[FIXED] SpringBoot atomically convert integer to boolean with @RequestBody annotation? How can I reject integer to be converted to boolean?

Issue

My request was an application/json type like this: {"able": true}, but when I send the request like this {"able":12345}, the field able still can get a correct value true. Why?

@PatchMapping("/{id}/path/{name}")
public ResponseEntity someMethod(
    @Valid @RequestBody SomeRequest request) {
    // do something
}

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class SomeRequest {
    @AssertTrue
    @NotNull
    private Boolean able;
}

Solution

Because jackson.databind will parse int to bool when field type is bool. Find code in NumberDeserializers.BooleanDeserializer

            JsonToken t = p.getCurrentToken();
            if (t == JsonToken.VALUE_TRUE) {
                return Boolean.TRUE;
            }
            if (t == JsonToken.VALUE_FALSE) {
                return Boolean.FALSE;
            }
            return _parseBoolean(p, ctxt);

_parseBoolean(p, ctxt) will parse int to bool.

We can do it by ourselves not use default.

1. Create our bool deser class.

public class MyDeser extends JsonDeserializer {
    @Override
    public Object deserialize(JsonParser p, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        JsonToken t = p.getCurrentToken();
        if (t == JsonToken.VALUE_TRUE) {
            return Boolean.TRUE;
        }
        if (t == JsonToken.VALUE_FALSE) {
            return Boolean.FALSE;
        }
        return null; 
        // not parse int to bool but null and it may work ok.
        // if throw new IOException(), it will work fail. Maybe return null means use other deser to deal it. throw Exception means fail. I don't know it clearly.
    }
}

2. Create a configuration and inject a SimpleModule bean. I write in application

 @SpringBootApplication
 @Configuration
 public class DemoApplication {
     @Bean
     public SimpleModule addDeser() {
         return new SimpleModule().addDeserializer(Boolean.class, new MyDeser());
     }
     public static void main(String[] args) {
         SpringApplication.run(DemoApplication.class, args);
     }
 }

Answered By - sunsunsun
Answer Checked By - Marie Seifert (JavaFixing Admin)