Custom JSON Marshaller Supporting Base64 encoding | error calling MarshalJSON for type routes.Temp: invalid character 'e'

huangapple
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英文:

Custom JSON Marshaller Supporting Base64 encoding | error calling MarshalJSON for type routes.Temp: invalid character 'e'

问题

我想编写一个自定义的Marshaller。我已经按照以下方式实现了代码。

  1. type Temp struct {
  2. 	Time time.Time
  3. }
  5. func (t Temp) MarshalJSON() ([]byte, error) {
  6. 	type __ Temp
  7. 	var x = __(t)
  8. 	var buff bytes.Buffer
  9. 	if err := json.NewEncoder(&buff).Encode(x); err != nil {
  10. 		return nil, err
  11. 	}
  12. 	raw := buff.Bytes()
  13. 	dst := make([]byte, base64.StdEncoding.EncodedLen(len(raw)))
  14. 	base64.StdEncoding.Encode(dst, raw)
  15. 	return dst, nil
  16. }

路由逻辑如下。

  1. func health(c *gin.Context) {
  2. 	c.JSON(http.StatusOK, gin.H{
  3. 		"token": Temp{time.Now()},
  4. 	})
  5. }

运行后，我得到了以下错误。

  1. 2022/08/06 00:36:53 [Recovery] 2022/08/06 - 00:36:53 panic recovered:
  2. GET /health HTTP/1.1
  3. Host: localhost:9000
  4. Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
  5. Accept-Encoding: gzip, deflate, br
  6. Accept-Language: en-US,en;q=0.9
  7. Cache-Control: max-age=0
  8. Connection: keep-alive
  9. Sec-Ch-Ua: ".Not/A)Brand";v="99", "Google Chrome";v="103", "Chromium";v="103"
  10. Sec-Ch-Ua-Mobile: ?0
  11. Sec-Ch-Ua-Platform: "macOS"
  12. Sec-Fetch-Dest: document
  13. Sec-Fetch-Mode: navigate
  14. Sec-Fetch-Site: none
  15. Sec-Fetch-User: ?1
  16. Upgrade-Insecure-Requests: 1
  17. User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36
  20. json: error calling MarshalJSON for type routes.Temp: invalid character 'e' looking for beginning of value
  21. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/render/json.go:56 (0x19448bd)
  22. 	JSON.Render: panic(err)
  23. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:915 (0x194fd3c)
  24. 	(*Context).Render: if err := r.Render(c.Writer); err != nil {
  25. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:958 (0x19502f3)
  26. 	(*Context).JSON: c.Render(code, render.JSON{Data: obj})
  27. /Users/vajahat/work/dotpe/order/routes/routes.go:43 (0x1f61b9c)
  28. 	health: c.JSON(200, gin.H{
  29. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:165 (0x194a0bc)
  30. 	(*Context).Next: c.handlers[c.index](c)
  31. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/recovery.go:99 (0x195c437)
  32. 	CustomRecoveryWithWriter.func1: c.Next()
  33. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:165 (0x194a0bc)
  34. 	(*Context).Next: c.handlers[c.index](c)
  35. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/logger.go:241 (0x195ae31)
  36. 	LoggerWithConfig.func1: c.Next()
  37. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:165 (0x194a0bc)
  38. 	(*Context).Next: c.handlers[c.index](c)
  39. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/gin.go:489 (0x1958a7b)
  40. 	(*Engine).handleHTTPRequest: c.Next()
  41. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/gin.go:445 (0x1958584)
  42. 	(*Engine).ServeHTTP: engine.handleHTTPRequest(c)
  43. /usr/local/go/src/net/http/server.go:2947 (0x14ca5d3)
  44. 	serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
  45. /usr/local/go/src/net/http/server.go:1991 (0x14c413b)
  46. 	(*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
  47. /usr/local/go/src/runtime/asm_amd64.s:1594 (0x1072640)
  48. 	goexit: BYTE	$0x90	// NOP
  50. [GIN] 2022/08/06 - 00:36:53 | 500 |   5.20548072s |             ::1 | GET      "/health"

错误json: error calling MarshalJSON for type routes.Temp: invalid character 'e' looking for beginning of value困扰了我很长时间。

我期望的输出如下所示。

  1. {
  2.     "token":"eyJUaW1lIjoiMjAyMi0wOC0wNlQwMDo0ODoyOS4yNDEzNTUrMDU6MzAifQo="
  3. }

在调试器中，它是正常工作的。
问题可能出现在渲染时，我希望得到上述输出。

非常感谢您的任何建议或帮助。

英文:

I want to write a custom Marshaller. I have done the implementations as Following.

  1. type Temp struct {
  2. 	Time time.Time
  3. }
  5. func (t Temp) MarshalJSON() ([]byte, error) {
  6. 	type __ Temp
  7. 	var x = __(t)
  8. 	var buff bytes.Buffer
  9. 	if err := json.NewEncoder(&buff).Encode(x); err != nil {
  10. 		return nil, err
  11. 	}
  12. 	raw := buff.Bytes()
  13. 	dst := make([]byte, base64.StdEncoding.EncodedLen(len(raw)))
  14. 	base64.StdEncoding.Encode(dst, raw)
  15. 	return dst, nil
  16. }

The router logic is as follow.

