應(yīng)用場景
最近碰到一個問題噪裕，就是想把json字符串中的字段名稱都改成首字母小寫利虫，當(dāng)然這個json是非常大的光坝，手動改不理智肴熏，那有沒有什么辦法通過什么方式直接將json字符串的首字母都改成小寫的呢取视？一開始是想通過Newtonsoft.Json.dll這個類庫硝皂，直接反序列化為動態(tài)的類(dynamic)，然后重新序列化成json字符串時指定：ContractResolver = new CamelCasePropertyNamesContractResolver()作谭，但是還是行不通稽物。如果我們有實現(xiàn)定義好的實體類，再序列化的時候通過上面的設(shè)置是可以輸出首字母小寫的json字符串折欠，基于這個考慮贝或，是否可以通過原json字符串然后動態(tài)生成實體類，再通過反序列化成該實體類锐秦，最后把得到的對象再序列化成json字符串咪奖，是否可達(dá)目的呢。請往下看农猬。
動態(tài)生成實體類
創(chuàng)建一個控制臺項目：
dotnet new console -o JsonToObject新建一個json文件赡艰，里面就是需要轉(zhuǎn)換的json內(nèi)容
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讀取json內(nèi)容，拼接json中涉及到的所有的類的定義
Action<string> Write = Console.WriteLine; var jsonString = File.ReadAllText("demo.json");//讀取json文件里的內(nèi)容 var jObject = JObject.Parse(jsonString);//Newtonsoft.Json中的JObject.Parse轉(zhuǎn)換成json對象 Dictionary<string, string> classDicts = new Dictionary<string, string>();//key為類名斤葱，value為類中的所有屬性定義的字符串 classDicts.Add("Root", GetClassDefinion(jObject));//拼接頂層的類 foreach (var item in jObject.Properties()) { classDicts.Add(item.Name, GetClassDefinion(item.Value)); GetClasses(item.Value, classDicts); } //下面是將所有的類定義完整拼接起來 StringBuilder sb = new StringBuilder(1024); sb.AppendLine("using System;"); sb.AppendLine("using System.Collections.Generic;"); sb.AppendLine("namespace JsonToObject"); sb.AppendLine("{"); foreach (var item in classDicts) { sb.Append($"public class {item.Key}" + Environment.NewLine); sb.Append("{" + Environment.NewLine); sb.Append(item.Value); sb.Append("}" + Environment.NewLine); } sb.AppendLine("}"); Write(sb.ToString()); //遞歸遍歷json節(jié)點慷垮，把需要定義的類存入classes void GetClasses(JToken jToken, Dictionary<string, string> classes) { if (jToken is JValue) { return; } var childToken = jToken.First; while (childToken != null) { if (childToken.Type == JTokenType.Property) { var p = (JProperty)childToken; var valueType = p.Value.Type; if (valueType == JTokenType.Object) { classes.Add(p.Name, GetClassDefinion(p.Value)); GetClasses(p.Value, classes); } else if (valueType == JTokenType.Array) { foreach (var item in (JArray)p.Value) { if (item.Type == JTokenType.Object) { if (!classes.ContainsKey(p.Name)) { classes.Add(p.Name, GetClassDefinion(item)); } GetClasses(item, classes); } } } } childToken = childToken.Next; } } //獲取類中的所有的屬性 string GetClassDefinion(JToken jToken) { StringBuilder sb = new(256); var subValueToken = jToken.First(); while (subValueToken != null) { if (subValueToken.Type == JTokenType.Property) { var p = (JProperty)subValueToken; var valueType = p.Value.Type; if (valueType == JTokenType.Object) { sb.Append("public " + p.Name + " " + p.Name + " {get;set;}" + Environment.NewLine); } else if (valueType == JTokenType.Array) { var arr = (JArray)p.Value; //a.First switch (arr.First().Type) { case JTokenType.Object: sb.Append($"public List<{p.Name}> " + p.Name + " {get;set;}" + Environment.NewLine); break; case JTokenType.Integer: sb.Append($"public List<int> " + p.Name + " {get;set;}" + Environment.NewLine); break; case JTokenType.Float: sb.Append($"public List<float> " + p.Name + " {get;set;}" + Environment.NewLine); break; case JTokenType.String: sb.Append($"public List<string> " + p.Name + " {get;set;}" + Environment.NewLine); break; case JTokenType.Boolean: sb.Append($"public List<bool> " + p.Name + " {get;set;}" + Environment.NewLine); break; default: break; } } else { switch (valueType) { case JTokenType.Integer: sb.Append($"public int " + p.Name + " {get;set;}" + Environment.NewLine); break; case JTokenType.Float: sb.Append($"public float " + p.Name + " {get;set;}" + Environment.NewLine); break; case JTokenType.String: sb.Append($"public string " + p.Name + " {get;set;}" + Environment.NewLine); break; case JTokenType.Boolean: sb.Append($"public bool " + p.Name + " {get;set;}" + Environment.NewLine); break; default: break; } } } subValueToken = subValueToken.Next; } return sb.ToString(); }-
