\n\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u67e5\u770b GetCompanies action\u7684\u56de\u590d\u6765\u786e\u8ba4\u8fd9\u4e00\u70b9:
\nhttps:\/\/localhost:5001\/api\/companies<\/a><\/p>\n
![\"alt](\"\/images\/ultimateaspnetcorewebapi6\/0701.jpg\")
<\/p>\n
We can clearly see that the default result when calling GET on \/api\/companies returns the JSON result. We have also used the Accept header (as you can see in the picture above) to try forcing the server to return other media types like plain text and XML.
\n\u6211\u4eec\u53ef\u4ee5\u6e05\u695a\u5730\u770b\u5230\uff0c\u5728 \/api\/companies \u4e0a\u8c03\u7528 GET \u65f6\uff0c\u9ed8\u8ba4\u7ed3\u679c\u8fd4\u56de\u7684\u662f JSON \u7ed3\u679c\u3002\u6211\u4eec\u8fd8\u4f7f\u7528\u4e86 Accept \u6807\u5934\uff08\u5982\u4e0a\u56fe\u6240\u793a\uff09\u6765\u5c1d\u8bd5\u5f3a\u5236\u670d\u52a1\u5668\u8fd4\u56de\u5176\u4ed6\u5a92\u4f53\u7c7b\u578b\uff0c\u5982\u7eaf\u6587\u672c\u548c XML\u3002<\/p>\n
But that doesn\u2019t work. Why?
\n\u4f46\u8fd9\u884c\u4e0d\u901a\u3002\u4e3a\u4ec0\u4e48\uff1f<\/p>\n
Because we need to configure server formatters to format a response the way we want it.
\n\u56e0\u4e3a\u6211\u4eec\u9700\u8981\u914d\u7f6e\u670d\u52a1\u5668\u683c\u5f0f\u5316\u7a0b\u5e8f\u4ee5\u6309\u7167\u6211\u4eec\u60f3\u8981\u7684\u65b9\u5f0f\u683c\u5f0f\u5316\u54cd\u5e94\u3002<\/p>\n
Let\u2019s see how to do that.
\n\u8ba9\u6211\u4eec\u770b\u770b\u5982\u4f55\u505a\u5230\u8fd9\u4e00\u70b9\u3002<\/p>\n
7.2 Changing the Default Configuration of Our Project<\/h2>\n
7.2 \u66f4\u6539\u6211\u4eec\u9879\u76ee\u7684\u9ed8\u8ba4\u914d\u7f6e<\/p>\n
A server does not explicitly specify where it formats a response to JSON.\u200c But you can override it by changing configuration options through the AddControllers method.
\n\u670d\u52a1\u5668\u6ca1\u6709\u660e\u786e\u6307\u5b9a\u5b83\u5bf9 JSON \u7684\u54cd\u5e94\u7684\u683c\u5f0f\u3002\u4f46\u662f\uff0c\u60a8\u53ef\u4ee5\u901a\u8fc7 AddControllers \u65b9\u6cd5\u66f4\u6539\u914d\u7f6e\u9009\u9879\u6765\u8986\u76d6\u5b83\u3002<\/p>\n
We can add the following options to enable the server to format the XML response when the client tries negotiating for it:
\n\u6211\u4eec\u53ef\u4ee5\u6dfb\u52a0\u4ee5\u4e0b\u9009\u9879\uff0c\u4f7f\u670d\u52a1\u5668\u80fd\u591f\u5728\u5ba2\u6237\u7aef\u5c1d\u8bd5\u534f\u5546 XML \u54cd\u5e94\u65f6\u683c\u5f0f\u5316 XML \u54cd\u5e94\uff1a<\/p>\n
using CompanyEmployees.Extensions;\nusing Contracts;\nusing Microsoft.AspNetCore.HttpOverrides;\nusing NLog;\n\nvar builder = WebApplication.CreateBuilder(args);\n\n\/\/ Add services to the container.\nLogManager.LoadConfiguration(\n string.Concat(Directory.GetCurrentDirectory(),\n "\/nlog.config"));\nbuilder.Services.ConfigureLoggerService();\n\nbuilder.Services.ConfigureCors();\nbuilder.Services.ConfigureIISIntegration();\nbuilder.Services.ConfigureRepositoryManager();\nbuilder.Services.ConfigureServiceManager();\nbuilder.Services.ConfigureSqlContext(builder.Configuration);\nbuilder.Services.AddAutoMapper(typeof(Program));\n\/\/ builder.Services.AddControllers().AddApplicationPart(typeof(CompanyEmployees.Presentation.AssemblyReference).Assembly);\nbuilder.Services.AddControllers(config => { config.RespectBrowserAcceptHeader = true; }).AddXmlDataContractSerializerFormatters().AddApplicationPart(typeof(CompanyEmployees.Presentation.AssemblyReference).Assembly);<\/code><\/pre>\nFirst things first, we must tell a server to respect the Accept header. After that, we just add the AddXmlDataContractSerializerFormatters method to support XML formatters.
