ORM之Dapper运用

一、前言

上一篇【分层架构设计】我们已经有了架构的轮廓,现在我们就在这个轮廓里面造轮子。项目要想开始,肯定先得确定ORM框架,目前市面上的ORM框架有很多,对于.net人员来说很容易就想到以ADO.NET为基础所发展出来的ORM框架EntityFramework。不得不说EntityFramework是一个功能很强大的ORM框架,到现在最新的EF分别是EF6(.Net Framework)和EF Core(.Net Core)两个版本。

但是这里我使用的另一个叫Dapper的ORM框架,原因是因为EF太重了,而Dapper是一个轻量级开源的ORM类,他是通过扩展IDbConnection提供一些有用的扩展方法去查询您的数据库,所以Ado.Net支持的数据库,他都可以支持。在速度方面具有“King of Micro ORM”的头衔,几乎与使用原始的ADO.NET数据读取器一样快。第一次使用了他之后,就深深的喜欢上他了。

github地址:https://github.com/StackExchange/Dapper

Dapper文档:https://dapper-tutorial.net/dapper

二、Dapper实现

2.1、Dapper的方法

从Dapper文档中,我们知道,Dapper支持一下的方法:

Execute:执行一次或多次命令并返回受影响的行数,包括存储过程
Query:执行查询,返回类型为t的数据(返回数据为集合)
QueryFirst:执行查询并映射第一个结果,如果没有就为null
QueryFirstOrDefault:行查询并映射第一个结果,如果序列不包含任何元素,则可以映射默认值
QuerySingle:行查询并映射第一个结果,如果序列中没有一个元素,则抛出异常
QuerySingleOrDefault:执行查询并映射第一个结果,如果序列为空则映射默认值;如果序列中有多个元素,则此方法抛出异常
QueryMultiple:在同一命令中执行多个查询并映射结果

Dapper还提供了上面方法相同功能的异步方法,同时每个方法也支持多种形式的传参。

2.2、Dapper的使用

在前面的项目中,我们在 “04-DataLayer”文件下面添加类库“PFT.Snail.DataAccess”。PFT.Snail.DataAccess主要是 用来完成Dapper方法的使用。

在PFT.Snail.DataAccess项目下面创建文件“DapperSqlDB.cs”,代码如下:

 public class DapperSqlDB
    {
        /// <summary>
        /// 连接字符串
        /// </summary>
        public string ConnectionString { get; set; }
        /// <summary>
        /// 数据库连接时间
        /// </summary>
        private int _commondTimeout { get { return 1200; } }

        public DapperSqlDB()
        {
        }
        public DapperSqlDB(string connectionString)
        {
            ConnectionString = connectionString;
        }

        #region 查询

        /// <summary>
        /// 查询列表
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public List<T> Query<T>(string sql, object param)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return conn.Query<T>(sql, param, commandTimeout: _commondTimeout).ToList();
            }
        }

        /// <summary>
        /// 异步查询列表
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public async Task<IEnumerable<T>> QueryAsync<T>(string sql, object param)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return await conn.QueryAsync<T>(sql, param, commandTimeout: _commondTimeout);
            }
        }

        /// <summary>
        /// 查询列表第一条数据
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public T QueryFirstOrDefault<T>(string sql, object param)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return conn.QueryFirstOrDefault<T>(sql, param, commandTimeout: _commondTimeout);
            }
        }

        /// <summary>
        /// 异步查询列表第一条数据
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public async Task<T> QueryFirstOrDefaultAsync<T>(string sql, object param)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return await conn.QueryFirstOrDefaultAsync<T>(sql, param, commandTimeout: _commondTimeout);
            }
        }

        /// <summary>
        /// 查询选择单个值
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public T ExecuteScalar<T>(string sql, object param)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return conn.ExecuteScalar<T>(sql, param, commandTimeout: _commondTimeout);
            }
        }

        /// <summary>
        /// 异步查询选择单个值
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public async Task<T> ExecuteScalarAsync<T>(string sql, object param)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return await conn.ExecuteScalarAsync<T>(sql, param, commandTimeout: _commondTimeout);
            }
        }

