简单代码生成器原理剖析
上篇文章（深入浅出三层架构）分析了简单三层架构的实现。包括Model,DAL（数据访问层）,BLL（业务逻辑层）的实现。
实际开发中，由于重复代码的操作，会花费大量时间，如果以代码生成器来自动生成三层架构代码，即节省精力，又可以节省大量的时间来做其他业务逻辑的代码，提高开发效率。
常用的代码生成器有：动软，CodeSmith 等。
简单代码生成器的基本功能描述：
一键生成Model，DAL，BLL，包括对应数据库中表的Model的自动生成，包括生成属性、添加、修改、删除、查询。
界面展示：
生成器开发技术要点：
- 查询系统视图：INFORMATION_SCHEMA.TABLES、 INFORMATION_SCHEMA.COLUMNS 可以获得数据库中表、列的相关信息。
- 字符串的拼接：StringBuilder的使用，其AppendLine()会自动换行。
- 将字符串写入文本文件：File.WriteAllText()
- 为了降低开发难度，先假设条件多一些，如表的主键都为Id,且自动增长，之后再逐步完善
关键代码：
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 System.Data.SqlClient;
using System.IO;
namespace CodeGenerator
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
/// <summary>
/// 执行ExecuteDataTable()，得到DataTable
/// </summary>
/// <param name="cmdText"></param>
/// <param name="parameters"></param>
/// <returns></returns>
public DataTable ExecuteDataTable(string cmdText,
params SqlParameter[] parameters)
{
using (SqlConnection conn=new SqlConnection(txtConnStr.Text))
{
conn.Open();
using(SqlCommand cmd=conn.CreateCommand())
{
cmd.CommandText = cmdText;
cmd.Parameters.AddRange(parameters);
using (SqlDataAdapter adapter=new SqlDataAdapter (cmd))
{
DataTable dt = new DataTable();
adapter.Fill(dt);
return dt;
}
}
}
}
private void Form1_Load(object sender, EventArgs e)
{
txtConnStr.Text = @"Data Source=EYES\SQLEXPRESS;Initial Catalog=SanCeng;Integrated Security=True";
}
private void btnConnStr_Click(object sender, EventArgs e)
{
//清空
clbTables.Items.Clear();
//查询系统试图
string sql = "select * from INFORMATION_SCHEMA.TABLES";
DataTable dt = ExecuteDataTable(sql);
//根据系统视图取得TABLE_NAME
foreach (DataRow row in dt.Rows)
{
string tablename = Convert.ToString(row["TABLE_NAME"]);
clbTables.Items.Add(tablename);
}
}
private void btnGo_Click(object sender, EventArgs e)
{
//连接字符串
//方法AppendLine()追加字符串且自动执行换行
foreach (string tableName in clbTables.CheckedItems)
{
string sql = "select * from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME=@TABLE_NAME ";
DataTable dt = ExecuteDataTable(sql,new SqlParameter("TABLE_NAME",tableName));
#region 生成Model
CreatModel(tableName, dt);
#endregion
#region 生成DAL
CreatDAL(tableName, dt);
#endregion
#region 生成BLL
CreatBLL(tableName, dt);
#endregion
}
}
private static void CreatDAL(string tableName, DataTable dt)
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("using System;");
sb.AppendLine("using System.Collections.Generic;");
sb.AppendLine("using System.Linq;");
sb.AppendLine("using System.Text;");
sb.AppendLine("using 三层架构Demo.Model;");
sb.AppendLine("using System.Data.SqlClient;");
sb.AppendLine("using System.Data;");
sb.AppendLine("namespace 三层架构Demo.DAL");
sb.AppendLine("{");
sb.AppendLine("class " + tableName + "DAL");
sb.AppendLine("{");
//去掉Id
sb.AppendLine(" public int Addnew(" + tableName + " model)");
sb.AppendLine("{");
List<String> cols = new List<string>();
List<String> parameters = new List<string>();
foreach (DataRow row in dt.Rows)
{
string col = Convert.ToString(row["COLUMN_NAME"]);
string parameter = "";
if (col.ToLower()!="id")
{
parameter= "@" + Convert.ToString(row["COLUMN_NAME"]);
cols.Add(col);
parameters.Add(parameter);
}
//parameters.Add(parameter)放外面加上一个NULL，所以会多出一个逗号
// parameters.Add(parameter);
