Unable to convert a json array into java list

Question

I have the following Json string:

String jsonString = "[
  {
    "nameOnCard": "Test T",
    "active": true,
    "declineReason": null
  },
  {
    "nameOnCard": "TestT",
    "active": false,
    "declineReason": "payment_stolen"
  }
]";

The string is contained in an object called ApiResponse in a field called data. E.g.

APIResponse apiResponse = APIResponse.builder()
                .data(jsonString)
                .build();

I am trying to map the contents of the string into a list of PaymentObject. The payment object looks like this:

@Data
@Builder
@NoArgsConstructor
@AllArgsConstructor
public class PaymentObject {

    private String declineReason;
    private String nameOnCard;
    private String active; 
}

I am using the following to convert the String into a List<PaymentObject> by the following:

List<PaymentObject> paymentObjectDTOs = mapper.convertValue(apiResponse.getData(), new TypeReference<>() {});

where mapper is ObjectMapper from Jackson 2.13.2.2.

But I am getting the following error:

Cannot deserialize value of type `java.util.ArrayList<com.abc.PaymentObject>` from String value (token `JsonToken.VALUE_STRING`)
 at [Source: UNKNOWN; byte offset: #UNKNOWN]

I can't see what's going wrong.

qdoot · Accepted Answer · 2022-08-16 15:45:31Z

1

You're missing the referenced type. This will work:

List<PaymentObject> paymentObjectDTOs =mapper.readValue(apiResponse.getData(), new TypeReference<List<PaymentObject>>(){});

But make sure you've all the getters and setters methods on the PaymentObject class, as well as the default constructor.

answered Aug 16, 2022 at 15:45

qdoot

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1 Comment

Klitos Kyriacou Over a year ago

The generic type parameters can be inferred from the type on the left-hand side, but your answer works because you're using the correct method, readValue.

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