系列導航
使用Hot Chocolate和.NET 6構建GraphQL應用文章索引
需求
在本文中，我們將會准備好用於實現GraphQL接口所依賴的底層數據，為下一篇文章具體實現GraphQL接口做准備。
實現
實體定義
在上一篇文章使用Hot Chocolate和.NET 6構建GraphQL應用(1) —— GraphQL及示例項目介紹我們給出的實體關系圖稍微進行一些簡化，去掉了關於評論回復的實體定義。我們先來實現關於Post/Comment/Tag的實體以及對應的Configuration：
Post.cs
namespace PostGraphi.Domain.Post.Entities;
public class Post : AuditableEntity, IEntity<Guid>, IHasDomainEvent
{
public Guid Id { get; set; }
public string? Title { get; set; }
public string? Author { get; set; }
public string? Abstraction { get; set; }
public string? Content { get; set; }
public string? Link { get; set; }
public DateTime PublishedAt { get; set; }
public ICollection<Tag> Tags { get; set; } = new HashSet<Tag>();
public ICollection<Comment> Comments { get; set; } = new List<Comment>();
public List<DomainEvent> DomainEvents { get; set; } = new();
}
Comment.cs
namespace PostGraphi.Domain.Post.Entities;
public class Comment : IEntity<Guid>
{
public Guid Id { get; set; }
public string? Content { get; set; }
public string? Name { get; set; }
public DateTime CreatedAt { get; set; }
public Guid PostId { get; set; }
public Post Post { get; set; }
}
Tag.cs
namespace PostGraphi.Domain.Post.Entities;
public class Tag : IEntity<Guid>
{
public Guid Id { get; set; }
public string? Name { get; set; }
public ICollection<Post> Posts { get; set; } = new HashSet<Post>();
}
PostConfiguration.cs
namespace PostGraphi.Infrastructure.Persistence.Configurations;
public class PostConfiguration : IEntityTypeConfiguration<Post>
{
public void Configure(EntityTypeBuilder<Post> builder)
{
builder.Ignore(e => e.DomainEvents);
builder.Property(t => t.Title).HasMaxLength(200).IsRequired();
builder.HasMany(t => t.Tags).WithMany(a => a.Posts);
builder.HasMany(t => t.Comments).WithOne(c => c.Post).HasForeignKey(c => c.PostId);
}
}
CommentConfiguration.cs
namespace PostGraphi.Infrastructure.Persistence.Configurations;
public class CommentConfiguration : IEntityTypeConfiguration<Comment>
{
public void Configure(EntityTypeBuilder<Comment> builder)
{
builder.Property(t => t.Content).HasMaxLength(255).IsRequired();
builder.HasOne(t => t.Post).WithMany(a => a.Comments).HasForeignKey(t=>t.PostId);
}
}
TagConfiguration.cs
namespace PostGraphi.Infrastructure.Persistence.Configurations;
public class TagConfiguration : IEntityTypeConfiguration<Tag>
{
public void Configure(EntityTypeBuilder<Tag> builder)
{
builder.Property(t => t.Name).HasMaxLength(30).IsRequired();
builder.HasMany(t => t.Posts).WithMany(a => a.Tags);
}
}
並在DbContext類中添加：
PostGraphiDbContext.cs
public DbSet<Post> Posts => Set<Post>();
public DbSet<Tag> Tags => Set<Tag>();
public DbSet<Comment> Comments => Set<Comment>();
數據庫注入
我們需要修改模版里默認的數據庫注入的方式，為了演示重點內容起見，我將數據庫修改為SQLite：
InfrastructureDependencyInjections.cs
// 省略其他...
