.

src/WireMock.Net.Minimal/ResponseBuilders/Response.WithBody.cs

@@ -2,8 +2,10 @@
 
 using System.Text;
 using JsonConverter.Abstractions;
+using JsonConverter.Newtonsoft.Json;
 using Stef.Validation;
 using WireMock.Models;
+using WireMock.Serialization;
 using WireMock.Types;
 using WireMock.Util;
 
@@ -119,11 +121,13 @@ public partial class Response
     }
 
     /// <inheritdoc />
-    public IResponseBuilder WithBody(string body, string? destination = BodyDestinationFormat.SameAsSource, Encoding? encoding = null)
+    public IResponseBuilder WithBody(string body, string? destination = BodyDestinationFormat.SameAsSource, Encoding? encoding = null, IJsonConverter? jsonConverter = null, JsonConverterOptions? options = null)
     {
         Guard.NotNull(body);
 
         encoding ??= Encoding.UTF8;
+        jsonConverter ??= new NewtonsoftJsonConverter();
+        options ??= JsonSerializationConstants.JsonConverterOptionsWithDateParsingNone;
 
         ResponseMessage.BodyDestination = destination;
         ResponseMessage.BodyData = new BodyData
@@ -140,7 +144,7 @@ public partial class Response
 
             case BodyDestinationFormat.Json:
                 ResponseMessage.BodyData.DetectedBodyType = BodyType.Json;
-                ResponseMessage.BodyData.BodyAsJson = JsonUtils.DeserializeObject(body);
+                ResponseMessage.BodyData.BodyAsJson = jsonConverter.Deserialize<object>(body, options);
                 break;
 
             default:

src/WireMock.Net.Minimal/Settings/WireMockServerSettingsParser.cs

@@ -3,14 +3,15 @@
 using System.Collections;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
-using System.Linq;
 using JetBrains.Annotations;
+using JsonConverter.Newtonsoft.Json;
+using JsonConverter.System.Text.Json;
 using Stef.Validation;
 using WireMock.Constants;
 using WireMock.Logging;
 using WireMock.Models;
-using WireMock.Types;
 using WireMock.Transformers;
+using WireMock.Types;
 using WireMock.Util;
 
 namespace WireMock.Settings;
@@ -58,11 +59,9 @@ public static class WireMockServerSettingsParser
             DisableRequestBodyDecompressing = parser.GetBoolValue(nameof(WireMockServerSettings.DisableRequestBodyDecompressing)),
             DisableDeserializeFormUrlEncoded = parser.GetBoolValue(nameof(WireMockServerSettings.DisableDeserializeFormUrlEncoded)),
             DoNotSaveDynamicResponseInLogEntry = parser.GetBoolValue(nameof(WireMockServerSettings.DoNotSaveDynamicResponseInLogEntry)),
-            GraphQLSchemas = parser.GetObjectValueFromJson<Dictionary<string, GraphQLSchemaDetails>>(nameof(settings.GraphQLSchemas)),
             HandleRequestsSynchronously = parser.GetBoolValue(nameof(WireMockServerSettings.HandleRequestsSynchronously)),
             HostingScheme = parser.GetEnumValue<HostingScheme>(nameof(WireMockServerSettings.HostingScheme)),
             MaxRequestLogCount = parser.GetIntValue(nameof(WireMockServerSettings.MaxRequestLogCount)),
-            ProtoDefinitions = parser.GetObjectValueFromJson<Dictionary<string, string[]>>(nameof(settings.ProtoDefinitions)),
             QueryParameterMultipleValueSupport = parser.GetEnumValue<QueryParameterMultipleValueSupport>(nameof(WireMockServerSettings.QueryParameterMultipleValueSupport)),
             ReadStaticMappings = parser.GetBoolValue(nameof(WireMockServerSettings.ReadStaticMappings)),
             RequestLogExpirationDuration = parser.GetIntValue(nameof(WireMockServerSettings.RequestLogExpirationDuration)),
@@ -75,14 +74,13 @@ public static class WireMockServerSettingsParser
             WatchStaticMappingsInSubdirectories = parser.GetBoolValue(nameof(WireMockServerSettings.WatchStaticMappingsInSubdirectories)),
         };
 
-        settings.DefaultJsonBodyTransformer = new NewtonsoftJsonBodyTransformer(settings);
-
 #if USE_ASPNETCORE
         settings.CorsPolicyOptions = parser.GetEnumValue(nameof(WireMockServerSettings.CorsPolicyOptions), CorsPolicyOptions.None);
         settings.ClientCertificateMode = parser.GetEnumValue(nameof(WireMockServerSettings.ClientCertificateMode), ClientCertificateMode.NoCertificate);
         settings.AcceptAnyClientCertificate = parser.GetBoolValue(nameof(WireMockServerSettings.AcceptAnyClientCertificate));
 #endif
 