        /*调用方式
         * var multi=DBSqlHelper.QueryMultiple("",null);
         * var invoice = multi.Read<Invoice>().First();
         * var invoiceItems = multi.Read<InvoiceItem>().ToList();
         */
        /// <summary>
        /// 执行多个查询并映射结果
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public GridReader QueryMultiple(string sql, object param)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return conn.QueryMultiple(sql, param, commandTimeout: _commondTimeout);
            }

        }

        /* 调用方式
         * await DBSqlHelper.QueryMultipleAsync(sql, para, async (reader) =>
         *  {
         *      rs.A= (await reader.ReadFirstAsync<SingleValue<decimal>>()).Value;
         *      rs.B= (await reader.ReadFirstAsync<SingleValue<decimal>>()).Value;
         *      ...
         *  });
         */
        /// <summary>
        /// 异步执行多个查询并映射结果
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <param name="readerCallback"></param>
        /// <returns></returns>
        public async Task QueryMultipleAsync(string sql, object param, Action<GridReader> readerCallback)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                using (var reader = await conn.QueryMultipleAsync(sql, param, commandTimeout: _commondTimeout))
                {
                    if (readerCallback != null)
                    {
                        readerCallback(reader);
                    }
                }

            }
        }

        #endregion

        #region 执行sql

        /// <summary>
        /// 执行sql语句
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public int Execute(string sql, object param)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return conn.Execute(sql, param, commandTimeout: _commondTimeout);
            }
        }

        /// <summary>
        /// 异步执行sql语句
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public async Task<int> ExecuteAsync(string sql, object param)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return await conn.ExecuteAsync(sql, param, commandTimeout: _commondTimeout);
            }
        }

        /// <summary>
        /// 执行sql语句(主要指存储过程)
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public int Execute(string sql, object param, CommandType type)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return conn.Execute(sql, param, commandTimeout: _commondTimeout, commandType: type);
            }
        }

        /// <summary>
        /// 异步执行sql语句(主要指存储过程)
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public async Task<int> ExecuteAsync(string sql, object param, CommandType type)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                return await conn.ExecuteAsync(sql, param, commandTimeout: _commondTimeout, commandType: type);
            }
        }
        #endregion





    }

同时Nuget添加System.Data.SqlClient和Dapper的引用。

上面已经实现了数据的增删改查操作,但是再使用过程就会发现,没有事务机制和分页功能。

添加事务功能

在PFT.Snail.DataAccess中添加接口“ITransaction.cs”

public interface ITransaction
    {
        List<T> Query<T>(string sql, object param);
        T QueryFirstOrDefault<T>(string sql, object param);
        T ExecuteScalar<T>(string sql, object param);
        int Execute(string sql, object param);

    }

在“DapperSqlDB.cs”添加事务对象

        #region 事务方法

        /// <summary>
        /// 事务执行方法对象
        /// </summary>
        private class Transaction : IDisposable, ITransaction
        {
            private IDbConnection conn = null;
            private IDbTransaction tran = null;
            public Transaction(IDbConnection conn, IDbTransaction tran)
            {
                this.conn = conn;
                this.tran = tran;
            }


            List<T> ITransaction.Query<T>(string sql, object param)
            {
                return conn.Query<T>(sql, param, tran).ToList();
            }

            T ITransaction.QueryFirstOrDefault<T>(string sql, object param)
            {
                return conn.QueryFirstOrDefault<T>(sql, param, tran);
            }

            T ITransaction.ExecuteScalar<T>(string sql, object param)
            {
                return conn.ExecuteScalar<T>(sql, param, tran);
            }

            int ITransaction.Execute(string sql, object param)
            {
                return conn.Execute(sql, param, tran);
            }

            void IDisposable.Dispose()
            {
                if (this.tran != null)
                {
                    this.tran.Dispose();
                }

                if (this.conn != null)
                {
                    this.conn.Dispose();
                }
            }
        }

