在进行数据库添加、修改、删除时，为了保证事务的一致性，即操作要么全部成功，要么全部失败。例如银行A、B两个账户的转账业务。一方失败都会导致事务的不完整性，从而事务回滚。而工作单元模式可以跟踪事务，在操作完成时对事务进行统一提交。
具体实践
首先，讲解下设计思想：领域层通过相应的库实现泛型仓储接口来持久化聚合类，之后在抽象库中将对泛型仓储接口提供基础实现，并将对应的实体转化为SQl语句。这样领域层就不需要操作Sql语句即可完成CRUD操作，同时使用工作单元对事务进行统一提交。
1）定义仓储接口，包含基本的CRUD操作及其重载不同的查询
public interface IRepository<T> { /// <summary> /// 插入对象 /// </summary> /// <param name="entity"></param> int Insert(T entity); /// <summary> /// 更新对象 /// </summary> /// <param name="entity"></param> /// <param name="predicate"></param> int Update(T entity, Expression<Func<T, bool>> express); /// <summary> /// 删除对象 /// </summary> /// <param name="predicate"></param> int Delete(Expression<Func<T, bool>> express = null); /// <summary> /// 查询对象集合 /// </summary> /// <param name="predicate"></param> /// <returns></returns> List<T> QueryAll(Expression<Func<T, bool>> express = null); /// <summary> /// 查询对象集合 /// </summary> /// <param name="index"></param> /// <param name="pagesize"></param> /// <param name="order"></param> /// <param name="asc"></param> /// <param name="express"></param> /// <returns></returns> List<T> QueryAll(int index,int pagesize,List<PropertySortCondition> orderFields, Expression<Func<T, bool>> express = null); /// <summary> /// 查询对象集合 /// </summary> /// <param name="type"></param> /// <param name="predicate"></param> /// <returns></returns> List<object> QueryAll(Type type, Expression<Func<T, bool>> express = null); /// <summary> /// 查询对象 /// </summary> /// <param name="predicate"></param> /// <returns></returns> T Query(Expression<Func<T, bool>> express); /// <summary> /// 查询数量 /// </summary> /// <param name="predicate"></param> /// <returns></returns> object QueryCount(Expression<Func<T, bool>> express = null); }
其次，对仓储接口提供基本实现，这里由于使用了Lambda表达式，所以就需要进行表达式树的解析(这里我希望园友能自己去研究)。
public abstract class BaseRepository<T> : IRepository<T> where T:class,new() { private IUnitOfWork unitOfWork; private IUnitOfWorkContext context; public BaseRepository(IUnitOfWork unitOfWork, IUnitOfWorkContext context) { this.unitOfWork = unitOfWork; this.context = context; } Lazy<ConditionBuilder> builder = new Lazy<ConditionBuilder>(); public string tableName { get { TableNameAttribute attr= (TableNameAttribute)typeof(T).GetCustomAttribute(typeof(TableNameAttribute)); return attr.Name; } } /// <summary> /// 插入对象 /// </summary> /// <param name="entity"></param> public virtual int Insert(T entity) { Func<PropertyInfo[], string, IDictionary<string, object>, int> excute = (propertys, condition, parameters) => { List<string> names = new List<string>(); foreach (PropertyInfo property in propertys) { if (property.GetCustomAttribute(typeof(IncrementAttribute)) == null) { string attrName = property.Name; object value = property.GetValue(entity); names.Add(string.Format("@{0}", attrName)); parameters.Add(attrName, value); } } string sql = "Insert into {0} values({1})"; string combineSql = string.Format(sql, tableName, string.Join(",", names), builder.Value.Condition); return unitOfWork.Command(combineSql, parameters); }; return CreateExcute<int>(null, excute); } /// <summary> /// 修改对象 /// </summary> /// <param name="entity"></param> /// <param name="express"></param> public virtual int Update(T entity, Expression<Func<T, bool>> express) { Func<PropertyInfo[], string, IDictionary<string, object>, int> excute = (propertys, condition, parameters) => { List<string> names = new List<string>(); foreach (PropertyInfo property in propertys) { if (property.GetCustomAttribute(typeof(IncrementAttribute)) == null) { string attrName = property.Name; object value = property.GetValue(entity); names.Add(string.Format("{0}=@{1}", attrName, attrName)); parameters.Add(attrName, value); } } string sql = "update {0} set {1} where {2}"; string combineSql = string.Format(sql, tableName, string.Join(",", names), builder.Value.Condition); return unitOfWork.Command(combineSql, parameters); }; return