php editor Baicao introduces to you how to receive JSON data and images in the Golang gin framework. During the development process, we often need to process JSON data and image files passed from the front end. Golang's gin framework provides simple and easy-to-use methods to receive and process this data. Through the introduction of this article, you will learn how to use structures in the gin framework to receive JSON data and how to process uploaded image files. Let’s explore together!
I have the code for the request handler:
func (h *handlers) updateprofile() gin.handlerfunc { type request struct { username string `json:"username" binding:"required,min=4,max=20"` description string `json:"description" binding:"required,max=100"` } return func(c *gin.context) { var updaterequest request if err := c.bindjson(&updaterequest); err != nil { var validationerrors validator.validationerrors if errors.as(err, &validationerrors) { validateerrors := base.bindingerror(validationerrors) c.abortwithstatusjson(http.statusbadrequest, gin.h{"error": validateerrors}) } else { c.abortwitherror(http.statusbadrequest, err) } return } avatar, err := c.formfile("avatar") if err != nil { c.abortwithstatusjson(http.statusbadrequest, gin.h{ "error": "image not contains in request", }) return } log.print(avatar) if avatar.size > 3<<20 { // if avatar size more than 3mb c.abortwithstatusjson(http.statusbadrequest, gin.h{ "error": "image is too large", }) return } file, err := avatar.open() if err != nil { c.abortwitherror(http.statusinternalservererror, err) } session := sessions.default(c) id := session.get("sessionid") log.printf("id type: %t", id) err = h.userservice.updateprofile(fmt.sprintf("%v", id), file, updaterequest.username, updaterequest.description) if err != nil { c.abortwithstatusjson(http.statusbadrequest, gin.h{}) return } c.indentedjson(http.statusnocontent, gin.h{"message": "succesfull update"}) } }
I unit tested this handler:
func testuser_updateprofile(t *testing.t) { type testcase struct { name string image io.reader username string description string expectedstatuscode int } router := gin.default() memstore := memstore.newstore([]byte("secret")) router.use(sessions.sessions("session", memstore)) usergroup := router.group("user") repo := user.newmemory() service := userservice.new(repo) userhandlers.register(usergroup, service) testimage := make([]byte, 100) rand.read(testimage) image := bytes.newreader(testimage) testcases := []testcase{ { name: "request with image", image: image, username: "bobik", description: "wanna be sharik", expectedstatuscode: http.statusnocontent, }, { name: "request without image", image: nil, username: "sharik", description: "wanna be bobik", expectedstatuscode: http.statusnocontent, }, } for _, tc := range testcases { t.run(tc.name, func(t *testing.t) { body := &bytes.buffer{} writer := multipart.newwriter(body) imagewriter, err := writer.createformfile("avatar", "test_avatar.jpg") if err != nil { t.fatal(err) } if _, err := io.copy(imagewriter, image); err != nil { t.fatal(err) } data := map[string]interface{}{ "username": tc.username, "description": tc.description, } jsondata, err := json.marshal(data) if err != nil { t.fatal(err) } jsonwriter, err := writer.createformfield("json") if err != nil { t.fatal(err) } if _, err := jsonwriter.write(jsondata); err != nil { t.fatal(err) } writer.close() // creating request req := httptest.newrequest( http.methodpost, "http://localhost:8080/user/account/updateprofile", body, ) req.header.set("content-type", writer.formdatacontenttype()) log.print(req) w := httptest.newrecorder() router.servehttp(w, req) assert.equal(t, tc.expectedstatuscode, w.result().statuscode) }) } }
The following error occurred during the test: Error #01: Invalid character '-' in numeric literal
This is the request body (I print it using log.print(req)):
&{POST http://localhost:8080/user/account/updateprofile HTTP/1.1 1 1 map[Content-Type:[multipart/form-data; boundary=30b24345de9d8d83ecbdd146262d86894c45b4f3485e4615553621fd2035]] {--30b24345de9d8d83ecbdd146262d86894c45b4f3485e4615553621fd2035 Content-Disposition: form-data; name="avatar"; filename="test_avatar.jpg" Content-Type: application/octet-stream --30b24345de9d8d83ecbdd146262d86894c45b4f3485e4615553621fd2035 Content-Disposition: form-data; name="json" {"description":"wanna be bobik","username":"sharik"} --30b24345de9d8d83ecbdd146262d86894c45b4f3485e4615553621fd2035-- } 414 [] false localhost:8080 map[] map[] map[] 192.0.2.1:1234 http://localhost:8080/user/account/updateprofile }
First, I have only string as json data and convert it to bytes. When the error occurred, I converted the json data using json.marshal without success. I want to parse json data using c.bind and given image using c.formfile, is this possible?
renew. I replaced the code to get the avatar first and then get the json through the bind structure. Now I have eof error.
