根据java已经定义好的Class生成DDL SQL

package com.ai.exchange.generator;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;
import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.core.toolkit.StringUtils;
import io.swagger.annotations.ApiModel;
import io.swagger.annotations.ApiModelProperty;
import lombok.extern.slf4j.Slf4j;
import java.io.File;
import java.io.FileOutputStream;
import java.lang.reflect.Field;
import java.util.*;

/** * @Title SqlGenerator * 
@Description 根据JAVA实体生成SQL建表语句工具 

*/
@Slf4j
public class JavaObject2SqlDDLGenerator {

    /**
     * 常见MYSQL字段类型 VS java对象属性类型 映射集合
     */
    public static Map<String, String> javaFiled2TableColumnMappingMap = new HashMap<>();
    static {
        javaFiled2TableColumnMappingMap.put("integer", "int(10)");
        javaFiled2TableColumnMappingMap.put("short", "tinyint");
        javaFiled2TableColumnMappingMap.put("long", "bigint");
        javaFiled2TableColumnMappingMap.put("bigDecimal", "decimal(19,2)");
        javaFiled2TableColumnMappingMap.put("double", "double(10,2)");
        javaFiled2TableColumnMappingMap.put("float", "float");
        javaFiled2TableColumnMappingMap.put("boolean", "bit");
        javaFiled2TableColumnMappingMap.put("timeStamp", "datetime");
        javaFiled2TableColumnMappingMap.put("date", "datetime");
        javaFiled2TableColumnMappingMap.put("string", "varchar(200)");
        javaFiled2TableColumnMappingMap.put("localDateTime", "datetime");
    }

    /**
     * 生成SQL
     * @param className
     * @param tableName
     * @param primaryKey
     * @param filePath
     * @return
     */
    public static String ddlSqlGenerate(String className,String tableName,String primaryKey,String filePath){
        try {
            Class<?> clz = Class.forName(className);
            Field[] fields = clz.getDeclaredFields();
            // 获取该类的父类下的字段
            Class<?> superclass = clz.getSuperclass();
            Field[] declaredFields = superclass.getDeclaredFields();
            List<Field> fieldList = new ArrayList<>();
            for (Field declaredField : declaredFields) {
                fieldList.add(declaredField);
            }
            for (Field declaredField : fields) {
                fieldList.add(declaredField);
            }

            // 查询主键字段
            String sqlPrimaryKey = null;
            Field keyField = null;
            StringBuffer column = new StringBuffer();
            for (int i = 0; i < fieldList.size(); i++) {
                Field f = fieldList.get(i);
                if (StringUtils.isNotBlank(primaryKey) && f.getName().equals(primaryKey)){
                    // 根据TableId 注释获取逐渐信息
                    TableId annotation = f.getAnnotation(TableId.class);
                    if(null != annotation){
                        IdType type = annotation.type();
                        if(IdType.AUTO == type){
                            sqlPrimaryKey = " \n `"+primaryKey+"` int(16) not null auto_increment primary key,";
                        }else{
                            sqlPrimaryKey = " \n `"+primaryKey+"` varchar(100),";
                        }
                    }else{
                        sqlPrimaryKey = " \n `"+primaryKey+"` varchar(100) ,";
                    }
                    continue;
                }

                // 剔除序列化自动生成的字段
                if(f.getName().equalsIgnoreCase("serialVersionUID")){
                    continue;
                }
                TableId tableId = f.getAnnotation(TableId.class);
                if(null != tableId){
                    keyField = f;
                    continue;
                }
                // 跳过不是表字段的属性@TableField(exist=false)
                TableField annotation = f.getAnnotation(TableField.class);
                if(null != annotation){
                    boolean exist = annotation.exist();
                    if(!exist){
                        continue;
                    }
                }
                // 最后一行SQL字符串特殊处理
                if(i == fieldList.size() - 1){
                    column.append(wrapperTableColumnSql(f,false));
                }else{
                    column.append(wrapperTableColumnSql(f,true));
                }