CreateExcute<int>(express, excute); } /// <summary> /// 删除对象 /// </summary> /// <param name="express"></param> public virtual int Delete(Expression<Func<T, bool>> express = null) { Func<PropertyInfo[], string, IDictionary<string, object>, int> excute = (propertys, condition, parameters) => { string sql = "delete from {0} {1}"; string combineSql = string.Format(sql, tableName, condition); return unitOfWork.Command(combineSql, parameters); }; return CreateExcute<int>(express, excute); } /// <summary> /// 查询对象集合 /// </summary> /// <param name="express"></param> /// <returns></returns> public virtual List<T> QueryAll(Expression<Func<T, bool>> express = null) { Func<PropertyInfo[], string, IDictionary<string, object>, List<T>> excute = (propertys, condition, parameters) => { string sql = "select {0} from {1} {2}"; string combineSql = string.Format(sql, string.Join(",", propertys.Select(x => x.Name)), tableName, condition); return context.ReadValues<T>(combineSql, parameters); }; return CreateExcute<List<T>>(express, excute); } /// <summary> /// 查询对象集合(分页) /// </summary> /// <param name="index"></param> /// <param name="pagesize"></param> /// <param name="order"></param> /// <param name="asc"></param> /// <param name="express"></param> /// <returns></returns> public virtual List<T> QueryAll(int index,int pagesize,List<PropertySortCondition> orderFields,Expression<Func<T, bool>> express = null) { Func<PropertyInfo[], string, IDictionary<string, object>, List<T>> excute = (propertys, condition, parameters) => { if (orderFields == null) { throw new Exception("排序字段不能为空"); } string sql = "select * from (select {0} , ROW_NUMBER() over(order by {1}) as rownum from {2} {3}) as t where t.rownum >= {4} and t.rownum < {5}"; string combineSql = string.Format(sql, string.Join(",", propertys.Select(x => x.Name)),string.Join(",", orderFields), tableName, condition, (index - 1) * pagesize + 1, index * pagesize); return context.ReadValues<T>(combineSql, parameters); }; return CreateExcute<List<T>>(express, excute); } /// <summary> /// 查询对象集合 /// </summary> /// <param name="type"></param> /// <param name="express"></param> /// <returns></returns> public virtual List<object> QueryAll(Type type, Expression<Func<T, bool>> express = null) { Func<PropertyInfo[], string, IDictionary<string, object>, List<object>> excute = (propertys, condition, parameters) => { string sql = "select {0} from {1} {2}"; string combineSql = string.Format(sql, string.Join(",", propertys.Select(x => x.Name)), tableName, condition); return context.ReadValues(combineSql, type, parameters); }; return CreateExcute<List<object>>(express, excute); } /// <summary> /// 查询对象 /// </summary> /// <param name="express"></param> /// <returns></returns> public virtual T Query(Expression<Func<T, bool>> express) { Func<PropertyInfo[], string, IDictionary<string, object>, T> excute = (propertys, condition, parameters) => { string sql = "select {0} from {1} {2}"; string combineSql = string.Format(sql, string.Join(",", propertys.Select(x => x.Name)), tableName, condition); return context.ExecuteReader<T>(combineSql, parameters); }; return CreateExcute<T>(express, excute); } /// <summary> /// 查询数量 /// </summary> /// <param name="express"></param> /// <returns></returns> public virtual object QueryCount(Expression<Func<T, bool>> express = null) { Func<PropertyInfo[], string, IDictionary<string, object>, object> excute = (propertys, condition, parameters) => { string sql = "select * from {0} {1}"; string combineSql = string.Format(sql, string.Join(",", propertys.Select(x => x.Name)), tableName, condition); return context.ExecuteScalar(combineSql, parameters); }; return CreateExcute<object>(express, excute); } private TValue CreateExcute<TValue>(Expression<Func<T, bool>> express, Func<PropertyInfo[], string, IDictionary<string, object>, TValue> excute) { Dictionary<string, object> parameters = new Dictionary<string, object>(); PropertyInfo[] propertys = typeof(T).GetProperties(); string condition = ""; if (express != null) { builder.Value.Build(express, tableName); condition = string.Format("where {0} ", builder.Value.Condition); for (int i = 0; i < builder.Value.Arguments.Length; i++) { parameters.Add(string.Format("Param{0}", i), builder.Value.Arguments[i]); } } return excute(propertys, condition, parameters); } }