We can define a structure to receive json data and image files at the same time (note the field labels):
var updaterequest struct { avatar *multipart.fileheader `form:"avatar" binding:"required"` user struct { username string `json:"username" binding:"required,min=4,max=20"` description string `json:"description" binding:"required,max=100"` } `form:"user" binding:"required"` } // c.shouldbind will choose binding.formmultipart based on the content-type header. // we call c.shouldbindwith to make it explicitly. if err := c.shouldbindwith(&updaterequest, binding.formmultipart); err != nil { _ = c.abortwitherror(http.statusbadrequest, err) return }
multipart/form-data?For example,xmloryaml.
The current gin (@1.9.0) does not automatically parsexmloryamlinmultipart/form-data.jsonWe're lucky, because gin happens to usejson.unmarshalto parse form field values when the target field is a struct or map. Seebinding.setwithpropertype.
We can parse them ourselves like this (updaterequest.eventis the string value in the form):
var event struct { at time.time `xml:"time" binding:"required"` player string `xml:"player" binding:"required"` action string `xml:"action" binding:"required"` } if err := binding.xml.bindbody([]byte(updaterequest.event), &event); err != nil { _ = c.abortwitherror(http.statusbadrequest, err) return }
(not to be confused withyamlin theapplication/xmlrequest orxmlin theapplication/x-yamlrequest. This is only required if thexmlcontent or theyamlcontent is in amultipart/form-datarequest) .
c.bindjsoncannot be used to read json frommultipart/form-databecause it assumes the request body starts with valid json. But it starts with a boundary that looks like--30b24345d.... That's why it fails with the error messageinvalid character '-' in numeric literal.c.bindjsonafterc.formfile("avatar")will not work because callingc.formfilewill cause the entire request body to be Read. And there is nothing readable afterc.bindjson. That's why you see the eof error.This is the complete demo. Run ./... -v -count 1:using
package m import ( "bytes" "crypto/rand" "fmt" "io" "mime/multipart" "net/http" "net/http/httptest" "testing" "time" "github.com/gin-gonic/gin" "github.com/gin-gonic/gin/binding" "github.com/stretchr/testify/assert" ) func handle(c *gin.Context) { var updateRequest struct { Avatar *multipart.FileHeader `form:"avatar" binding:"required"` User struct { Username string `json:"username" binding:"required,min=4,max=20"` Description string `json:"description" binding:"required,max=100"` } `form:"user" binding:"required"` Event string `form:"event" binding:"required"` } // c.ShouldBind will choose binding.FormMultipart based on the Content-Type header. // We call c.ShouldBindWith to make it explicitly. if err := c.ShouldBindWith(&updateRequest, binding.FormMultipart); err != nil { _ = c.AbortWithError(http.StatusBadRequest, err) return } fmt.Printf("%#v\n", updateRequest) var event struct { At time.Time `xml:"time" binding:"required"` Player string `xml:"player" binding:"required"` Action string `xml:"action" binding:"required"` } if err := binding.XML.BindBody([]byte(updateRequest.Event), &event); err != nil { _ = c.AbortWithError(http.StatusBadRequest, err) return } fmt.Printf("%#v\n", event) } func TestMultipartForm(t *testing.T) { testImage := make([]byte, 100) if _, err := rand.Read(testImage); err != nil { t.Fatal(err) } image := bytes.NewReader(testImage) body := &bytes.Buffer{} writer := multipart.NewWriter(body) imageWriter, err := writer.CreateFormFile("avatar", "test_avatar.jpg") if err != nil { t.Fatal(err) } if _, err := io.Copy(imageWriter, image); err != nil { t.Fatal(err) } if err := writer.WriteField("user", `{"username":"bobik","description":"wanna be sharik"}`); err != nil { t.Fatal(err) } xmlBody := ` playerOne strike (miss) ` if err := writer.WriteField("event", xmlBody); err != nil { t.Fatal(err) } writer.Close() req := httptest.NewRequest( http.MethodPost, "http://localhost:8080/update", body, ) req.Header.Set("Content-Type", writer.FormDataContentType()) fmt.Printf("%v\n", req) w := httptest.NewRecorder() c, engine := gin.CreateTestContext(w) engine.POST("/update", handle) c.Request = req engine.HandleContext(c) assert.Equal(t, 200, w.Result().StatusCode) }
Thank you for reading!
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