知っておきたい組み込みGatewayFilter

Before writing custom filters, know that Spring Cloud Gateway ships with dozens of ready-made GatewayFilter factories. You attach them per route in configuration.

This lesson tours the ones you will reach for most often.

AddRequestHeader injects a header into every request before it reaches the backend, useful for tagging traffic from the gateway.

Likewise, AddResponseHeader adds a header to the response sent back to the client, for example a marker showing which gateway handled it.

RewritePath uses a regex to transform the incoming path before forwarding. Strip a public prefix while keeping the rest.

When you just need to drop leading path segments, StripPrefix is simpler than a rewrite. StripPrefix=1 removes the first segment.

The reverse of stripping, PrefixPath prepends a segment to the path sent upstream.

SetStatus forces the HTTP status code of the response, handy for maintenance routes or deprecation notices.

RedirectTo returns a redirect response with a status and target URL instead of proxying.

Strip a header before it reaches the backend with RemoveRequestHeader, for example to drop a client-supplied header you do not trust.

Filters stack in declared order. Here a route strips a prefix, tags the request, and marks the response.

Use default-filters to apply a filter to every route at once, such as adding a correlation header everywhere.

You want to turn /api/users into /users by dropping the first path segment. Which filter is the simplest fit?

You now have a toolbox of built-in filters:

• Header filters: Add/Remove request and response headers
• Path filters: StripPrefix, PrefixPath, RewritePath
• Response control: SetStatus, RedirectTo
• default-filters apply globally

Reach for these before writing custom code, then build custom filters only when nothing fits.