現(xiàn)在有了類的定義字符串，接下來就可以動態(tài)編譯成實體類
Write("Let's compile!"); Write("Parsing the code into the SyntaxTree"); SyntaxTree syntaxTree = CSharpSyntaxTree.ParseText(sb.ToString()); string assemblyName = Path.GetRandomFileName(); var refPaths = new[] { typeof(object).GetTypeInfo().Assembly.Location, typeof(Console).GetTypeInfo().Assembly.Location, Path.Combine(Path.GetDirectoryName(typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly.Location), "System.Runtime.dll") }; MetadataReference[] references = refPaths.Select(r => MetadataReference.CreateFromFile(r)).ToArray(); Write("Adding the following references"); foreach (var r in refPaths) Write(r); Write("Compiling ..."); CSharpCompilation compilation = CSharpCompilation.Create( assemblyName, syntaxTrees: new[] { syntaxTree }, references: references, options: new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)); using (var ms = new MemoryStream()) { EmitResult result = compilation.Emit(ms); if (!result.Success) { Write("Compilation failed!"); IEnumerable<Diagnostic> failures = result.Diagnostics.Where(diagnostic => diagnostic.IsWarningAsError || diagnostic.Severity == DiagnosticSeverity.Error); foreach (Diagnostic diagnostic in failures) { Console.Error.WriteLine("\t{0}: {1}", diagnostic.Id, diagnostic.GetMessage()); } } else { Write("Compilation successful! Now instantiating and executing the code ..."); ms.Seek(0, SeekOrigin.Begin); Assembly assembly = AssemblyLoadContext.Default.LoadFromStream(ms); var type = assembly.GetType("JsonToObject.Root"); var instance = assembly.CreateInstance("JsonToObject.Root"); //反射獲取靜態(tài)的 DeserializeObject方法 var deserializeObject = typeof(JsonConvert).GetGenericMethod("DeserializeObject", BindingFlags.Public | BindingFlags.Static, new Type[] { typeof(string), typeof(JsonSerializerSettings) }); var genericDeserializeObject = deserializeObject.MakeGenericMethod(type); //執(zhí)行反序列化 var root = genericDeserializeObject.Invoke(null, new object[] { jsonString, null }); //輸出序列化的結(jié)果 Write(JsonConvert.SerializeObject(root, new JsonSerializerSettings { ContractResolver = new CamelCasePropertyNamesContractResolver() })); } }通過反射獲取靜態(tài)方法的擴(kuò)展
public static class Extension { public static MethodInfo GetGenericMethod(this Type targetType, string name, BindingFlags flags, params Type[] parameterTypes) { var methods = targetType.GetMethods(flags).Where(m => m.Name == name && m.IsGenericMethod); var flag = false; foreach (MethodInfo method in methods) { var parameters = method.GetParameters(); if (parameters.Length != parameterTypes.Length) continue; for (var i = 0; i < parameters.Length; i++) { if (parameters[i].ParameterType != parameterTypes[i]) { break; } if (i == parameters.Length - 1) { flag = true; } } if (flag) { return method; } } return null; } }至此揍堕，我們已經(jīng)實現(xiàn)了文章開頭說的將json字符串的首字母都變成小寫的料身。
總結(jié)
本文主要涉及以下的內(nèi)容
如何通過json字符串拼接類的定義
如何通過動態(tài)編譯的方式動態(tài)生成類
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反射動態(tài)調(diào)用反序列化的方法
希望本文能夠?qū)Υ蠹矣兴鶐椭暾仨椖康刂房梢詤⒖迹?a target="_blank">dynamic_demo項目
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