Id
private String id;
private String name;
}
Now, my requirement is to find the sum of salaries Department-wise.. I need the data to be in the following way:
[
{
"department": {
"id": "625f09bb1a96bf42ff4c4006",
"name": "Engineering"
},
"cost": 31894773.01
},
{
"department": {
"id": "625f09bb1a96bf42ff4c4006",
"name": "Marketing"
},
"cost": 4552325.25
}
]
I created an aggregate function like this in Spring Data:
public List<DepartmentCost> getDepartmentCosting() {
GroupOperation groupByDepartment = group("department").sum("currentCTC").as("cost").first("$$ROOT").as("department");
Aggregation aggregation = Aggregation.newAggregation(groupByDepartment);
AggregationResults<DepartmentCost> results = mongoTemplate.aggregate(aggregation, "employee", DepartmentCost.class);
return results.getMappedResults();
}
And my expected DepartmentCost.java
#Data
#Document
public class DepartmentCost {
#DBRef
private Department department;
private double cost;
}
Now when I try this API out, I get the data correctly, but I do not get department name. It comes as null. I get a response like
[
{
"department": {
"id": "625f09bb1a96bf42ff4c4006",
"name": null,
},
"cost": 2241117.6100000003
},
{
"department": {
"id": "625f09bb1a96bf42ff4c400a",
"name": null,
},
"cost": 14774021.43
},
{
"department": {
"id": "625f09bc1a96bf42ff4c4013",
"name": null,
},
"cost": 14879633.97
}
]
How can I get the department details expanded in my model? Please help..

After a couple of attempts, I figured it out. All I had to do was this:
GroupOperation groupByDepartment = group("department").sum("currentCTC").as("cost").first("$department").as("department");
as opposed to:
GroupOperation groupByDepartment = group("department").sum("currentCTC").as("cost").first("$$ROOT").as("department");

Java Spring Deserializing Nested objects using RestTemplate

I am using Java Spring boot restTemplate and I am trying to deserialize the below JSON into their corresponding objects. However it is returning null.
Am I doing this the right way? Should I return a String response Entity and then convert?
{
"Events": [
{
"Id": 3584588,
"Url": "https://api.wildapricot.org/v2/accounts/257051/Events/3584588",
"EventType": "Regular",
"StartDate": "2019-10-07T07:00:00-05:00",
"EndDate": "2019-10-11T12:00:00-05:00",
"Location": "Renaissance Montgomery Hotel & Spa",
"RegistrationEnabled": false,
"RegistrationsLimit": null,
"PendingRegistrationsCount": 0,
"ConfirmedRegistrationsCount": 0,
"CheckedInAttendeesNumber": 0,
"InviteeStat": {
"NotResponded": 0,
"NotAttended": 0,
"Attended": 0,
"MaybeAttended": 0
},
"Tags": [
"event"
],
"AccessLevel": "AdminOnly",
"StartTimeSpecified": true,
"EndTimeSpecified": true,
"HasEnabledRegistrationTypes": false,
"Name": "2020 Montgomery IT Summit"
},
{
"Id": 3584591,
"Url": "https://api.wildapricot.org/v2/accounts/257051/Events/3584591",
"EventType": "Rsvp",
"StartDate": "2019-10-03T00:00:00-05:00",
"EndDate": "2019-10-31T00:00:00-05:00",
"Location": "Here",
"RegistrationEnabled": true,
"RegistrationsLimit": null,
"PendingRegistrationsCount": 0,
"ConfirmedRegistrationsCount": 0,
"CheckedInAttendeesNumber": 0,
"InviteeStat": {
"NotResponded": 0,
"NotAttended": 0,
"Attended": 0,
"MaybeAttended": 0
},
"Tags": [
"volunteer"
],
"AccessLevel": "Public",
"StartTimeSpecified": false,
"EndTimeSpecified": false,
"HasEnabledRegistrationTypes": true,
"Name": "Volunteer Event"
}
]
}
Here is my call:
ResponseEntity<WaEvents> response = restTemplate.exchange(uri,
HttpMethod.GET,
request,
WaEvents.class
);
return response.getBody().getEvents();
Here is my WaEvents Class:
#Data
public class WaEvents implements Serializable {
#JsonUnwrapped
#JsonProperty("Events")
private List<WaEvent> events;
}
Here is the WaEvent Class
#Data
#JsonIgnoreProperties(ignoreUnknown = true)
public class WaEvent {
#JsonProperty("Id")
public Integer id;
#JsonProperty("Name")
public String name;
#JsonProperty("Location")
public String location;
#JsonProperty("StartDate")
public LocalDate startDate;
#JsonProperty("EndDate")
public LocalDate endDate;
#JsonProperty("IsEnabled")
public Boolean isEnabled;
#JsonProperty("Description")
public String description;
#JsonProperty("RegistrationLimit")
public Integer RegistrationLimit;
}

