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自定义ORMapping—动态生成SQL语句
概述
之前在自定义ORMapping——关系表转换为实体或实体集合对象中提到过ORMapping的东西，在那片博客中也有ORMapping实现的一个简单思路，当时只实现了关系表转换为实体或实体集合这个功能，没有实现动态生成SQL这个部分，本片博客就是完善之前的那片博客，实现动态生成SQL语句这么一个功能。
实现思路
1、创建两个自定义特性，分别为表特性和字段特性，目的就是给相应的实体类的类名和属性名，打上相应的特性，从而创建类名和表名，属性和表字段名之间的对应关系
2、创建一个特性解析类，用来解析，这个实体类和表之间的对应关系，即获得这种对应关系
3、创建相应常量类和枚举，常量类用来生成相应的各种运算符或者排序时的关键字，枚举用来说明，生成字段对应的value是否需要添加引号
4、创建相应的where，order生成器类，用来添加相应的条件
5、创建一个整合类，将上面说的那些东西，整个为一个整体，生成相应的SQL语句，并且执行，并将返回的DataTable转换为集合对象
下面的每块内容就是相应的实现
自定义特性类
a、自定义特性的定义
/// <summary>
/// 自定义字段特性
/// </summary>
[AttributeUsage(AttributeTargets.Property, AllowMultiple = true, Inherited = false)]
public class ORFieldMappingAttribute : Attribute
{
/// <summary>
/// 属性和字段的对应
/// </summary>
/// <param name="strFieldName">字段名称</param>
/// <param name="IsAutoIncreate">是否自增</param>
/// <param name="ORFieldValueHaveCommaEnum">有没有逗号</param>
public ORFieldMappingAttribute(string strFieldName, bool IsAutoIncreate = false, ORFieldValueHaveCommaEnum ORFieldValueHaveCommaEnum = ORFieldValueHaveCommaEnum.True)
{
this.strFieldName = strFieldName;
this.ORFieldValueHaveCommaEnum = ORFieldValueHaveCommaEnum;
this.IsAutoIncreate = IsAutoIncreate;
}
public string strFieldName { get; set; }
public ORFieldValueHaveCommaEnum ORFieldValueHaveCommaEnum { get; set; }
public bool IsAutoIncreate { get; set; }
}
/// <summary>
/// 自定义表特性
/// </summary>
[AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
public class ORTableMappingAttribute : Attribute
{
/// <summary>
/// 类名和表明的对应
/// </summary>
/// <param name="strTableName">表名</param>
public ORTableMappingAttribute(string strTableName)
{
this.strTableName = strTableName;
}
public string strTableName { get; set; }
} b、自定义特性的使用，使用在具体的一个实体类上，具体如下：<span style="font-size:12px;"> [ORTableMapping("T_Users")]
public class User
{
[ORFieldMapping("Id",true,ORFieldValueHaveCommaEnum.False)]
public int UserId { get; set; }
[ORFieldMapping("Name",false,ORFieldValueHaveCommaEnum.True)]
public string UserName { get; set; }
[ORFieldMapping("Sex", false, ORFieldValueHaveCommaEnum.True)]
public string UserSex { get; set; }
[ORFieldMapping("Address", false, ORFieldValueHaveCommaEnum.True)]
public string Addr { get; set; }
[ORFieldMapping("Contents", false, ORFieldValueHaveCommaEnum.True)]
public string Content { get; set; }
}</span>解析自定义特性类
a、解析自定义特性类的代码如下
<span style="font-size:12px;"> /// <summary>
/// 获得实体的表名
/// </summary>
/// <param name="obj">实体的type对象</param>
/// <returns>实体对象对应的表名</returns>
public static string GetTableName()
{
T obj = new T();
Type type = obj.GetType();
string strTableName="";
object[] Attarrs = type.GetCustomAttributes(false);
for (int i = 0; i < Attarrs.Length; i++)
{
if (Attarrs[i] is ORTableMappingAttribute)
{
ORTableMappingAttribute attribute = Attarrs[i] as ORTableMappingAttribute;
strTableName = attribute.strTableName;
}
}
return strTableName;
}
/// <summary>
/// 获得实体属性对应的字段,并给字段赋值
/// </summary>
/// <param name="obj">实体的type对象</param>
/// <returns>字典：key=字段名；value=http://www.mamicode.com/字段值> 该类是在生成SQL语句时使用的，只要你的实体类用上相应的特性，只要你把这个类型传递给这个解析类，他就可以给你解决出该类的类名和属性名，与数据库中的表名和字段名的对应关系
常量和枚举
定义如下常量和枚举类型
<span style="font-size:12px;"> /// <summary>
/// 逻辑运算符
/// </summary>
public class LogicOperatorConst
{
public const string And = "and";
public const string Or = "or";
