C# Newtonsoft.Json JsonSerializerSettings配置
JsonSerializerSettings常用配置整理
1.忽略某些属性
MemberSerialization.OptIn
默认情况下,所有的成员不会被序列化,类中的成员只有标有特性JsonProperty的才会被序列化,当类的成员很多,但客户端仅仅需要一部分数据时,很有用
1 [JsonObject(MemberSerialization.OptIn)]
2 public class TestClass
3 {
4 public int A { get; set; }
5 public long B { get; set; }
6 public string C { get; set; }
7 [JsonProperty]
8 public DateTime D { get; set; }
9 public TestEnum E { get; set; }
10 [JsonIgnore]
11 public TestClass F { get; set; }
12 public List<TestClass> G { get; set; }
13 public bool H { get; set; }
14 }
15 public enum TestEnum
16 {
17 TestEnum0 = 0,
18 TestEnum1 = 1,
19 TestEnum2 = 2,
20 TestEnum3 = 3,
21 }
22 [JsonObject(MemberSerialization.OptIn)]
23 public class Person
24 {
25 [JsonIgnore]
26 public string Name { get; set; }
27 [JsonProperty]
28 public int Age { get; set; }
29 public DateTime BirthDay { get; set; }
30 }
1 Console.WriteLine(JsonConvert.SerializeObject(new Person { Name = "test", Age = 18, BirthDay = new DateTime(2011, 1, 1) }));
2 TestClass testClass = new TestClass
3 {
4 A = 1,
5 B = 2,
6 C = "C",
7 D = DateTime.Now,
8 E = TestEnum.TestEnum1,
9 F = new TestClass
10 {
11 A = 11,
12 B = 22,
13 C = "Cc",
14 D = DateTime.Now,
15 E = TestEnum.TestEnum2,
16 F = new TestClass()
17 },
18 G = new List<TestClass>
19 {
20 new TestClass
21 {
22 A=111,
23 B=222,
24 C="CCC",
25 E=TestEnum.TestEnum1,
26 F=new TestClass()
27 }
28 }
29 };
30 Console.WriteLine(JsonConvert.SerializeObject(testClass));
输出结果：
{"Age":18}
{"D":"2019-11-26T10:37:33.7655514+08:00"}
MemberSerialization.OptOut
默认类中所有公有成员会被序列化,如果不想被序列化,可以用特性JsonIgnore
将上面的代码OptIn改为OptOut输出结果：
{"Age":18,"BirthDay":"2011-01-01T00:00:00"}
{"A":1,"B":2,"C":"C","D":"2019-11-26T15:49:37.9507028+08:00","E":1,"G":[{"A":111,"B":222,"C":"CCC","D":"0001-01-01T00:00:00","E":1,"G":null,"H":false}],"H":false}
2.默认值的处理
DefaultValueHandling.Ignore 序列化和反序列化时,忽略默认值
1 TestClass testClass = new TestClass
2 {
3 A = 1,
4 B = 2,
5 C = "C",
6 D = DateTime.Now,
7 E = TestEnum.TestEnum1,
8 F = new TestClass
9 {
10 A = 11,
11 B = 22,
12 C = "Cc",
13 D = DateTime.Now,
14 E = TestEnum.TestEnum2,
15 F = new TestClass()
16 },
17 G = new List<TestClass>
18 {
19 new TestClass
20 {
21 A=111,
22 B=222,
23 C="CCC",
24 E=TestEnum.TestEnum1,
25 F=new TestClass()
26 }
27 }
28 };
29 JsonSerializerSettings settings = new JsonSerializerSettings();
30 settings.DefaultValueHandling = DefaultValueHandling.Ignore;
31 Console.WriteLine(JsonConvert.SerializeObject(testClass,settings));
输出结果：
{"A":1,"B":2,"C":"C","D":"2019-11-26T15:56:21.7204132+08:00","E":1,"G":[{"A":111,"B":222,"C":"CCC","E":1}]}
DefaultValueHandling.Include 序列化和反序列化时,包含默认值
将JsonSerializerSettings.DefaultValueHandling属性设为DefaultValueHandling.Include输出结果：
{"A":1,"B":2,"C":"C","D":"2019-11-26T16:21:48.5429746+08:00","E":1,"G":[{"A":111,"B":222,"C":"CCC","D":"0001-01-01T00:00:00","E":1,"G":null,"H":false}],"H":false}
DefaultValueHandling.Populate 在反序列化时，具有默认值但没有JSON的成员将被设置为其默认值。
DefaultValueHandling.IgnoreAndPopulate 在序列化对象时忽略成员值与成员默认值相同的成员，在反序列化时将成员设置为其默认值
不指定的情况下，序列化时 默认 包含-DefaultValueHandling.Include
3.空值的处理
设置JsonSerializerSettings.NullValueHandling属性
对序列化过程中所有属性生效的，想单独对某一个属性生效可以使用JsonProperty
值为NullValueHandling.Ignore时，输出结果为：
{"A":1,"B":2,"C":"C","D":"2019-11-26T16:34:21.3205145+08:00","E":1,"G":[{"A":111,"B":222,"C":"CCC","D":"0001-01-01T00:00:00","E":1,"H":false}],"H":false}
值为NullValueHandling.Include时，输出结果为：
{"A":1,"B":2,"C":"C","D":"2019-11-26T16:34:21.3205145+08:00","E":1,"G":[{"A":111,"B":222,"C":"CCC","D":"0001-01-01T00:00:00","E":1,"G":null,"H":false}],"H":false}
4.支持非公共成员
序列化时默认都是处理公共成员，如果需要处理非公共成员，就要在该成员上加特性JsonProperty
5.日期处理（DateFormatHandling）
对于Dateime类型日期的格式化，系统自带的会格式化成iso日期标准{"BirthDay":"2011-01-01T00:00:00"}
