摘要：
通常，我们将使用数据库表将它们转换为javabean、dao或mapper，这称为反向工程。然而，由于工作的临时需要，我需要将javabean转换为表构建语句和Mybatis Mapper文件。所以我在互联网上搜索了一下，其中大部分都是作为bean解析和输出的工具类。根据自己项目的命名设计要求，将javabean小驼峰命名方法转换为数据库表字段下划线命名方法。参考packagecom的简化示例如下。效用；importjava.io。IOException；导入java.lang.reflect。字段；/***由Jeffon2018年12月5日创建。*/publicclassGenerateSqlMapperUtil｛/***@paramargs*@throwsIOException*/publicstaticvoidmaintrowsIOException｛generateSqlMapper；｝PublicstaticvoidgenerateSqlMapperrowsIOException｛Field[]fields=obj.getDeclaredFields（）；Stringparam=null；StringcameCaseColumn=null；StringunderScoreCaseColumn=null；StringBuildersql=newStringBuilder（）；if｛//No transfer表示默认类名为tableName=obj.getName（）.substring；｝/***以下部分生成创建Sql*/Sql的表。追加追加追加（“；”）；sql.append.append。追加System.out。打印ln；/***以下部分生成Mapper*/firstId=true；StringBuildermapper=newStringBuilder（）；StringBuilderresultMap=newStringBuilder（）；StringBuilderinsert=newStringBuilder（）；StringBuilder插入值=newStringBuilder（）；StringBuilderupdate=newStringBuilder（）；StringBuilderupdateWhere=newStringBuilder（）；StringBuilderdelete=newStringBuilder（）；StringBuilderdeleteWhere=newStringBuilder（）；mapper.append（“˂？
一般上，我们会使用数据库表转换为javabean、dao、或是mapper，就叫逆向工程。做项目时一般也是先设计数据库，再进行系统开发，所以一般使用逆向工程。
但我这边由于工作临时的需要，需要将javabean转换为建表语句和Mybatis的Mapper文件，于是上网搜了一下，大部分是做一个工具类进行bean解析输出的。
根据自身项目命名设计要求，将javabean小驼峰命名法转换为数据库表字段下划线命名法，简化一个例子如下，供参考
package com.util; import java.io.IOException; import java.lang.reflect.Field; /** * Created by Jeff on 2018/12/5. */ public class GenerateSqlMapperUtil { /** * @param args * @throws IOException */ public static void main(String[] args) throws IOException { generateSqlMapper(com.entity.Test.class, null); } public static void generateSqlMapper(Class obj,String tableName) throws IOException{ Field[] fields = obj.getDeclaredFields(); String param = null; String cameCaseColumn = null; String underScoreCaseColumn = null; StringBuilder sql = new StringBuilder(); if(tableName==null||tableName.equals("")){ // 未传表明默认用类名 tableName = obj.getName().substring(obj.getName().lastIndexOf(".")+1); } /** * 以下部分生成建表Sql */ sql.append("drop table if exists ").append(tableName).append("; "); sql.append("create table ").append(tableName).append("( "); boolean firstId = true; for(Field f : fields){ cameCaseColumn = f.getName(); underScoreCaseColumn = cameCaseColumn; for(int i = 0; i < cameCaseColumn.length(); i++) if(Character.isUpperCase(cameCaseColumn.charAt(i))) // 将javabean中小驼峰命名变量的“大写字母”转换为“_小写字母” underScoreCaseColumn = cameCaseColumn.substring(0, i) + '_' + cameCaseColumn.substring(i, i+1).toLowerCase() + cameCaseColumn.substring(i+1, cameCaseColumn.length()); sql.append(underScoreCaseColumn).append(" "); param = f.getType().getTypeName(); if(param.equals("java.lang.Integer")){ sql.append("INTEGER"); }else{ // 根据需要自行修改 sql.append("VARCHAR(20)"); } if(firstId){ // 默认第一个字段为ID主键 sql.append(" PRIMARY KEY AUTO_INCREMENT"); firstId = false; } sql.append(", "); } sql.delete(sql.lastIndexOf(","), sql.length()).append(" )ENGINE=INNODB DEFAULT CHARSET=UTF8 AUTO_INCREMENT=1; "); System.out.println(sql); /** * 以下部分生成Mapper */ firstId = true; StringBuilder mapper = new StringBuilder(); StringBuilder resultMap = new StringBuilder(); StringBuilder insert = new StringBuilder(); StringBuilder insertValues = new StringBuilder(); StringBuilder update = new StringBuilder(); StringBuilder updateWhere = new StringBuilder(); StringBuilder delete = new StringBuilder(); StringBuilder deleteWhere = new StringBuilder(); mapper.append("<?xml version="1.0" encoding="UTF-8"?> "); mapper.append("<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> "); mapper.append("<mapper namespace="com..mapper.").append(tableName).append("Mapper"> "); resultMap.append(" <resultMap id="Base").append(tableName).append("" type="").append(obj.getName()).append(""> "); insert.append(" <insert id="save").append(tableName).append("" parameterType="").append(obj.getName()).append(""> "); insert.append(" INSERT INTO ").append(tableName.toLowerCase()).append(" ("); update.append(" <update id="update").append(tableName).append("" parameterType="").append(obj.getName()).append(""> "); update.append(" UPDATE ").append(tableName.toLowerCase()).append(" SET "); delete.append(" <delete id="delete").append(tableName).append("" parameterType="int"> "); delete.append(" DELETE FROM ").append(tableName.toLowerCase()); for(Field f : fields){ cameCaseColumn = f.getName(); underScoreCaseColumn = cameCaseColumn; for(int i = 0; i < cameCaseColumn.length(); i++) if(Character.isUpperCase(cameCaseColumn.charAt(i))) // 将javabean中小驼峰命名变量的“大写字母”转换为“_小写字母” underScoreCaseColumn = cameCaseColumn.substring(0, i) + '_' + cameCaseColumn.substring(i, i+1).toLowerCase() + cameCaseColumn.substring(i+1, cameCaseColumn.length()); resultMap.append(" "); if(firstId){ resultMap.append("<id column="").append(underScoreCaseColumn).append("" property="").append(cameCaseColumn).append("" jdbcType=""); updateWhere.append(" WHERE ").append(underScoreCaseColumn).append(" = #{").append(cameCaseColumn).append("} "); deleteWhere.append(" WHERE ").append(underScoreCaseColumn).append(" = #{").append(cameCaseColumn).append("} "); firstId = false; } else { resultMap.append("<result column="").append(underScoreCaseColumn).append("" property="").append(cameCaseColumn).append("" jdbcType=""); insert.append(underScoreCaseColumn).append(", "); insertValues.append("#{").append(cameCaseColumn).append("},"); update.append(underScoreCaseColumn).append(" = #{").append(cameCaseColumn).append("}, "); } param = f.getType().getTypeName(); if(param.equals("java.lang.Integer")){ resultMap.append("INTEGER" /> "); }else{ // 根据需要自行修改 resultMap.append("VARCHAR" /> "); } } resultMap.append(" </resultMap> "); insert.delete(insert.lastIndexOf(","), insert.length()).append(") "); insertValues.delete(insertValues.lastIndexOf(","), insertValues.length()); insert.append(" VALUES ("); insert.append(insertValues).append(") "); insert.append(" </insert> "); update.delete(update.lastIndexOf(","), update.length()).append(" "); update.append(updateWhere); update.append(" </update> "); delete.append(deleteWhere); delete.append(" </delete> "); mapper.append(resultMap).append(insert).append(update).append(delete); mapper.append("</mapper>"); System.out.println(mapper); } }