\n\u9996\u5148\uff0c\u6211\u4eec\u5fc5\u987b\u544a\u8bc9\u670d\u52a1\u5668\u9075\u5b88 Accept \u6807\u5934\u3002\u4e4b\u540e\uff0c\u6211\u4eec\u53ea\u9700\u6dfb\u52a0 AddXmlDataContractSerializerFormatters \u65b9\u6cd5\u6765\u652f\u6301 XML \u683c\u5f0f\u5316\u7a0b\u5e8f\u3002<\/p>\n
Now that we have our server configured, let\u2019s test the content negotiation once more.
\n\u73b0\u5728\u6211\u4eec\u5df2\u7ecf\u914d\u7f6e\u4e86\u670d\u52a1\u5668\uff0c\u8ba9\u6211\u4eec\u518d\u6b21\u6d4b\u8bd5\u5185\u5bb9\u534f\u5546\u3002<\/p>\n
7.3 Testing Content Negotiation<\/h2>\n
7.3 \u6d4b\u8bd5 Content Negotiation<\/p>\n
Let\u2019s see what happens now if we fire the same request through Postman:\u200c
\n\u8ba9\u6211\u4eec\u770b\u770b\u5982\u679c\u6211\u4eec\u901a\u8fc7 Postman \u89e6\u53d1\u76f8\u540c\u7684\u8bf7\u6c42\uff0c\u73b0\u5728\u4f1a\u53d1\u751f\u4ec0\u4e48\uff1a
\nhttps:\/\/localhost:5001\/api\/companies<\/a><\/p>\n![\"alt](\"\/images\/ultimateaspnetcorewebapi6\/0702.jpg\")
<\/p>\n
We get an error because XmlSerializer cannot easily serialize our positional record type. There are two solutions to this. The first one is marking our CompanyDto record with the [Serializable] attribute:
\n\u6211\u4eec\u6536\u5230\u4e00\u4e2a\u9519\u8bef\uff0c\u56e0\u4e3a XmlSerializer \u65e0\u6cd5\u8f7b\u677e\u5730\u5e8f\u5217\u5316\u6211\u4eec\u7684\u4f4d\u7f6e\u8bb0\u5f55\u7c7b\u578b\u3002\u6709\u4e24\u79cd\u89e3\u51b3\u65b9\u6848\u3002\u7b2c\u4e00\u4e2a\u662f\u4f7f\u7528 [Serializable] \u5c5e\u6027\u6807\u8bb0\u6211\u4eec\u7684 CompanyDto \u8bb0\u5f55\uff1a<\/p>\n
[Serializable] \npublic record CompanyDto(Guid Id, string Name, string FullAddress);<\/code><\/pre>\nNow, we can send the same request again:
\n\u73b0\u5728\uff0c\u6211\u4eec\u53ef\u4ee5\u518d\u6b21\u53d1\u9001\u76f8\u540c\u7684\u8bf7\u6c42\uff1a<\/p>\n
![\"alt](\"\/images\/ultimateaspnetcorewebapi6\/0703.jpg\")
<\/p>\n
This time, we are getting our XML response but, as you can see,properties have some strange names. That\u2019s because the compiler behind the scenes generates the record as a class with fields named like that (name_BackingField) and the XML serializer just serializes those fields with the same names.