}
sb.AppendLine("string sql = \"insert into " + tableName + "(" + String.Join(",", cols) + ") output inserted.Id values(" + String.Join(",", parameters) + ")\";");
sb.AppendLine("object obj= SQLHelper.ExecuteScalar(sql");
foreach (DataRow row in dt.Rows)
{
string col = Convert.ToString(row["COLUMN_NAME"]);
if (col.ToLower() != "id")
{
sb.AppendLine(",new SqlParameter(\"" + col + "\",model." + col + ")");
}
}
sb.AppendLine(");");
sb.AppendLine("return Convert.ToInt32(obj);");
sb.AppendLine("}");
//Delete方法
sb.AppendLine(" public int Delete(int id)");
sb.AppendLine("{");
sb.AppendLine(" string sql = \"delete from " + tableName + " where Id=@Id\";");
sb.AppendLine("return SQLHelper.ExecuteNonQuery(sql,new SqlParameter(\"Id\",id));");
sb.AppendLine("}");
//Update方法
sb.AppendLine("public int Update("+tableName+" model)");
sb.AppendLine("{");
string[] uParams1=(from col in cols select col+"=@"+col).ToArray();
sb.AppendLine(" string sql = \"update "+tableName+" set "+String.Join(",",uParams1)+" where Id=@Id\";");
string[] uParams2 = (from col in cols select "new SqlParameter(\"" + col + "\",model." + col + ")").ToArray();
sb.AppendLine(" return SQLHelper.ExecuteNonQuery(sql, " + String.Join(",", uParams2) + " ,new SqlParameter(\"Id\",model.Id));");
sb.AppendLine("}");
//GetId方法
sb.AppendLine(" public "+tableName+" Get(int id)");
sb.AppendLine("{");
sb.AppendLine("string sql=\"select * from "+tableName+" where Id=@Id\";");
sb.AppendLine(" DataTable dt=SQLHelper.ExecuteDataTable(sql,new SqlParameter(\"Id\",id));");
sb.AppendLine("if (dt.Rows.Count<=0)");
sb.AppendLine("{");
sb.AppendLine(" return null;");
sb.AppendLine("}");
sb.AppendLine(" else if (dt.Rows.Count==1)");
sb.AppendLine("{");
sb.AppendLine(""+tableName+" model1 = new "+tableName+"();");
foreach (DataRow row in dt.Rows)
{
string col = Convert.ToString(row["COLUMN_NAME"]);
string dataType = Convert.ToString(row["data_TYPe"]);
sb.AppendLine("model1." + col + " = Convert." + Get(GetType(dataType).ToString()) + "(dt.Rows[0][\"" + col + "\"]);");
}
sb.AppendLine("return model1;");
sb.AppendLine("}");
sb.AppendLine("else");
sb.AppendLine("{");
sb.AppendLine(" throw new Exception(\"数据库中有两条及以上重复数据\");");
sb.AppendLine("}");
sb.AppendLine("}");
//IEnumerable()方法
sb.AppendLine(" public IEnumerable<"+tableName+"> GetAll()");
sb.AppendLine("{");
sb.AppendLine(" string sql = \"select * from "+tableName+"\";");
sb.AppendLine("DataTable dt = SQLHelper.ExecuteDataTable(sql);");
sb.AppendLine(" List<"+tableName+"> list = new List<"+tableName+">();");
sb.AppendLine(" foreach (DataRow row in dt.Rows)");
sb.AppendLine("{");
sb.AppendLine("" + tableName + " model = new " + tableName + "();");
foreach (DataRow row in dt.Rows)
{
string col = Convert.ToString(row["COLUMN_NAME"]);
string dataType = Convert.ToString(row["data_TYPE"]);
sb.AppendLine("model." + col + " = Convert." + Get(GetType(dataType).ToString()) + "(row[\"" + col + "\"]);");
}
sb.AppendLine(" list.Add(model);");
sb.AppendLine("}");
sb.AppendLine("return list;");
sb.AppendLine("}");
sb.AppendLine("}");
sb.AppendLine("}");
File.WriteAllText(@"d:\"+tableName+"DAL.cs",sb.ToString());
}
/// <summary>
/// 数据库类型转换为C#类型
