Castle ActiveRecord学习笔记五：一对多(One-Many)映射关系

本节主要是实现数据库表一对多之间的映射关系。首先，我们需要创建一个Blogs表和一个Posts表，一个Blogs表中可以有多个文章(Posts)，典型的一对多的关系：

Blogs表：

CREATE TABLE [dbo].[Blogs](
    [blog_id] [int] IDENTITY(1,1) NOT NULL,
    [blog_name] [varchar](50) NULL,
    [blog_author] [varchar](50) NULL,
 CONSTRAINT [PK_Blogs] PRIMARY KEY CLUSTERED 
(
    [blog_id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

 

Posts表：

CREATE TABLE [dbo].[Posts](
    [post_id] [int] IDENTITY(1,1) NOT NULL,
    [post_title] [varchar](50) NULL,
    [post_contents] [text] NULL,
    [post_categories] [varchar](50) NULL,
    [post_blogid] [int] NULL,
    [post_created] [datetime] NULL,
    [post_published] [bit] NULL,
 CONSTRAINT [PK_Posts] PRIMARY KEY CLUSTERED 
(
    [post_id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

GO

然后根据前面几章的学习，很轻松的就能够创建Blog和Post操作类：

Blog类如下：

using Castle.ActiveRecord;
using System.Collections;
using NHibernate.Mapping;

namespace CastleLib
{
    [ActiveRecord("Blogs")]
    public class Blog:ActiveRecordBase
    {
        private int _id;
        private string _name;
        private string _author;
        private IList _posts;

        [PrimaryKey(PrimaryKeyType.Native,"blog_id")]
        public int ID
        {
            get { return _id; }
            set { _id = value; }
        }

        [Property("blog_name")]
        public string Name
        {
            get { return _name; }
            set { _name = value; }
        }

        [Property("blog_author")]
        public string Author
        {
            get { return _author; }
            set { _author = value; }
        }

        //需要注意的是，这里指定了Blogs表和Posts表之间的对应关系，二者之间是通过post_blogid来进行对应的
        //并且通过HasMany指定Blogs为主表，可以有多个Posts
        [HasMany(typeof(Post),Table="Posts",ColumnKey="post_blogid",Cascade=ManyRelationCascadeEnum.SaveUpdate)]
        public IList Posts
        {
            get { return _posts; }
            set { _posts = value; }
        }

        public static void DeleteAll()
        {
            DeleteAll(typeof(Blog));
        }

        public static Blog[] FindAll()
        {
            return (Blog[])FindAll(typeof(Blog));
        }

        public static Blog Find(int id)
        {
            return (Blog)FindByPrimaryKey(typeof(Blog), id);
        }
    }
}

Post类如下：

using System;
using Castle.ActiveRecord;

namespace CastleLib
{
    [ActiveRecord("Posts")]
    public class Post:ActiveRecordBase
    {
        private int _id;

        private string _title;

        private string _content;

        private string _category;

        private DateTime _created;

        private bool _published;

        private Blog _blog;

        [PrimaryKey(PrimaryKeyType.Native,"post_id")]
        public int ID
        {
            get { return _id; }
            set { _id = value; }
        }

        [Property("post_title")]
        public string Title
        {
            get { return _title; }
            set { _title = value; }
        }

        [Property(Column="post_contents",ColumnType="StringClob")]
        public string Contents
        {
            get { return _content; }
            set { _content = value; }
        }

        [Property("post_categories")]
        public string Category
        {
            get { return _category; }
            set { _category = value; }
        }
        
        //注意，这里主要是用来指明Posts和Blogs表之间的对应关系，即Posts表属于Blogs，并且通过post_blogid关联
        [BelongsTo("post_blogid")]
        public Blog Blog
        {
            get { return _blog; }
            set { _blog = value; }
        }

        [Property("post_created")]
        public DateTime Created
        {
            get { return _created; }
            set { _created = value; }
        }

