What causes "pagination parameters are not a valid number type!" in pagehelper-org/Mybatis-PageHelper?

Validate/sanitize pageNum and pageSize before calling the paging API (parse with NumberUtils and fall back to defaults)

pagehelper-org/Mybatis-PageHelper · error · PageException

pagination parameters are not a valid number type!

Error message

pagination parameters are not a valid number type!

What it means

PageHelper read the pageNum/pageSize values from the parameter object but could not parse them into integers — Integer.parseInt failed with NumberFormatException, which is wrapped in a PageException. The paging parameters exist but are not valid number types (e.g. "abc", "12.5", or a non-numeric object).

Solutions

Validate/sanitize pageNum and pageSize before calling the paging API (parse with NumberUtils and fall back to defaults)
Ensure values are whole numbers: trim strings, reject/round decimals, and empty-check before paging
If values come from HTTP, bind them as Integer in the DTO so the framework fails fast with a clean 400
Wrap the paging call in try-catch for PageException and degrade to default paging instead of failing the request

Example fix

// before
params.put("pageNum", request.getParameter("page")); // may be "abc"
PageHelper.startPage(params);
// after
int pageNum = NumberUtils.toInt(request.getParameter("page"), 1);
int pageSize = NumberUtils.toInt(request.getParameter("size"), 10);
PageHelper.startPage(pageNum, pageSize);

Defensive patterns

Strategy: validation

Validate before calling

Object pn = map.get("pageNum"), ps = map.get("pageSize");
if (pn == null || ps == null
    || !pn.toString().matches("\\d+")
    || !ps.toString().matches("\\d+")) {
    throw new IllegalArgumentException("pageNum/pageSize must be positive integers");
}
PageHelper.startPage(map);

Try / catch

try {
    PageHelper.startPage(params);
} catch (PageException e) {
    log.warn("invalid paging numbers, using defaults: {}", e.getMessage());
    PageHelper.startPage(1, 10);
}

Prevention

Bind HTTP paging params as Integer fields in DTOs, not String
Reject decimals/empty strings at the API boundary with 400 responses
Use NumberUtils.toInt(value, default) for tolerant parsing before paging

When it happens

Trigger: Passing pageNum="abc" or pageSize="3.5" in a Map used for paging; passing a non-numeric Object (e.g. a Locale or array) under the _pageNum/_pageSize keys; HTTP query params bound as raw strings with typos or empty strings placed into the paging map.

Common situations: Spring binds request parameters as Strings and a user supplies page=two; frontend sends pageSize=10.0 from JS floats; a config file supplies non-numeric defaults; a JSON deserializer yields Doubles with decimal points that fail parseInt.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

AI-assisted analysis of pagehelper-org/Mybatis-PageHelper@c692616c5b (2026-09-08). Data as JSON: /api/errors/2c1a132e339baa55. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/com/github/pagehelper/util/PageObjectUtil.java:126

        if (orderBy != null && orderBy.toString().length() > 0) {
            hasOrderBy = true;
        }
        try {
            Object _pageNum = getParamValue(paramsObject, "pageNum", required);
            Object _pageSize = getParamValue(paramsObject, "pageSize", required);
            if (_pageNum == null || _pageSize == null) {
                if(hasOrderBy){
                    Page page = new Page();
                    page.setOrderBy(orderBy.toString());
                    page.setOrderByOnly(true);
                    return page;
                }
                return null;
            }
            pageNum = Integer.parseInt(String.valueOf(_pageNum));
            pageSize = Integer.parseInt(String.valueOf(_pageSize));
        } catch (NumberFormatException e) {
            throw new PageException("pagination parameters are not a valid number type!", e);
        }
        Page page = new Page(pageNum, pageSize);
        //count查询
        Object _count = getParamValue(paramsObject, "count", false);
        if (_count != null) {
            page.setCount(Boolean.valueOf(String.valueOf(_count)));
        }
        //排序
        if (hasOrderBy) {
            page.setOrderBy(orderBy.toString());
        }
        //分页合理化
        Object reasonable = getParamValue(paramsObject, "reasonable", false);
        if (reasonable != null) {
            page.setReasonable(Boolean.valueOf(String.valueOf(reasonable)));
        }
        //查询全部
        Object pageSizeZero = getParamValue(paramsObject, "pageSizeZero", false);

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