ASP.NET Web API中展示实体Link相关的方面
有时候，向服务端请求一个实体，我们希望返回如下的格式：
links: [
href: http://localhost:8901/api/user/diaries/2013-08-17,
rel: "self",
method: "GET",
isTemplated: false
],
currentDate:"2013-08-17"
首先抽象出一个与Link相关的类：
public class LinkModel { public stirng Href{get;set;} public stirng Rel{get;set;} public string Method{get;set;} public bool IsTemplated{get;set;} }
再放到某个视图模型中：
public class DiaryModel { //存储和模型相关的链接 public ICollection<LinkModel> Links{get;set;} public DateTime CurrentDate{get;set;} } public class Diary { public int Id{get;set;} public DateTime CurrentDate{get;set;} }
ModelFactory用来实现视图模型和领域模型之间的转化。
public class ModelFactory { private UrlHelper _urlHelper; public ModelFactory(HttpRequestMessage request) { _urlHelper = new UrlHelper(request); } //领域模型转换成视图模型 public DiaryModel Create(Diary d) { return new DiaryModel() { Links = new List<LinkModel> { CreateLink(_urlHelper.Link("Diaryis", new {diaryid=d.CurrentDate.ToString("yyyy-MM-dd")}),"self"); }, CurrentDate = d.CurrentDate } } public LinkModel CreateLink(string href, string rel, string method = "GET", bool isTemplated = false) { return new LinkModel() { Href = href, Rel = rel, Method = method, IsTemplated = isTemplated } } //视图模型转换成领域模型 public Diary Parse(DiaryModel model) { try { var entity = new Diary(); var selfLink = model.Links.Where(l => l.Rel == "self").FirstOrDefault(); if(selfLink != null && !string.IsNullOrWhiteSpace(selfLink.Href)) { //从Uri中取出主键 var uri = new Uri(selfLink.Href); entity.Id = int.Parse(uri.Segments.Last()); } entity.CurrentDate = model.CurrentDate; return entity; } catch(Exception ex) { } } }
Diaries这个controller略，路由方面：
//api/user/diaries //api/user/diaries/2001-01-01 config.Routes.MapHttpRoute( name: "Diaries", routeTemplate: "api/user/diaries/{dairyid}", defaults: new {controller="diaries", diaryid=RouteParameter.Optional} )
这样，在客户端发出 http://localhost:8901/api/user/diaries/2013-08-17 GET请求，得到如下的响应：
links: [
href: http://localhost:8901/api/user/diaries/2013-08-17,
rel: "self",
method: "GET",
isTemplated: false
],
currentDate:"2013-08-17"
在返回分页相关的action中，也可以返回相关的Link部分。
先定义一个基类控制器：
public abstract class BaseController : ApiController { ICountingKsRepository _repo; ModelFactory _modelFactory; public BaseController(ICountingKsRepository repo) { _repo = repo; //写在构造函数里的话有点迟，必须等实例化_modelFactory才有值 //_modelFactory = new ModelFactory(this.Request); } protected ModelFactory TheModelFactory { get { if(_modelFactory == null) { _modelFactory = new ModelFactory(this.Request, TheRepository); } return _modelFactory; } } protected ICountingsRepository TheRepoisitory { get { return _repo; } } }
可见，把共同的部分封装到基类控制器中是很好的习惯，然后基类控制器的子类通过属性获取一些方面。
再到具体的控制器：
public class FoodsController : BaseController { ICountingKsRepoisotry _repo; ModelFactory _modelFactory; public FoodsController(ICountingKsRepository repo) : base(repo) { } const int PAGE_SIZE = 50; public object Get(bool includeMeasures = true, int page = 0) { IQueryable<Food> query; if(includeMeausres) { query = TheRepository.GetAllFoodsWithMeausres(); } else { query = TheRepository.GetAllFoods(); } //方便统计总数 var baseQuery = query.OrderBy(f =>f.Description); //using System.Web.Http.Routing var helper = new UrlHelper(Request); var links = new List<LinkModel>(); if(page > 0) { links.Add(TheModelFactory.CreateLink(helper.Link("Food", new {page = page - 1},"prevPage")); } if(page < totalPages - 1) { links.Add(TheModelFactory.CreateLink(helper.Link("Food", new {page = page + 1},"nextPage")); } //把上一页和下一页的url保存下来 //var prevUrl = page > 0 ? helper.Link("Food", new {page = page - 1}) : ""; //var nextUrl = page > 0 ? helper.Link("Food", new {page = page + 1}) : ""; //输出总数 var totalCount = baseQuery.Count(); var totalPages = Math.Ceiling((double)totalCount/PAGE_SIZE); var result = baseQuery .Skip(PAGE_SIZE * page) .Take(PAGE_SIZE) .ToList() .Select(f => TheModelFactory.FoodFromDomainToView(f)); //方便客户端接收 return new { TotalCount = totalCount, TotalPages = totalPages, Result = result， Links = links //PrevPageUrl = prevUrl, //NextPageUrl = nextUrl, } } public FoodModel Get(int foodid) { return TheModelFactory.FoodFromDomainToView(TheRepository.GetFood(foodid)); } }
客户端请求：localhost:8901/api/nutrition/foods
{
totalCount:800,
totalPages:151,
links: [
{
href: http://localhost:8901/api/nutrition/foods?page=1,
rel: "prevPage",
method: "GET",
isTemplated: false,
},
{
href: http://localhost:8901/api/nutrition/foods?page=2,
rel: "nextPage",
method: "GET",
isTemplated: false
}
],
result: [...]
}
另外，还可以控制序列化过程。
在LinkModel这个视图中:
public class LinkModel { public stirng Href{get;set;} public stirng Rel{get;set;} public string Method{get;set;} public bool IsTemplated{get;set;} }
在显示的时候，可能不想让IsTemplated显示出来，如何在序列化的过程中做到呢？
--通过jsonFormatter.SerializerSettings.Converts属性，用来控制序列化为json数据时的显示方式。
在WebApiConfig.cs中：
var jsonFormatter = config.Formatters.OfType<JsonMediaTypeFormatter>().FirstOrDefault(); jsonFormatter.SerializerSettings.ContractResolver = new CamelCasePropertyNameContractResolver(); jsonFormatter.SerializerSettings.Converts(new LinkModelConverter());
而LinkModelConverter类需要继承JsonConverter类。
public class LinkModelConverter : JsonConverter { public override bool CanConvert(Type objectType) { return objectType.Equals(typeof(LinkModel)); } public override object ReadJson(JsonReader reader, Type object) { return reader.Value; } public override void WriteJson(JsonWriter wrtier, object value) { var model = value as LinkModel; if(model != null) { wirter.WriteStartObject(); writer.WirteProeprtyName("href"); writer.WriteValue(model.Href); writer.WriteProeprtyName("rel"); writer.WriteValue(model.Rel); if(!model.Method.Equals("GET",StringComparison.ordinalIgnoreCase)) { writer.WritePropertyName("method"); writer.WriteValue(model.Method); } if(model.IsTemplated) { writer.WriterPropertyName("isTemplated"); writer.WriteValue(model.IsTemplated); } writer.WriteEndObject(); } } }
