JsonMappingException: Can not deserialize instance of java.lang.Integer out of START_OBJECT token

Question

I wanted to write a small and simple REST service using Spring Boot. Here is the REST service code:

@Async
@RequestMapping(value = "/getuser", method = POST, consumes = "application/json", produces = "application/json")
public @ResponseBody Record getRecord(@RequestBody Integer userId) {
    Record result = null;
    // Omitted logic

    return result;
}

The JSON object I sent is the following:

{
    "userId": 3
}

And here is the exception I got:

WARN 964 --- [ XNIO-2 task-7] .w.s.m.s.DefaultHandlerExceptionResolver : Failed to read HTTP message: org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not deserialize instance of java.lang.Integer out of START_OBJECT token at [Source: java.io.PushbackInputStream@12e7333c; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.Integer out of START_OBJECT token at [Source: java.io.PushbackInputStream@12e7333c; line: 1, column: 1]

Ali Dehghani · Accepted Answer · 2016-05-26 21:28:52Z

24

Obviously Jackson can not deserialize the passed JSON into an Integer. If you insist to send a JSON representation of a User through the request body, you should encapsulate the userId in another bean like the following:

public class User {
    private Integer userId;
    // getters and setters
}

Then use that bean as your handler method argument:

@RequestMapping(...)
public @ResponseBody Record getRecord(@RequestBody User user) { ... }

If you don't like the overhead of creating another bean, you could pass the userId as part of Path Variable, e.g. /getuser/15. In order to do that:

@RequestMapping(value = "/getuser/{userId}", method = POST, produces = "application/json")
public @ResponseBody Record getRecord(@PathVariable Integer userId) { ... }

Since you no longer send a JSON in the request body, you should remove that consumes attribute.

answered May 26, 2016 at 21:28

Ali Dehghani

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4 Comments

user2581426 Over a year ago

I know the problem is with the Jackson Object Mapper, but I'm not really know the JSON object sending via HTTP. My original tipp was that the problem is with my JSON object. Thanks your answer Ali Dehghani!

user2581426 Over a year ago

There is no other way to send a simple Integer in POST method without use the PathVariable annotation? Are there any other de/serialization tech beside Jackson that can be deserialize a simple Integer in the request body?

Ali Dehghani Over a year ago

Instead of application/json, you can send a key-value pair, e.g. userId=15 in the request body using application/x-www-form-urlencoded

Indrajeet Gour Over a year ago

if not @PathVariable you can use @RequestParam("userId") that will be the query parameter into URI, and will be treated as "?userId=15" a the end of the your service URI.

Javier Sanchez C · Accepted Answer · 2018-10-14 00:46:33Z

16

Perhaps you are trying to send a request with JSON text in its body from a Postman client or something similar like this:

{
 "userId": 3
}

This cannot be deserialized by Jackson since this is not an Integer (it seems to be, but it isn't). An Integer object from java.lang Integer is a little more complex.

For your Postman request to work, simply put (without curly braces { }):

answered Oct 14, 2018 at 0:46

Javier Sanchez C

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2 Comments

Gimnath Over a year ago

I know this is late but how can I make my controller method to send the request like { "userId": 3 }

Noumenon Over a year ago

@Gimnath Send { "userId": "{{userIdVariable}}" }, wrapped in quotes and with no spaces between the variable name and the braces.

Procrastinator · Accepted Answer · 2024-04-17 06:20:09Z

0

I had a similar issue and I did this (@RequestBody JsonNode json). This ensures that the information isn't passed in the url.

When you want to use the value as a number, just use: json.get(<variableName>).asInt();

edited Apr 17, 2024 at 6:20

Procrastinator

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answered Apr 16, 2024 at 19:09

Eno

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