        #endregion

添加事务方法

/*调用方式
         * DBSqlHelper.ExecuteTransaction((trans) =>
         * {
         *     trans.Execute(sqlinsertct, selectedClass);
         *     trans.Execute(sqlinsertict, selectedClass);
         * });
         */
        /// <summary>
        /// 事务方法
        /// </summary>
        /// <param name="tranAction"></param>
        /// <param name="level"></param>
        /// <param name="newConnectionString"></param>
        public void ExecuteTransaction(Action<ITransaction> tranAction, IsolationLevel? level = null, string newConnectionString = null)
        {
            using (IDbConnection conn = new SqlConnection(ConnectionString))
            {
                conn.Open();
                IDbTransaction tran = null;
                if (level == null)
                {
                    tran = conn.BeginTransaction();
                }
                else
                {
                    tran = conn.BeginTransaction(level.Value);
                }
                using (Transaction tranHelper = new Transaction(conn, tran))
                {
                    try
                    {
                        tranAction(tranHelper);
                        tran.Commit();
                    }
                    catch
                    {
                        tran.Rollback();
                        throw;
                    }
                }
            }
        }

添加分页功能

在“PFT.Snail.Dto”中添加“Common”文件夹,下面在添加“PageResponse.cs”

/// <summary>
    /// 通用分页返回
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public class PageResponse<T>
    {
        /// <summary>
        /// 总条数
        /// </summary>
        public long TotalCount { get; set; }

        /// <summary>
        /// 返回
        /// </summary>
        public List<T> Items { get; set; }

        /// <summary>
        /// 当前页
        /// </summary>
        public long PageIndex { get; set; }

        /// <summary>
        /// 每页条数
        /// </summary>
        public long PageSize { get; set; }

        /// <summary>
        /// 总页数
        /// </summary>
        public long TotalPages { get; set; }

        /// <summary>
        /// 返回筛选集合
        /// </summary>
        public Dictionary<string, List<string>> ResultFilter = new Dictionary<string, List<string>>();

    }

在“DapperSqlDB.cs”添加分页功能

        /// <summary>
        /// Sqlserver 分页查询(只支持Sqlserver2012以上数据库)
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="page"></param>
        /// <param name="sql"></param>
        /// <param name="param"></param>
        /// <returns></returns>
        public PageResponse<T> QueryPageSql<T>(PageRequest page, string sql, object param)
        {
            var pageResult = new PageResponse<T>();
            pageResult.PageIndex = page.PageIndex;

            var queryNumSql = new StringBuilder($"SELECT COUNT(1) FROM ({sql}) AS maptable");
            pageResult.TotalCount = ExecuteScalar<int>(queryNumSql.ToString(), param);
            if (pageResult.TotalCount == 0)
            {
                return pageResult;
            }

            var pageMinCount = (page.PageIndex - 1) * page.PageSize + 1;
            if (pageResult.TotalCount < pageMinCount)
            {
                page.PageIndex = (int)((pageResult.TotalCount - 1) / page.PageSize) + 1;
            }

            var querySql = new StringBuilder($@"SELECT maptable.* FROM ({sql}) AS maptable ");
            if (!string.IsNullOrWhiteSpace(page.SortBy))
            {
                querySql.AppendLine(page.GetOrderBySql());
            }
            querySql.AppendLine($" OFFSET {(page.PageIndex - 1) * page.PageSize} ROWS FETCH NEXT {page.PageSize} ROWS ONLY;");

            pageResult.Items = Query<T>(querySql.ToString(), param);
            return pageResult;
        }

分页的代码只支持SQl2012以上的版本,如果是一下的版本,可以自己重构代码。

到现在才算把Dapper框架的运用方法全部实现了。

三、总结

虽然实现了Dapper框架的运用方法,但是在真实的项目中,运用这样的方法或多或少有很多不便。同时在架构的设计来说,也不是太合理,因为Repository依赖DapperSqlDB的具体实现,需要抽象出接口。既然存在所说的问题,那为什么不直接写出最终方法呢?这是因为必须弄清楚Dapper的运用,我们才能够对他进行定制化的优化。

  

posted @ 2019-09-13 11:02  园子的蜗牛  阅读(...)  评论(... 编辑 收藏