Cannot deserialize value of type `java.lang.Long` from Object value (token `JsonToken.START_OBJECT`)

Question

Getting the following error while hitting the POST API call via postman for the following code.

Requirement : Place an order given the list of <component_id>, and . Consider that an order only implies reducing the current stock of each <component_id> by .

Spring Boot Application is Running fine just getting 400 Bad request in Postman and following in the console.

Error Log 2023-03-01T00:43:19.065+05:30 WARN 53443 --- [nio-8090-exec-1] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize value of type java.lang.Long from Object value (token JsonToken.START_OBJECT)]

Following are the details of my classes added:

**Controller Class**

@PostMapping("/shop/order")
public ResponseEntity<String> placeOrder(@RequestBody Map<String, Long> orderDetails) {
    try {
        partService.placeOrder(orderDetails);
        return ResponseEntity.ok().body("Order placed successfully!");
    } catch (Exception e) {
        return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("Failed to place order");
    }
}

Repository class

    public interface PartRepository extends CrudRepository < PartDetails, String > {

    @Query("SELECT p FROM PartDetails p WHERE p.carModelId = :carModelId")

    List < PartDetails > findByCarModelId(String carModelId);

    @Query("SELECT p FROM PartDetails p WHERE p.componentId = :componentId")

    List < PartDetails > findByComponentId(String componentId);

    **Service Class Logic**

    @Transactional
    public void placeOrder(Map < String, Long > orderDetails) {
        for (Map.Entry < String, Long > entry: orderDetails.entrySet()) {
            String componentId = entry.getKey();
            Long unitInStock = entry.getValue();
            List < PartDetails > partStockOptional = partRepository.findByComponentId(componentId);
            // PartDetails partStock = partStockOptional.orElseThrow(() -> new ResourceNotFoundException("Part stock not found with component ID: " + componentId));
            PartDetails partStock = (PartDetails) partStockOptional;
            Long currentUnits = partStock.getUnitInStock();
            if (currentUnits < unitInStock) {
                throw new RuntimeException("Insufficient units in stock for component ID: " + componentId);
            }
            partStock.setUnitInStock(currentUnits - unitInStock);
            partRepository.save(partStock);
        }
    }

    **Entity Class**

    package com.example.ecombackend.Entity;

    import jakarta.persistence.*;

    @Entity
    @Table
    public class PartDetails {

        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        private Long id;
        @Column(name = "car_model_id")
        private String carModelId;
        @Column
        private String componentName;
        @Column
        private String componentId;
        @Column(name = "unit_in_stock")
        private Long unitInStock;

        public PartDetails() {}

        public PartDetails(String carModelIds, String componentNames, String componentIds, Long unitInStocks) {
            carModelId = carModelIds;
            componentName = componentNames;
            componentId = componentIds;
            unitInStock = unitInStocks;
        }

        public Long getId() {
            return id;
        }

        public void setId(Long id) {
            this.id = id;
        }

        public String getCarModelId() {
            return carModelId;
        }

        public String getComponentName() {
            return componentName;
        }

        public String getComponentId() {
            return componentId;
        }

        public Long getUnitInStock() {
            return unitInStock;
        }

        public void setCarModelId(String carModelId) {
            this.carModelId = carModelId;
        }

        public void setComponentName(String componentName) {
            this.componentName = componentName;
        }

        public void setComponentId(String componentId) {
            this.componentId = componentId;
        }

        public void setUnitInStock(Long unitInStock) {
            this.unitInStock = unitInStock;
        }

    }

`

Answer 1

Not This : { "id":4 }

just give :

 4

In the body in postman... I hope this will work

Answer 2

Your body in Postman needs to be { "EA1": 5, "BA1": 3 } not { "orderDetails": { "EA1": 5, "BA1": 3 } }