PageHelper分页插件拼接动态排序语句

<!-- pagehelper 分页插件 -->
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper-spring-boot-starter</artifactId>
        </dependency>

# PageHelper分页插件
pagehelper: 
  helperDialect: mysql
  supportMethodsArguments: true
  params: count=countSql 

@PostMapping("/list")
  @ResponseBody
  public TableDataInfo list(AreaInfo areaInfo)
  {
    if (areaInfo.getParams().get("orderByColumn") == null){
      ServletUtils.getRequest().setAttribute("orderByColumn","create_time");
    }
    if (areaInfo.getParams().get("isAsc") == null){
      ServletUtils.getRequest().setAttribute("isAsc","desc");
    }
    startPage();
        List<AreaInfo> list = areaInfoService.selectAreaInfoList(areaInfo);
    return getDataTable(list);
  }

/**
     * 设置请求分页数据
     */
    protected void startPage()
    {
        PageDomain pageDomain = TableSupport.buildPageRequest();
        Integer pageNum = pageDomain.getPageNum();
        Integer pageSize = pageDomain.getPageSize();
        if (StringUtils.isNotNull(pageNum) && StringUtils.isNotNull(pageSize))
        {
            String orderBy = SqlUtil.escapeOrderBySql(pageDomain.getOrderBy());
            PageHelper.startPage(pageNum, pageSize, orderBy);
        }
    }

public class TableSupport
{
    /**
     * 封装分页对象
     */
    public static PageDomain getPageDomain()
    {
        PageDomain pageDomain = new PageDomain();
        pageDomain.setPageNum(ServletUtils.getParameterToInt(Constants.PAGE_NUM));
        pageDomain.setPageSize(ServletUtils.getParameterToInt(Constants.PAGE_SIZE));
        pageDomain.setOrderByColumn(ServletUtils.getParameter(Constants.ORDER_BY_COLUMN));
        pageDomain.setIsAsc(ServletUtils.getParameter(Constants.IS_ASC));
        return pageDomain;
    }
    public static PageDomain buildPageRequest()
    {
        return getPageDomain();
    }
}

public class Constants
{
    /**
     * 当前记录起始索引
     */
    public static final String PAGE_NUM = "pageNum";
    /**
     * 每页显示记录数
     */
    public static final String PAGE_SIZE = "pageSize";
    /**
     * 排序列
     */
    public static final String ORDER_BY_COLUMN = "orderByColumn";
    /**
     * 排序的方向 "desc" 或者 "asc".
     */
    public static final String IS_ASC = "isAsc";
}

public class SqlUtil
{
    /**
     * 仅支持字母、数字、下划线、空格、逗号（支持多个字段排序）
     */
    public static String SQL_PATTERN = "[a-zA-Z0-9_\\ \\,]+";
    /**
     * 检查字符，防止注入绕过
     */
    public static String escapeOrderBySql(String value)
    {
        if (StringUtils.isNotEmpty(value) && !isValidOrderBySql(value))
        {
            return StringUtils.EMPTY;
        }
        return value;
    }
    /**
     * 验证 order by 语法是否符合规范
     */
    public static boolean isValidOrderBySql(String value)
    {
        return value.matches(SQL_PATTERN);
    }
}