// 為了注入數據庫實例時還能在構造函數中使用依賴注入
services.AddEntityFrameworkSqlite();
// 使用AddPooledDbContextFactory進行數據庫的注入，因為在GraphQL的並發請求下，直接AddDbContext在執行時會報錯。
services.AddPooledDbContextFactory<PostGraphiDbContext>((serviceProvider, options) =>
{
options.UseSqlite("Data Source=PostGraphi.db");
// 允許在DbContext的構造函數中使用依賴注入容器
options.UseInternalServiceProvider(serviceProvider);
});
准備種子數據
修改PostGraphiDbContextSeed內容，准備一些種子數據：
PostGraphiDbContextSeed.cs
public static async Task SeedSampleDataAsync(PostGraphiDbContext context)
{
if (!context.Posts.Any())
{
var posts = new List<Post>
{
new()
{
Title = "1 - introduction to graphql",
Abstraction = "this is an introduction post for graphql",
Content = "some random content for post 1",
Author = "code4nothing",
PublishedAt = DateTime.Now.AddDays(-2),
Link = "http://link-to-post-1.html",
Comments = new List<Comment>
{
new() { CreatedAt = DateTime.Now.AddHours(-3), Content = "comment 01 for post 1", Name = "kindUser01" },
new() { CreatedAt = DateTime.Now.AddHours(-2), Content = "comment 02 for post 1", Name = "kindUser01" },
new() { CreatedAt = DateTime.Now, Content = "comment 03 for post 1", Name = "kindUser02" }
},
Tags = new List<Tag>
{
new() { Name = "graphql" },
new() { Name = ".net6" }
}
},
new()
{
Title = "2 - integrate graphql with hot chocolate to .net6",
Abstraction = "this is an introduction post for how to integrate graphql to .net6",
Content = "some random content for post 2",
Author = "code4nothing",
PublishedAt = DateTime.Now.AddDays(-1),
Link = "http://link-to-post-2.html",
Comments = new List<Comment>
{
new() { CreatedAt = DateTime.Now.AddHours(-5), Content = "comment 01 for post 2", Name = "kindUser02" },
new() { CreatedAt = DateTime.Now.AddHours(-1), Content = "comment 02 for post 2", Name = "kindUser03" },
new() { CreatedAt = DateTime.Now, Content = "comment 03 for post 2", Name = "kindUser04" }
},
Tags = new List<Tag>
{
new() { Name = "graphql" },
new() { Name = ".net6" },
new() { Name = "hot chocolate" }
}
},
new()
{
Title = "3 - use Dapr with .net6",
Abstraction = "this is an introduction post for how to use dapr in .net6 applications",
Content = "some random content for post 3",
Author = "code4dapr",
PublishedAt = DateTime.Now.AddDays(-1),
Link = "http://link-to-post-3.html",
Comments = new List<Comment>
{
new() { CreatedAt = DateTime.Now.AddHours(-3), Content = "comment 01 for post 3", Name = "kindUser01" },
new() { CreatedAt = DateTime.Now.AddHours(-2), Content = "comment 02 for post 3", Name = "kindUser02" },
new() { CreatedAt = DateTime.Now, Content = "comment 03 for post 3", Name = "kindUser04" },
new() { CreatedAt = DateTime.Now, Content = "comment 04 for post 3", Name = "kindUser03" }
},
Tags = new List<Tag>
{
new() { Name = "dapr" },
new() { Name = ".net6" }
}
},
new()
{
Title = "4 - use dapr service invocation in .net6",
Abstraction = "this is an introduction post for how to use dapr service invocation in .net6",
Content = "some random content for post 4",
Author = "code4dapr",
PublishedAt = DateTime.Now.AddDays(-1),
Link = "http://link-to-post-4.html",
Comments = new List<Comment>
{
new() { CreatedAt = DateTime.Now.AddHours(-3), Content = "comment 01 for post 4", Name = "kindUser04" }
},
Tags = new List<Tag>
{
new() { Name = "dapr" },
new() { Name = ".net6" },
new() { Name = "service invocation" }
}
}
};
context.Posts.AddRange(posts);
await context.SaveChangesAsync();
}
}
應用數據庫遷移和種子數據生成
Program.cs
public static void ApplyDatabaseMigration(this WebApplication app)
{
using var scope = app.Services.CreateScope();
var retryPolicy = CreateRetryPolicy(app.Configuration, Log.Logger);
// 注意因為數據庫的注入方式變了，所以獲取數據庫Context的方法也相應修改
using var context = scope.ServiceProvider.GetRequiredService<IDbContextFactory<PostGraphiDbContext>>().CreateDbContext();
// 應用Migration
retryPolicy.Execute(context.Database.Migrate);
// 生成種子數據
PostGraphiDbContextSeed.SeedSampleDataAsync(context).Wait();
}
執行dotnet migrations add命令行去生成第一次migration數據，運行程序，可以通過數據庫工具看到種子數據已經被成功生成到數據庫了。
總結
下一篇文章起，我們就開始使用Hot Chocolate來完成GraphQL接口的實現。在進入之前，我想先簡單介紹一下在Hot Chocolate中編寫GraphQL相關功能的三種方式，為下一節內容作准備：
Schema First
這種實現方式完全采用了GraphQL Schema定義語言，寫起來比較繁瑣，我們一般不采用這種方式。
Code First
這種方式不需要寫Schema，但是每個C#定義的實體類必須有對應Mapping的GraphQL C#類。
Annotation First
不需要寫Schema，也不要求有對應的GraphQL C#類，僅僅需要定義的實體類。實現方式比較簡單，具體的Schema生成由GraphQL服務器自動實現。
這三種方式可以混搭着使用，為了演示盡量多的Hot Chocolate特性，在系列文章中會以第二種和第三種方式為主。