无依赖的LitJSON

发表于
字数统计 1654

将JSON映射到对象，反之亦然

为了在内部使用JSON格式的数据。网络程序，自然 我想到的方法是使用JSON文本填充新实例 属于某一特定类别；要么是定制的，与结构相匹配 输入JSON文本或充当字典的更通用的文本。

相反地为了从存储在对象中的数据构建新的JSON字符串， 一个简单的export-like操作听起来是个好主意。

为此，LitJSON包括JsonMapper类， 它提供了两种主要的方法来处理JSON-to-object和 对象到JSON转换。这些方法是 JsonMapper.ToObject和JsonMapper.ToJson。

简单的JsonMapper示例

如下例所示，ToObject方法具有泛型 变体JsonMapper.ToObject<T>，用于指定 待归还的物品。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
using LitJson;
using System;

public class Person
{
    // C# 3.0 auto-implemented properties
    public string   Name     { get; set; }
    public int      Age      { get; set; }
    public DateTime Birthday { get; set; }
}

public class JsonSample
{
    public static void Main()
    {
        PersonToJson();
        JsonToPerson();
    }

    public static void PersonToJson()
    {
        Person bill = new Person();

        bill.Name = "William Shakespeare";
        bill.Age  = 51;
        bill.Birthday = new DateTime(1564, 4, 26);

        string json_bill = JsonMapper.ToJson(bill);

        Console.WriteLine(json_bill);
    }

    public static void JsonToPerson()
    {
        string json = @"
            {
                ""Name""     : ""Thomas More"",
                ""Age""      : 57,
                ""Birthday"" : ""02/07/1478 00:00:00""
            }";

        Person thomas = JsonMapper.ToObject<Person>(json);

        Console.WriteLine("Thomas' age: {0}", thomas.Age);
    }
}

示例输出：

1
2
{"Name":"William Shakespeare","Age":51,"Birthday":"04/26/1564 00:00:00"}
Thomas' age: 57

使用JsonMapper.ToObject的非泛型变体

当要读取JSON数据和与特定对象匹配的自定义类时 数据结构不可用或不需要，用户可以使用非通用的 ToObject的变体，它返回一个JsonData实例。JsonData是一个 通用类型，可以保存JSON支持的任何数据类型， 包括列表和词典。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
using LitJson;
using System;

public class JsonSample
{
    public static void Main()
    {
        string json = @"
          {
            ""album"" : {
              ""name""   : ""The Dark Side of the Moon"",
              ""artist"" : ""Pink Floyd"",
              ""year""   : 1973,
              ""tracks"" : [
                ""Speak To Me"",
                ""Breathe"",
                ""On The Run""
              ]
            }
          }
        ";

        LoadAlbumData(json);
    }

    public static void LoadAlbumData(string json_text)
    {
        Console.WriteLine("Reading data from the following JSON string: {0}",
                          json_text);

        JsonData data = JsonMapper.ToObject(json_text);

        // Dictionaries are accessed like a hash-table
        Console.WriteLine("Album's name: {0}", data["album"]["name"]);

        // Scalar elements stored in a JsonData instance can be cast to
        // their natural types
        string artist = (string) data["album"]["artist"];
        int    year   = (int) data["album"]["year"];

        Console.WriteLine("Recorded by {0} in {1}", artist, year);

        // Arrays are accessed like regular lists as well
        Console.WriteLine("First track: {0}", data["album"]["tracks"][0]);
    }
}

示例输出：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
Reading data from the following JSON string:
          {
            "album" : {
              "name"   : "The Dark Side of the Moon",
              "artist" : "Pink Floyd",
              "year"   : 1973,
              "tracks" : [
                "Speak To Me",
                "Breathe",
                "On The Run"
              ]
            }
          }

Album's name: The Dark Side of the Moon
Recorded by Pink Floyd in 1973
First track: Speak To Me

读者和作家

处理JSON数据的另一种接口，可能对 一些开发人员通过类来实现读写 以流式方式传输数据。这些类是JsonReader和 JsonWriter 。

这两种类型实际上是这个库的基础 JsonMapper的类型构建在它们之上，因此在某种程度上，开发人员可以 将读者和作者类视为低级编程 LitJSON的接口。

使用JsonReader

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
using LitJson;
using System;

public class DataReader
{
    public static void Main()
    {
        string sample = @"{
            ""name""  : ""Bill"",
            ""age""   : 32,
            ""awake"" : true,
            ""n""     : 1994.0226,
            ""note""  : [ ""life"", ""is"", ""but"", ""a"", ""dream"" ]
          }";

        PrintJson(sample);
    }

    public static void PrintJson(string json)
    {
        JsonReader reader = new JsonReader(json);

        Console.WriteLine ("{0,14} {1,10} {2,16}", "Token", "Value", "Type");
        Console.WriteLine (new String ('-', 42));

        // The Read() method returns false when there's nothing else to read
        while (reader.Read()) {
            string type = reader.Value != null ?
                reader.Value.GetType().ToString() : "";

            Console.WriteLine("{0,14} {1,10} {2,16}",
                              reader.Token, reader.Value, type);
        }
    }
}

