工具集核心教程 | 第五篇： 利用Velocity模板引擎生成模板代码

前言不知道大家有没有这样的感觉，在平时开发中，经常有很多dao、service类中存着很多重复的代码，Velocity提供了模板生成工具，今天我教大家怎么和这些大量的重复代码说再见。参考项目：https://github.com/bigbeef/cppba-codeTemplate个人博客：http://www.zhangbox.cn注意大家可以写适合自己的模板，这里为了演示，就直接拿cppba-web的模板来示范，至于velocity的语法大家可以查看这篇文章：工具集核心教程 | 第四篇： Velocity模板引擎入门到大神maven配置 <!– velocity –><dependency> <groupId>org.apache.velocity</groupId> <artifactId>velocity</artifactId> <version>1.7</version></dependency>创建模板文件首先看下目录结构：这里演示我就只贴出ServiceImplTemplate.java，需要其他模板代码可以到我github里面下载#set ($domain = $!domainName.substring(0,1).toLowerCase()+$!domainName.substring(1))package $!{packageName}.service.impl;import $!{packageName}.core.bean.PageEntity;import $!{packageName}.dao.$!{domainName}Dao;import $!{packageName}.dto.$!{domainName}Dto;import $!{packageName}.dto.BaseDto;import $!{packageName}.entity.$!{domainName};import $!{packageName}.service.$!{domainName}Service;import org.springframework.stereotype.Service;import org.springframework.transaction.annotation.Transactional;import javax.annotation.Resource;import java.util.HashMap;import java.util.List;import java.util.Map;import java.util.Objects;/** * 开发者 * nickName:星缘 * email:1342541819@qq.com * github:https://github.com/bigbeef * velocity模板生成 cppba-codeTemplate /@Service@Transactionalpublic class $!{domainName}ServiceImpl implements $!{domainName}Service{ @Resource private $!{domainName}Dao $!{domain}Dao; @Override public void save($!{domainName} $!{domain}) { $!{domain}Dao.save($!{domain}); } @Override public void delete($!{domainName} $!{domain}) { $!{domain}Dao.delete($!{domain}); } @Override public void update($!{domainName} $!{domain}) { $!{domain}Dao.update($!{domain}); } @Override public $!{domainName} findById(int id) { return ($!{domainName}) $!{domain}Dao.get($!{domainName}.class, id); } @Override public PageEntity<$!{domainName}> query(BaseDto baseDto) { String hql = " select distinct $!{domain} from $!{domainName} $!{domain} where 1=1 “; Map params = new HashMap<String,Object>(); $!{domainName}Dto $!{domain}Dto = ($!{domainName}Dto)baseDto; $!{domainName} $!{domain} = $!{domain}Dto.get$!{domainName}(); int page = $!{domain}Dto.getPage(); int pageSize = $!{domain}Dto.getPageSize(); List list = $!{domain}Dao.query(hql,params,page,pageSize); long count = $!{domain}Dao.count(hql,params); PageEntity<$!{domainName}> pe = new PageEntity<$!{domainName}>(); pe.setCount(count); pe.setList(list); return pe; }}模板生成接下来是生成模板的主函数：package com.cppba.core;import org.apache.velocity.Template;import org.apache.velocity.VelocityContext;import org.apache.velocity.app.Velocity;import org.apache.velocity.app.VelocityEngine;import java.io.BufferedWriter;import java.io.File;import java.io.FileOutputStream;import java.io.OutputStreamWriter;import java.util.HashMap;import java.util.Map;import java.util.Properties;/* * 开发者 * nickName:星缘 * email:1342541819@qq.com * github:https://github.com/bigbeef /public class Main { static String domainName = “Articles”; //类名 static String packageName = “com.cppba”;//类包 static String templateDir = “\src\main\webapp\template\”; static String sourcePath = System.getProperty(“user.dir”)+templateDir; static String resultDir = “\out”; static String targetPath = System.getProperty(“user.dir”) + resultDir + “\” + packageName.replace(”.", “\”); public static void main(String []args) throws