原文章
https://blog.csdn.net/weixin_36090220/article/details/114213993
改了一些部分

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import java.io.File;

import java.io.FileOutputStream;

import java.io.IOException;

import java.lang.reflect.Field;

import java.util.*;

/***
 *
 * @Author : 吟雪情枫

 * @Description 根据实体类生成建库语句

 * @Version : v1.0.0

 * @Date : Created in 2020/7/31 10:12

 * @Modified By :
 **/

//https://blog.csdn.net/weixin_36090220/article/details/114213993
public class SqlGenerator {
    private static final Logger logger = LoggerFactory.getLogger(SqlGenerator.class);

    /**
     * 用来存储Java等属性类型与sql中属性类型的对照
     * <p>
     * <p>
     * <p>
     * 例如：java.lang.Integer 对应 integer
     */

    public static Map map = new HashMap<>();

    public static void main(String[] args) throws ClassNotFoundException {
        map.put("class java.lang.String", "varchar(255)");

        map.put("class java.lang.Integer", "int");

        map.put("class java.lang.Long", "integer unsigned");

        map.put("class java.lang.byte[]", "blob");

        map.put("class java.lang.Boolean", "bit");

        map.put("class java.math.BigInteger", "bigint unsigned");

        map.put("class java.lang.Float", "float");

        map.put("class java.lang.Double", "float");

        map.put("class java.sql.Date", "datetime");

        map.put("class java.sql.Time", "time");

        map.put("class java.sql.Timestamp", "datetime");

        map.put("class java.util.Date", "datetime");

        map.put("class java.lang.Byte", "tinyint");

        sqlConstruction();

    }

    /**
     * 生成sql建库语句
     */

    private static void sqlConstruction() {
//实体类所在的package在磁盘上的绝对路径


      String packageName = "F:/article/newbee-mall/src/main/java/ltd/newbee/mall/entity";
//
生成sql的文件夹
        这个是整个path  sqlFile.sql
      String filePath = "F:/article/newbee-mall/newbee";
//
//
项目中实体类的路径
//
      String prefix = "ltd.newbee.mall.entity.";



        String className = "";

        StringBuilder sqls = new StringBuilder();

//获取包下的所有类名称

        List list = getAllClasses(packageName);

        for (Object oStr : list) {
            String str = (String) oStr;
            className = prefix + str.substring(0, str.lastIndexOf("."));

            String sql = generateSql(className, filePath);

            sqls.append(sql);

        }

        System.out.println(sqls.toString());

        StringToSql(sqls.toString(), filePath + ".sql");

    }

    /**
     * 根据实体类生成建表语句
     *
     * @param className 全类名
     * @param filePath  磁盘路径
     * @return
     */

    public static String generateSql(String className, String filePath) {

      return   generateSql(className,filePath,"");

    }


    public static String generateSql(String className, String filePath,String clzNamePrefix) {
        try {
//            System.out.println(className);
//            System.out.println("className: "+className);
//          Class  redPacketRecordClz= 
//            System.out.println(redPacketRecordClz.getName());
            Class clz = Class.forName(className);

            className = clz.getSimpleName();

// 表表名adminUser → tb_admin_user

            className = clzNamePrefix+ getStandardFields(className);

            Field[] fields = clz.getDeclaredFields();

            StringBuilder column = new StringBuilder();

            String varchar = " CHARACTER SET utf8 COLLATE utf8_general_ci DEFAULT NULL,";

            for (Field f : fields) {
                if ("class java.lang.String".equals(f.getType().toString())) {
                    column.append(" \n `").append(getStandardFields(f.getName())).append("`").append(" ")
                            .append(map.get(f.getType().toString())).append(varchar);

                } else {
                    column.append(" \n `").append(getStandardFields(f.getName())).append("`").append(" ")
                            .append(map.get(f.getType().toString())).append(",");

                }

            }

            return "\n DROP TABLE IF EXISTS `" + className + "`; " +
                    " \n CREATE TABLE `" + className + "` (" +
                    " \n `id` int(11) NOT NULL AUTO_INCREMENT," +
                    " \n " + column +
                    " \n PRIMARY KEY (`id`) USING BTREE," +
                    "\n INDEX `id`(`id`) USING BTREE" +
                    " \n ) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8 COLLATE = utf8_general_ci;\n";

        } catch (ClassNotFoundException e) {
            logger.debug("该类未找到！"+className);

            return null;

        }

    }

    /**
     * 转换为标准等sql字段 例如 adminUser → admin_user
     *
     * @param str 转换为字符串的字段名
     * @return
     */

    public static String getStandardFields(String str) {
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);

            if (i != 0 && (c > 'A' && c < 'Z')) {
                sb.append("_");

            }

            sb.append(c);

        }

        return sb.toString();

    }

    /**
     * 获取包下面等所有实体类名称，类似于获取 XXX.java
     *
     * @param packageName 全类名
     * @return
     */

    public static List getAllClasses(String packageName) {
        List classList = new ArrayList();

        String className = "";

        File f = new File(packageName);

        if (f.exists() && f.isDirectory()) {
            File[] files = f.listFiles();

// 遍历实体类下面等所有.java文件 获取其类名

            for (File file : files) {
                className = file.getName();

                classList.add(className);

            }

            return classList;

        } else {
            logger.debug("包路径未找到！");

            return null;

        }

    }

    /**
     * 将生成等String字符串 写进sql文件
     *
     * @param str  String字符串
     * @param path sql文件路径路径
     */

    public static void StringToSql(String str, String path) {
        byte[] sourceByte = str.getBytes();

        FileOutputStream os = null;

        if (null != sourceByte) {
            try {
//文件路径(路径+文件名)

                File file = new File(path);
                if (file.exists()) {
                    System.out.println("文件已经存在: " + file);
//                    System.out.println("所以我就不写入了");
                    Scanner scanner = new Scanner(System.in);
                    System.out.println("是否覆盖文件?(y/n)");
                    String select = scanner.next();
                    scanner.close();
                    if (select.equals("y")) {

                        //文件输出流用于将数据写入文件

                        os = new FileOutputStream(file);

                        os.write(sourceByte);

                        os.flush();
                        os.close();

                        System.out.println("生成成功!! 位置: " + file);

                    }
                    return;
                }


//文件不存在则创建文件，先创建目录

                File dir = new File(file.getParent());

                dir.mkdirs();

                file.createNewFile();

//文件输出流用于将数据写入文件

                os = new FileOutputStream(file);

                os.write(sourceByte);

                os.flush();
                os.close();
//                不close的话，我打开文件，文件管理器就出问题了
//                System.out.println("生成成功!!");
                System.out.println("生成成功!! 位置: " + file);
//                if (!file.exists()) {
//                    File dir = new File(file.getParent());
//
//                    dir.mkdirs();
//
//                    file.createNewFile();
//
//                }


            } catch (Exception e) {
                e.printStackTrace();

            } finally {
// 关闭文件输出流

                try {
                    if (os != null) {
                        os.close();

                    }

                } catch (IOException e) {
                    e.printStackTrace();

                }

            }

        }

    }

}
//————————————————
//        版权声明：本文为CSDN博主「我爱香菜」的原创文章，遵循CC4.0BY-SA版权协议，转载请附上原文出处链接及本声明。
//        原文链接：https://blog.csdn.net/weixin_36090220/article/details/114213993

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