解决方案1：添加特性，指定转换格式
1 public class LongDateTimeConvert: Newtonsoft.Json.Converters.IsoDateTimeConverter
2 {
3 public LongDateTimeConvert() : base()
4 {
5 base.DateTimeFormat = "yyyy-MM-dd";
6 }
7 }
8 //[JsonConverter(typeof(LongDateTimeConvert))]
9 public DateTime BirthDay { get; set; }
输出结果：{"BirthDay":"2011-01-01"}
解决方案2：指定JsonSerializerSettings.DateFormatString的值
1 JsonSerializerSettings settings = new JsonSerializerSettings();
2 settings.DateFormatString = "yyyy-MM-dd HH:mm:ss";
3 var str = JsonConvert.SerializeObject(new Person { Name = "test", Age = 18, BirthDay = new DateTime(2011, 1, 1) }, settings);
4 Console.WriteLine(str);
输出结果：{"BirthDay":"2011-01-01 00:00:00"}
同时指定时以特性（即方案1）为准
解决方案3：
object model = new object();
var jsonSettings = new JsonSerializerSettings();
jsonSettings.DateFormatHandling = DatFormatHandling.IsoDateFormat;
jsonSettings.Converters.Add(new Newtonsoft.Json.Converters.IsoDateTimeConverter () {DateTimeFormat = "yyyy-MM-dd HH:mm:ss.fff"});
string content = JsonConvert.SerializeObject (model,Formatting.Indented,jsonSettings);
6.自定义序列化的字段名称
实体中定义的属性名可能不是自己想要的名称，但是又不能更改实体定义，这个时候可以自定义序列化字段名称
[JsonProperty(PropertyName = "age")]
public int Age { get; set; }
输出结果：{"age":18}
7.动态决定属性是否序列化
指定JsonSerializerSettings.ContractResolver的实例，继承DefaultContractResolver类，重写方法
1 public class JsonContractResolver : DefaultContractResolver
2 {
3 protected IEnumerable<string> _excludedProperties;
4 public JsonContractResolver(IEnumerable<string> excludedProperties)
5 {
6 this._excludedProperties = excludedProperties;
7 }
8 protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
9 {
10 return base.CreateProperties(type, memberSerialization).Where(a=>!this._excludedProperties.Contains(a.PropertyName)).ToList();
11 }
12 }
13 JsonSerializerSettings settings = new JsonSerializerSettings();
14 settings.ContractResolver =new JsonContractResolver(new[] { "Sign" });
15 settings.DateFormatHandling = DateFormatHandling.MicrosoftDateFormat;
16 settings.DateFormatString = "yyyy-MM-dd HH:mm:ss";
17 var str = JsonConvert.SerializeObject(new Person { Name = "test", Age = 18, BirthDay = new DateTime(2011, 1, 1) }, settings);
18 Console.WriteLine(str);
过滤属性名为Sign的字段，输出结果：{"age":18,"BirthDay":"2011-01-01T00:00:00"}
8.枚举值的自定义格式化问题
默认枚举输出的是枚举的 值 {"E":1}
在属性上加上JsonConverter(typeof(StringEnumConverter))表示将枚举值转换成对应的字符串,StringEnumConverter是Newtonsoft.Json内置的转换类型
输出结果：{"E":"TestEnum1"}
9.自定义类型转换
需要扩展类JsonConverter类
10.全局序列化设置
1 JsonSerializerSettings settings = new JsonSerializerSettings();
2 settings.ContractResolver =new JsonContractResolver(new[] { "Sign" });
3 settings.DateFormatHandling = DateFormatHandling.MicrosoftDateFormat;
4 settings.DateFormatString = "yyyy-MM-dd HH:mm:ss";
5 JsonConvert.DefaultSettings = () => settings;
指定JsonConvert.DefaultSettings
11.指定序列化时Key的处理方式：驼峰样式，默认样式（ContractResolver）
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.ContractResolver = new CamelCasePropertyNamesContractResolver();
var str = JsonConvert.SerializeObject(new Person { Name = "test", Age = 18, BirthDay = new DateTime(2011, 1, 1) },Formatting.Indented);
Formatting.Indented 格式化json字符串数据,锯齿状的
输出结果：
{
"sign": false,
"age": 18,
"birthDay": "2011-01-01T00:00:00"
}
12.序列化循环 引用及处理层数
对于关联表的 对象或列表都不会序列化出来
//设置循环引用，及引用类型序列化的层数。
//注：目前在 EF core中目前不支持延迟加载，无所谓循环引用了
JsonSerializerSettings settings = new JsonSerializerSettings();
settings.Formatting = Formatting.Indented;
settings.MaxDepth = 10; //设置序列化的最大层数
settings.ReferenceLoopHandling = ReferenceLoopHandling.Serialize;//指定如何处理循环引用，None--不序列化，Error-抛出异常，Serialize--仍要序列化
本文参考文档：
https://blog.csdn.net/u011127019/article/details/72801033
Newtonsoft.Json 官方文档：https://www.newtonsoft.com/json/help/html/T_Newtonsoft_Json_JsonSerializerSettings.htm
