System.Text.Json

https://blog.csdn.net/u010476739/article/details/129337119
# 一、写入时的控制
System.Text.Json.JsonSerializerOptions的属性清单

| 描述 | 属性 | 值 |
| --- | --- | --- |
| 汉字显示 | Encoder  | System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping |
| 首字母小写 | PropertyNamingPolicy  | System.Text.Json.JsonNamingPolicy.CamelCase |
| 字典key首字母小写 | DictionaryKeyPolicy  | System.Text.Json.JsonNamingPolicy.CamelCase |
| 缩进格式输出 | WriteIndented | true |
| 枚举转成字符串输出 | options.Converters.Add | new System.Text.Json.Serialization.JsonStringEnumConverter() |
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```java
var options = new System.Text.Json.JsonSerializerOptions
{
    //汉字
    Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping,
    //属性名首字母小写
    PropertyNamingPolicy = System.Text.Json.JsonNamingPolicy.CamelCase,
    //字典key首字母小写
    DictionaryKeyPolicy = System.Text.Json.JsonNamingPolicy.CamelCase,
    //缩进输出
    WriteIndented = true,
    //忽略null值属性的输出
    DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull,
    //忽略循环引用
    ReferenceHandler = System.Text.Json.Serialization.ReferenceHandler.IgnoreCycles,
    // 允许输出Field（默认情况下，Field不会被输出）
    IncludeFields = true,
    // 不输出只读Field（默认输出）
    IgnoreReadOnlyFields = true,
    // 不输出只读属性（默认输出）
    IgnoreReadOnlyProperties = true,
    //输出是 number => string, 读取时允许 string => number(慎用)
    NumberHandling = System.Text.Json.Serialization.JsonNumberHandling.AllowReadingFromString | System.Text.Json.Serialization.JsonNumberHandling.WriteAsString,
    //忽略默认值的属性(慎用)
DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingDefault,

};
// 举转成字符串
options.Converters.Add(new System.Text.Json.Serialization.JsonStringEnumConverter());
//自定义日期格式（DateTime、DateTimeOffset）
options.Converters.Add(new JsonConverterDatetime("yyyy-MM-dd HH:mm:ss.fff zz"));
options.Converters.Add(new JsonConverterDateTimeOffset("yyyy-MM-dd HH:mm:ss.fff zz"));
//支持输出 DateOnly、TimeOnly
//默认.net 6 （.net7可以）不支持 DateOnly、TimeOnly
options.Converters.Add(new JsonConverterDateOnly("yyyy-MM-dd"));
options.Converters.Add(new JsonConverterTimeOnly("HH:mm:ss.fffffff"));
```
```java
public class JsonConverterDatetime : System.Text.Json.Serialization.JsonConverter<DateTime>
{
    public string Format { get; set; }
    public JsonConverterDatetime(string format)
    {
        if (format == null) throw new ArgumentNullException("format");
        Format = format;
    }
    public override DateTime Read(ref System.Text.Json.Utf8JsonReader reader, Type typeToConvert, System.Text.Json.JsonSerializerOptions options)
    {
        return DateTime.Parse(reader.GetString());
    }

public override void Write(System.Text.Json.Utf8JsonWriter writer, DateTime value, System.Text.Json.JsonSerializerOptions options)
    {
        writer.WriteStringValue(value.ToString(Format));
    }
}

public class JsonConverterDateTimeOffset : System.Text.Json.Serialization.JsonConverter<DateTimeOffset>
{
    public string Format { get; set; }
    public JsonConverterDateTimeOffset(string format)
    {
        if (format == null) throw new ArgumentNullException("format");
        Format = format;
    }
    public override DateTimeOffset Read(ref System.Text.Json.Utf8JsonReader reader, Type typeToConvert, System.Text.Json.JsonSerializerOptions options)
    {
        return DateTimeOffset.Parse(reader.GetString());
    }

public override void Write(System.Text.Json.Utf8JsonWriter writer, DateTimeOffset value, System.Text.Json.JsonSerializerOptions options)
    {
        writer.WriteStringValue(value.ToString(Format));
    }
}

