ASP.NET Core 3.1系列（30）——Newtonsoft.Json实现JSON的序列化和反序列化

1、前言

在早期版本的ASP.NET Core项目中，Newtonsoft.Json的使用率非常高。虽然微软当前主推System.Text.Json来处理JSON的序列化和反序列化，但Newtonsoft.Json在这方面做的也是相当不错，下面就来介绍一下它的用法。

2、引入Newtonsoft.Json

新建一个Web API项目，使用NuGet引入如下组件：

Microsoft.AspNetCore.Mvc.NewtonsoftJson

新建一个实体类Person，代码如下：

using System;namespace App
{public class Person{public int Id { get; set; }public string PersonName { get; set; }public string PersonGender { get; set; }public DateTime? BirthOfDate { get; set; }}
}

新建一个控制器PersonController，添加一个Get方法，代码如下：

using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;namespace App.Controllers
{[Route("api/[controller]/[action]")][ApiController]public class PersonController : ControllerBase{[HttpGet]public JsonResult Get(){List<Person> list = new List<Person>{new Person { Id = 1, PersonName = "张三", PersonGender = "男", PersonAge = 30 },new Person { Id = 2, PersonName = "李四", PersonGender = "女", PersonAge = 31 },new Person { Id = 3, PersonName = "王五", PersonGender = "男", PersonAge = 32 }};return new JsonResult(list);}}
}

运行结果如下所示：

[{"id":1,"personName":"\u5F20\u4E09","personGender":"\u7537","birthOfDate":"2000-01-01T00:00:00"},{"id":1,"personName":"\u674E\u56DB","personGender":"\u5973","birthOfDate":"2000-02-02T00:00:00"},{"id":1,"personName":"\u738B\u4E94","personGender":"\u7537","birthOfDate":"2000-03-03T00:00:00"}]

与之前一样，这里存在中文乱码、时间格式等等，下面就来说一说如何在Newtonsoft.Json中去设置它们。

3、序列化操作

3.1、JSON数据编码

这里与System.Text.Json需要指定编码格式不同，我们只需要指定Newtonsoft.Json为全局序列化的工具即可，代码如下：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;namespace App
{public class Startup{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }// This method gets called by the runtime. Use this method to add services to the container.public void ConfigureServices(IServiceCollection services){services.AddControllers().AddNewtonsoftJson(options =>{});}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}app.UseHttpsRedirection();app.UseRouting();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllers();});}}
}

运行结果如下所示，可以发现中文编码正确。

[{"id":1,"personName":"张三","personGender":"男","birthOfDate":"2000-01-01T00:00:00"},{"id":2,"personName":"李四","personGender":"女","birthOfDate":"2000-02-02T00:00:00"},{"id":3,"personName":"王五","personGender":"男","birthOfDate":"2000-03-03T00:00:00"}]

3.2、JSON文本格式化

如果希望将输出的JSON文本格式化，可以对Formatting进行设置，代码如下：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;namespace App
{public class Startup{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }// This method gets called by the runtime. Use this method to add services to the container.public void ConfigureServices(IServiceCollection services){services.AddControllers().AddNewtonsoftJson(options =>{// 格式化JSON文本options.SerializerSettings.Formatting = Formatting.Indented;});}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}app.UseHttpsRedirection();app.UseRouting();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllers();});}}
}

运行结果如下所示：

[{"id": 1,"personName": "张三","personGender": "男","birthOfDate": "2000-01-01T00:00:00"},{"id": 2,"personName": "李四","personGender": "女","birthOfDate": "2000-02-02T00:00:00"},{"id": 3,"personName": "王五","personGender": "男","birthOfDate": "2000-03-03T00:00:00"}
]

3.3、JSON字段命名格式

如果你希望采用驼峰式命名，可以设置ContractResolver为CamelCasePropertyNamesContractResolver，代码如下：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;namespace App
{public class Startup{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }// This method gets called by the runtime. Use this method to add services to the container.public void ConfigureServices(IServiceCollection services){services.AddControllers().AddNewtonsoftJson(options =>{// 格式化JSON文本options.SerializerSettings.Formatting = Formatting.Indented;// 驼峰式命名options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();});}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}app.UseHttpsRedirection();app.UseRouting();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllers();});}}
}

