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# Responses
# Introduction
Handlers receive a goyave.Response
and a goyave.Request
as parameters.
goyave.Response
implements http.ResponseWriter
. This object brings a number of convenient methods to write HTTP responses.
If you didn't write anything before the request lifecycle ends, 204 No Content
is automatically written.
# Reference
All functions below require the goyave
package to be imported.
import "goyave.dev/goyave/v3"
List of response methods:
GetStatus GetError GetStacktrace IsEmpty IsHeaderWritten Header Status JSON String Write File Download Error Cookie Redirect TemporaryRedirect Render RenderHTML HandleDatabaseError
# Response.GetStatus
Returns the response code for this request or 0
if not yet set.
Parameters | Return |
---|---|
int |
Example:
fmt.Println(response.GetStatus()) // 200
# Response.GetError
Returns the value which caused a panic in the request's handling, or nil
. The response error is also set when Error()
is called.
This method is mainly used in status handlers.
Parameters | Return |
---|---|
interface{} |
Example:
fmt.Println(response.GetError()) // "panic: something wrong happened"
# Response.GetStacktrace
Return the stacktrace of when the error occurred, or an empty string. The stacktrace is captured by the recovery middleware.
Parameters | Return |
---|---|
string |
Example:
fmt.Println(response.GetStacktrace()) // "goroutine 1 [running]:
// main.main()
// /tmp/sandbox930868764/prog.go:8 +0x39"
# Response.IsEmpty
Return true if nothing has been written to the response body yet.
Parameters | Return |
---|---|
bool |
Example:
fmt.Println(response.IsEmpty()) // true
# Response.IsHeaderWritten
return true if the response header has been written. Once the response header is written, you cannot change the response status and headers anymore.
Parameters | Return |
---|---|
bool |
Example:
fmt.Println(response.IsHeaderWritten()) // false
# Response.Header
Returns the Header map that will be sent.
Parameters | Return |
---|---|
http.Header |
Example:
header := response.Header()
header.Set("Content-Type", "application/json")
# Response.Status
Set the response status code. Calling this method a second time will have no effect.
Parameters | Return |
---|---|
status int | void |
Example:
response.Status(http.StatusOK)
# Response.JSON
Write JSON data as a response. This method automatically sets the Content-Type
header.
Parameters | Return |
---|---|
responseCode int | error |
data interface{} |
Example:
response.JSON(http.StatusOK, map[string]interface{}{
"name": "John Doe",
"tags": []string{"tag1", "tag2"},
})
# Response.String
Write a string as a response.
Parameters | Return |
---|---|
responseCode int | error |
message string |
Example:
response.String(http.StatusOK, "Hello there!")
# Response.Write
Write the data as a response. Can be used to write in-memory files. This method can be called successively.
Returns the number of bytes written.
Parameters | Return |
---|---|
data []byte | int |
error |
Example:
response.Write([]byte("Hello there!"))
# Response.File
Write a file as an inline element.
Automatically detects the file MIME type and sets the "Content-Type" header accordingly. If the file doesn't exist, respond with status 404 Not Found
. The given path can be relative or absolute.
If you want the file to be sent as a download ("Content-Disposition: attachment"), use the Download
function instead.
Parameters | Return |
---|---|
file string | error |
Example:
response.File("/path/to/file")
# Response.Download
Write a file as an attachment element.
Automatically detects the file MIME type and sets the "Content-Type" header accordingly. If the file doesn't exist, respond with status 404 Not Found
. The given path can be relative or absolute.
The fileName
parameter defines the name the client will see. In other words, it sets the header "Content-Disposition" to "attachment; filename="${fileName}""
If you want the file to be sent as an inline element ("Content-Disposition: inline"), use the File
function instead.
Parameters | Return |
---|---|
file string | error |
fileName string |
Example:
response.Download("/path/to/file", "awesome.txt")
# Response.Error
Print the error in the console and return it with an error code 500
.
If debugging is enabled in the config, the error is also written in the response using the JSON format, and the stacktrace is printed in the console. If debugging is not enabled, only the stauts code is set, which means you can still write to the response, or use your error status handler.
Parameters | Return |
---|---|
err interface{} | error |
Example:
v, err := strconv.Atoi("-42")
response.Error(err)
# Response.Cookie
Add a Set-Cookie header to the response. The provided cookie must have a valid Name. Invalid cookies may be silently dropped.
Parameters | Return |
---|---|
cookie *http.Cookie* | void |
Example:
cookie := &http.Cookie{
Name: "cookie-name",
Value: "value",
}
response.Cookie(cookie)
WARNING
Protect yourself from CSRF attacks (opens new window) when using cookies!
