Spring-cloud-gateway: How to modify spring cloud gateway response headers

[DarrenJiang1990]

I am trying to modify a header of response in a post filter of gateway,the filter handle a cors problem which would filt websockt service ,the websockt service is a micro-service which must been decorated with cors configuration，so a websockt request will get a response with multiple header like “Access-Control-Allow-Origin”, to solve this question，i must modify the response header of the key “Access-Control-Allow-Origin”。However ,when i do this, a error occured：

java.lang.UnsupportedOperationException: null at org.springframework.http.ReadOnlyHttpHeaders.set(ReadOnlyHttpHeaders.java:99) ~[spring-web-5.1.6.RELEASE.jar:5.1.6.RELEASE] at com.apigw.filter.CORSFilter.lambda$filter$0(CORSFilter.java:84) ~[classes/:na] at reactor.core.publisher.MonoRunnable.call(MonoRunnable.java:73) ~[reactor-core-3.2.8.RELEASE.jar:3.2.8.RELEASE]

It seems the response header cannot be modifed in post filter,the following is my code,please tell me a way to solve this problem.

code.txt

[ryanjbaxter]

Can you provide a complete, minimal, verifiable sample that reproduces the problem? It should be available as a GitHub (or similar) project or attached to this issue as a zip file.

[DarrenJiang1990]

@ryanjbaxter thanks, the core code is a filter https://github.com/spring-cloud/spring-cloud-gateway/files/3244970/code.txt ,but it can't modify header in a post filter,is it a right way writing like this?

[ryanjbaxter]

That is not a complete working sample, it is just some code.

There should be no reason why a filter cannot modify a response header. We do this already
https://github.com/spring-cloud/spring-cloud-gateway/blob/master/spring-cloud-gateway-core/src/main/java/org/springframework/cloud/gateway/filter/factory/SetResponseHeaderGatewayFilterFactory.java

[DarrenJiang1990]

@ryanjbaxter it seems a route filter,can i modify a response header in a global post filter,thanks

[ryanjbaxter]

yes

[spring-projects-issues]

If you would like us to look at this issue, please provide the requested information. If the information is not provided within the next 7 days this issue will be closed.

[spring-projects-issues]

Closing due to lack of requested feedback. If you would like us to look at this issue, please provide the requested information and we will re-open the issue.

[shi98013]

For those that find this when searching for similar issue...
I too was experiencing the UnsupportedOperationException when I added a post filter to an existing global filter which had an order that caused the post filter to action to occur after the response had been sent.

[M-Thirumal]

Facing same issue, found any solution?

[shi98013]

I suppose your issue may have been different than mine, but when I turned on trace logging I saw that my filter was executing after the response was sent and so I gave the filter a different order value that put it in the right order. Here is a link to someone asking about ordered filters that may provide more insight: https://github.com/spring-cloud/spring-cloud-gateway/issues/1341