在Go中使用JSON时出现恐慌

huangapple
go评论117阅读模式
英文:

panic with JSON in go

问题

我尝试运行以下代码

  1. package main
  3. import (
  4.     "encoding/json"
  5.     "fmt"
  6.     /*"labix.org/v2/mgo"
  7.     "labix.org/v2/mgo/bson"*/
  8. )
  10. func insertEntry(j *map[string]interface{}, entry string) {
  11.     err := json.Unmarshal([]byte(entry), j)
  12.     if err != nil {
  13.         panic(err)
  14.     }
  16. }
  18. func main() {
  19.     c1 := "{" +
  20.         `"mw" : 42.0922,` +
  21.         `"ΔfH°gas" : {` +
  22.         `   "value" : 372.38,` +
  23.         `   "units" : "kJ/mol"` +
  24.         `},` +
  25.         `"S°gas" : {` +
  26.         `   "value" : 216.81,` +
  27.         `   "units" : "J/mol×K"` +
  28.         `},` +
  29.         `"index" : [` +
  30.         `   {"name" : "mw", "value" : 42.0922},` +
  31.         `   {"name" : "ΔfH°gas", "value" : 372.38},` +
  32.         `   {"name" : "S°gas", "value" : 216.81}` +
  33.         `]` +
  34.         `}`
  36.     c2 := "{" +
  37.         `"name" : "silicon",` +
  38.         `"mw" : 32.1173,` +
  39.         `}` +
  40.         `"index" : [` +
  41.         `   {"name" : "mw", "value" : 32.1173}` +
  42.         `]` +
  43.         `}`
  45.     var m map[string]interface{}
  47.     insertEntry(&m, c1)
  48.     insertEntry(&m, c2)
  49.     chemical := m["ΔfH°gas"].(map[string]interface{})
  50.     fmt.Println("value: %s\n", chemical["value"].(string))
  51.     fmt.Println("units: %s\n", chemical["units"].(string))

But I got the following error message:

  1.     $ go run chemeo.go 
  2.     panic: invalid character '}' looking for beginning of object key string
  4.     goroutine 1 [running]:
  5.     main.insertEntry(0xf840045100, 0x4badc4, 0x7f5e00000056, 0x20043115c)
  6.             /media/mictadlo/projects/mgo/chemeo/chemeo.go:19 +0xd8
  7.     main.main()
  8.             /media/mictadlo/projects/mgo/chemeo/chemeo.go:54 +0xa3
  10.     goroutine 2 [syscall]:
  11.     created by runtime.main
  12.             /usr/local/go/src/pkg/runtime/proc.c:221
  13.     exit status 2

What did I do wrong?

英文:

I tried to run the following code

  1. package main
  3. import (
  4.     "encoding/json"
  5.     "fmt"
  6.     /*"labix.org/v2/mgo"
  7.     "labix.org/v2/mgo/bson"*/
  8. )
  10. func insertEntry(j *map[string]interface{}, entry string) {
  11.     err := json.Unmarshal([]byte(entry), j)
  12.     if err != nil {
  13. 	    panic(err)
  14.     }
  16. }
  18. func main() {
  19.     c1 := "{" +
  20. 	    `"mw" : 42.0922,` +
  21. 	    `"ΔfH°gas" : {` +
  22. 	    `   "value" : 372.38,` +
  23. 	    `   "units" : "kJ/mol"` +
  24. 	    `},` +
  25. 	    `"S°gas" : {` +
  26. 	    `   "value" : 216.81,` +
  27. 	    `   "units" : "J/mol×K"` +
  28. 	    `},` +
  29. 	    `"index" : [` +
  30. 	    `   {"name" : "mw", "value" : 42.0922},` +
  31. 	    `   {"name" : "ΔfH°gas", "value" : 372.38},` +
  32. 	    `   {"name" : "S°gas", "value" : 216.81}` +
  33. 	    `]` +
  34. 	    `}`
  36.     c2 := "{" +
  37. 	    `"name" : "silicon",` +
  38. 	    `"mw" : 32.1173,` +
  39. 	    `}` +
  40. 	    `"index" : [` +
  41. 	    `   {"name" : "mw", "value" : 32.1173}` +
  42. 	    `]` +
  43. 	    `}`
  45.     var m map[string]interface{}
  47.     insertEntry(&m, c1)
  48.     insertEntry(&m, c2)
  49.     chemical := m["ΔfH°gas"].(map[string]interface{})
  50.     fmt.Println("value: %s\n", chemical["value"].(string))
  51.     fmt.Println("units: %s\n", chemical["units"].(string))

But I got the following error message:

  1.     $ go run chemeo.go 
  2.     panic: invalid character '}' looking for beginning of object key string
  4.     goroutine 1 [running]:
  5.     main.insertEntry(0xf840045100, 0x4badc4, 0x7f5e00000056, 0x20043115c)
  6.             /media/mictadlo/projects/mgo/chemeo/chemeo.go:19 +0xd8
  7.     main.main()
  8.             /media/mictadlo/projects/mgo/chemeo/chemeo.go:54 +0xa3
  10.     goroutine 2 [syscall]:
  11.     created by runtime.main
  12.             /usr/local/go/src/pkg/runtime/proc.c:221
  13.     exit status 2

What did I do wrong?

答案1

得分: 12

你的c2变量保存的是无效的JSON：

  1. c2 := "{" +
  2. `"name" : "silicon",` +
  3. `"mw" : 32.1173,` +
  4. `}` +
  5. `"index" : [` +
  6. ` {"name" : "mw", "value" : 32.1173}` +
  7. `]` +
  8. `}`

清理后，它应该是这样的：

  1. c2 := `{
  2.     "name" : "silicon",
  3.     "mw" : 32.1173,
  4. }
  5. "index" : [
  6.     {"name" : "mw", "value" : 32.1173}
  7. ]
  8. }`

你可以看到中间多了一个}。

它应该是这样的：

  1. c2 := `{
  2.     "name": "silicon",
  3.     "mw": 32.1173,
  4.     "index": [
  5.         {
  6.             "name": "mw",
  7.             "value": 32.1173
  8.         }
  9.     ]
  10. }`
英文:

Your c2 variable is holding invalid JSON:

  1. c2 := "{" +
  2. `"name" : "silicon",` +
  3. `"mw" : 32.1173,` +
  4. `}` +
  5. `"index" : [` +
  6. ` {"name" : "mw", "value" : 32.1173}` +
  7. `]` +
  8. `}`

Cleaned up, it'll look like this:

  1. c2 := `{
  2.     "name" : "silicon",
  3.     "mw" : 32.1173,
  4. }
  5. "index" : [
  6.     {"name" : "mw", "value" : 32.1173}
  7. ]
  8. }`

You can see there's an extra } in the middle.

It should look like this:

  1. c2 := `{
  2.     "name": "silicon",
  3.     "mw": 32.1173,
  4.     "index": [
  5.         {
  6.             "name": "mw",
  7.             "value": 32.1173
  8.         }
  9.     ]
  10. }`

huangapple
  • 本文由 发表于 2013年3月14日 07:34:48
  • 转载请务必保留本文链接：https://go.coder-hub.com/15398559.html
  • go
  • json
  • mgo
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