.netcore webapi json返回值序列化null替换为空字符串
场景：数据库中部分表字段允许空值，则代码中实体类对应的字段类型为可空类型Nullable<>，如int?，DateTime?，null值字段序列化返回的值都为null，前端对应字段赋值需要做null值判断，随想到全局把null替换为””
网上找的方案都是重写了DefaultContractResolver，但是该方法只能解决string类型null→””的问题，对其他可空类型无效。
研究了下git 上Newtonsoft.Json和.netcore MVC的源码
最终使用自定义JsonOutputFormatter方式实现：
public void ConfigureServices(IServiceCollection services) { services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1); //过滤器 services.AddMvc(config => { var settings = new JsonSerializerSettings(); settings.ContractResolver = new DefaultContractResolver(); //统一设置JsonResult中的日期格式 settings.DateFormatString = “yyyy-MM-dd HH:mm:ss”; config.OutputFormatters.Insert(0, new MyJsonOutputFormatter(settings)); }); //services.AddMvc().AddJsonOptions(options => //{ // //options.SerializerSettings.ContractResolver = new SubstituteNullWithEmptyStringContractResolver(); // 统一设置JsonResult中的日期格式 // //options.SerializerSettings.DateFormatString = “yyyy-MM-dd HH:mm:ss”; //}); services.AddMvcCore().AddApiExplorer(); }
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public class MyJsonOutputFormatter : JsonOutputFormatter 便宜香港vps { public MyJsonOutputFormatter(JsonSerializerSettings serializerSettings) : base(serializerSettings, ArrayPool<char>.Shared) { } public new JsonSerializerSettings SerializerSettings => base.SerializerSettings; protected override JsonWriter CreateJsonWriter(TextWriter writer) { if (writer == null) { throw new ArgumentNullException(nameof(writer)); } var jsonWriter = new NullJsonWriter(writer) { ArrayPool = new JsonArrayPool<char>(ArrayPool<char>.Shared), CloseOutput = false, AutoCompleteOnClose = false }; return jsonWriter; } } public class NullJsonWriter : JsonTextWriter { public NullJsonWriter(TextWriter textWriter):base(textWriter) { } public override void WriteNull() { this.WriteValue(String.Empty); } }
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