  1. func health(c *gin.Context) {
  2. 	c.JSON(http.StatusOK, gin.H{
  3. 		"token": Temp{time.Now()},
  4. 	})
  5. }

After running, I get the error like.

  1. 2022/08/06 00:36:53 [Recovery] 2022/08/06 - 00:36:53 panic recovered:
  2. GET /health HTTP/1.1
  3. Host: localhost:9000
  4. Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
  5. Accept-Encoding: gzip, deflate, br
  6. Accept-Language: en-US,en;q=0.9
  7. Cache-Control: max-age=0
  8. Connection: keep-alive
  9. Sec-Ch-Ua: ".Not/A)Brand";v="99", "Google Chrome";v="103", "Chromium";v="103"
  10. Sec-Ch-Ua-Mobile: ?0
  11. Sec-Ch-Ua-Platform: "macOS"
  12. Sec-Fetch-Dest: document
  13. Sec-Fetch-Mode: navigate
  14. Sec-Fetch-Site: none
  15. Sec-Fetch-User: ?1
  16. Upgrade-Insecure-Requests: 1
  17. User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/103.0.0.0 Safari/537.36
  20. json: error calling MarshalJSON for type routes.Temp: invalid character 'e' looking for beginning of value
  21. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/render/json.go:56 (0x19448bd)
  22. 	JSON.Render: panic(err)
  23. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:915 (0x194fd3c)
  24. 	(*Context).Render: if err := r.Render(c.Writer); err != nil {
  25. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:958 (0x19502f3)
  26. 	(*Context).JSON: c.Render(code, render.JSON{Data: obj})
  27. /Users/vajahat/work/dotpe/order/routes/routes.go:43 (0x1f61b9c)
  28. 	health: c.JSON(200, gin.H{
  29. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:165 (0x194a0bc)
  30. 	(*Context).Next: c.handlers[c.index](c)
  31. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/recovery.go:99 (0x195c437)
  32. 	CustomRecoveryWithWriter.func1: c.Next()
  33. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:165 (0x194a0bc)
  34. 	(*Context).Next: c.handlers[c.index](c)
  35. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/logger.go:241 (0x195ae31)
  36. 	LoggerWithConfig.func1: c.Next()
  37. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/context.go:165 (0x194a0bc)
  38. 	(*Context).Next: c.handlers[c.index](c)
  39. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/gin.go:489 (0x1958a7b)
  40. 	(*Engine).handleHTTPRequest: c.Next()
  41. /Users/vajahat/go/pkg/mod/github.com/gin-gonic/gin@v1.7.0/gin.go:445 (0x1958584)
  42. 	(*Engine).ServeHTTP: engine.handleHTTPRequest(c)
  43. /usr/local/go/src/net/http/server.go:2947 (0x14ca5d3)
  44. 	serverHandler.ServeHTTP: handler.ServeHTTP(rw, req)
  45. /usr/local/go/src/net/http/server.go:1991 (0x14c413b)
  46. 	(*conn).serve: serverHandler{c.server}.ServeHTTP(w, w.req)
  47. /usr/local/go/src/runtime/asm_amd64.s:1594 (0x1072640)
  48. 	goexit: BYTE	$0x90	// NOP
  50. [GIN] 2022/08/06 - 00:36:53 | 500 |   5.20548072s |             ::1 | GET      "/health"

The error json: error calling MarshalJSON for type routes.Temp: invalid character 'e' looking for beginning of value is troubling me for very long.

I am expecting an output as following.

  1. {
  2.     "token":"eyJUaW1lIjoiMjAyMi0wOC0wNlQwMDo0ODoyOS4yNDEzNTUrMDU6MzAifQo="
  3. }

While in debugger, It is working.
The problem is at rendering time, i belive. I want to get above as output.

Any suggestion or help is highly appreciated.

Custom JSON Marshaller Supporting Base64 encoding | error calling MarshalJSON for type routes.Temp: invalid character 'e'

答案1

得分: 2

你的MarshalJSON()函数必须返回一个有效的JSON值；然而，你的示例生成了一个原始的Base64字符串，这不是有效的JSON。

你可以通过简单地在当前的返回值外面添加引号来修复它，使其成为一个有效的JSON字符串！

  1. b64len := base64.StdEncoding.EncodedLen(len(raw))
  2. dst := make([]byte, b64len+2)
  3. base64.StdEncoding.Encode(dst[1:], raw)
  4. dst[0], dst[b64len+1] = '"', '"'
  5. return dst, nil
英文:

Your MarshalJSON() function must return a valid JSON value; however, your example produces a raw Base64 string, which is not valid JSON.

You can fix it by simply wrapping your current return value in quotes to make it a valid JSON string!

<!-- language: lang-go -->

  1. b64len := base64.StdEncoding.EncodedLen(len(raw))
  2. dst := make([]byte, b64len+2)
  3. base64.StdEncoding.Encode(dst[1:], raw)
  4. dst[0], dst[b64len+1] = &#39;&quot;&#39;, &#39;&quot;&#39;
  5. return dst, nil

huangapple
  • 本文由 发表于 2022年8月6日 03:28:22
  • 转载请务必保留本文链接：https://go.coder-hub.com/73254490.html
  • encoding-json-go
  • go
  • go-gin
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