接下来，定义工作单元，所有的添加、删除、修改操作都会被储存到工作单元中。
public interface IUnitOfWork { /// <summary> /// 命令 /// </summary> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <returns></returns> int Command(string commandText, IDictionary<string, object> parameters); /// <summary> /// 事务的提交状态 /// </summary> bool IsCommited { get; set; } /// <summary> /// 提交事务 /// </summary> /// <returns></returns> void Commit(); /// <summary> /// 回滚事务 /// </summary> void RollBack(); }
接下来是对工作单元的实现，其内部维护了一个命令集合，存储Sql语句。
public class UnitOfWork:IUnitOfWork { /// <summary> /// 注入对象 /// </summary> private IUnitOfWorkContext context; /// <summary> /// 维护一个Sql语句的命令列表 /// </summary> private List<CommandObject> commands; public UnitOfWork(IUnitOfWorkContext context) { commands = new List<CommandObject>(); this.context = context; } /// <summary> /// 增、删、改命令 /// </summary> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <returns></returns> public int Command(string commandText, IDictionary<string, object> parameters) { IsCommited = false; commands.Add(new CommandObject(commandText, parameters)); return 1; } /// <summary> /// 提交状态 /// </summary> public bool IsCommited{ get; set; } /// <summary> /// 提交方法 /// </summary> /// <returns></returns> public void Commit() { if (IsCommited) { return ; } using (TransactionScope scope = new TransactionScope()) { foreach (var command in commands) { context.ExecuteNonQuery(command.command, command.parameters); } scope.Complete(); IsCommited = true; } } /// <summary> /// 事务回滚 /// </summary> public void RollBack() { IsCommited = false; } }
最后定义工作单元对事务提交处理的上下文及其实现，同仓储模式中的代码。
public interface IUnitOfWorkContext { /// <summary> /// 注册新对象到上下文 /// </summary> /// <param name="commandText"></param> /// <param name="parameters"></param> int ExecuteNonQuery(string commandText, IDictionary<string, object> parameters = null); /// <summary> /// 查询对象集合 /// </summary> /// <typeparam name="T"></typeparam> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <param name="load">自定义处理</param> /// <returns></returns> List<T> ReadValues<T>(string commandText, IDictionary<string, object> parameters = null, Func<IDataReader, T> load = null) where T : class, new(); /// <summary> /// 查询对象集合 /// </summary> /// <param name="commandText"></param> /// <param name="type"></param> /// <param name="parameters"></param> /// <param name="setItem"></param> /// <returns></returns> List<object> ReadValues(string commandText, Type type, IDictionary<string, object> parameters = null, Action<dynamic> setItem = null); /// <summary> /// 查询对象 /// </summary> /// <typeparam name="TEntity"></typeparam> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <param name="excute"></param> /// <returns></returns> T ExecuteReader<T>(string commandText, IDictionary<string, object> parameters = null, Func<IDataReader, T> load = null) where T : class,new(); /// <summary> /// 查询数量 /// </summary> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <returns></returns> object ExecuteScalar(string commandText, IDictionary<string, object> parameters = null); }
最后实现。
