使用结构字段（而不是 JSON 键）将结构体写入 JSON 文件

huangapple
go评论124阅读模式
英文:

Write Struct to Json File using Struct Fields (not json keys)

问题

如何将一个json文件读入一个结构体中，然后将其重新编组为一个json字符串，其中结构体字段作为键（而不是原始的json键）？

（请参见下面的“期望的输出到Json文件”...）

代码：

  1. package main
  3. import (
  4.     "encoding/json"
  5.     "fmt"
  6.     "io/ioutil"
  7. )
  9. type Rankings struct {
  10.     Keyword  string `json:"keyword"`
  11.     GetCount uint32 `json:"get_count"`
  12.     Engine   string `json:"engine"`
  13.     Locale   string `json:"locale"`
  14.     Mobile   bool   `json:"mobile"`
  15. }
  17. func main() {
  18.     var jsonBlob = []byte(`
  19.         {"keyword":"hipaa compliance form", "get_count":157, "engine":"google", "locale":"en-us", "mobile":false}
  20.     `)
  21.     rankings := Rankings{}
  22.     err := json.Unmarshal(jsonBlob, &rankings)
  23.     if err != nil {
  24.         // nozzle.printError("opening config file", err.Error())
  25.     }
  27.     rankingsJson, _ := json.Marshal(rankings)
  28.     err = ioutil.WriteFile("output.json", rankingsJson, 0644)
  29.     fmt.Printf("%+v", rankings)
  30. }

屏幕上的输出：

  1. {Keyword:hipaa compliance form GetCount:157 Engine:google Locale:en-us Mobile:false}

输出到Json文件：

  1. {"keyword":"hipaa compliance form","get_count":157,"engine":"google","locale":"en-us","mobile":false}

期望的输出到Json文件：

  1. {"Keyword":"hipaa compliance form","GetCount":157,"Engine":"google","Locale":"en-us","Mobile":false}
英文:

How can I read a json file into a struct, and then Marshal it back out to a json string with the Struct fields as keys (rather than the original json keys)?

(see Desired Output to Json File below...)

Code:

  1. package main
  3. import (
  4. 	"encoding/json"
  5. 	"fmt"
  6. 	"io/ioutil"
  7. )
  9. type Rankings struct {
  10. 	Keyword  string `json:"keyword"`
  11. 	GetCount uint32 `json:"get_count"`
  12. 	Engine   string `json:"engine"`
  13. 	Locale   string `json:"locale"`
  14. 	Mobile   bool   `json:"mobile"`
  15. }
  17. func main() {
  18. 	var jsonBlob = []byte(`
  19. 		{"keyword":"hipaa compliance form", "get_count":157, "engine":"google", "locale":"en-us", "mobile":false}
  20. 	`)
  21. 	rankings := Rankings{}
  22. 	err := json.Unmarshal(jsonBlob, &rankings)
  23. 	if err != nil {
  24. 		// nozzle.printError("opening config file", err.Error())
  25. 	}
  27. 	rankingsJson, _ := json.Marshal(rankings)
  28. 	err = ioutil.WriteFile("output.json", rankingsJson, 0644)
  29. 	fmt.Printf("%+v", rankings)
  30. }

Output on screen:

  1. {Keyword:hipaa compliance form GetCount:157 Engine:google Locale:en-us Mobile:false}

Output to Json File:

  1. {"keyword":"hipaa compliance form","get_count":157,"engine":"google","locale":"en-us","mobile":false}

Desired Output to Json File:

  1. {"Keyword":"hipaa compliance form","GetCount":157,"Engine":"google","Locale":"en-us","Mobile":false}

答案1

得分: 30

如果我正确理解你的问题，你只想从结构定义中删除json标签。

所以：

  1. package main
  3. import (
  4.     "encoding/json"
  5.     "fmt"
  6.     "io/ioutil"
  7. )
  9. type Rankings struct {
  10.     Keyword  string 
  11.     GetCount uint32 
  12.     Engine   string 
  13.     Locale   string 
  14.     Mobile   bool   
  15. }
  17. func main() {
  18.     var jsonBlob = []byte(`
  19.         {"keyword":"hipaa compliance form", "get_count":157, "engine":"google", "locale":"en-us", "mobile":false}
  20.     `)
  21.     rankings := Rankings{}
  22.     err := json.Unmarshal(jsonBlob, &rankings)
  23.     if err != nil {
  24.         // nozzle.printError("opening config file", err.Error())
  25.     }
  27.     rankingsJson, _ := json.Marshal(rankings)
  28.     err = ioutil.WriteFile("output.json", rankingsJson, 0644)
  29.     fmt.Printf("%+v", rankings)
  30. }

结果为：

  1. {Keyword:hipaa compliance form GetCount:0 Engine:google Locale:en-us Mobile:false}

输出文件为：

  1. {"Keyword":"hipaa compliance form","GetCount":0,"Engine":"google","Locale":"en-us","Mobile":false}

在http://play.golang.org/p/dC3s37HxvZ上运行示例。

注意：GetCount显示为0，因为它被读取为"get_count"。如果你想读取具有"get_count"而输出"GetCount"的JSON，那么你需要进行一些额外的解析。

有关此特定情况的其他信息，请参见https://stackoverflow.com/q/11527935/1162491。

英文:

If I understand your question correctly, all you want to do is remove the json tags from your struct definition.

