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      .NET Core开发日志之OData£¨Open Data Protocol£©

       更新时间£º2019年02月12日 11:22:30   作者£ºKen.W   我要评论

      这篇文章主要给大家介绍了关于.NET Core开发日志之OData£¨Open Data Protocol£©的相关资料£¬文中通过示例代码介绍的非常详细£¬对大家的学习或者工作具有一定的参考学习价值£¬需要的朋友们下面来一起学习学习吧

      简述

      OData£¬即Open Data Protocol£¬是由微软在2007年推出的一款开放协议£¬旨在通过简单¡¢标准的方式创建和使用查询式及交互式RESTful API¡£

      类库

      在.NET Core中想要使用OData功能的话需要添加Microsoft.AspNetCore.OData包¡£

      dotnet add package Microsoft.AspNetCore.OData

      准备模型类

      public class Address
      {
       public string City { get; set; }
       public string Street { get; set; }
      }
      public enum Category
      {
       Book,
       Magazine,
       EBook
      }
      public class Press
      {
       public int Id { get; set; }
       public string Name { get; set; }
       public string Email { get; set; }
       public Category Category { get; set; }
      }
      public class Book
      {
       public int Id { get; set; }
       public string ISBN { get; set; }
       public string Title { get; set; }
       public string Author { get; set; }
       public decimal Price { get; set; }
       public Address Address { get; set; }
       public Press Press { get; set; }
      }

      创建Edm模型

      OData使用EDM£¬即Entity Data Model来描述数据的结构¡£在Startup文件中添加创建方法¡£

      private static IEdmModel GetEdmModel()
      {
        var builder = new ODataConventionModelBuilder();
        builder.EntitySet<Book>("Books");
        builder.EntitySet<Press>("Presses");
        return builder.GetEdmModel();
      }

      注册OData服务

      在Startup文件的ConfigureServices方法里注册OData服务¡£

      services.AddOData();
      services.AddMvc(options =>
        {
          options.EnableEndpointRouting = false;
        }).SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

      这里要注意的是在.NET Core 2.2里£¬默认已经有终结点£¬所以要使用OData的终结点的话需要将默认选项禁用掉¡£

      注册OData终结点

      同样在Startup文件里£¬在其Configure方法内将原来的注册路由内容改为注册OData的终结点¡£

      app.UseMvc(b =>
      {
        b.MapODataServiceRoute("odata", "odata", GetEdmModel());
      });

      显示元数据

      运行程序后访问https://localhost:5001/odata/$metadata地址£¬可以看到所有可用模型的元数据¡£

      <edmx:Edmx xmlns:edmx="http://docs.oasis-open.org/odata/ns/edmx" Version="4.0">
        <edmx:DataServices>
          <Schema xmlns="http://docs.oasis-open.org/odata/ns/edm" Namespace="Default">
            <EntityType Name="Book">
              <Key>
                <PropertyRef Name="Id"/>
              </Key>
              <Property Name="Id" Type="Edm.Int32" Nullable="false"/>
              <Property Name="ISBN" Type="Edm.String"/>
              <Property Name="Title" Type="Edm.String"/>
              <Property Name="Author" Type="Edm.String"/>
              <Property Name="Price" Type="Edm.Decimal" Nullable="false"/>
              <Property Name="Address" Type="Default.Address"/>
              <NavigationProperty Name="Press" Type="Default.Press"/>
            </EntityType>
            <EntityType Name="Press">
              <Key>
                <PropertyRef Name="Id"/>
              </Key>
              <Property Name="Id" Type="Edm.Int32" Nullable="false"/>
              <Property Name="Name" Type="Edm.String"/>
              <Property Name="Email" Type="Edm.String"/>
              <Property Name="Category" Type="Default.Category" Nullable="false"/>
            </EntityType>
            <ComplexType Name="Address">
              <Property Name="City" Type="Edm.String"/>
              <Property Name="Street" Type="Edm.String"/>
            </ComplexType>
            <EnumType Name="Category">
              <Member Name="Book" Value="0"/>
              <Member Name="Magazine" Value="1"/>
              <Member Name="EBook" Value="2"/>
            </EnumType>
            <EntityContainer Name="Container">
              <EntitySet Name="Books" EntityType="Default.Book">
                <NavigationPropertyBinding Path="Press" Target="Presses"/>
              </EntitySet>
              <EntitySet Name="Presses" EntityType="Default.Press"/>
            </EntityContainer>
          </Schema>
        </edmx:DataServices>
      </edmx:Edmx>

