c#基于NVelocity实现代码生成

2021-01-25 08:40:55 作者：code2roc

这篇文章主要介绍了c#基于NVelocity实现代码生成的方法，帮助大家更好的理解和使用c#，感兴趣的朋友可以了解下

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;
    }
  }

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