Exception{ Map<String,Object> map = new HashMap(); map.put(“DaoTemplate.java”,“dao/” + domainName + “Dao.java”); map.put(“ServiceTemplate.java”,“service/” + domainName + “Service.java”); map.put(“ServiceImplTemplate.java”,“service/impl/” + domainName + “ServiceImpl.java”); map.put(“DtoTemplate.java”,“dto/” + domainName + “Dto.java”); for(String templateFile:map.keySet()){ String targetFile = (String) map.get(templateFile); Properties pro = new Properties(); pro.setProperty(Velocity.OUTPUT_ENCODING, “UTF-8”); pro.setProperty(Velocity.INPUT_ENCODING, “UTF-8”); pro.setProperty(Velocity.FILE_RESOURCE_LOADER_PATH, sourcePath); VelocityEngine ve = new VelocityEngine(pro); VelocityContext context = new VelocityContext(); context.put(“domainName”,domainName); context.put(“packageName”,packageName); Template t = ve.getTemplate(templateFile, “UTF-8”); File file = new File(targetPath, targetFile); if (!file.getParentFile().exists()) file.getParentFile().mkdirs(); if (!file.exists()) file.createNewFile(); FileOutputStream outStream = new FileOutputStream(file); OutputStreamWriter writer = new OutputStreamWriter(outStream, “UTF-8”); BufferedWriter sw = new BufferedWriter(writer); t.merge(context, sw); sw.flush(); sw.close(); outStream.close(); System.out.println(“成功生成Java文件:” + (targetPath + targetFile).replaceAll("/", “\\”)); } }}生成java文件我们可以修改domainName和packageName来修改我们的包名和类名，我们运行下看：我们看到生成成功，我们打开ArticlesServiceImpl.java看下：package com.cppba.service.impl;import com.cppba.core.bean.PageEntity;import com.cppba.dao.ArticlesDao;import com.cppba.dto.ArticlesDto;import com.cppba.dto.BaseDto;import com.cppba.entity.Articles;import com.cppba.service.ArticlesService;import org.springframework.stereotype.Service;import org.springframework.transaction.annotation.Transactional;import javax.annotation.Resource;import java.util.HashMap;import java.util.List;import java.util.Map;import java.util.Objects;/* * 开发者 * nickName:星缘 * email:1342541819@qq.com * github:https://github.com/bigbeef * velocity模板生成 cppba-codeTemplate */@Service@Transactionalpublic class ArticlesServiceImpl implements ArticlesService{ @Resource private ArticlesDao articlesDao; @Override public void save(Articles articles) { articlesDao.save(articles); } @Override public void delete(Articles articles) { articlesDao.delete(articles); } @Override public void update(Articles articles) { articlesDao.update(articles); } @Override public Articles findById(int id) { return (Articles) articlesDao.get(Articles.class, id); } @Override public PageEntity<Articles> query(BaseDto baseDto) { String hql = " select distinct articles from Articles articles where 1=1 “; Map params = new HashMap<String,Object>(); ArticlesDto articlesDto = (ArticlesDto)baseDto; Articles articles = articlesDto.getArticles(); int page = articlesDto.getPage(); int pageSize = articlesDto.getPageSize(); List list = articlesDao.query(hql,params,page,pageSize); long count = articlesDao.count(hql,params); PageEntity<Articles> pe = new PageEntity<Articles>(); pe.setCount(count); pe.setList(list); return pe; }}生成成功，我们拷贝到cppba-web中可完美运行！写在最后欢迎关注、喜欢、和点赞后续将推出更多的工具集教程，敬请期待。欢迎关注我的微信公众号获取更多更全的学习资源，视频资料，技术干货！公众号回复“学习”，拉你进程序员技术讨论群，干货资源第一时间分享。公众号回复“视频”，领取800GJava视频学习资源。公众号回复“全栈”，领取1T前端，Java，产品经理，微信小程序，Python等资源合集大放送。公众号回复“慕课”，领取1T慕课实战学习资源。公众号回复“实战”，领取750G项目实战学习资源。公众号回复“面试”，领取8G面试实战学习资源。