public const string None = "";
}
/// <summary>
/// 字段的排序方向定义
/// </summary>
public class FieldSortConst
{
public const string Asc = "asc";
public const string Desc = "desc";
}
/// <summary>
/// 比较运算符
/// </summary>
public class CompareOperationConst
{
//条件项的运算符常量定义
public const string EqualTo = "=";
public const string GreaterThanOrEqualTo = ">=";
public const string GreaterThan = ">";
public const string LessThanOrEqualTo = "<=";
public const string LessThan = "<";
public const string NotEqualTo = "<>";
public const string Like = "LIKE";
public const string Is = "IS";
public const string In = "IN";
}
/// <summary>
/// 是否有单引号
/// </summary>
public enum ORFieldValueHaveCommaEnum
{
False = 0, True = 1
};</span> 定义这些常量和枚举是为了帮助我们生成相应SQL语句时，使用
定义Where和Order生成对象
<span style="font-size:12px;"> public abstract class SqlClauseBuilder
{
//便于之后的扩展：ToSqlString(ISqlBuilder sqlBuilder)
public abstract string ToSqlString();
}
/// <summary>
/// 拼接Where后的条件语句
/// </summary>
public class WhereSqlClauseBuilder : SqlClauseBuilder
{
private Dictionary<SqlConditionItem, string> dicSqlConditions = new Dictionary<SqlConditionItem, string>();
/// <summary>
/// 添加条件
/// </summary>
/// <param name="strFieldName">字段名</param>
/// <param name="strFieldValue">字段值</param>
/// <param name="strCompareOperation">比较运算符</param>
/// <param name="strLogicOperation">连接符(and or none)</param>
public void Append(string strFieldName, string strFieldValue, string strCompareOperation = CompareOperationConst.EqualTo, string strLogicOperation = LogicOperatorConst.None)
{
SqlConditionItem item = new SqlConditionItem();
item.SetOperationItem(strFieldName, strFieldValue, strCompareOperation);
dicSqlConditions.Add(item, strLogicOperation);
}
/// <summary>
/// 生成Sql语句
/// </summary>
/// <returns></returns>
public override string ToSqlString()
{
StringBuilder sb = new StringBuilder();
foreach (var item in dicSqlConditions)
{
sb.Append(item.Key.GetOperationItem() + " " + item.Value);
}
return sb.ToString();
}
}
/// <summary>
/// 单个where项
/// </summary>
public class SqlConditionItem
{
private string strFieldName;
private string strFieldValue;
private string strCompareOperation;
/// <summary>
/// 以字符串的形式获得条件
/// </summary>
/// <returns>单个条件的字符串</returns>
public string GetOperationItem()
{
StringBuilder sb = new StringBuilder();
sb.Append(" " + strFieldName + " " + strCompareOperation + " " + strFieldValue);
return sb.ToString();
}
/// <summary>
/// 赋值
/// </summary>
/// <param name="strFieldName">字段名</param>
/// <param name="strFieldValue">字段值</param>
/// <param name="strCompareOperation">比较运算符</param>
public void SetOperationItem(string strFieldName, string strFieldValue, string strCompareOperation)
{
this.strFieldName = strFieldName;
this.strCompareOperation = strCompareOperation;
this.strFieldValue = http://www.mamicode.com/strFieldValue;> 使用这些对象帮助我们生成相应的SQL语句中的where和order部分，当然，也可以定义其他的
定义整合类
整合类是将上述运用起来形成的一个整体，从而实现增删该查这些功能，具体如下
<span style="font-size:12px;"> public class DataManager<T> where T : class,new()
{
#region 增加
/// <summary>
/// 添加
/// </summary>
/// <param name="obj">实体对象</param>
/// <returns>SQL语句</returns>
public static int Add(T obj)
{
StringBuilder sb = new StringBuilder();
string strTableName = GetTableName();
string strFieldNames;
string strFieldValues;
GetInsertFieldAndValue(obj, out strFieldNames, out strFieldValues);