/// </summary>
/// <param name="dataType"></param>
/// <returns></returns>
private static Type GetType(string dataType)
{
switch (dataType.ToLower())
{
case "nvarchar":
case "varchar":
case "nchar":
case "char":
return typeof(string);
case "int" :
return typeof(int);
case "bigint":
return typeof(long);
case "bit":
return typeof(bool);
case "datetime":
return typeof(DateTime);
default:
return typeof(object);
}
}
private static string Get(string dataType)
{
switch (dataType.ToLower())
{
case "system.string":
return "ToString";
case "system.int32":
return "ToInt32";
case "system.int64":
return "ToInt64";
case "system.datetime":
return "ToDateTime";
case "system.boolean":
return "ToBoolean";
default:
throw new Exception("找不到匹配的数据类型");
}
}
private static void CreatModel(string tableName, DataTable dt)
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("using System;");
sb.AppendLine("using System.Collections.Generic;");
sb.AppendLine("using System.Linq;");
sb.AppendLine("using System.Text;");
sb.AppendLine("namespace 三层架构Demo.Model");
sb.AppendLine("{");
sb.AppendLine("");
sb.AppendLine("class " + tableName);
sb.AppendLine("{");
foreach (DataRow row in dt.Rows)
{
string dataType = Convert.ToString(row["DATA_TYPE"]);
string columnName = Convert.ToString(row["COLUMN_NAME"]);
sb.AppendLine("public " + GetType(dataType) + " " + columnName + " { get;set;}");
}
sb.AppendLine("}");
sb.AppendLine("}");
File.WriteAllText(@"d:\" + tableName + ".cs", sb.ToString());
//MessageBox.Show(sb.ToString());
}
private static void CreatBLL(string tableName, DataTable dt)
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("using System;");
sb.AppendLine("using System.Collections.Generic;");
sb.AppendLine("using System.Linq;");
sb.AppendLine("using System.Text;");
sb.AppendLine("using 三层架构Demo.Model;");
sb.AppendLine("using 三层架构Demo.DAL;");
sb.AppendLine("using System.Data.SqlClient;");
sb.AppendLine("using System.Data;");
sb.AppendLine("namespace 三层架构Demo.BLL");
sb.AppendLine("{");
sb.AppendLine("class " + tableName+"BLL");
sb.AppendLine("{");
sb.AppendLine("public int Addnew("+tableName+" model)");
sb.AppendLine("{");
sb.AppendLine(" return new "+tableName+"DAL().Addnew(model);");
sb.AppendLine("}");
sb.AppendLine(" public int Delete(int id)");
sb.AppendLine("{");
sb.AppendLine(" return new "+tableName+"DAL().Delete(id);");
sb.AppendLine("}");
sb.AppendLine(" public int Update("+tableName+" model)");
sb.AppendLine("{");
sb.AppendLine(" return new " + tableName + "DAL().Update(model);");
sb.AppendLine("}");
sb.AppendLine(" public "+tableName+" Get(int id)");
sb.AppendLine("{");
sb.AppendLine(" return new "+tableName+"DAL().Get(id);");
sb.AppendLine("}");
sb.AppendLine(" public IEnumerable<"+tableName+"> GetAll()");
sb.AppendLine("{");
sb.AppendLine(" return new "+tableName+"DAL().GetAll();");
sb.AppendLine("}");
sb.AppendLine("}");
sb.AppendLine("}");
File.WriteAllText(@"d:\" + tableName + "BLL.cs", sb.ToString());
}
}
}
总结：
忽略了很多限制因素，所以代码生成器功能不是很完善。随着要考虑的条件增多，代码生成器越加复杂。但万变不离其中，只要有耐心，继续AppendLine（）添加新语句，相信功能会愈加完善。“工欲善其事必先利其器“，程序员不仅会用代码生成器，而且知道其原理才是优秀的程序员。切勿”知其然而不知其所以然“。
引用自 ：http://www.cnblogs.com/OceanEyes/archive/2012/02/16/CodeGenerator.html