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

    [JsonObject(MemberSerialization.OptIn)]
    public class TestClass
    {
        public int A { get; set; }
        public long B { get; set; }
        public string C { get; set; }
        [JsonProperty]
        public DateTime D { get; set; }
        public TestEnum E { get; set; }
        [JsonIgnore]
        public TestClass F { get; set; }
        public List<TestClass> G { get; set; }
        public bool H { get; set; }
    }
    public enum TestEnum
    {
        TestEnum0 = 0,
        TestEnum1 = 1,
        TestEnum2 = 2,
        TestEnum3 = 3,
    }
    [JsonObject(MemberSerialization.OptIn)]
    public class Person
    {
        [JsonIgnore]
        public string Name { get; set; }
        [JsonProperty]
        public int Age { get; set; }
        public DateTime BirthDay { get; set; }
    }

                Console.WriteLine(JsonConvert.SerializeObject(new Person { Name = "test", Age = 18, BirthDay = new DateTime(2011, 1, 1) }));
                TestClass testClass = new TestClass
                {
                    A = 1,
                    B = 2,
                    C = "C",
                    D = DateTime.Now,
                    E = TestEnum.TestEnum1,
                    F = new TestClass
                    {
                        A = 11,
                        B = 22,
                        C = "Cc",
                        D = DateTime.Now,
                        E = TestEnum.TestEnum2,
                        F = new TestClass()
                    },
                    G = new List<TestClass>
                {
                    new TestClass
                    {
                        A=111,
                        B=222,
                        C="CCC",
                        E=TestEnum.TestEnum1,
                        F=new TestClass()
                    }
                }
                };
                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

                TestClass testClass = new TestClass
                {
                    A = 1,
                    B = 2,
                    C = "C",
                    D = DateTime.Now,
                    E = TestEnum.TestEnum1,
                    F = new TestClass
                    {
                        A = 11,
                        B = 22,
                        C = "Cc",
                        D = DateTime.Now,
                        E = TestEnum.TestEnum2,
                        F = new TestClass()
                    },
                    G = new List<TestClass>
                     {
                         new TestClass
                         {
                             A=111,
                             B=222,
                             C="CCC",
                             E=TestEnum.TestEnum1,
                             F=new TestClass()
                         }
                     }
                };
                JsonSerializerSettings settings = new JsonSerializerSettings();
                settings.DefaultValueHandling = DefaultValueHandling.Ignore;
                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

    public class LongDateTimeConvert: Newtonsoft.Json.Converters.IsoDateTimeConverter
    {
        public LongDateTimeConvert() : base()
        {
            base.DateTimeFormat = "yyyy-MM-dd";
        }
    }
        //[JsonConverter(typeof(LongDateTimeConvert))]
        public DateTime BirthDay { get; set; }

输出结果：{"BirthDay":"2011-01-01"}

解决方案2：指定JsonSerializerSettings.DateFormatString的值

                JsonSerializerSettings settings = new JsonSerializerSettings();
                settings.DateFormatString = "yyyy-MM-dd HH:mm:ss";
                var str = JsonConvert.SerializeObject(new Person { Name = "test", Age = 18, BirthDay = new DateTime(2011, 1, 1) }, settings);
                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

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

    public class JsonContractResolver : DefaultContractResolver
    {
        protected IEnumerable<string> _excludedProperties;
        public JsonContractResolver(IEnumerable<string> excludedProperties)
        {
            this._excludedProperties = excludedProperties;
        }
        protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
        {
            return base.CreateProperties(type, memberSerialization).Where(a=>!this._excludedProperties.Contains(a.PropertyName)).ToList();
        }
    }
                JsonSerializerSettings settings = new JsonSerializerSettings();
                settings.ContractResolver =new JsonContractResolver(new[] { "Sign" });
                settings.DateFormatHandling = DateFormatHandling.MicrosoftDateFormat;
                settings.DateFormatString = "yyyy-MM-dd HH:mm:ss";
                var str = JsonConvert.SerializeObject(new Person { Name = "test", Age = 18, BirthDay = new DateTime(2011, 1, 1) }, settings);
                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

                JsonSerializerSettings settings = new JsonSerializerSettings();
                settings.ContractResolver =new JsonContractResolver(new[] { "Sign" });
                settings.DateFormatHandling = DateFormatHandling.MicrosoftDateFormat;
                settings.DateFormatString = "yyyy-MM-dd HH:mm:ss";
                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