此示例将产生以下输出：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
         Token      Value             Type
------------------------------------------
   ObjectStart                            
  PropertyName       name    System.String
        String       Bill    System.String
  PropertyName        age    System.String
           Int         32     System.Int32
  PropertyName      awake    System.String
       Boolean       True   System.Boolean
  PropertyName          n    System.String
        Double  1994.0226    System.Double
  PropertyName       note    System.String
    ArrayStart                            
        String       life    System.String
        String         is    System.String
        String        but    System.String
        String          a    System.String
        String      dream    System.String
      ArrayEnd                            
     ObjectEnd

使用JsonWriter

JsonWriter类非常简单。记住，如果你想 将任意对象转换为JSON字符串，通常只需使用 JsonMapper.ToJson。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
using LitJson;
using System;
using System.Text;

public class DataWriter
{
    public static void Main()
    {
        StringBuilder sb = new StringBuilder();
        JsonWriter writer = new JsonWriter(sb);

        writer.WriteArrayStart();
        writer.Write(1);
        writer.Write(2);
        writer.Write(3);

        writer.WriteObjectStart();
        writer.WritePropertyName("color");
        writer.Write("blue");
        writer.WriteObjectEnd();

        writer.WriteArrayEnd();

        Console.WriteLine(sb.ToString());
    }
}

示例输出：

1
[1,2,3,{"color":"blue"}]

配置库的行为

JSON是一种非常简洁的数据交换格式；没有更多，也没有更少。 因此，在程序内处理JSON格式的数据可能需要 你对一些细节的深思熟虑的决定 超出了JSON规范的范围。

例如，考虑从JSON字符串中读取数据，其中 单引号用于分隔字符串，或Javascript样式 评论作为一种文档形式包含在内。这些东西不是一部分 JSON标准，但它们通常被一些开发人员使用，所以你 根据情况，可能想要宽容或严格。或者呢 如果你想转换一个.Net对象转换为JSON字符串，但 打印得漂亮（使用缩进）？

要声明您想要的行为，您可以更改您的 JsonReader和JsonWriter对象。

JsonReader的配置

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
using LitJson;
using System;

public class JsonReaderConfigExample
{
    public static void Main()
    {
        string json;

        json = " /* these are some numbers */ [ 2, 3, 5, 7, 11 ] ";
        TestReadingArray(json);

        json = " [ \"hello\", 'world' ] ";
        TestReadingArray(json);
    }

    static void TestReadingArray(string json_array)
    {
        JsonReader defaultReader, customReader;

        defaultReader = new JsonReader(json_array);
        customReader  = new JsonReader(json_array);

        customReader.AllowComments            = false;
        customReader.AllowSingleQuotedStrings = false;

        ReadArray(defaultReader);
        ReadArray(customReader);
    }

    static void ReadArray(JsonReader reader)
    {
        Console.WriteLine("Reading an array");

        try {
            JsonData data = JsonMapper.ToObject(reader);

            foreach (JsonData elem in data)
                Console.Write("  {0}", elem);

            Console.WriteLine("  [end]");
        }
        catch (Exception e) {
            Console.WriteLine("  Exception caught: {0}", e.Message);
        }
    }
}

输出将是：

1
2
3
4
5
6
7
8
Reading an array
  2  3  5  7  11  [end]
Reading an array
  Exception caught: Invalid character '/' in input string
Reading an array
  hello  world  [end]
Reading an array
  Exception caught: Invalid character ''' in input string

JsonWriter的配置

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
using LitJson;
using System;

public enum AnimalType
{
    Dog,
    Cat,
    Parrot
}

public class Animal
{
    public string     Name { get; set; }
    public AnimalType Type { get; set; }
    public int        Age  { get; set; }
    public string[]   Toys { get; set; }
}

public class JsonWriterConfigExample
{
    public static void Main()
    {
        var dog = new Animal {
            Name = "Noam Chompsky",
            Type = AnimalType.Dog,
            Age  = 3,
            Toys = new string[] { "rubber bone", "tennis ball" }
        };

        var cat = new Animal {
            Name = "Colonel Meow",
            Type = AnimalType.Cat,
            Age  = 5,
            Toys = new string[] { "cardboard box" }
        };

        TestWritingAnimal(dog);
        TestWritingAnimal(cat, 2);
    }

    static void TestWritingAnimal(Animal pet, int indentLevel = 0)
    {
        Console.WriteLine("\nConverting {0}'s data into JSON..", pet.Name);
        JsonWriter writer1 = new JsonWriter(Console.Out);
        JsonWriter writer2 = new JsonWriter(Console.Out);

        writer2.PrettyPrint = true;
        if (indentLevel != 0)
            writer2.IndentValue = indentLevel;

        Console.WriteLine("Default JSON string:");
        JsonMapper.ToJson(pet, writer1);

        Console.Write("\nPretty-printed:");
        JsonMapper.ToJson(pet, writer2);
        Console.WriteLine("");
    }
}

此示例的输出为：

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27

Converting Noam Chompsky's data into JSON..
Default JSON string:
{"Name":"Noam Chompsky","Type":0,"Age":3,"Toys":["rubber bone","tennis ball"]}
Pretty-printed:
{
    "Name" : "Noam Chompsky",
    "Type" : 0,
    "Age"  : 3,
    "Toys" : [
        "rubber bone",
        "tennis ball"
    ]
}

Converting Colonel Meow's data into JSON..
Default JSON string:
{"Name":"Colonel Meow","Type":1,"Age":5,"Toys":["cardboard box"]}
Pretty-printed:
{
  "Name" : "Colonel Meow",
  "Type" : 1,
  "Age"  : 5,
  "Toys" : [
    "cardboard box"
  ]
}