根據javabean轉換為mysql建表語句與mapper內容

一般上，我們會使用數據庫表轉換為javabean、dao、或是mapper，就叫逆向工程。做項目時一般也是先設計數據庫，再進行系統開發，所以一般使用逆向工程。

但我這邊由於工作臨時的需要，需要將javabean轉換為建表語句和Mybatis的Mapper文件，於是上網搜了一下，大部分是做一個工具類進行bean解析輸出的。

根據自身項目命名設計要求，將javabean小駝峰命名法轉換為數據庫表字段下划線命名法，簡化一個例子如下，供參考

 

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("")){
            // 未傳表明默認用類名
            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(";\r\n");
        sql.append("create table ").append(tableName).append("( \r\n");
        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)))
                    // 將javabean中小駝峰命名變量的“大寫字母”轉換為“_小寫字母”
                    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{
                // 根據需要自行修改
                sql.append("VARCHAR(20)");
            }
            if(firstId){
                // 默認第一個字段為ID主鍵
                sql.append(" PRIMARY KEY AUTO_INCREMENT");
                firstId = false;
            }
            sql.append(",\n");
        }
        sql.delete(sql.lastIndexOf(","), sql.length()).append("\n)ENGINE=INNODB DEFAULT CHARSET=UTF8 AUTO_INCREMENT=1;\r\n");
        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\"?>\r\n");
        mapper.append("<!DOCTYPE mapper PUBLIC \"-//mybatis.org//DTD Mapper 3.0//EN\" \"http://mybatis.org/dtd/mybatis-3-mapper.dtd\">\r\n");
        mapper.append("<mapper namespace=\"com..mapper.").append(tableName).append("Mapper\">\r\n");
        resultMap.append("    <resultMap id=\"Base").append(tableName).append("\" type=\"").append(obj.getName()).append("\">\r\n");
        insert.append("    <insert id=\"save").append(tableName).append("\" parameterType=\"").append(obj.getName()).append("\">\r\n");
        insert.append("        INSERT INTO ").append(tableName.toLowerCase()).append(" (");
        update.append("    <update id=\"update").append(tableName).append("\" parameterType=\"").append(obj.getName()).append("\">\r\n");
        update.append("        UPDATE ").append(tableName.toLowerCase()).append(" SET ");
        delete.append("    <delete id=\"delete").append(tableName).append("\" parameterType=\"int\">\r\n");
        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)))
                    // 將javabean中小駝峰命名變量的“大寫字母”轉換為“_小寫字母”
                    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("}\r\n");
                deleteWhere.append(" WHERE ").append(underScoreCaseColumn).append(" = #{").append(cameCaseColumn).append("}\r\n");
                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\" />\r\n");
            }else{
                // 根據需要自行修改
                resultMap.append("VARCHAR\" />\r\n");
            }
        }
        resultMap.append("    </resultMap>\r\n");
        insert.delete(insert.lastIndexOf(","), insert.length()).append(")\r\n");
        insertValues.delete(insertValues.lastIndexOf(","), insertValues.length());
        insert.append("              VALUES (");
        insert.append(insertValues).append(")\r\n");
        insert.append("    </insert>\r\n");
        update.delete(update.lastIndexOf(","), update.length()).append("\r\n");
        update.append(updateWhere);
        update.append("    </update>\r\n");
        delete.append(deleteWhere);
        delete.append("    </delete>\r\n");
        mapper.append(resultMap).append(insert).append(update).append(delete);
        mapper.append("</mapper>");
        System.out.println(mapper);
    }
}