\n\u8fd9\u4e00\u6b21\uff0c\u6211\u4eec\u6536\u5230\u4e86 XML \u54cd\u5e94\uff0c\u4f46\u6b63\u5982\u4f60\u6240\u770b\u5230\u7684\uff0c\u5c5e\u6027\u6709\u4e00\u4e9b\u5947\u602a\u7684\u540d\u79f0\u3002\u8fd9\u662f\u56e0\u4e3a\u540e\u53f0\u7f16\u8bd1\u5668\u5c06\u8bb0\u5f55\u751f\u6210\u4e3a\u4e00\u4e2a\u7c7b\uff0c\u5176\u4e2d\u5305\u542b\u7c7b\u4f3c \uff08name_BackingField\uff09 \u7684\u5b57\u6bb5\uff0c\u800c XML \u5e8f\u5217\u5316\u7a0b\u5e8f\u53ea\u662f\u5e8f\u5217\u5316\u5177\u6709\u76f8\u540c\u540d\u79f0\u7684\u8fd9\u4e9b\u5b57\u6bb5\u3002<\/p>\n
If we don\u2019t want these property names in our response, but the regular ones, we can implement a second solution. Let\u2019s modify our record with the init only property setters:
\n\u5982\u679c\u6211\u4eec\u4e0d\u5e0c\u671b\u54cd\u5e94\u4e2d\u5305\u542b\u8fd9\u4e9b\u5c5e\u6027\u540d\u79f0\uff0c\u800c\u662f\u5e38\u89c4\u5c5e\u6027\u540d\u79f0\uff0c\u5219\u53ef\u4ee5\u5b9e\u73b0\u7b2c\u4e8c\u4e2a\u89e3\u51b3\u65b9\u6848\u3002\u8ba9\u6211\u4eec\u4f7f\u7528 init only \u5c5e\u6027 setter \u4fee\u6539\u6211\u4eec\u7684\u8bb0\u5f55\uff1a<\/p>\n
namespace Shared.DataTransferObjects\n{\n [Serializable]\n \/\/ public record CompanyDto(Guid Id, string Name, string FullAddress);\n public record CompanyDto\n {\n public Guid Id { get; init; }\n public string? Name { get; init; }\n public string? FullAddress { get; init; }\n }\n}<\/code><\/pre>\nThis object is still immutable and init-only properties protect the state of the object from mutation once initialization is finished.
\n\u6b64\u5bf9\u8c61\u4ecd\u7136\u662f\u4e0d\u53ef\u53d8\u7684\uff0c\u5e76\u4e14\u4ec5 init-only \u5c5e\u6027\u53ef\u5728\u521d\u59cb\u5316\u5b8c\u6210\u540e\u4fdd\u62a4\u5bf9\u8c61\u7684\u72b6\u6001\u514d\u53d7\u66f4\u6539\u3002<\/p>\n
Additionally, we have to make one more change in the MappingProfile class:
\n\u6b64\u5916\uff0c\u6211\u4eec\u8fd8\u5fc5\u987b\u5728 MappingProfile \u7c7b\u4e2d\u518d\u8fdb\u884c\u4e00\u9879\u66f4\u6539\uff1a<\/p>\n
using AutoMapper;\nusing Entities.Models;\nusing Shared.DataTransferObjects;\n\nnamespace CompanyEmployees\n{\n public class MappingProfile : Profile\n {\n public MappingProfile()\n {\n \/\/CreateMap<Company, CompanyDto>().ForCtorParam("FullAddress", opt => opt.MapFrom(x => string.Join(' ', x.Address, x.Country)));\n CreateMap<Company, CompanyDto>().ForMember(c => c.FullAddress, opt => opt.MapFrom(x => string.Join(' ', x.Address, x.Country)));\n\n CreateMap<Employee, EmployeeDto>();\n }\n }\n}<\/code><\/pre>\nWe are returning this mapping rule to a previous state since now, we do have properties in our object.
\n\u6211\u4eec\u5c06\u6b64\u6620\u5c04\u89c4\u5219\u8fd4\u56de\u5230\u4ee5\u524d\u7684\u72b6\u6001\uff0c\u56e0\u4e3a\u4ece\u73b0\u5728\u5f00\u59cb\uff0c\u6211\u4eec\u7684\u5bf9\u8c61\u4e2d\u786e\u5b9e\u6709\u5c5e\u6027\u3002<\/p>\n
Now, we can send the same request again:
\n\u73b0\u5728\uff0c\u6211\u4eec\u53ef\u4ee5\u518d\u6b21\u53d1\u9001\u76f8\u540c\u7684\u8bf7\u6c42\uff1a<\/p>\n
![\"alt](\"\/images\/ultimateaspnetcorewebapi6\/0704.jpg\")
<\/p>\n
There is our XML response.
\n\u4e0b\u9762\u662f\u6211\u4eec\u7684 XML \u54cd\u5e94\u3002<\/p>\n
Now by changing the Accept header from text\/xml to text\/json, we can get differently formatted responses \u2014 and that is quite awesome, wouldn\u2019t you agree?
\n\u73b0\u5728\uff0c\u901a\u8fc7\u5c06 Accept \u6807\u5934\u4ece text\/xml \u66f4\u6539\u4e3a text\/json\uff0c\u6211\u4eec\u53ef\u4ee5\u83b7\u5f97\u4e0d\u540c\u683c\u5f0f\u7684\u54cd\u5e94 \u2014 \u8fd9\u771f\u662f\u592a\u68d2\u4e86\uff0c\u4f60\u4e0d\u540c\u610f\u5417\uff1f<\/p>\n
Okay, that was nice and easy.
\n\u597d\u5427\uff0c\u8fd9\u5f88\u597d\uff0c\u5f88\u5bb9\u6613\u3002<\/p>\n
But what if despite all this flexibility a client requests a media type that a server doesn\u2019t know how to format?
