java PageHelper 会自动对orderBy关键字进行处理

1.查询对象

public class child{
    public String name;
    public String orderBy;
}

2.设置值

child ch = new Child();
ch.setOrderBy(" test");
ch.setName("123");

3.实际生成的sql

select  * from child where name = "123" test

4.实现是用mybatils的拦截器，可看 PageHelper 的 SqlUtil类，实现代码如下(第20行代码处理orderBy关键字)

public static <T> Page<T> getPageFromObject(Object params) {
    int pageNum;
    int pageSize;
    MetaObject paramsObject = null;
    if (params == null) {
        throw new NullPointerException("无法获取分页查询参数!");
    }
    if (hasRequest && requestClass.isAssignableFrom(params.getClass())) {
        try {
            paramsObject = SystemMetaObject.forObject(getParameterMap.invoke(params, new Object[]{}));
        } catch (Exception e) {
            //忽略
        }
    } else {
        paramsObject = SystemMetaObject.forObject(params);
    }
    if (paramsObject == null) {
        throw new NullPointerException("分页查询参数处理失败!");
    }
    Object orderBy = getParamValue(paramsObject, "orderBy", false);
    boolean hasOrderBy = false;
    if (orderBy != null && orderBy.toString().length() > 0) {
        hasOrderBy = true;
    }
    try {
        Object _pageNum = getParamValue(paramsObject, "pageNum", hasOrderBy ? false : true);
        Object _pageSize = getParamValue(paramsObject, "pageSize", hasOrderBy ? false : true);
        if (_pageNum == null || _pageSize == null) {
            Page page = new Page();
            page.setOrderBy(orderBy.toString());
            page.setOrderByOnly(true);
            return page;
        }
        pageNum = Integer.parseInt(String.valueOf(_pageNum));
        pageSize = Integer.parseInt(String.valueOf(_pageSize));
    } catch (NumberFormatException e) {
        throw new IllegalArgumentException("分页参数不是合法的数字类型!");
    }
    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);
    if (pageSizeZero != null) {
        page.setPageSizeZero(Boolean.valueOf(String.valueOf(pageSizeZero)));
    }
    return page;
}