Spring - Handling null values in Request Parameters

Question

In Spring (4.3.9):

A Request param sent from client as null to server, the null object is getting treated as string null in the request when obtained via request-param like:

@RequestParam(value = key, required = false) Integer key

As for as the solution goes, I can handle this via client and prevent the null from being passed in the first place and I couldn't get a clear solution from this (JavaScript: Formdata append null value - NumberFormatException).

Can anyone please help me out as to what class or method in spring framework does this conversion from a null object to string null.

You're looking for HttpMessageConverter and the Converter framework generally, but you haven't really described enough of your case to understand if there's an underlying problem (for example, it's not clear whether you mean s == null or s.equals("null")). Including an actual HTTP request would be helpful. — chrylis -cautiouslyoptimistic-
– chrylis -cautiouslyoptimistic-, Commented Nov 8, 2018 at 19:54

Facundo Ch. · Accepted Answer · 2022-10-19 06:16:13Z

4

Whatever the content you provide for the @RequestParam by default it will treat as string, that is the reason null is treating as "null" string. In the spring framework the Converter<S, R> and ConverterFactory<S, R> will convert from String to corresponding type.

You can write custom converter and add it to spring registry here

public class StringToIntegerConverter implements Converter<String, Integer> {

@Override
public Integer convert(String from) {
    // custom logic
   }
}

register

@Configuration
public class WebConfig implements WebMvcConfigurer {

@Override
public void addFormatters(FormatterRegistry registry) {
    registry.addConverter(new StringToIntegerConverter());
       }
 }

edited Oct 19, 2022 at 6:16

Facundo Ch.

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answered Nov 8, 2018 at 19:55

Ryuzaki L

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3 Comments

Mohan Krishnan Over a year ago

Thanks for the info.The converter you pointed out converts the string to the desired type mentioned in the @RequestParam, but can you point me where does the null object passed from client is getting converted to string null. --------------------------------------------------------------------------------------------------------- I could see that when i do request.getParameter("key") it return me string null ("null") in my first filter itself. So am assuming this conversion happens in the apache http layer. I just need to know the class file , method that parses this.

Ryuzaki L Over a year ago

i'm not sure to that point, may be front controller is the main point of request

Mohan Krishnan Over a year ago

Thanks for the prompt help. I'll just handle this client to avoid issues for now and also i'll keep this open for better explanation.

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