（转）使用T4模板批量生成代码
原文地址：http://www.cnblogs.com/K_tommy/archive/2013/04/06/T4.html
前言
之前在 “使用T4模板生成代码 - 初探” 文章简单的使用了T4模板的生成功能，但对于一个模板生成多个实例文件，如何实现这个方式呢？无意发现一个解决方案 “MultipleOutputHelper.ttinclude” ，它让基于T4模板批量生成文件实例变得简单起来了。
什么是MultipleOutputHelper.ttinclude
Damien Guard是一个在加利福尼亚州圣何塞的开发人员，他构建出处理使用T4模板输出多文件的解决方案“MultipleOutputHelper.ttinclude”
使用
1. 初始化
获取MultipleOutputHelper.ttinclude文件模板
注意： 文件可以上github.com 托管上面获取（ https://github.com/damieng/DamienGKit/tree/master/T4/MultipleOutputHelper）
在T4模板中使用include指令导入MultipleOutputHelper.ttinclude文件或者将MultipleOutputHelper.ttinclude的代码复制在T4模板内。
然后初始化Manager对象,代码如下：
注意： 这里的Manager.ttinclude 就是MultipleOutputHelper.ttinclude文件模板
2. 文件块
使用代码标识区分生成的代码块的范围
该代码声明了一个Employee.generated.cs文件，文件代码内容为：
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public class Employee { ... } |
3. 页眉和页脚
很多模板需要共享一个共同的页眉和页脚时，可以使用import语句进行打开和关闭。简单的使用StartHeader和StartFooter的代码方法进行分割。
4. 编译执行
使用Process方法，进行文件分割。
场景应用
基于之前的“使用T4模板生成代码 - 初探” 文章的场景，进行基于NHibernate Mapper 来获取Domain对象，然后进行批量生成多个代码文件。
1. 自定义T4模板，文件名为“EntityRepositoryTemplate.tt”，代码如下：
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<#@ template language="C#" debug="true" hostspecific="True"#> // 导入MultipleOutputHelper.ttinclude文件<#@include file="$(SolutionDir)app\T4\MultipleOutputHelper.ttinclude"#> // 导入相关的DLL<#@ Assembly Name="$(SolutionDir)lib\SharpArch.2.0.2\NHibernate.dll" #><#@ Assembly Name="$(SolutionDir)lib\SharpArch.2.0.2\SharpArch.NHibernate.dll" #><#@ Assembly Name="$(SolutionDir)lib\SharpArch.2.0.2\SharpArch.Domain.dll" #><#@ Assembly Name="$(SolutionDir)lib\SharpArch.2.0.2\FluentNHibernate.dll" #><#@ Assembly Name="$(SolutionDir)app\Cotide.Data\bin\$(ConfigurationName)\Cotide.Infrastructure.dll" #><#@ Assembly Name="$(SolutionDir)app\Cotide.Core\bin\$(ConfigurationName)\Cotide.Domain.dll" #><#@ Assembly Name="$(SolutionDir)app\Cotide.Framework\bin\$(ConfigurationName)\Cotide.Framework.dll" #><#@ import namespace="System.IO"#><#@ import namespace="System"#><#@ import namespace="System.Configuration"#> <# // 初始化 SharpArch.NHibernate.NHibernateSession.CloseAllSessions(); SharpArch.NHibernate.NHibernateSession.Reset(); string projectPath = @"C:\资料\Person\项目\Codeplex\电子商务\app\"; string nhibernatePath = projectPath + @"Cotide.Web\NHibernate.config"; string[] mappingAssemblies = new[] { @"C:\资料\Person\项目\Codeplex\电子商务\app\Cotide.Data\bin\Release\Cotide.Infrastructure.dll" }; // 加载配置 NHibernate.Cfg.Configuration configuration = SharpArch.NHibernate.NHibernateSession.Init( new SharpArch.NHibernate.SimpleSessionStorage(), mappingAssemblies, new Cotide.Infrastructure.NHibernateMaps.AutoPersistenceModelGenerator().Generate(), nhibernatePath); // 获取所有类映射 var allClassMetadata = SharpArch.NHibernate.NHibernateSession.GetDefaultSessionFactory().GetAllClassMetadata(); var manager = Manager.Create(Host, GenerationEnvironment); foreach (var entry in allClassMetadata) { var entityName = entry.Value.EntityName.Split('.'); var className = entityName[entityName.Length - 1]; // 定义输出文件 manager.StartNewFile("I"+className+"Repository.cs"); #>//-------------------------------------------------------------------//版权所有：版权所有(C) 2012，Microsoft(China) Co.,LTD//系统名称： //文件名称：I<#=className#>Repository.cs//模块名称：//模块编号：//作 者：xcli//创建时间：2013/4/6 12:49:50 //功能说明：//-----------------------------------------------------------------//修改记录： //修改人： //修改时间： //修改内容： //----------------------------------------------------------------- using System;using System.Collections.Generic;using System.Linq; using System.Text;using Cotide.Domain.Contracts.Repositories.Extension; namespace Cotide.Domain.Contracts.Repositories { public interface I<#=className#>Repository : IDbProxyRepository<<#=className#>> { } } <# // 结束输出文件 manager.EndBlock(); } // 执行编译 manager.Process(true); #> |
输出文件效果：
让程序自动执行基于T4文件的编译工作
在MSDN-”演练：创建自定义文本模板宿主“ 文章里面看到一段代码，进行了T4文件的编译工作,代码如下：
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using System;using System.IO;using System.CodeDom.Compiler;using System.Collections.Generic;using System.Text;using Microsoft.VisualStudio.TextTemplating;namespace CustomHost{ //The text template transformation engine is responsible for running //the transformation process. //The host is responsible for all input and output, locating files, //and anything else related to the external environment. //------------------------------------------------------------------------- class CustomCmdLineHost : ITextTemplatingEngineHost { //the path and file name of the text template that is being processed //--------------------------------------------------------------------- internal string TemplateFileValue; public string TemplateFile { get { return TemplateFileValue; } } //This will be the extension of the generated text output file. //The host can provide a default by setting the value of the field here. //The engine can change this value based on the optional output directive //if the user specifies it in the text template. //--------------------------------------------------------------------- private string fileExtensionValue = ".txt"; public string FileExtension { get { return fileExtensionValue; } } //This will be the encoding of the generated text output file. //The host can provide a default by setting the value of the field here. //The engine can change this value based on the optional output directive //if the user specifies it in the text template. //--------------------------------------------------------------------- private Encoding fileEncodingValue = Encoding.UTF8; public Encoding FileEncoding { get { return fileEncodingValue; } } //These are the errors that occur when the engine processes a template. //The engine passes the