        [Property("post_published")]
        public bool Published
        {
            get { return _published; }
            set { _published = value; }
        }

        public static void DeleteAll()
        {
            DeleteAll(typeof(Post));
        }

        public static Post[] FindAll()
        {
            return (Post[])FindAll(typeof(Post));
        }

        public static Post FindByPrimaryKey(int id)
        {
            return (Post)FindByPrimaryKey(typeof(Post),id);
        }

    }
}

下面就来测试，这里我们需要一个Init()函数来初始化Post和Blog类，当然是需要加入到ActiveRecord容器中进行初始化。

下面具体看代码，需要注意的是，在我的测试过程中，出现过两次错误，这两次错误也是很多人在初次使用ActiveRecord的时候容易犯的：

 //You have accessed an ActiveRecord class that wasn't properly initialized. 
 //The only explanation is that the call to ActiveRecordStarter.Initialize() didn't include 

出现这个错误是你没有进行初始化。

//Could not perform Save for Post

出现这个的最可能原因是你的数据格式化不对，我这里主要是试图往DateTime类型中插入超出范围的日期导致出错。

具体见代码：

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Castle.ActiveRecord.Framework.Config;
using Castle.ActiveRecord;
using CastleLib;

namespace CastleAPP
{
    public partial class OneMany : Form
    {
        public OneMany()
        {
            InitializeComponent();
            //记住，如果Init()函数没有调用的话，会出现：
            //You have accessed an ActiveRecord class that wasn't properly initialized. 
            //The only explanation is that the call to ActiveRecordStarter.Initialize() didn't include 
            Init();  
        }

        private void Init()
        {
            InPlaceConfigurationSource source = new InPlaceConfigurationSource();
            IDictionary<string, string> properties = new Dictionary<string, string>();
            properties.Add("connection.driver_class", "NHibernate.Driver.SqlClientDriver");
            properties.Add("dialect", "NHibernate.Dialect.MsSql2008Dialect");
            properties.Add("connection.provider", "NHibernate.Connection.DriverConnectionProvider");
            properties.Add("proxyfactory.factory_class", "NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle");
            properties.Add("connection.connection_string", "UID=sa;Password=251147;Initial Catalog=CastleBase;Data Source=.;");
            source.Add(typeof(ActiveRecordBase), properties);
            ActiveRecordStarter.Initialize(source, typeof(Post),typeof(Blog));
        }

        private void OneMany_Load(object sender, EventArgs e)
        {
           
        }

        ///<summary>
        /// 执行事务，持久化对象到数据库
        ///</summary>
        public void TestCascadingSave()
        {
            //创建Blog对象
            Blog blog = new Blog();
            blog.Name = "程序诗人的博客空间";
            blog.Author = "程序诗人";

            //执行事务，持久化对象到数据库
            
            using (TransactionScope tran = new TransactionScope())
            {
                using (new SessionScope());
                try
                {
                    blog.Create();
                    for (int i = 0; i < 11; i++)
                    {
                        Post post = new Post();
                        post.Title = "这是我的第"+i+"篇文章";
                        post.Category = "Castle Learn";
                        post.Created = DateTime.Now;  //要给时间赋值，否则会出现Could not perform Save for Post的错误
                        post.Blog = blog;
                        post.Save();  //这个地方将文章保存到session中
                    }
                    tran.VoteCommit();  //统一提交到数据库中
                }
                catch
                {
                    tran.VoteRollBack();
                }
            }
        }

        ///<summary>
        /// 级联更新
        ///</summary>
        public void TestCascadingUpdate()
        {
            Blog blog = Blog.Find(5);
            using (TransactionScope tran = new TransactionScope())
            {
                try
                {
                    for (int i = 0; i < 5; i++)
                    {
                        Post post = new Post();
                        post.Title = "哈哈哈，这是第"+i+"次写文章了。";
                        post.Category = "杂记";
                        post.Created = DateTime.Now;
                        post.Save();
                        //blog.Posts.Add(post);
                        //准确的来讲，这两句话作用相同
                        post.Blog = blog;
                    }
                    blog.Update();
                    tran.VoteCommit();
                }
                catch
                {
                    tran.VoteRollBack();
                }
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            TestCascadingSave();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            TestCascadingUpdate();
        }
    }
}

希望有用，谢谢。