      创建Controller

      本文实例中不考虑数据库的操作£¬故而使用hard code方式构建必要的模型对象¡£

      public class BooksController : ODataController
      {
        private static IList<Book> Books {get; set;}
        public BooksController()
        {
          Books = new List<Book>
          {
            new Book
            {
              Id = 1,
              ISBN = "111-0-321-56789-1",
              Title = "Calculus",
              Price = 66.6m,
              Address = new Address
              {
                City = "Shanghai",
                Street = "Beijin Xi Road"
              },
              Press = new Press
              {
                Id = 1,
                Name = "Shanghai Tongji",
                Category = Category.Book
              }
            },
            new Book
            {
              Id = 2,
              ISBN = "222-2-654-00000-2",
              Title = "Linear Algebra",
              Price = 53.2m,
              Address = new Address
              {
                City = "Shanghai",
                Street = "Beijin Dong Road"
              },
              Press = new Press
              {
                Id = 2,
                Name = "Shanghai Fudan",
                Category = Category.EBook
              }
            }      
          };  
        }
      
        [EnableQuery]
        public IActionResult Get()
        {
          return Ok(Books);
        }
      
        [EnableQuery]
        public IActionResult Get(int key)
        {
          return Ok(Books.FirstOrDefault(b => b.Id == key));
        }
      }

      EnableQuery特性在需要高级查询的场景时必须添加¡£

      查询

      加入Controller之后£¬访问https://localhost:5001/odata/Books地址£¬可得到所有Book数据¡£

      {
        "@odata.context": "https://localhost:5001/odata/$metadata#Books",
        "value": [
          {
            "Id": 1,
            "ISBN": "111-0-321-56789-1",
            "Title": "Calculus",
            "Author": null,
            "Price": 66.6,
            "Address": {
              "City": "Shanghai",
              "Street": "Beijin Xi Road"
            }
          },
          {
            "Id": 2,
            "ISBN": "222-2-654-00000-2",
            "Title": "Linear Algebra",
            "Author": null,
            "Price": 53.2,
            "Address": {
              "City": "Shanghai",
              "Street": "Beijin Dong Road"
            }
          }
        ]
      }

      访问https://localhost:5001/odata/Books(1)地址£¬可得到key值为1的Book数据¡£

      {
        "@odata.context": "https://localhost:5001/odata/$metadata#Books/$entity",
        "Id": 1,
        "ISBN": "111-0-321-56789-1",
        "Title": "Calculus",
        "Author": null,
        "Price": 66.6,
        "Address": {
          "City": "Shanghai",
          "Street": "Beijin Xi Road"
        }
      }

      高级查询

      如果想要使用OData查询的高级功能£¬可以在注册终结点时额外?#30001;?#30456;应的配置¡£

      app.UseMvc(b =>
      {
        b.Select().Expand().Filter().OrderBy().MaxTop(100).Count();
        b.MapODataServiceRoute("odata", "odata", GetEdmModel());
      });

      访问网址时?#30001;?#25152;需的查询内容£º
      https://localhost:5001/odata/Books?$select=Id,Title

      {
        "@odata.context": "https://localhost:5001/odata/$metadata#Books(Id,Title)",
        "value": [
          {
            "Id": 1,
            "Title": "Calculus"
          },
          {
            "Id": 2,
            "Title": "Linear Algebra"
          }
        ]
      }

      如果想要按特定条件过滤数据内容的话也很容易£º
      https://localhost:5001/odata/Books?$filter=Price%20le%2060

      {
        "@odata.context": "https://localhost:5001/odata/$metadata#Books",
        "value": [
          {
            "Id": 2,
            "ISBN": "222-2-654-00000-2",
            "Title": "Linear Algebra",
            "Author": null,
            "Price": 53.2,
            "Address": {
              "City": "Shanghai",
              "Street": "Beijin Dong Road"
            }
          }
        ]
      }

      总结

      不难看出£¬OData的真正魅力在于其对那些高级查询功能的支持£¬所以在创建RESTful API时£¬不妨考虑使用OData£¬这样应该能减少许多不必要的代码工作¡£

      好了£¬以上就是这篇文章的全部内容了£¬希望本文的内容对大家的学习或者工作具有一定的参考学习价值£¬如果有疑问大家可以留言交流£¬谢谢大家对脚本之家的支持¡£

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