How to get Authorization header from an MethodInterpcetor on micronaut?

Question

Before everything I tried this two solution but didn't work for me
Equivalent of javax.ws.rs NameBinding in Micronaut?
https://blogs.ashrithgn.com/custom-annotation-to-handle-authorisation-in-micronaut-aop-tutorial/

In my application I have to get a string in the Authorization header and then decode it from base64 and the json transform it into a POJO. Certainly the string is a jwt and I need to decode the public part of the json to get a data from a field.
Technically speaking a client will forward the header to me to take it, decode it and extract the data. (It's very bad practice but that's what I have to do).

For this I am using micronaut 2.4.1 and this is my code:

Interceptor:

public class HeadInterceptor implements MethodInterceptor<Object, Object> {
    @SneakyThrows
    @Override
    public Object intercept(MethodInvocationContext<Object, Object> context) {

        Request request = (Request) context.getParameterValueMap().get("request");
        // Where do i get Authorization header?
        // i.e String token = (String) context.getParameterValueMap().get("Authorization");
        String token = "eyJhdWQiOiJ0ZXN0IiwiaXNzIjoidGVzdCIsInN1YiI6InRlc3QiLCJleHAiOjExMTExMTEsImlhdCI6MTExMTExMTEsImRhdGEiOiJ0ZXN0In0=";

        ObjectMapper mapper = new ObjectMapper();
        Info info = mapper.readValue(new String(Base64.getDecoder().decode(token)), Info.class);
        request.setData(info.getSub().toUpperCase());

        return context.proceed();
    }
}

Controller:

@Controller("/main")
public class MainController {

    @Post
    @Head
    public Single<Response> index(@Body @Valid Request request) {
        return Single.just(
                Response.builder()
                        .message(String.format("%s-%s", request.getData(), request.getInfo()))
                        .build()
        );
    }
}

Here's a sample app https://github.com/j1cs/micronaut-jacksonxml-error
(ignore the name is for other issue)

Answer 1

In your implementation, the header cannot be shown in the interceptor because your index method doesn't receive it as a parameter.

So, if you add it as a parameter as below:

...
@Post
@Head
public Single<Response> index(@Body @Valid Request request, @Header("Authorization") String authorizationHeader) {
    return Single.just(
            Response.builder()
                    .message(String.format("%s-%s", request.getData(), request.getInfo()))
                    .build()
    );
}
...

Then, you can retrieve it in the intercept method via getParameterValues(). Basically, it will be the second argument.

...
@SneakyThrows
@Override
public Object intercept(MethodInvocationContext<Object, Object> context) {
    ...
    String token = (String) context.getParameterValues()[1];
    ...
}
...

Update

Since you want your Request to contain both body and header, I edited the solution a bit. Basically, the header is added as a member variable to Request as below:

public class Request {
    @NotNull
    @NotBlank
    private String info;
    private String data;

    @Header("Authorization")
    String authorizationHeader;
} 

Then, use @RequestBean rather than a @Body annotation on your Request parameter:

...
@Post
@Head
public Single<Response> index(@RequestBean @Valid Request request) {
    return Single.just(
            Response.builder()
                    .message(String.format("%s-%s", request.getData(), request.getInfo()))
                    .build()
    );
}
...

Finally, you can access the header easily in your intercept() method as follows:

@SneakyThrows
@Override
public Object intercept(MethodInvocationContext<Object, Object> context) {
    ...   
    Request request = (Request) context.getParameterValueMap().get("request");
    String token = request.authorizationHeader;
    ...
}

I created a pull request for this change here, so you can check how it works.