import com.vci.web.util.WebUtil;

import java.util.Locale;

/**
 * @Description
 * @Author dangsn
 * @Date 2024/12/3 17:07
 */
public class StrTest {
    public static void main(String[] args) {
        String sql = "select AA AS AB FROM dual";
        String selectSql = sql.substring(sql.toLowerCase(Locale.ROOT).indexOf("select") + 6, sql.toLowerCase(Locale.ROOT).indexOf(" from")).trim();
        String[] selectKeys = selectSql.split(",");
        for(int j = 0 ; j < selectKeys.length; j ++){
            String field = selectKeys[j];
            if(WebUtil.isNotNull(field)){
                //field = field.toLowerCase();
                //有可能有as的情况  或者空格 或者有.的情况
                //必须优先处理as和空格的情况，最后处理.
                if(field.indexOf(" as ")>-1){
                    field = field.substring(field.lastIndexOf(" as ") + 4);
                }else if(field.indexOf(" ")>-1){
                    field =field.substring(field.lastIndexOf(" ") + 1);
                }else if(field.indexOf(".")>-1){
                    field = field.substring(field.lastIndexOf(".") + 1);
                }
                System.out.println(field);
            }
        }
    }
}