Response

Okapi Response Helpers

For aborts, error handlers, and RFC 7807 Problem Details, see the error_handling/ skill.

JSON Responses

c.OK(data)            // 200
c.Created(data)       // 201
c.NoContent()         // 204, empty body
c.JSON(code, data)    // custom status

Other Formats

c.XML(code, data)
c.YAML(code, data)
c.Text(code, data) / c.String(code, data)   // String is an alias for Text
c.Data(code, contentType, []byte)           // raw bytes with an explicit content type
c.HTML(code, file, data)                    // parse and render a template file
c.HTMLView(code, templateStr, data)         // render an inline template string
c.Render(code, name, data)                  // named template via the configured Renderer
c.Redirect(code, location)                  // writes the redirect; returns nothing

c.Redirect has no return value — write c.Redirect(...); return nil.

File Serving

c.ServeFile(path)
c.ServeFileFromFS(filepath, fs)         // from any http.FileSystem
c.ServeFileAttachment(path, filename)   // Content-Disposition: attachment (download)
c.ServeFileInline(path, filename)       // Content-Disposition: inline

Structured Response (Body / Status / Header Pattern)

c.Respond (alias c.Return) introspects a struct and writes status, headers, cookies, and body from its fields.

type BookResponse struct {
    Status    int    // HTTP status code (defaults to 200 when absent/zero)
    Body      Book   // response payload
    RequestID string `header:"X-Request-ID"` // response header
    Session   string `cookie:"session"`      // response cookie (Path=/)
}

return c.Respond(&BookResponse{Status: 201, Body: book, RequestID: rid})

Field rules:

That last rule is easy to trip over: a stray field on the response struct silently becomes a header. Keep response structs to Status, Body, and explicitly tagged fields.

The output format comes from the request's Accept header:

okapi.HandleIO and okapi.HandleO write their typed output through the same path.

The target must be a struct or a non-nil pointer to one; otherwise Okapi responds 500.

Response Control

c.WriteStatus(code)              // write the status code only
c.SetHeader(key, value)          // set a response header
c.SetCookie(name, value, maxAge, path, domain, secure, httpOnly) // path defaults to "/"
c.Response()                     // okapi.ResponseWriter (extended interface)
c.ResponseWriter()               // the underlying http.ResponseWriter

Write-Once Semantics

Once a response is committed — by any write helper, including an Abort* call — later calls to c.JSON, c.OK, c.XML, c.Text, c.Render, c.Data, c.Error, c.AbortNotModified, etc. are silent no-ops (logged at debug level). This prevents the double-body bug where a helper aborts without its return value being propagated and the caller then writes a success body:

func loadBook(c *okapi.Context, id int) (*Book, error) {
    b := find(id)
    if b == nil {
        return nil, c.AbortNotFound("book not found") // response already committed
    }
    return b, nil
}

o.Get("/books/{id:int}", func(c *okapi.Context) error {
    b, err := loadBook(c, c.Param("id"))
    if err != nil {
        return err        // preferred: propagate
    }
    return c.OK(b)        // no-op if the response was already written
})

ResponseWriter Extensions

okapi.ResponseWriter extends http.ResponseWriter with:

StatusCode() int                                   // status written, or 0
BytesWritten() int                                 // body bytes written
Close() error                                      // close the writer if supported
Hijack() (net.Conn, *bufio.ReadWriter, error)      // raw TCP (WebSockets, proxies)
Flush()                                            // flush buffered data (streaming, SSE, gzip)
Push(target string, opts *http.PushOptions) error  // HTTP/2 server push

Status Class Helpers

okapi.IsError(code)        // 4xx or 5xx
okapi.IsClientError(code)  // 4xx
okapi.IsServerError(code)  // 5xx