sb.AppendFormat("insert into {0}({1}) values({2})", strTableName, strFieldNames, strFieldValues);
return SQLHelper.GetInstance().ExecuteNonQuery(sb.ToString(), CommandType.Text);
}
#endregion
#region 删除
/// <summary>
/// 全部删除
/// </summary>
/// <param name="obj">这个类型的对象</param>
/// <returns>操作影响行数</returns>
public static int Delete(T obj)
{
return Delete(obj, null);
}
/// <summary>
/// 带有条件的删除
/// </summary>
/// <param name="obj">被删除对象</param>
/// <param name="whereSqlClauseBuilder">条件</param>
/// <returns>操作影响行数</returns>
public static int Delete(T obj, Action<WhereSqlClauseBuilder> whereSqlClauseBuilder)
{
StringBuilder sb = new StringBuilder();
string strTableName = GetTableName();
WhereSqlClauseBuilder w = new WhereSqlClauseBuilder();
if (whereSqlClauseBuilder != null)
{
whereSqlClauseBuilder(w);
sb.AppendFormat("delete from {0} where {1}", strTableName, w.ToSqlString());
}
else
{
sb.AppendFormat("delete from {0}", strTableName);
}
return SQLHelper.GetInstance().ExecuteNonQuery(sb.ToString(), CommandType.Text);
}
#endregion
#region 查询
/// <summary>
/// 无条件，无排序的查询
/// </summary>
/// <param name="whereSqlClauseBuilder">lambda表达式</param>
/// <returns>集合</returns>
public static List<T> Load()
{
return Load(null,null);
}
/// <summary>
/// 有条件，无排序的查询
/// </summary>
/// <param name="whereSqlClauseBuilder">lambda表达式</param>
/// <returns>集合</returns>
public static List<T> Load(Action<WhereSqlClauseBuilder> whereSqlClauseBuilder)
{
return Load(whereSqlClauseBuilder, null);
}
/// <summary>
/// 无条件，有排序的查询
/// </summary>
/// <param name="whereSqlClauseBuilder">lambda表达式</param>
/// <returns>集合</returns>
public static List<T> Load(Action<OrderBySqlClauseBuilder> orderBySqlClauseBuilder)
{
return Load(null, orderBySqlClauseBuilder);
}
/// <summary>
/// 有条件，有排序的查询
/// </summary>
/// <param name="whereSqlClauseBuilder">whereSqlClauseBuilder</param>
/// <param name="orderBySqlClauseBuilder">orderBySqlClauseBuilder</param>
/// <returns>集合</returns>
public static List<T> Load(Action<WhereSqlClauseBuilder> whereSqlClauseBuilder, Action<OrderBySqlClauseBuilder> orderBySqlClauseBuilder)
{
StringBuilder sb = new StringBuilder();
string strTableName = GetTableName();
WhereSqlClauseBuilder w = new WhereSqlClauseBuilder();
OrderBySqlClauseBuilder o = new OrderBySqlClauseBuilder();
if (whereSqlClauseBuilder != null)
{
whereSqlClauseBuilder(w);
sb.AppendFormat("select * from {0} where {1}", strTableName, w.ToSqlString());
}
else
{
sb.AppendFormat("select * from {0}", strTableName);
}
if (orderBySqlClauseBuilder != null) {
orderBySqlClauseBuilder(o);
sb.Append(" order by " + w.ToSqlString());
}
DataTable dt = SQLHelper.GetInstance().ExecuteQuery(sb.ToString(), CommandType.Text);
return ORMapping.ToList<T>(dt);
}
#endregion
#region 修改
/// <summary>
/// 更新
/// </summary>
/// <param name="obj">更新的对象</param>
/// <param name="whereSqlClauseBuilder">条件</param>
/// <returns></returns>
public static int Update(T obj, Action<WhereSqlClauseBuilder> whereSqlClauseBuilder = null)
{
StringBuilder sb = new StringBuilder();
string strTableName = GetTableName();
string strFieldValues;
GetUpdateFieldAndValue(obj, out strFieldValues);
WhereSqlClauseBuilder w = new WhereSqlClauseBuilder();
if (whereSqlClauseBuilder != null)
{
whereSqlClauseBuilder(w);