As explained here with an example :
public class Parent {
public int age;
public Name name;
}
public class Name {
public String first, last;
}
Without #JsonUnwrapped, the JSON is :
{
"age" : 18,
"name" : {
"first" : "Joey",
"last" : "Sixpack"
}
}
With #JsonUnwrapped, the JSON is :
{
"age" : 18,
"first" : "Joey",
"last" : "Sixpack"
}
So #JsonUnwrapped will flatten the properties and events won't exist anymore :
{
"Id": 3584588,
"Name": "2020 Montgomery IT Summit",
"Location": "Renaissance Montgomery Hotel & Spa",
"StartDate": "2019-10-07T07:00:00-05:00",
"EndDate": "2019-10-11T12:00:00-05:00",
...
}
Try to remove #JsonUnwrapped

How do I parse an input JSON, and based on the existing JSON, which represents a product inventory, generate the bill

I am trying to parse JSON using GSON library.
I have a product inventory in the form of a JSON like this:
[
{
"id": 2000,
"name": "Child Shoes",
"variants": [
{
"size": "size 7",
"price": 19.99,
"tax_code": 0
}
]
},
{
"id": 3000,
"name": "Eggs",
"variants": [
{
"size": "6",
"price": 1.50,
"tax_code": 7
},
{
"size": "12",
"price": 2.25,
"tax_code": 1
}
]
},
{
"id": 3100,
"name": "Apples",
"variants": [
{
"size": "1",
"price": 0.30,
"tax_code": 7
},
{
"size": "10",
"price": 2.50,
"tax_code": 7
}
]
},
{
"id": 5423,
"name": "Book",
"variants": [
{
"size": "Assorted",
"price": 11.00,
"tax_code": 1
}
]
}
]
And Tax codes as follows :
[
{
"code": 0,
"name": "HST",
"rate": 0.13
},
{
"code": 1,
"name": "HST - Books",
"rate": 0.05
},
{
"code": 7,
"name": "EXEMPT - Food",
"rate": 0
}
]
Now, how do I generate the total bill, if I get an input like this:
[
{
"product": 3000,
"variant": 1,
"quantity": 1
},
{
"product": 3100,
"variant": 1,
"quantity": 1
}
]
I am new to JSON and having a tough time trying to identify the correct strategy to solve this problem.

I hope below solution give you some idea -
Map your json to pojo like below -
public class ProductInventory {
private Integer id;
private String name;
private List<Variant> variants = null;
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List<Variant> getVariants() {
return variants;
}
public void setVariants(List<Variant> variants) {
this.variants = variants;
}
}
//class Variant
public class Variant {
private String size;
private Double price;
private Integer taxCode;
public String getSize() {
return size;
}
public void setSize(String size) {
this.size = size;
}
public Double getPrice() {
return price;
}
public void setPrice(Double price) {
this.price = price;
}
public Integer getTaxCode() {
return taxCode;
}
public void setTaxCode(Integer taxCode) {
this.taxCode = taxCode;
}
}
Use Gson library to parse json into java object and vice-versa:
Gson gson = new Gson();
Type jsonType = new TypeToken<List<ProductInventory>>(){}.getType();
List<ProductInventory> piList = gson.fromJson(json, jsonType);
Now Iterate over the piList and populate your other pojos and parse it into json using toJson() method.
Note:- You have to create pojo classes for the target json, that you can create here - http://www.jsonschema2pojo.org/