            }
            // 如果没参数中指定主键，则根据注释@TableId自动捕获
            if(StringUtils.isBlank(primaryKey)){
                if(null != keyField){
                    TableId tableId = keyField.getAnnotation(TableId.class);
                    IdType type = tableId.type();
                    String columnName = StringUtils.camelToUnderline(keyField.getName()).toLowerCase();
                    if(IdType.AUTO == type){
                        sqlPrimaryKey = " \n `"+columnName+"` int(16) not null auto_increment primary key,";
                    }else{
                        sqlPrimaryKey = " \n `"+columnName+"` varchar(100),";
                    }
                }
            }

            // 从注解@ApiModel获取表名称（description、value）
            ApiModel annotation = clz.getAnnotation(ApiModel.class);
            String tableNameCn = null;
            if(null != annotation){
                tableNameCn = annotation.description();
                if(StringUtils.isNotBlank(tableNameCn)){
                    if(!tableNameCn.endsWith("表")){
                        tableNameCn += "表";
                    }
                }else{
                    tableNameCn = annotation.value();
                    if(!tableNameCn.endsWith("表")){
                        tableNameCn += "表";
                    }
                }
            }

            // 从注解@TableName获取表名称
            if(StringUtils.isBlank(tableName)){
                TableName tName = clz.getAnnotation(TableName.class);
                String value = tName.value();
                tableName = value;
            }

            StringBuffer sql = new StringBuffer();
            sql.append("\n drop table if exists `"+tableName+"`; ")
                    .append(" \n create table `"+tableName+"` (")
                    .append(StringUtils.isNotBlank(sqlPrimaryKey) ? sqlPrimaryKey : "")
                    .append(" \n "+column)
                    .append(" ) engine = innodb  character set = utf8 collate = utf8_general_ci")
                    .append(StringUtils.isNotBlank(tableName) ? " comment='"+tableNameCn+"'" : "")
                    .append(";");
            String sqlText = sql.toString();
            if(StringUtils.isNotBlank(filePath)){
                sqlSave2File(sqlText,filePath);
            }
            return sqlText;
        } catch (ClassNotFoundException e) {
            log.debug("SQL生成异常：",e);
            return null;
        }
    }

    /**
     * 构建字段部分
     * @param field
     * @return
     */
    private static String wrapperTableColumnSql(Field field,boolean containQuota){
        String tpl = containQuota ? "`%s` %s default null comment '%s', \n" : "`%s` %s default null comment '%s' \n";
        String typeName = field.getType().getSimpleName().toLowerCase();
        String sqlType = javaFiled2TableColumnMappingMap.get(typeName);
        if (sqlType == null || sqlType.isEmpty()){
            log.info(field.getName() + ":"+field.getType().getName()+" 需要单独创建表");
            return "";
        }
        String comment = "";
        // 从注解@ApiModelProperty获取字段信息
        ApiModelProperty annotation = field.getAnnotation(ApiModelProperty.class);
        if(null != annotation){
            comment = annotation.value();
            if("".equalsIgnoreCase(comment)){
                comment = annotation.name();
            }
            if("".equalsIgnoreCase(comment)){
                comment = annotation.notes();
            }
        }
        // 将java对象属性值的驼峰写法转换为下划线模式
        String column = StringUtils.camelToUnderline(field.getName()).toLowerCase();
        String sql = String.format(tpl,column,sqlType.toLowerCase(),comment);
        return sql;
    }

    /**
     * 生成的SQL保存指定文件
     * @param str
     * @param path
     */
    private static void sqlSave2File(String str,String path){
        byte[] sourceByte = str.getBytes();
        if(null != sourceByte){
            try {
                File file = new File(path);
                if (!file.exists()) {
                    File dir = new File(file.getParent());
                    dir.mkdirs();
                    file.createNewFile();
                }
                FileOutputStream outStream = new FileOutputStream(file);
                outStream.write(sourceByte);
                outStream.flush();
                outStream.close();
                System.out.println("生成成功");
            } catch (Exception e) {
                log.debug("保存SQL文件异常：",e);
            }
        }
    }
    
    public static void main(String[] args) {
        String str = ddlSqlGenerate("com.ai.exchange.entity.ExApiZabbixCloudHostMonitorItem", "ex_api_zabbix_cloud_host_monitor_item", null, null);
        log.error(str);
    }
}