So:

  1. package main
  3. import (
  4.     "encoding/json"
  5.     "fmt"
  6.     "io/ioutil"
  7. )
  9. type Rankings struct {
  10.     Keyword  string 
  11.     GetCount uint32 
  12.     Engine   string 
  13.     Locale   string 
  14.     Mobile   bool   
  15. }
  17. func main() {
  18.     var jsonBlob = []byte(`
  19.         {"keyword":"hipaa compliance form", "get_count":157, "engine":"google", "locale":"en-us", "mobile":false}
  20.     `)
  21.     rankings := Rankings{}
  22.     err := json.Unmarshal(jsonBlob, &rankings)
  23.     if err != nil {
  24.         // nozzle.printError("opening config file", err.Error())
  25.     }
  27.     rankingsJson, _ := json.Marshal(rankings)
  28.     err = ioutil.WriteFile("output.json", rankingsJson, 0644)
  29.     fmt.Printf("%+v", rankings)
  30. }

Results in:

  1. {Keyword:hipaa compliance form GetCount:0 Engine:google Locale:en-us Mobile:false}

And the file output is:

  1. {"Keyword":"hipaa compliance form","GetCount":0,"Engine":"google","Locale":"    en-us","Mobile":false}

Running example at http://play.golang.org/p/dC3s37HxvZ

Note: GetCount shows 0, since it was read in as "get_count". If you want to read in JSON that has "get_count" vs. "GetCount", but output "GetCount" then you'll have to do some additional parsing.

See https://stackoverflow.com/q/11527935/1162491 for additional info about this particular situation.

答案2

得分: 1

尝试在结构体中更改JSON格式：

  1. type Rankings struct {
  2.     Keyword  string `json:"关键词"`
  3.     GetCount uint32 `json:"获取次数"`
  4.     Engine   string `json:"引擎"`
  5.     Locale   string `json:"区域"`
  6.     Mobile   bool   `json:"移动设备"`
  7. }

请注意，我将JSON标签翻译为中文，以便更符合中文语境。

英文:

Try to change the json format in the struct

  1. type Rankings struct {
  2.     Keyword  string `json:"Keyword"`
  3.     GetCount uint32 `json:"Get_count"`
  4.     Engine   string `json:"Engine"`
  5.     Locale   string `json:"Locale"`
  6.     Mobile   bool   `json:"Mobile"`
  7. }

答案3

得分: 1

使用json.Marshal() / json.MarshalIndent()时发生了一个问题。
它会覆盖现有文件，这在我的情况下是次优的。我只想向当前文件添加内容，并保留旧内容。

这段代码使用了一个字节缓冲区（bytes.Buffer类型）来写入数据。

这是我目前总结出来的代码：

  1. package srf
  3. import (
  4. 	"bytes"
  5. 	"encoding/json"
  6. 	"os"
  7. )
  9. func WriteDataToFileAsJSON(data interface{}, filedir string) (int, error) {
  10. 	// 将数据写入缓冲区
  11. 	buffer := new(bytes.Buffer)
  12. 	encoder := json.NewEncoder(buffer)
  13. 	encoder.SetIndent("", "\t")
  15. 	err := encoder.Encode(data)
  16. 	if err != nil {
  17. 		return 0, err
  18. 	}
  20. 	// 打开文件
  21. 	file, err := os.OpenFile(filedir, os.O_RDWR|os.O_CREATE, 0755)
  22. 	if err != nil {
  23. 		return 0, err
  24. 	}
  26. 	// 将缓冲区的数据写入文件
  27. 	n, err := file.Write(buffer.Bytes())
  28. 	if err != nil {
  29. 		return 0, err
  30. 	}
  32. 	return n, nil
  33. }