# Response.Redirect
Send a permanent redirect response. (HTTP 308)
Parameters | Return |
---|---|
url string | void |
Example:
response.Redirect("/login")
# Response.TemporaryRedirect
Send a temporary redirect response. (HTTP 307)
Parameters | Return |
---|---|
url string | void |
Example:
response.TemporaryRedirect("/maintenance")
# Response.Render
Render a text template with the given data. This method uses the Go's template API (opens new window).
The template path is relative to the resources/template
directory.
Parameters | Return |
---|---|
responseCode int | error |
templatePath string | |
data interface{} |
Example:
type Inventory struct {
Material string
Count uint
}
sweaters := Inventory{"wool", 17}
// data can also be a map[string]interface{}
// Here, "resources/template/template.txt" will be used.
if err := response.Render(http.StatusOK, "template.txt", sweaters); err != nil {
response.Error(err)
}
# Response.RenderHTML
Render an HTML template with the given data. This method uses the Go's template API (opens new window).
The template path is relative to the resources/template
directory.
Parameters | Return |
---|---|
responseCode int | error |
templatePath string | |
data interface{} |
Example:
type Inventory struct {
Material string
Count uint
}
sweaters := Inventory{"wool", 17}
// data can also be a map[string]interface{}
// Here, "resources/template/inventory.html" will be used.
if err := response.RenderHTML(http.StatusOK, "inventory.html", sweaters); err != nil {
response.Error(err)
}
# Response.HandleDatabaseError
Takes a database query result and checks if any error has occurred.
Automatically writes HTTP status code 404 Not Found if the error is a "Not found" error. Calls Response.Error()
if there is another type of error.
Returns true
if there is no error.
Parameters | Return |
---|---|
db *gorm.DB | bool |
Example:
product := model.Product{}
result := database.Conn().First(&product, id)
if response.HandleDatabaseError(result) {
response.JSON(http.StatusOK, product)
}
# Chained writers
Since v2.7.0
It is possible to replace the io.Writer
used by the Response
object. This allows for more flexibility when manipulating the data you send to the client. It makes it easier to compress your response, write it to logs, etc. You can chain as many writers as you want.
Note that at the time your writer's Write()
method is called, the request header is already written, therefore, changing headers or status doesn't have any effect. If you want to alter the headers, do so in a PreWrite(b []byte)
function (from the goyave.PreWriter
interface).
The writer replacement is most often done in a middleware. If your writer implements io.Closer
, it will be automatically closed at the end of the request's lifecycle.
The following example is a simple implementation of a middleware logging everything sent by the server to the client.
import (
"io"
"log"
"goyave.dev/goyave/v3"
)
type LogWriter struct {
writer io.Writer
response *goyave.Response
body []byte
}
func (w *LogWriter) PreWrite(b []byte) {
// All chained writers should implement goyave.PreWriter
// to allow the modification of headers and status before
// they are written.
if pr, ok := w.writer.(goyave.PreWriter); ok {
pr.PreWrite(b)
}
}
func (w *LogWriter) Write(b []byte) (int, error) {
w.body = append(w.body, b...)
return w.writer.Write(b)
}
func (w *LogWriter) Close() error {
// The chained writer MUST be closed if it's closeable.
// Therefore, all chained writers should implement io.Closer.
goyave.Logger.Println("RESPONSE", w.response.GetStatus(), string(w.body))
if wr, ok := w.writer.(io.Closer); ok {
return wr.Close()
}
return nil
}
func LogMiddleware(next goyave.Handler) goyave.Handler {
return func(response *goyave.Response, request *goyave.Request) {
logWriter := &LogWriter{
writer: response.Writer(),
response: response,
}
response.SetWriter(logWriter)
next(response, request)
}
}
# Response.Writer
Return the current writer used to write the response.
Note that the returned writer is not necessarily a http.ResponseWriter
, as it can be replaced using SetWriter
.
Parameters | Return |
---|---|
io.Writer |
# Response.SetWriter
Set the writer used to write the response.
This can be used to chain writers, for example to enable gzip compression, or for logging. The original http.ResponseWriter
is always kept.
Parameters | Return |
---|---|
writer io.Writer |
# Hijack
Since v3.7.0
Goyave responses implement http.Hijacker
(opens new window).
# Response.Hijack
Hijack lets the caller take over the connection.
Returns goyave.ErrNotHijackable
if the underlying http.ResponseWriter
doesn't implement http.Hijacker
. This can happen with HTTP/2 connections.
Middleware executed after controller handlers, as well as status handlers, keep working as usual after a connection has been hijacked. Callers should properly set the response status to ensure middleware and status handler execute correctly. Usually, callers of the Hijack
method set the HTTP status to http.StatusSwitchingProtocols
.
If no status is set, the regular behavior will be kept and 204 No Content
will be set as the response status.
Parameters | Return |
---|---|
net.Conn | |
*bufio.ReadWriter | |
error |
# Response.Hijacked
Returns true
if the underlying connection has been successfully hijacked via the Hijack
method.
Parameters | Return |
---|---|
bool |
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