sb.AppendFormat("update {0} set {1} Where {2}", strTableName, strFieldValues, w.ToSqlString());
}
else
{
sb.AppendFormat("update {0} set {1}", strTableName, strFieldValues);
}
return SQLHelper.GetInstance().ExecuteNonQuery(sb.ToString(), CommandType.Text);
}
#endregion
#region 内部方法
//获得表名
private static string GetTableName()
{
T obj = new T();
string strTableName = AttributeManager<T>.GetTableName();
return strTableName;
}
//insert所用的字段名和相应值
private static void GetInsertFieldAndValue(T obj, out string strFieldNames, out string strFieldValues)
{
Dictionary<string, string> dic = AttributeManager<T>.GetFieldName(obj);
strFieldNames = "";
strFieldValues = "";
foreach (var item in dic)
{
strFieldNames = strFieldNames + "," + item.Key;
strFieldValues = strFieldValues + "," + item.Value;
}
if (strFieldNames.Length > 0)
{
strFieldNames = strFieldNames.Substring(1);
strFieldValues = strFieldValues.Substring(1);
}
}
//insert所用的字段名和相应值
private static void GetUpdateFieldAndValue(T obj, out string strFieldNameAndValue)
{
Dictionary<string, string> dic = AttributeManager<T>.GetFieldName(obj);
strFieldNameAndValue = http://www.mamicode.com/"";>
测试
<span style="font-size:12px;"></span><span style="font-size:12px;"> </span><span style="font-size:12px;"> static void Main(string[] args)
{
//Father father1 = DataManager<Father>.Load().First();
List<Father> father2 = DataManager<Father>.Load(p =>
{
p.Append("Id", "2", CompareOperationConst.EqualTo, LogicOperatorConst.None);
});
//List<Son> sonList = father1.ListSon;
User user = new User() {UserName="青山111",UserSex="男111", Addr="地址", Content="内容" };
#region Table转换为实体
//DataTable dt = new DataTable("T_Users");
//dt.Columns.Add(new DataColumn("Id", typeof(string)));
//dt.Columns.Add(new DataColumn("Name", typeof(string)));
//dt.Columns.Add(new DataColumn("Sex", typeof(string)));
////1、创建行
//DataRow dr = dt.NewRow();
////2、赋值行
//dr["Id"] = "10040242041";
//dr["Name"] = "青山";
//dr["Sex"] = "青山";
//dt.Rows.Add(dr);
//List<User> userList = ORMapping.ToList<User>(dt);
#endregion
#region insert语句
int insertCount = DataManager<User>.Add(user);
#endregion
#region delete删除
int intDelete1 = DataManager<User>.Delete(user);
int intDelete2 = DataManager<User>.Delete(user, p =>
{
p.Append("Id", "1", CompareOperationConst.EqualTo, LogicOperatorConst.And);
p.Append("Name", "qingshan", CompareOperationConst.Like, LogicOperatorConst.Or);
p.Append("Sex", "男", CompareOperationConst.Like, LogicOperatorConst.None);
});
#endregion
#region select语句
List<User> userList1 = DataManager<User>.Load();
List<User> userList2 = DataManager<User>.Load(p =>
{
p.Append("Id", "2", CompareOperationConst.EqualTo, LogicOperatorConst.And);
p.Append("Name", "女", CompareOperationConst.Like, LogicOperatorConst.None);
});
#endregion
#region update语句
int intUpdateCount1 = DataManager<User>.Update(user);
int intUpdateCount2 = DataManager<User>.Update(user, p => {
p.Append("Id", "1", CompareOperationConst.EqualTo, LogicOperatorConst.And);
p.Append("Name", "qingshan", CompareOperationConst.Like, LogicOperatorConst.Or);
p.Append("Sex", "男", CompareOperationConst.Like, LogicOperatorConst.None);
});
#endregion
Console.ReadKey();
}</span>总结
自定义ORMapping，主要完成两个功能，第一：SQL语句的生成和执行；第二：DataTable转换为相应的集合，本片博客和之前的那篇博客只是简单的完成了这个功能，具体的代码大家可以在这里下载。
自定义ORMapping—动态生成SQL语句
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