\n\u4f46\u662f\uff0c\u5982\u679c\u5c3d\u7ba1\u6709\u6240\u6709\u8fd9\u4e9b\u7075\u6d3b\u6027\uff0c\u4f46\u5ba2\u6237\u7aef\u8bf7\u6c42\u7684\u5a92\u4f53\u7c7b\u578b\u670d\u52a1\u5668\u4e0d\u77e5\u9053\u5982\u4f55\u683c\u5f0f\u5316\uff0c\u8be5\u600e\u4e48\u529e\uff1f<\/p>\n
7.4 Restricting Media Types<\/h2>\n
7.4 \u9650\u5236\u5a92\u4f53\u7c7b\u578b<\/p>\n
Currently, it \u2013 the server - will default to a JSON type.\u200c
\n\u76ee\u524d\uff0c\u5b83\uff08\u670d\u52a1\u5668\uff09\u5c06\u9ed8\u8ba4\u4e3a JSON \u7c7b\u578b\u3002<\/p>\n
But we can restrict this behavior by adding one line to the configuration:
\n\u4f46\u662f\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7\u5728\u914d\u7f6e\u4e2d\u6dfb\u52a0\u4e00\u884c\u6765\u9650\u5236\u8fd9\u79cd\u884c\u4e3a\uff1a<\/p>\n
using CompanyEmployees.Extensions;\nusing Contracts;\nusing Microsoft.AspNetCore.HttpOverrides;\nusing NLog;\n\nvar builder = WebApplication.CreateBuilder(args);\n\n\/\/ Add services to the container.\nLogManager.LoadConfiguration(\n string.Concat(Directory.GetCurrentDirectory(),\n "\/nlog.config"));\nbuilder.Services.ConfigureLoggerService();\n\nbuilder.Services.ConfigureCors();\nbuilder.Services.ConfigureIISIntegration();\nbuilder.Services.ConfigureRepositoryManager();\nbuilder.Services.ConfigureServiceManager();\nbuilder.Services.ConfigureSqlContext(builder.Configuration);\nbuilder.Services.AddAutoMapper(typeof(Program));\n\/\/ builder.Services.AddControllers().AddApplicationPart(typeof(CompanyEmployees.Presentation.AssemblyReference).Assembly);\n\/\/ builder.Services.AddControllers(config => { config.RespectBrowserAcceptHeader = true; }).AddXmlDataContractSerializerFormatters().AddApplicationPart(typeof(CompanyEmployees.Presentation.AssemblyReference).Assembly);\nbuilder.Services.AddControllers(config => { config.RespectBrowserAcceptHeader = true; config.ReturnHttpNotAcceptable = true; }).AddXmlDataContractSerializerFormatters().AddApplicationPart(typeof(CompanyEmployees.Presentation.AssemblyReference).Assembly);\nvar app = builder.Build();<\/code><\/pre>\nWe added the ReturnHttpNotAcceptable = true option, which tells the server that if the client tries to negotiate for the media type the server doesn\u2019t support, it should return the 406 Not Acceptable status code.
\n\u6211\u4eec\u6dfb\u52a0\u4e86 ReturnHttpNotAcceptable = true \u9009\u9879\uff0c\u8be5\u9009\u9879\u544a\u8bc9\u670d\u52a1\u5668\uff0c\u5982\u679c\u5ba2\u6237\u7aef\u5c1d\u8bd5\u534f\u5546\u670d\u52a1\u5668\u4e0d\u652f\u6301\u7684\u5a92\u4f53\u7c7b\u578b\uff0c\u5b83\u5e94\u8fd4\u56de 406 Not Acceptable \u72b6\u6001\u4ee3\u7801\u3002<\/p>\n
This will make our application more restrictive and force the API consumer to request only the types the server supports. The 406 status code is created for this purpose.
\n\u8fd9\u5c06\u4f7f\u6211\u4eec\u7684\u5e94\u7528\u7a0b\u5e8f\u66f4\u5177\u9650\u5236\u6027\uff0c\u5e76\u5f3a\u5236 API \u4f7f\u7528\u8005\u4ec5\u8bf7\u6c42\u670d\u52a1\u5668\u652f\u6301\u7684\u7c7b\u578b\u3002406 \u72b6\u6001\u4ee3\u7801\u5c31\u662f\u4e3a\u6b64\u76ee\u7684\u800c\u521b\u5efa\u7684\u3002<\/p>\n
![\"alt](\"\/images\/ultimateaspnetcorewebapi6\/0705.jpg\")
<\/p>\n![\"alt](\"\/images\/ultimateaspnetcorewebapi6\/0706.jpg\")
<\/p>\n