下面是调用该函数的代码，同时还包括了使用json.Marshal()或json.MarshalIndent()覆盖文件的代码：

  1. package main
  3. import (
  4. 	"encoding/json"
  5. 	"fmt"
  6. 	"io/ioutil"
  7. 	"log"
  9. 	minerals "./minerals"
  10. 	srf "./srf"
  11. )
  13. func main() {
  14. 	// Test 结构体的数组
  15. 	var SomeType [10]minerals.Test
  17. 	// 创建 10 个随机数据单元以进行写入
  18. 	for a := 0; a < 10; a++ {
  19. 		SomeType[a] = minerals.Test{
  20. 			Name:   "Rand",
  21. 			Id:     123,
  22. 			A:      "desc",
  23. 			Num:    999,
  24. 			Link:   "somelink",
  25. 			People: []string{"John Doe", "Aby Daby"},
  26. 		}
  27. 	}
  29. 	// 向现有文件添加额外数据，或创建新文件
  30. 	n, err := srf.WriteDataToFileAsJSON(SomeType, "test2.json")
  31. 	if err != nil {
  32. 		log.Fatal(err)
  33. 	}
  34. 	fmt.Println("srf printed", n, "bytes to", "test2.json")
  36. 	// 覆盖之前的文件
  37. 	b, _ := json.MarshalIndent(SomeType, "", "\t")
  38. 	ioutil.WriteFile("test.json", b, 0644)
  39. }

为什么这很有用？
File.Write() 返回写入文件的字节数！因此，如果您想管理内存或存储，这非常完美。

WriteDataToFileAsJSON() 函数返回写入的字节数和错误信息。

英文:

An accourance happened by just using json.Marshal() / json.MarshalIndent().
It overwrites the existing file, which in my case was suboptimal. I just wanted to add content to current file, and keep old content.

This writes data through a buffer, with bytes.Buffer type.

This is what I gathered up so far:

  1. package srf
  3. import (
  4. 	&quot;bytes&quot;
  5. 	&quot;encoding/json&quot;
  6. 	&quot;os&quot;
  7. )
  9. func WriteDataToFileAsJSON(data interface{}, filedir string) (int, error) {
  10. 	//write data as buffer to json encoder
  11. 	buffer := new(bytes.Buffer)
  12. 	encoder := json.NewEncoder(buffer)
  13. 	encoder.SetIndent(&quot;&quot;, &quot;\t&quot;)
  15. 	err := encoder.Encode(data)
  16. 	if err != nil {
  17. 		return 0, err
  18. 	}
  19. 	file, err := os.OpenFile(filedir, os.O_RDWR|os.O_CREATE, 0755)
  20. 	if err != nil {
  21. 		return 0, err
  22. 	}
  23. 	n, err := file.Write(buffer.Bytes())
  24. 	if err != nil {
  25. 		return 0, err
  26. 	}
  27. 	return n, nil
  28. }

This is the execution of the function, together with the standard json.Marshal() or json.MarshalIndent() which overwrites the file

  1. package main
  3. import (
  4. 	&quot;encoding/json&quot;
  5. 	&quot;fmt&quot;
  6. 	&quot;io/ioutil&quot;
  7. 	&quot;log&quot;
  9. 	minerals &quot;./minerals&quot;
  10. 	srf &quot;./srf&quot;
  11. )
  13. func main() {
  15. 	//array of Test struct
  16. 	var SomeType [10]minerals.Test
  18. 	//Create 10 units of some random data to write
  19. 	for a := 0; a &lt; 10; a++ {
  20. 		SomeType[a] = minerals.Test{
  21. 			Name:   &quot;Rand&quot;,
  22. 			Id:     123,
  23. 			A:      &quot;desc&quot;,
  24. 			Num:    999,
  25. 			Link:   &quot;somelink&quot;,
  26. 			People: []string{&quot;John Doe&quot;, &quot;Aby Daby&quot;},
  27. 		}
  28. 	}
  30. 	//writes aditional data to existing file, or creates a new file
  31. 	n, err := srf.WriteDataToFileAsJSON(SomeType, &quot;test2.json&quot;)
  32. 	if err != nil {
  33. 		log.Fatal(err)
  34. 	}
  35. 	fmt.Println(&quot;srf printed &quot;, n, &quot; bytes to &quot;, &quot;test2.json&quot;)
  36. 	
  37. 	//overrides previous file
  38. 	b, _ := json.MarshalIndent(SomeType, &quot;&quot;, &quot;\t&quot;)
  39. 	ioutil.WriteFile(&quot;test.json&quot;, b, 0644)
  41. }

Why is this useful?
File.Write() returns bytes written to the file! So this is perfect if you want to manage memory or storage.

  1. WriteDataToFileAsJSON() (numberOfBytesWritten, error)

huangapple
  • 本文由 发表于 2014年7月16日 08:39:18
  • 转载请务必保留本文链接：https://go.coder-hub.com/24770403.html
  • go
  • json
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