Receive array of objects in JSON by Spring Boot RestApi Controller

Question

I want to send array of objects like this to Spring REST Controller:

{
    "measureList": [
        {
            "apiKey": "exampleKEY",
            "stationId": "abcdef123",
            "date": "2022-02-18T17:43:51.787535Z",
            "temp": "20.5",
            "humidity": "60.4",
            "pressure": "1020.5",
            "pm25": "100.0",
            "pm25Corr": "150.0",
            "pm10": "90.0"
        },
        {
            "apiKey": "exampleKEY",
            "stationId": "abcdef123",
            "date": "2022-02-18T17:43:53.254309Z",
            "temp": "20.5",
            "humidity": "60.4",
            "pressure": "1020.5",
            "pm25": "100.0",
            "pm25Corr": "150.0",
            "pm10": "90.0"
        }
    ]
}

I have created NewMeausurePackageDto like this:

package com.weather.server.domain.dto;

import java.util.ArrayList;
import java.util.List;

public class NewMeasurePackageDto {
    private ArrayList<NewMeasureDto> measureList;

    public NewMeasurePackageDto(ArrayList<NewMeasureDto> measureList) {
        this.measureList = measureList;
    }

    public NewMeasurePackageDto() {
    }

    public ArrayList<NewMeasureDto> getNewMeasureListDto() {
        return measureList;
    }

    @Override
    public String toString() {
        return "NewMeasurePackageDto{" +
                "measureList=" + measureList +
                '}';
    }
}

NewMeasureDto class:

package com.weather.server.domain.dto;

public class NewMeasureDto {
    private String apiKey;
    private String stationId;
    private String date;
    private String temp;
    private String humidity;
    private String pressure;
    private String pm25;
    private String pm10;
    private String pm25Corr;
    //station_id

    public NewMeasureDto() {
    }

    private NewMeasureDto(Builder builder){
        apiKey = builder.apiKey;
        stationId = builder.stationId;
        date = builder.date;
        temp = builder.temp;
        humidity = builder.humidity;
        pressure = builder.pressure;
        pm25 = builder.pm25;
        pm10 = builder.pm10;
        pm25Corr = builder.pm25Corr;
    }


    public String getApiKey() {
        return apiKey;
    }

    public String getStationID() {
        return stationId;
    }

    public String getDate() {
        return date;
    }

    public String getTemp() {
        return temp;
    }

    public String getHumidity() {
        return humidity;
    }

    public String getPressure() {
        return pressure;
    }

    public String getPm25() {
        return pm25;
    }

    public String getPm10() {
        return pm10;
    }

    public String getPm25Corr() {
        return pm25Corr;
    }


    public static final class Builder {
        private String apiKey;
        private String stationId;
        private String date;
        private String temp;
        private String humidity;
        private String pressure;
        private String pm25;
        private String pm10;
        private String pm25Corr;

        public Builder() {
        }

        public Builder apiKey(String apiKey) {
            this.apiKey = apiKey;
            return this;
        }

        public Builder stationID(String stationId) {
            this.stationId = stationId;
            return this;
        }

        public Builder date(String date) {
            this.date = date;
            return this;
        }

        public Builder temp(String temp) {
            this.temp = temp;
            return this;
        }

        public Builder humidity(String humidity) {
            this.humidity = humidity;
            return this;
        }

        public Builder pressure(String pressure){
            this.pressure = pressure;
            return this;
        }

        public Builder pm25(String pm25){
            this.pm25 = pm25;
            return this;
        }

        public Builder pm10(String pm10){
            this.pm10 = pm10;
            return this;
        }

        public Builder pm25Corr(String pm25Corr){
            this.pm25Corr = pm25Corr;
            return this;
        }

        public NewMeasureDto build() {
            return new NewMeasureDto(this);
        }
    }
}

And request mapping in RestController:

@PostMapping(value="/new-measure-package") //addStation id
    public ResponseEntity<Void> newMeasure(@RequestBody NewMeasurePackageDto measureList){
        //if api key is valid
        return measureService.saveMeasurePackage(measureList.getNewMeasureListDto()) ? new ResponseEntity<>(HttpStatus.OK) :
                new ResponseEntity<>(HttpStatus.BAD_REQUEST);
    }

With this code all I got is error about null measureList in Service function when trying to iterate over the list. I tried changing @RequestBody to List<NewMeasureDto> measureList, and to Map<String, NewMeasureDto> measureList but still measureList is null or empty.

Answer 1

Thanks to ShaharT suggestion I found the answer. There was missing setter in NewMeasurePackageDto, the class should look like this:

package com.weather.server.domain.dto;

import java.util.ArrayList;

public class NewMeasurePackageDto {
    private ArrayList<NewMeasureDto> measureList;

    public NewMeasurePackageDto(ArrayList<NewMeasureDto> measureList) {
        this.measureList = measureList;
    }

    public NewMeasurePackageDto() {
    }

    public ArrayList<NewMeasureDto> getMeasureList() {
        return measureList;
    }


    public void setMeasureList(ArrayList<NewMeasureDto> measureList) {
        this.measureList = measureList;
    }


    @Override
    public String toString() {
        return "NewMeasurePackageDto{" +
                "measureList=" + measureList +
                '}';
    }
}

Conclusion is: when dealing with object of arrays in JSON, there must be setter method for variable storing list in DTO.