运行结果如下所示：

[{"id": 1,"personName": "张三","personGender": "男","birthOfDate": "2000-01-01T00:00:00"},{"id": 2,"personName": "李四","personGender": "女","birthOfDate": "2000-02-02T00:00:00"},{"id": 3,"personName": "王五","personGender": "男","birthOfDate": "2000-03-03T00:00:00"}
]

如果你希望采用帕斯卡命名，可以设置ContractResolver为DefaultContractResolver，代码如下：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;namespace App
{public class Startup{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }// This method gets called by the runtime. Use this method to add services to the container.public void ConfigureServices(IServiceCollection services){services.AddControllers().AddNewtonsoftJson(options =>{// 格式化JSON文本options.SerializerSettings.Formatting = Formatting.Indented;// 帕斯卡命名options.SerializerSettings.ContractResolver = new DefaultContractResolver();});}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}app.UseHttpsRedirection();app.UseRouting();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllers();});}}
}

运行结果如下所示：

[{"Id": 1,"PersonName": "张三","PersonGender": "男","BirthOfDate": "2000-01-01T00:00:00"},{"Id": 2,"PersonName": "李四","PersonGender": "女","BirthOfDate": "2000-02-02T00:00:00"},{"Id": 3,"PersonName": "王五","PersonGender": "男","BirthOfDate": "2000-03-03T00:00:00"}
]

3.4、忽略JSON中的null值

如果希望忽略null值，可设置NullValueHandling属性，代码如下：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;namespace App
{public class Startup{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }// This method gets called by the runtime. Use this method to add services to the container.public void ConfigureServices(IServiceCollection services){services.AddControllers().AddNewtonsoftJson(options =>{// 格式化JSON文本options.SerializerSettings.Formatting = Formatting.Indented;// 驼峰式命名options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();// 忽略null值options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;});}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}app.UseHttpsRedirection();app.UseRouting();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllers();});}}
}

修改一下PersonController，将BirthOfDate设置为null，代码如下：

using Microsoft.AspNetCore.Mvc;
using System.Collections.Generic;namespace App.Controllers
{[Route("api/[controller]/[action]")][ApiController]public class PersonController : ControllerBase{[HttpGet]public JsonResult Get(){List<Person> list = new List<Person>{new Person { Id = 1, PersonName = "张三", PersonGender = "男", BirthOfDate = null },new Person { Id = 2, PersonName = "李四", PersonGender = "女", BirthOfDate = null },new Person { Id = 3, PersonName = "王五", PersonGender = "男", BirthOfDate = null }};return new JsonResult(list);}}
}

运行结果如下所示，可以发现BirthOfDate字段并未被序列化。

[{"id": 1,"personName": "张三","personGender": "男"},{"id": 2,"personName": "李四","personGender": "女"},{"id": 3,"personName": "王五","personGender": "男"}
]

3.5.、JSON忽略只读字段

在Person中添加一个只读字段Info，代码如下：

using System;namespace App
{public class Person{public int Id { get; set; }public string PersonName { get; set; }public string PersonGender { get; set; }public DateTime? BirthOfDate { get; set; }public string Info{get { return $"姓名：{PersonName}，性别：{PersonGender}，出生日期：{BirthOfDate}"; }}}
}

关于忽略只读字段，System.Text.Json已经支持设置该属性，但Newtonsoft.Json并没有提供对应属性来支持它，因此我们需要自己动手实现。新建一个类IgnoreReadOnlyPropertiesResolver，代码如下：

using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
using System;
using System.Collections.Generic;
using System.Linq;namespace App
{public class IgnoreReadOnlyPropertiesResolver : DefaultContractResolver{protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization){IList<JsonProperty> props = base.CreateProperties(type, memberSerialization);return props.Where(p => p.Readable && p.Writable).ToList();}}
}

然后将ContractResolver属性的值替换为IgnoreReadOnlyPropertiesResolver，代码如下：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;namespace App
{public class Startup{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }// This method gets called by the runtime. Use this method to add services to the container.public void ConfigureServices(IServiceCollection services){services.AddControllers().AddNewtonsoftJson(options =>{// 格式化JSON文本options.SerializerSettings.Formatting = Formatting.Indented;// 忽略只读字段options.SerializerSettings.ContractResolver = new IgnoreReadOnlyPropertiesResolver();// 忽略null值options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;});}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}app.UseHttpsRedirection();app.UseRouting();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllers();});}}
}