+        ParseJsonSerializerSettings(settings, parser);
         ParseLoggerSettings(settings, logger, parser);
         ParsePortSettings(settings, parser);
         ParseProxyAndRecordSettings(settings, parser);
@@ -91,6 +89,9 @@ public static class WireMockServerSettingsParser
         ParseActivityTracingSettings(settings, parser);
         ParseWebSocketSettings(settings, parser);
 
+        settings.GraphQLSchemas = parser.GetObjectValueFromJson<Dictionary<string, GraphQLSchemaDetails>>(nameof(settings.GraphQLSchemas), settings.DefaultJsonSerializer);
+        settings.ProtoDefinitions = parser.GetObjectValueFromJson<Dictionary<string, string[]>>(nameof(settings.ProtoDefinitions), settings.DefaultJsonSerializer);
+
         return true;
     }
 
@@ -262,4 +263,21 @@ public static class WireMockServerSettingsParser
             };
         }
     }
+
+    private static void ParseJsonSerializerSettings(WireMockServerSettings settings, SimpleSettingsParser parser)
+    {
+        var defaultJsonSerializer = parser.GetStringValue(nameof(WireMockServerSettings.DefaultJsonSerializer));
+        settings.DefaultJsonSerializer = defaultJsonSerializer switch
+        {
+            nameof(SystemTextJsonConverter) => new SystemTextJsonConverter(),
+            _ => new NewtonsoftJsonConverter(),
+        };
+
+        var defaultJsonBodyTransformer = parser.GetStringValue(nameof(WireMockServerSettings.DefaultJsonBodyTransformer));
+        settings.DefaultJsonBodyTransformer = defaultJsonBodyTransformer switch
+        {
+            nameof(SystemTextJsonBodyTransformer) => new SystemTextJsonBodyTransformer(),
+            _ => new NewtonsoftJsonBodyTransformer(settings),
+        };
+    }
 }

src/WireMock.Net.Shared/ResponseBuilders/IBodyResponseBuilder.cs

@@ -1,8 +1,6 @@
 // Copyright © WireMock.Net
 
-using System;
 using System.Text;
-using System.Threading.Tasks;
 using JsonConverter.Abstractions;
 using WireMock.Models;
 
@@ -19,8 +17,10 @@ public interface IBodyResponseBuilder : IFaultResponseBuilder
     /// <param name="body">The body.</param>
     /// <param name="destination">The Body Destination format (SameAsSource, String or Bytes).</param>
     /// <param name="encoding">The body encoding.</param>
+    /// <param name="jsonConverter">The JSON converter.</param>
+    /// <param name="options">The JSON converter options.</param>
     /// <returns>A <see cref="IResponseBuilder"/>.</returns>
-    IResponseBuilder WithBody(string body, string? destination = BodyDestinationFormat.SameAsSource, Encoding? encoding = null);
+    IResponseBuilder WithBody(string body, string? destination = BodyDestinationFormat.SameAsSource, Encoding? encoding = null, IJsonConverter? jsonConverter = null, JsonConverterOptions? options = null);
 
     /// <summary>
     /// WithBody : Create a ... response based on a callback function.

src/WireMock.Net.Shared/Settings/SimpleSettingsParser.cs

@@ -1,6 +1,7 @@
 // Copyright © WireMock.Net
 
 using System.Collections;
+using JsonConverter.Abstractions;
 using WireMock.Extensions;
 using WireMock.Util;
 
@@ -191,9 +192,9 @@ internal class SimpleSettingsParser
         return GetValue(name, values => values.FirstOrDefault());
     }
 
-    public T? GetObjectValueFromJson<T>(string name)
+    public T? GetObjectValueFromJson<T>(string name, IJsonConverter jsonConverter)
     {
         var value = GetValue(name, values => values.FirstOrDefault());
-        return string.IsNullOrWhiteSpace(value) ? default : JsonUtils.DeserializeObject<T>(value!);
+        return string.IsNullOrWhiteSpace(value) ? default : jsonConverter.Deserialize<T>(value!);
     }
 }

src/WireMock.Net.Shared/Util/JsonUtils.cs

@@ -60,17 +60,6 @@ internal static class JsonUtils
         return JsonConvert.DeserializeObject(json, JsonSerializationConstants.JsonDeserializerSettingsWithDateParsingNone)!;
     }
 
-    /// <summary>
-    /// Deserializes the JSON to the specified .NET type.
-    /// Using : DateParseHandling = DateParseHandling.None
-    /// </summary>
-    /// <param name="json">A System.String that contains JSON.</param>
-    /// <returns>The deserialized object from the JSON string.</returns>
-    public static T DeserializeObject<T>(string json)
-    {
-        return JsonConvert.DeserializeObject<T>(json, JsonSerializationConstants.JsonDeserializerSettingsWithDateParsingNone)!;
-    }
-
     public static T? TryDeserializeObject<T>(string json)
     {
         try

test/WireMock.Net.Tests/Settings/SimpleSettingsParserTests.cs

@@ -1,5 +1,6 @@
 // Copyright © WireMock.Net
 
+using JsonConverter.Newtonsoft.Json;
 using WireMock.Settings;
 using WireMock.Types;
 