errors to the host when it is done processing, //and the host can decide how to display them. For example, the host //can display the errors in the UI or write them to a file. //--------------------------------------------------------------------- private CompilerErrorCollection errorsValue; public CompilerErrorCollection Errors { get { return errorsValue; } } //The host can provide standard assembly references. //The engine will use these references when compiling and //executing the generated transformation class. //-------------------------------------------------------------- public IList<string> StandardAssemblyReferences { get { return new string[] { //If this host searches standard paths and the GAC, //we can specify the assembly name like this. //--------------------------------------------------------- //"System" //Because this host only resolves assemblies from the //fully qualified path and name of the assembly, //this is a quick way to get the code to give us the //fully qualified path and name of the System assembly. //--------------------------------------------------------- typeof(System.Uri).Assembly.Location }; } } //The host can provide standard imports or using statements. //The engine will add these statements to the generated //transformation class. //-------------------------------------------------------------- public IList<string> StandardImports { get { return new string[] { "System" }; } } //The engine calls this method based on the optional include directive //if the user has specified it in the text template. //This method can be called 0, 1, or more times. //--------------------------------------------------------------------- //The included text is returned in the context parameter. //If the host searches the registry for the location of include files, //or if the host searches multiple locations by default, the host can //return the final path of the include file in the location parameter. //--------------------------------------------------------------------- public bool LoadIncludeText(string requestFileName, out string content, out string location) { content = System.String.Empty; location = System.String.Empty; //If the argument is the fully qualified path of an existing file, //then we are done. //---------------------------------------------------------------- if (File.Exists(requestFileName)) { content = File.ReadAllText(requestFileName); return true; } //This can be customized to search specific paths for the file. //This can be customized to accept paths to search as command line //arguments. //---------------------------------------------------------------- else { return false; } } //Called by the Engine to enquire about //the processing options you require. //If you recognize that option, return an //appropriate value. //Otherwise, pass back NULL. //-------------------------------------------------------------------- public object GetHostOption(string optionName) { object returnObject; switch (optionName) { case "CacheAssemblies": returnObject = true; break; default: returnObject = null; break; } return returnObject; } //The engine calls this method to resolve assembly references used in //the generated transformation class project and for the optional //assembly directive if the user has specified it in the text template. //This method can be called 0, 1, or more times. //--------------------------------------------------------------------- public string ResolveAssemblyReference(string assemblyReference) { //If the argument is the fully qualified path of an existing file, //then we are done. (This does not do any work.) //---------------------------------------------------------------- if (File.Exists(assemblyReference)) { return assemblyReference; } //Maybe the assembly is in the same folder as the text template that //called the directive. //---------------------------------------------------------------- string candidate = Path.Combine(Path.GetDirectoryName(this.TemplateFile), assemblyReference); if (File.Exists(candidate)) { return candidate; } //This can be customized to search specific paths for the file //or to search the GAC. //---------------------------------------------------------------- //This can be customized to accept paths to search as command line //arguments. //---------------------------------------------------------------- //If we cannot do better, return the original file name. return ""; } //The engine calls this method based on the directives the user has //specified in the text template. //This method can be called 0, 1, or more times. //--------------------------------------------------------------------- public Type ResolveDirectiveProcessor(string processorName) { //This host will not resolve any specific processors. //Check the processor name, and if it is the name of a processor the //host wants to support, return the type of the processor. //--------------------------------------------------------------------- if (string.Compare(processorName, "XYZ", StringComparison.OrdinalIgnoreCase) == 0) { //return typeof(); } //This can be customized to search specific paths for the file //or to search the GAC //If the directive processor cannot be found, throw an error. throw new Exception("Directive Processor not found"); } //A directive processor can call this method if a file name does not //have a path. //The host can attempt to provide path information by searching //specific paths for the file and returning the file and path if found. //This method can be called 0, 1, or more times. //--------------------------------------------------------------------- public string ResolvePath(string fileName) { if (fileName == null) { throw new ArgumentNullException("the file name cannot be null"); } //If the argument is the fully qualified path of an existing file, //then we are done //---------------------------------------------------------------- if (File.Exists(fileName)) { return fileName; } //Maybe the file is in the same folder as the text template that //called the directive. //---------------------------------------------------------------- string candidate = Path.Combine(Path.GetDirectoryName(this.TemplateFile), fileName); if (File.Exists(candidate)) { return candidate; } //Look more places. //---------------------------------------------------------------- //More code can go here... //If we cannot do better, return the original file name. return fileName; } //If a call to a directive in a text template does not provide a value //for a required parameter, the directive processor can try to get it //from the host by calling this method. //This method can be called 0, 1, or more times. //--------------------------------------------------------------------- public string ResolveParameterValue(string directiveId, string processorName, string parameterName) { if (directiveId == null) { throw new ArgumentNullException("the directiveId cannot be null"); } if (processorName == null) { throw new ArgumentNullException("the processorName cannot be null"); } if (parameterName == null) { throw new ArgumentNullException("the parameterName cannot be null"); } //Code to provide "hard-coded" parameter values goes here. //This code depends on the directive processors this host will interact with. //If we cannot do better, return the empty string. return String.Empty; } //The engine calls this method to change the extension of the //generated text output file based on the optional output directive //if the user specifies it in the text template. //--------------------------------------------------------------------- public void SetFileExtension(string extension) { //The parameter extension has a '.' in front of it already. //-------------------------------------------------------- fileExtensionValue = extension; } //The engine calls this method to change the encoding of the //generated text output file based on the optional output directive //if the user specifies it in the text template. //---------------------------------------------------------------------- public void SetOutputEncoding(System.Text.Encoding encoding, bool fromOutputDirective) { fileEncodingValue = encoding; } //The engine calls this method when it is done processing a text //template to pass any errors that occurred to the host. //The host can decide how to display them. //--------------------------------------------------------------------- public void LogErrors(CompilerErrorCollection errors) { errorsValue = errors; } //This is the application domain that is used to compile and run //the generated transformation class to create the generated text output. //---------------------------------------------------------------------- public AppDomain ProvideTemplatingAppDomain(string content) { //This host will provide a new application domain each time the //engine processes a text template. //------------------------------------------------------------- return AppDomain.CreateDomain("Generation App Domain"); //This could be changed to return the current appdomain, but new //assemblies are loaded into this AppDomain on a regular basis. //If the AppDomain lasts too long, it will grow indefintely, //which might be regarded as a leak. //This could be customized to cache the application domain for //a certain number of text template generations (for example, 10). //This could be customized based on the contents of the text //template, which are provided as a parameter for that purpose. } } //This will accept the path of a text template as an argument. //It will create an instance of the custom host and an instance of the //text templating transformation engine, and will transform the //template to create the generated text output file. //------------------------------------------------------------------------- class Program { static void Main(string[] args) { try { ProcessTemplate(args); } catch (Exception ex) { Console.WriteLine(ex.Message); } } static void ProcessTemplate(string[] args) { string templateFileName = null; if (args.Length == 0) { throw new System.Exception("you must provide a text template file path"); } templateFileName = args[0]; if (templateFileName == null) { throw new ArgumentNullException("the file name cannot be null"); } if (!File.Exists(templateFileName)) { throw new FileNotFoundException("the file cannot be found"); } CustomCmdLineHost host = new CustomCmdLineHost(); Engine engine = new Engine(); host.TemplateFileValue = templateFileName; //Read the text template. string input = File.ReadAllText(templateFileName); //Transform the text template. string output = engine.ProcessTemplate(input, host); string outputFileName = Path.GetFileNameWithoutExtension(templateFileName); outputFileName = Path.Combine(Path.GetDirectoryName(templateFileName), outputFileName); outputFileName = outputFileName + "1" + host.FileExtension; File.WriteAllText(outputFileName, output, host.FileEncoding); foreach (CompilerError error in host.Errors) { Console.WriteLine(error.ToString()); } } }} |
联想：基于这个代码实例，可以做一个基于T4模板来批量输出代码的小工具,待续.....
参考资料
- MultipleOutputHelper.ttinclude 文件作者（Damien Guard）- 博客（ http://damieng.com ）
- Damien Guard （Github）（ https://github.com/damieng ）
- 创建自定义文本模板宿主( ＭＳＤＮ) ( http://msdn.microsoft.com/zh-cn/library/vstudio/bb126579.aspx )
- 使用T4模板生成代码 - 初探 （ http://www.cotide.com/xcli/Blog/Article/44 ）