运行结果如下所示，可以发现Info字段并未被序列化。

[{"Id": 1,"PersonName": "张三","PersonGender": "男","BirthOfDate": "2000-01-01T00:00:00"},{"Id": 2,"PersonName": "李四","PersonGender": "女","BirthOfDate": "2000-02-02T00:00:00"},{"Id": 3,"PersonName": "王五","PersonGender": "男","BirthOfDate": "2000-03-03T00:00:00"}
]

3.6、JSON中的时间格式

在System.Text.Json中，我们需要通过自定义类来实现时间字段的格式化，而Newtonsoft.Json中的时间格式化则非常简单，我们只需要对DateFormatString进行设置即可，代码如下：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;namespace App
{public class Startup{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }// This method gets called by the runtime. Use this method to add services to the container.public void ConfigureServices(IServiceCollection services){services.AddControllers().AddNewtonsoftJson(options =>{// 格式化JSON文本options.SerializerSettings.Formatting = Formatting.Indented;// 忽略只读字段options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();// 忽略null值options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;// 设置时间格式options.SerializerSettings.DateFormatString = "yyyy年MM月dd日 HH时mm分ss秒";});}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}app.UseHttpsRedirection();app.UseRouting();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllers();});}}
}

运行结果如下所示，可以发现时间字段已经被格式化。

[{"id": 1,"personName": "张三","personGender": "男","birthOfDate": "2000年01月01日 00时00分00秒"},{"id": 2,"personName": "李四","personGender": "女","birthOfDate": "2000年02月02日 00时00分00秒"},{"id": 3,"personName": "王五","personGender": "男","birthOfDate": "2000年03月03日 00时00分00秒"}
]

3.7、忽略循环引用

如果涉及到一对多关联表的查询时，JSON序列化会产生循环引用问题，解决方法就是对ReferenceLoopHandling进行设置，代码如下：

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;namespace App
{public class Startup{public Startup(IConfiguration configuration){Configuration = configuration;}public IConfiguration Configuration { get; }// This method gets called by the runtime. Use this method to add services to the container.public void ConfigureServices(IServiceCollection services){services.AddControllers().AddNewtonsoftJson(options =>{// 格式化JSON文本options.SerializerSettings.Formatting = Formatting.Indented;// 忽略只读字段options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();// 忽略null值options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;// 设置时间格式options.SerializerSettings.DateFormatString = "yyyy年MM月dd日 HH时mm分ss秒";// 忽略循环引用options.SerializerSettings.ReferenceLoopHandling = ReferenceLoopHandling.Ignore;});}// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.public void Configure(IApplicationBuilder app, IWebHostEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}app.UseHttpsRedirection();app.UseRouting();app.UseAuthorization();app.UseEndpoints(endpoints =>{endpoints.MapControllers();});}}
}

4、反序列化操作

Newtonsoft.Json中的反序列化操作很简单，只需要调用JsonConvert.DeserializeObject即可，代码如下：

using Microsoft.AspNetCore.Mvc;
using Newtonsoft.Json;namespace App.Controllers
{[Route("api/[controller]/[action]")][ApiController]public class PersonController : ControllerBase{[HttpGet]public ActionResult<string> Get(){string json = "{\"Id\":1,\"PersonName\":\"张三\",\"PersonGender\":\"男\",\"BirthOfDate\":\"2000-01-01 00:00:00\"}";Person person = JsonConvert.DeserializeObject<Person>(json);return $"姓名：{person.PersonName}\n性别：{person.PersonGender}\n出生日期：{person.BirthOfDate}";}}
}

运行结果如下所示：

姓名：张三
性别：男
出生日期：2000/1/1 0:00:00

5、结语

本文主要介绍了Newtonsoft.Json的使用方法。其实System.Text.Json和Newtonsoft.Json的使用方法都很简便，具体在项目中使用哪个序列化工具可根据情况自行决定。