Json can not deserialize instance Error in Spring

Question

I am trying to send a json long list and take records from db.

My controller is:

@Api(tags = Endpoint.RESOURCE_customer, description = "customer Resource")
@RestController
@RequestMapping(produces = MediaType.APPLICATION_JSON_VALUE,consumes = MediaType.APPLICATION_JSON_VALUE)
@ResponseStatus(HttpStatus.OK)
public class CustomerResourceController {

    private final customerService customerService;


    public CustomerResourceController(customerService customerService) {

        this.customerService = customerService;
    }

    @ApiOperation(
            value = "Return customer",
            response = customerDto.class, responseContainer="List"
    )
    @PostMapping(value = Endpoint.RRESOURCE_customer_ID)
    public List<customerDto> getCustomersByIds(@RequestBody List<Long> ids) {
        return customerService.findcustomerIds(ids);
    }

}

and client class is:

@Headers("Content-Type: " + MediaType.APPLICATION_JSON_VALUE)
public interface CustomerClient {

@RequestLine("POST /customer/customers/search")
    List<LocGrpDto> getCustomersByIds(@RequestBody @Validated List<Long> ids);
}

And i test this service in postman with JSON:

{ "ids": [1,7,8] }

But I get this error:

{
    "timestamp": "2018-10-05T13:29:57.645+0000",
    "status": 400,
    "error": "Bad Request",
    "message": "Could not read document: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token\n at [Source: java.io.PushbackInputStream@3cb8b584; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token\n at [Source: java.io.PushbackInputStream@3cb8b584; line: 1, column: 1]",
    "path": "/api/v1/customer/customers/search",
    "errors": []
}

What is the problem? Do you see any problem here or it may be caused because of my service class or dto classes ?

If you look at @RequestBody List<Long> ids then you can tell that it takes a list (JSON equivalent JSONArray). You can change it to Map if you want to stick to { "ids": [1,7,8] } — nabster
– nabster, Commented Oct 5, 2018 at 13:53

score 3 · Accepted Answer · 2018-10-05 13:53:42Z

3

Try requesting with the payload [1,7,8], not {"ids": [1,7,8]}.

Your JSON would translate to a request body with the next format.

class Body {

    private List<Long> ids;

    // constructor, getters and setters 

}

For a REST client, you can take a look at RestTemplate.

RestTemplate template;
List<Long> ids;
List<CustomerDto> = template.exchange(
            "/customer/customers/search",
            HttpMethod.POST,
            new HttpEntity<>(ids),
            new ParameterizedTypeReference<List<CustomerDto>>() {}).getBody()

edited Oct 5, 2018 at 13:53

answered Oct 5, 2018 at 13:46

user10367961

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4 Comments

abidinberkay Over a year ago

now I have got 500 internal server error but probably it is because of my code right ? i mean now the json request format is correct probably.

user10367961 Over a year ago

What does the exception say on the server side?

user10367961 Over a year ago

Are you able to access the ids on the server with the debugger? If you can, your endpoint works as expected, at least on the request side.

abidinberkay Over a year ago

2018-10-05 17:07:55,020 ERROR [] o.a.c.c.C.[.[.[.[dispatcherServlet]:181 - Servlet.service() for servlet [dispatcherServlet] in context with path [/api/v1] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause java.lang.NullPointerException: null at com.customer.customers.service.customerService.findCustomerByIds(LocGrpService.java:33)

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