Deserialize complex JSON to Java, classes nested multiple levels deep

I am trying to make the Json output from Cucumber into a single Java object. This contains objects nested four levels deep, and I am having trouble deserializing it. I am presently using Jackson, but open to suggestions.
Here is my Json code:
{
"line": 1,
"elements": [
{
"line": 3,
"name": "Converteren centimeters naar voeten/inches",
"description": "",
"id": "applicatie-neemt-maten-in-cm-en-converteert-ze-naar-voet/inch,-en-vice-versa;converteren-centimeters-naar-voeten/inches",
"type": "scenario",
"keyword": "Scenario",
"steps": [
{
"result": {
"duration": 476796588,
"status": "passed"
},
"line": 4,
"name": "maak Maten-object aan met invoer in \"centimeters\"",
"match": {
"arguments": [
{
"val": "centimeters",
"offset": 37
}
],
"location": "StepDefinition.maakMatenObjectAanMetInvoerIn(String)"
},
"keyword": "Given "
},
{
"result": {
"duration": 36319,
"status": "passed"
},
"line": 5,
"name": "ik converteer",
"match": {
"location": "StepDefinition.converteerMaten()"
},
"keyword": "When "
},
{
"result": {
"duration": 49138,
"status": "passed"
},
"line": 6,
"name": "uitvoer bevat maat in \"voeten/inches\"",
"match": {
"arguments": [
{
"val": "voeten/inches",
"offset": 23
}
],
"location": "StepDefinition.uitvoerBevatMaatIn(String)"
},
"keyword": "Then "
}
]
},
{
"line": 8,
"name": "Converteren voeten/inches naar centimeters",
"description": "",
"id": "applicatie-neemt-maten-in-cm-en-converteert-ze-naar-voet/inch,-en-vice-versa;converteren-voeten/inches-naar-centimeters",
"type": "scenario",
"keyword": "Scenario",
"steps": [
{
"result": {
"duration": 84175,
"status": "passed"
},
"line": 9,
"name": "maak Maten-object aan met invoer in \"voeten/inches\"",
"match": {
"arguments": [
{
"val": "voeten/inches",
"offset": 37
}
],
"location": "StepDefinition.maakMatenObjectAanMetInvoerIn(String)"
},
"keyword": "Given "
},
{
"result": {
"duration": 23928,
"status": "passed"
},
"line": 10,
"name": "ik converteer",
"match": {
"location": "StepDefinition.converteerMaten()"
},
"keyword": "When "
},
{
"result": {
"duration": 55547,
"status": "passed"
},
"line": 11,
"name": "uitvoer bevat maat in \"centimeters\"",
"match": {
"arguments": [
{
"val": "centimeters",
"offset": 23
}
],
"location": "StepDefinition.uitvoerBevatMaatIn(String)"
},
"keyword": "Then "
}
]
}
],
"name": "Applicatie neemt maten in cm en converteert ze naar voet/inch, en vice versa",
"description": "",
"id": "applicatie-neemt-maten-in-cm-en-converteert-ze-naar-voet/inch,-en-vice-versa",
"keyword": "Feature",
"uri": "sample.feature"
}
I have tried a number of different approaches. First I used nested inner classes, but it appeared you had to make them static, which I feared would not work since I have multiple instances of the same object within one (multiple "element"-objects in the root, for example). Then I tried putting them in separate classes, with Json annotations. Here's where that got me (omitting setters):
public class CucumberUitvoer {
private String name;
private String description;
private String id;
private String keyword;
private String uri;
private int line;
#JsonProperty("elements")
private List<FeatureObject> elements;
public CucumberUitvoer(){}
}
public class FeatureObject {
private String name;
private String description;
private String id;
private String type;
private String keyword;
private int line;
#JsonProperty("steps")
private List<StepObject> steps;
public FeatureObject() {
}
}
public class StepObject {
#JsonProperty("result")
private ResultObject result;
private String name;
private String given;
private String location;
private String keyword;
private int line;
#JsonProperty("match")
private MatchObject match;
public StepObject(){}
}
public class ResultObject {
private int duration;
private String status;
public ResultObject(){}
}
public class MatchObject {
#JsonProperty("arguments")
private List<ArgumentObject> arguments;
private String location;
public MatchObject(){}
}
public class ArgumentObject {
private String val;
private String offset;
public ArgumentObject(){}
}
For clarification, here's a class diagram of how the nesting works.
This solution gives me the following error:
com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of nl.icaprojecten.TestIntegratieQuintor.JSONInterpreter.CucumberUitvoer out of START_ARRAY token
Here is the code doing the actual mapping:
ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
CucumberUitvoer obj1 = null;
try {
obj1 = mapper.readValue(json, CucumberUitvoer.class);
} catch (IOException e) {
e.printStackTrace();
}
Is there a quick fix to this approach to make it work, or should I try something entirely different?

