c#基于NVelocity实现代码生成

在框架开发过程中，通用代码生成是一项必不可少的功能，c#在这后端模板引擎这方面第三方组件较少，我这里选择的是NVelocity，现在升级到了NetStandard2.0，可以用于NetCore项目

添加引用

初始化模板引擎及设置模板读取路径

vltEngine = new VelocityEngine();
     vltEngine.SetProperty(RuntimeConstants.RESOURCE_LOADER, "file");
     vltEngine.SetProperty(RuntimeConstants.FILE_RESOURCE_LOADER_PATH, CloudUtil.GetContentPath() + "/" + "Template");
     vltEngine.Init();

读取模板渲染结果

VelocityContext vltContext = new VelocityContext();
     foreach (var item in RenderDataDic)
     {
       vltContext.Put(item.Key, item.Value);
     }
     Template vltTemplate = vltEngine.GetTemplate(TemplateFileName);
     System.IO.StringWriter vltWriter = new System.IO.StringWriter();
     vltTemplate.Merge(vltContext, vltWriter);
     string CodeContent = vltWriter.GetStringBuilder().ToString();

模板语法

示例Entity模板

using FastORM.Attribute;
using FastORM.Entity;
using System;
using System.Collections.Generic;
using System.Text;

namespace ${NameSpace}.Entity
{
 [Table(Name = "${TablePhysicalNameLowCase}")]
 public class ${TablePhysicalName} : BaseEntity
 {
   [Key]
   public string RowGuid { set; get; }
   #foreach( $Column in $ColumnList)
   #if (($Column.ColumnType == 10 || $Column.ColumnType == 50) && $Column.PhysicalColumnName!="RowGuid")
   public string $Column.PhysicalColumnName { set; get; }
   #end
   #if ($Column.ColumnType == 20 && $Column.PhysicalColumnName!="RowGuid")
   public int $Column.PhysicalColumnName { set; get; }
   #end
   #if ($Column.ColumnType == 30 && $Column.PhysicalColumnName!="RowGuid")
   public decimal $Column.PhysicalColumnName { set; get; }
   #end
   #if ($Column.ColumnType == 40 && $Column.PhysicalColumnName!="RowGuid")
   public DateTime? $Column.PhysicalColumnName { set; get; }
   #end
   #end
 }
}

常用语法

使用${xxx}占位替换具体字符串内容

使用 #foreach( $Itemin $ItemList)  #end 来进行循环渲染

使用 #if #end 来进行分支判断渲染

完整工具类代码

public class TemplateUtil
 {
   private static VelocityEngine vltEngine;
   public static string CodeTempPath;

private static void InitTemplateSetting()
   {
     CodeTempPath = AppConfigUtil.Configuration["Frame:GenerateCodeTemplatePath"];
     DirectoryInfo CodePath = new DirectoryInfo(CloudUtil.GetContentStaticFilePath() + CodeTempPath);
     if (!CodePath.Exists)
     {
       CodePath.Create();
     }
     vltEngine = new VelocityEngine();
     vltEngine.SetProperty(RuntimeConstants.RESOURCE_LOADER, "file");
     vltEngine.SetProperty(RuntimeConstants.FILE_RESOURCE_LOADER_PATH, CloudUtil.GetContentPath() + "/" + "Template");
     vltEngine.Init();
   }

public static string GeneratemeplateFile(string FileID, string TableName, string TemplateFileName, string CodeFileName, Dictionary<string, object> RenderDataDic)
   {
     InitTemplateSetting();
     DirectoryInfo CodePath = new DirectoryInfo(CloudUtil.GetContentStaticFilePath() + CodeTempPath + "/" + FileID);
     if (!CodePath.Exists)
     {
       CodePath.Create();
     }
     CodePath = new DirectoryInfo(CloudUtil.GetContentStaticFilePath() + CodeTempPath + "/" + FileID + "/" + TableName);
     if (!CodePath.Exists)
     {
       CodePath.Create();
     }
     VelocityContext vltContext = new VelocityContext();
     foreach (var item in RenderDataDic)
     {
       vltContext.Put(item.Key, item.Value);
     }
     Template vltTemplate = vltEngine.GetTemplate(TemplateFileName);
     System.IO.StringWriter vltWriter = new System.IO.StringWriter();
     vltTemplate.Merge(vltContext, vltWriter);
     string CodeContent = vltWriter.GetStringBuilder().ToString();
     string CodeFilePath = CloudUtil.GetContentStaticFilePath() + CodeTempPath + "/" + FileID + "/" + TableName + "/" + CodeFileName;
     //保存生成后的代码内容到文件
     FileUtil.SaveStringToFile(CodeFilePath, CodeContent);
     return CodeFilePath;
   }

public static string GenerateTemplateContent(string TemplateFileName, Dictionary<string, object> RenderDataDic)
   {
     InitTemplateSetting();
     VelocityContext vltContext = new VelocityContext();
     foreach (var item in RenderDataDic)
     {
       vltContext.Put(item.Key, item.Value);
     }
     Template vltTemplate = vltEngine.GetTemplate(TemplateFileName);
     System.IO.StringWriter vltWriter = new System.IO.StringWriter();
     vltTemplate.Merge(vltContext, vltWriter);
     string CodeContent = vltWriter.GetStringBuilder().ToString();
     return CodeContent;
   }
 }

来源：https://www.cnblogs.com/yanpeng19940119/p/14320593.html