(Quick Reference) # 8.4 CORS Version: 6.0.0 ## 8.4 CORS Spring Boot provides CORS support out of the box, but it is difficult to configure in a Grails application due to the way UrlMappings are used instead of annotations that define URLs. Starting with Grails 3.2.1, we have added a way to configure CORS that makes sense in a Grails application. Once enabled, the default setting is "wide open". application.yml
    grails:
        cors:
            enabled: true
That will produce a mapping to all urls `/**` with:
allowedOrigins | `['*']`
allowedMethods | `['*']`
allowedHeaders | `['*']`
exposedHeaders | `null`
maxAge | `1800`
allowCredentials | false
Some of these settings come directly from Spring Boot and can change in future versions. See Spring CORS Configuration Documentation All of those settings can be easily overridden. application.yml
    grails:
        cors:
            enabled: true
            allowedOrigins:
                - http://localhost:5000
In the example above, the `allowedOrigins` setting will replace `[*]`. You can also configure different URLs. application.yml
    grails:
        cors:
            enabled: true
            allowedHeaders:
                - Content-Type
            mappings:
                '[/api/**]':
                    allowedOrigins:
                        - http://localhost:5000
                    # Other configurations not specified default to the global config
Note that the mapping key must be made with bracket notation (see https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-Configuration-Binding#map-based-binding), which is a breaking change between Spring Boot 1.5 (Grails 3) and Spring Boot 2 (Grails 4).
| Specifying at least one mapping will disable the creation of the global mapping (`/**`). If you wish to keep that setting, you should specify it along with your other mappings.
The settings above will produce a single mapping of `/api/**` with the following settings:
allowedOrigins | `['http://localhost:5000']`
allowedMethods | `['*']`
allowedHeaders | `['Content-Type']`
exposedHeaders | `null`
maxAge | `1800`
allowCredentials | false
If you don’t wish to override any of the default settings, but only want to specify URLs, you can do so like this example: application.yml
    grails:
        cors:
            enabled: true
            mappings:
                '[/api/**]': inherit
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