public abstract class UnitOfWorkContext : IUnitOfWorkContext,IDisposable { /// <summary> /// 数据库连接字符串标识 /// </summary> public abstract string Key { get; } private SqlConnection connection; private SqlConnection Connection { get { if (connection == null) { ConnectionStringSettings settings = ConfigurationManager.ConnectionStrings[Key]; connection = new SqlConnection(settings.ConnectionString); } return connection; } } /// <summary> /// 注册新对象到事务 /// </summary> /// <typeparam name="TEntity"></typeparam> /// <param name="entity"></param> public int ExecuteNonQuery(string commandText, IDictionary<string, object> parameters = null) { Func<SqlCommand, int> excute = (commend) => { return commend.ExecuteNonQuery(); }; return CreateDbCommondAndExcute<int>(commandText, parameters, excute); } /// <summary> /// 查询对象集合 /// </summary> /// <typeparam name="T"></typeparam> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <param name="load">自定义处理</param> /// <returns>泛型实体集合</returns> public List<T> ReadValues<T>(string commandText, IDictionary<string, object> parameters = null, Func<IDataReader, T> load = null) where T : class,new() { Func<SqlCommand, List<T>> excute = (dbCommand) => { List<T> result = new List<T>(); using (IDataReader reader = dbCommand.ExecuteReader()) { while (reader.Read()) { if (load == null) { load = (s) => { return s.GetReaderData<T>(); }; } var item = load(reader); result.Add(item); } return result; } }; return CreateDbCommondAndExcute(commandText, parameters, excute); } /// <summary> /// 查询对象集合 /// </summary> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <param name="setItem"></param> /// <returns></returns> public List<object> ReadValues(string commandText, Type type, IDictionary<string, object> parameters = null, Action<dynamic> setItem = null) { Func<SqlCommand, List<object>> excute = (dbCommand) => { var result = new List<object>(); using (IDataReader dataReader = dbCommand.ExecuteReader()) { while (dataReader.Read()) { var item = dataReader.GetReaderData(type); if (setItem != null) { setItem(item); } result.Add(item); } } return result; }; return CreateDbCommondAndExcute<List<object>>(commandText, parameters, excute); } /// <summary> /// 查询对象 /// </summary> /// <typeparam name="TEntity"></typeparam> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <param name="excute"></param> /// <returns></returns> public T ExecuteReader<T>(string commandText, IDictionary<string, object> parameters = null, Func<IDataReader, T> load = null) where T : class,new() { Func<SqlCommand, T> excute = (dbCommand) => { var result = default(T); using (IDataReader reader = dbCommand.ExecuteReader()) { while (reader.Read()) { if (load == null) { load = (s) => { return s.GetReaderData<T>(); }; } result = load(reader); } return result; } }; return CreateDbCommondAndExcute<T>(commandText, parameters, excute); } /// <summary> /// 查询数量 /// </summary> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <returns></returns> public object ExecuteScalar(string commandText, IDictionary<string, object> parameters = null) { Func<SqlCommand, object> excute = (dbCommand) => { return dbCommand.ExecuteScalar(); }; return CreateDbCommondAndExcute(commandText, parameters, excute); } /// <summary> /// 创建命令并执行 /// </summary> /// <typeparam name="TValue"></typeparam> /// <param name="commandText"></param> /// <param name="parameters"></param> /// <param name="excute"></param> /// <returns></returns> private TValue CreateDbCommondAndExcute<TValue>(string commandText, IDictionary<string, object> parameters, Func<SqlCommand, TValue> excute) { if (Connection.State == ConnectionState.Closed) { Connection.Open(); }; using (SqlCommand command = new SqlCommand()) { command.CommandType = CommandType.Text; command.CommandText = commandText;; command.Connection = Connection; command.SetParameters(parameters); return excute(command); } } /// <summary> /// 关闭连接 /// </summary> public void Dispose() { if (connection != null) { Connection.Dispose();//非托管资源 } } }
在调用方法时需要注意，一个事务涉及多个聚合时，需要保证传递同一工作单元，并在方法的最后调用Commit() 方法。
public class Services : IService { private IMemberRespository member; private IUnitOfWork unitOfWork; public Services(IMemberRespository member, IUnitOfWork unitOfWork) { this.member = member; this.unitOfWork = unitOfWork; } /// <summary> /// 测试用例 /// </summary> public void Demo() { member.Test(); unitOfWork.Commit(); } }