switch off html wrapping of errors in nginx - nginx

Question

I use nginx on Ubuntu to forward requests to a Spring Boot-driven API server. Sometimes the API returns a body with 4xx and 5xx errors, that the client application consumes. E.g. in the API code I might return:
{
"message": "blah"
}
However nginx seems to wrap errors up into some HTML and embeds the response within them. Is there any way to disable this behavior? And is there a way to do it en masse (i.e. for all 4xx and 5xx errors, without explicitly writing them all out with error_page for example)
Similar question and accepted answer here, however that seems to be a bit of hack. I'm sure there's a better way of doing this...
EDIT: Config looks like this:
server {
listen 80;
server_name my.domain.com;
location / {
proxy_pass http://127.0.0.1:9001;
}
}

Answer 1

You just need to add a error_page directive inside the location
server {
listen 80;
server_name my.domain.com;
location / {
error_page 404 = 404;
proxy_pass http://127.0.0.1:9001;
}
}
What this would do is cancel error_page from previous directives set at the http block. And pass the result back to the client as it is. You don't want the codes for which JSON should be sent back to the client in this error_page directive.

Answer 2

You can try update your nginx conf and add:
error_page 403 /error403.html;
location = /error403.html {
root html;
}
or for group of erros:
error_page 500 502 504 /50x.html;
location = /50x.html {
root html;
}
And here you can replace html files to json so nginx will return json respnse, like:
error_page 404 /404.json;
location = /404.json {
root html;
}
and don't forget put 404.json (and all appropriate files) into root which is specified in config.
In your config it will look like:
server {
listen 80;
server_name my.domain.com;
location / {
proxy_pass http://127.0.0.1:9001;
}
error_page 404 /404.json;
location = /404.json {
root html;
}
error_page 500 502 504 /50x.json;
location = /50x.json {
root html;
}
}