Possible bug with TokenFilter #572
Description
Hello, I was trying to update a library I own, jackson-jaxrs-propertyfiltering, to use a TokenFilter and ran into an issue that struck me as surprising and/or a bug. For some background, this library extends the jackson-jaxrs-json-provider and let's callers filter JSON responses using query params (so if you just need the id and name of each object you could pass ?property=id&property=name).
Previously this library would serialize the response to a JsonNode, apply the filtering to the JsonNode, and then serialize the filtered JsonNode to the HTTP response. This worked fine, but is very inefficient. I tried updating this to use a TokenFilter to apply the filtering in a streaming fashion and things worked great except we had some test failures around empty objects. For example, given a JSON document like:
[
{
"id":123,
"name":"abc",
"other":"def"
},
{
"id":123,
"name":"abc",
"other":"def"
},
{
"id":123,
"name":"abc",
"other":"def"
}
]If the request looks like ?property=id&property=name then things work great and the response looks like:
[
{
"id":123,
"name":"abc"
},
{
"id":123,
"name":"abc"
},
{
"id":123,
"name":"abc"
}
]However, if the response filters out all the properties, such as ?property=fake, then we end up with just the empty string:
So we return an HTTP 200 with no JSON at all and the caller blows up. Before the switch to a TokenFilter, this would have filtered out all of the object keys but retained the JSON structure so you end up with something like:
[{},{},{}]I pushed a complete example to my fork:
jhaber@3e637a8
Is there a way to achieve this sort of behavior currently? If not, would you be open to a PR that adds a new option to FilteringGeneratorDelegate that enables this behavior?
Thanks in advance