Ok I spent some time debugging and trying to figure out what was the problem, and finally was something pretty obvious.
implements Serializable
Thats the line I added to MatchObject and worked.
When we try to deserialize some object first we have to make those classes implements the interface Serializable

I just tried your sample code and oddly, it works.
Can you please double check your imports, if the JSON is coming in as provided and the getters, setters, constructors are actually there?

You can get the idea from this code to deserialize,
public class testCustomDeSerializer extends JsonDeserializer<test> {
public testCustomDeSerializer() {
this(null);
}
public TestCustomDeSerializer(Class t) {
// super(t);
}
#Override
public Test deserialize(JsonParser p, DeserializationContext ctx) throws IOException, JsonProcessingException {
ObjectCodec objectCodec = p.getCodec();
JsonNode node = objectCodec.readTree(p);
ObjectMapper objectMapper = new ObjectMapper();
Test test= new Test();
test.setId(node.get("line").asText());
List<elements> elementList = new ArrayList<>();
JsonNode elementsNode = node.get("elements");
Iterator<JsonNode> slaidsIterator = elementsNode.elements();
while (slaidsIterator.hasNext()) {
Steps steps= new Steps();
JsonNode slaidNode = slaidsIterator.next();
JsonNode stepNode= (JsonNode) slaidNode.get("Steps");
BoundingPoly in = objectMapper.readValue(stepNode.toString(), Steps.class);
elementsNode.setSteps(in);
/// continue
return
}
Hope it helps

Creating Pojo for Jackson JSON deserializer

Ok I have some JSON I get from a service that I am trying to create a POJO for. My JSON looks similar to:
[
{
"id": "someid",
"values": {
"value1": {
"id": "someid"
}
}
},
{
"id": "391055",
"values": {
"value1": {
"id": "someid"
},
"value2": {
"id": "someid"
}
}
},
{
"id": "someid",
"values": {
"value1": {
"id": "someid"
}
}
}
]
and my POJO is like:
#JsonPropertyOrder({
"id",
"values"})
public class ValueTranslation {
#JsonProperty("id")
private String id;
#JsonProperty("values")
private Map<String, String> values;
public ValueTranslation(String id, Map<String, String> values) {
this.id = id;
this.values = values;
}
}
After I figure this out I will work on getting the inner string changed to some object, but I have no idea what is going wrong in the mapping. I have read several JACKSON tutorials and googled, but have found nothing to help me.