@@ -18,7 +19,7 @@ public class SimpleSettingsParserTests
     public void SimpleCommandLineParser_Parse_Arguments()
     {
         // Assign
-        _parser.Parse(new[] { "--test1", "one", "--test2", "2", "--test3", "3", "--test4", "true", "--test5", "Https" });
+        _parser.Parse(["--test1", "one", "--test2", "2", "--test3", "3", "--test4", "true", "--test5", "Https"]);
 
         // Act
         string? stringValue = _parser.GetStringValue("test1");
@@ -46,7 +47,7 @@ public class SimpleSettingsParserTests
             { "WireMockServerSettings__test1", "one" },
             { "WireMockServerSettings__test2", "two" }
         };
-        _parser.Parse(new string[0], env);
+        _parser.Parse([], env);
 
         // Act
         string? value1 = _parser.GetStringValue("test1");
@@ -61,7 +62,7 @@ public class SimpleSettingsParserTests
     public void SimpleCommandLineParser_Parse_ArgumentsAsCombinedKeyAndValue()
     {
         // Assign
-        _parser.Parse(new[] { "--test1 one", "--test2 two", "--test3 three" });
+        _parser.Parse(["--test1 one", "--test2 two", "--test3 three"]);
 
         // Act
         string? value1 = _parser.GetStringValue("test1");
@@ -78,7 +79,7 @@ public class SimpleSettingsParserTests
     public void SimpleCommandLineParser_Parse_ArgumentsMixed()
     {
         // Assign
-        _parser.Parse(new[] { "--test1 one", "--test2", "two", "--test3 three" });
+        _parser.Parse(["--test1 one", "--test2", "two", "--test3 three"]);
 
         // Act
         string? value1 = _parser.GetStringValue("test1");
@@ -95,7 +96,7 @@ public class SimpleSettingsParserTests
     public void SimpleCommandLineParser_Parse_GetBoolValue()
     {
         // Assign
-        _parser.Parse(new[] { "'--test1", "false'", "--test2 true" });
+        _parser.Parse(["'--test1", "false'", "--test2 true"]);
 
         // Act
         bool value1 = _parser.GetBoolValue("test1");
@@ -112,7 +113,7 @@ public class SimpleSettingsParserTests
     public void SimpleCommandLineParser_Parse_GetBoolWithDefault()
     {
         // Assign
-        _parser.Parse(new[] { "--test1", "true", "--test2", "false" });
+        _parser.Parse(["--test1", "true", "--test2", "false"]);
 
         // Act
         bool value1 = _parser.GetBoolWithDefault("test1", "test1_fallback", defaultValue: false);
@@ -134,7 +135,7 @@ public class SimpleSettingsParserTests
             { "WireMockServerSettings__test1", "false" },
             { "WireMockServerSettings__test2", "true" }
         };
-        _parser.Parse(new string[0], env);
+        _parser.Parse([], env);
 
         // Act
         bool value1 = _parser.GetBoolValue("test1");
@@ -151,7 +152,7 @@ public class SimpleSettingsParserTests
     public void SimpleCommandLineParser_Parse_GetIntValue()
     {
         // Assign
-        _parser.Parse(new[] { "--test1", "42", "--test2 55" });
+        _parser.Parse(["--test1", "42", "--test2 55"]);
 
         // Act
         int? value1 = _parser.GetIntValue("test1");
@@ -175,7 +176,7 @@ public class SimpleSettingsParserTests
             { "WireMockServerSettings__test1", "42" },
             { "WireMockServerSETTINGS__TEST2", "55" }
         };
-        _parser.Parse(new string[0], env);
+        _parser.Parse([], env);
 
         // Act
         int? value1 = _parser.GetIntValue("test1");
@@ -194,10 +195,10 @@ public class SimpleSettingsParserTests
     public void SimpleCommandLineParser_Parse_GetObjectValueFromJson()
     {
         // Assign
-        _parser.Parse(new[] { @"--json {""k1"":""v1"",""k2"":""v2""}" });
+        _parser.Parse([@"--json {""k1"":""v1"",""k2"":""v2""}"]);
 
         // Act
-        var value = _parser.GetObjectValueFromJson<Dictionary<string, string>>("json");
+        var value = _parser.GetObjectValueFromJson<Dictionary<string, string>>("json", new NewtonsoftJsonConverter());
 
         // Assert
         var expected = new Dictionary<string, string>