public class JsonConverterDateOnly : System.Text.Json.Serialization.JsonConverter<DateOnly>
{
    public string Format { get; set; }
    public JsonConverterDateOnly(string format)
    {
        if (format == null) throw new ArgumentNullException("format");
        Format = format;
    }
    public override DateOnly Read(ref System.Text.Json.Utf8JsonReader reader, Type typeToConvert, System.Text.Json.JsonSerializerOptions options)
    {
        return DateOnly.Parse(reader.GetString());
    }

public override void Write(System.Text.Json.Utf8JsonWriter writer, DateOnly value, System.Text.Json.JsonSerializerOptions options)
    {
        writer.WriteStringValue(value.ToString(Format));
    }
}

public class JsonConverterTimeOnly : System.Text.Json.Serialization.JsonConverter<TimeOnly>
{
    public string Format { get; set; }
    public JsonConverterTimeOnly(string format)
    {
        if (format == null) throw new ArgumentNullException("format");
        Format = format;
    }
    public override TimeOnly Read(ref System.Text.Json.Utf8JsonReader reader, Type typeToConvert, System.Text.Json.JsonSerializerOptions options)
    {
        return TimeOnly.Parse(reader.GetString());
    }

public override void Write(System.Text.Json.Utf8JsonWriter writer, TimeOnly value, System.Text.Json.JsonSerializerOptions options)
    {
        writer.WriteStringValue(value.ToString(Format));
    }
}

```

在类定义时声明忽略某些属性
```java
[System.Text.Json.Serialization.JsonIgnore]
public int Age { get; set; }
```

在类定义时声明控制属性输出的顺序
```java
[System.Text.Json.Serialization.JsonPropertyOrder(Order = 0)]
public int Age { get; set; }
```

在类定义时声明控制属性输出的名称
```java
[System.Text.Json.Serialization.JsonPropertyName("catAge")]
public int Age { get; set; }
```

# 1、汉字（非ascii码转换）
```java
var str = System.Text.Json.JsonSerializer.Serialize(new Model { Id = 1, Name = "小明" }, new System.Text.Json.JsonSerializerOptions
{
    Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping
});
//out: {"Id":1,"Name":"小明"}
public class Model
{
    public int Id { get; set; }
    public string Name { get; set; }
}

```

# 二、读取时控制（反序列化为模型）
```java
var options = new System.Text.Json.JsonSerializerOptions
{
    //允许json中多余的逗号
    AllowTrailingCommas = true,
    //因为我们是直接反序列化为模型,所以这里 跳过注释
    ReadCommentHandling = System.Text.Json.JsonCommentHandling.Skip,
    //※允许将 "123" 转为数字 123
    NumberHandling = System.Text.Json.Serialization.JsonNumberHandling.AllowReadingFromString,
    //※忽略属性名大小写(默认大小写敏感)
    PropertyNameCaseInsensitive = true
};
```

# 三、内置对象
类似 Newtonsoft，在没有实体类的情况下，也可以使用JsonNode/JsonValue/JsonArray/JsonObject操作json。

![](/media/202409/2024-09-09_184941_5055320.4680970305770311.png)
## 读取数据
```java
using System.Text.Json.Nodes;

string jsonString =
@"
{
    ""Name"":""小明"",
    ""Age"":20,
    ""Birth"":""2003-01-01"",
    ""Ext"":{
        ""Addrs"":[""天明路"",null],
        ""Scores"":[95,98,82],
        ""Desc"":""测试""
    }
}
";
JsonNode node = JsonNode.Parse(jsonString)!;

//GetValue 和 强转都可以
var name = node["Name"].GetValue<string>();
var age = (int)node["Age"]!;
var birth = (DateTime)node["Birth"]!;
Console.WriteLine($"name={name},age={age},birth={birth}");

//下探
var desc = (string)node["Ext"]["Desc"]!;
var addr1 = node["Ext"]["Addrs"][0].GetValue<string>();
var addr2 = (string?)node["Ext"]["Addrs"][1];//这里因为本身为null,使用GetValue方法会报错
Console.WriteLine($"desc={desc},addr1={addr1},addr2={addr2}");

//数组访问
foreach (var i in node["Ext"]["Scores"].AsArray())
{
    var score = i.GetValue<float>();
    Console.WriteLine($"score={score}");
}
```

## 写入数据
```java
using System.Text.Json.Nodes;

```