Rocket rust unprocessable entity returning json errors

Question

Rocket rust unprocessable entity returning json errors

402 Views Asked by Renato Cassino At 06 April 2025 at 06:26

I'm making an API using Rocket and I'm a newbie in this one yet.

I'm reading the documentation, but I cannot find a way to return a json error when the json received is incorrect.

This is my struct

#[derive(Deserialize, Serialize, Clone, Validate)]
#[serde(crate = "rocket::serde", rename_all = "camelCase")]
pub struct Point {
    #[validate(length(min = 10))]
    pub picture: String,
    pub geo_location: GeoLocation,
    pub description: String,
    pub address: String,
    pub place_name: String,
    pub user: String,
}

# My handle controller
#[post("/point", format = "application/json", data = "<data>")]
pub fn new_point(
    data: Validated<Json<Point>>,
) -> Result<status::Custom<Json<Point>>, status::Custom<Json<ErrorType>>> {
    let point: Point = data.into_inner().into_inner();
    // .........
}

And this works, but if I send some wrong json, I just receive a html page.

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="utf-8">
    <title>422 Unprocessable Entity</title>
</head>

<body align="center">
    <div role="main" align="center">
        <h1>422: Unprocessable Entity</h1>
        <p>The request was well-formed but was unable to be followed due to semantic errors.</p>
<!-- ...... -->

In the log appears the error:

Data guard `Validated < Json < Point > >` failed: Err(Parse("{\r\n    \"picture\": \"fdddddddddddd\",\r\n    \"eoLocation\": {\r\n        \"latitude\": 0.1,\r\n        \"longitud
e\": 0.1\r\n    },\r\n    \"description\": \"Works\",\r\n    \"address\": \"Full address\",\r\n    \"user\": \"Fulano\",\r\n    \"placeName\": \"....\"\r\n}", Error("missing field `geoLocation`", line: 11, column: 1))).

How can I do to return something like this:

{
  "error": {
    "message": "missing field `geoLocation`"
  }
}

I tried with catch:

#[catch(422)]
fn unprocessable_entity(req: &Request) -> String {
    format!("message: Some error happen")
}

But I cannot get the error message in instance Request.

How can I do to get the parse error and return in my body api?

Thanks for this.

Original Q&A

There are 1 best solutions below

**Allan Dias Marques** · Answer 1

You can try something like this:

#[catch(422)]
fn unprocessable_entity(req: &Request) -> String {
    let validation_errors = req.local_cache(|| CachedValidationErrors(None)).0.as_ref();

    let mut message = "Something goes wrong!".to_string();
 
    if validation_errors.is_some() {
        message.clear();
        
        let erros = validation_errors.unwrap().field_errors();
        
        for (_,val) in erros.iter() {
            for error in val.iter() {
                message.push_str(error.message.as_ref().unwrap());
            }
        }
    }
    ApiError { code: StatusCode::BadRequest, message: message }

}

Rocket rust unprocessable entity returning json errors

There are 1 best solutions below

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