ParameterUtil

获取作用域中的值，放置空指针异常

import javax.servlet.http.HttpServletRequest;

public class ParameterUtil {
    //从请求中获取String类型的参数
    public static String getString(HttpServletRequest request, String name) {
        String param = request.getParameter(name);
        if (param == null || param.trim().length() == 0) {
            return null;
        }
        return param.trim();
    }

    public static Integer getInteger(HttpServletRequest request, String name) {
        String param = getString(request, name);
        if (param == null) {//没传参数
            return null;
        }
        try {
            return Integer.parseInt(param);
        } catch (NumberFormatException e) {//如果参数不是数字格式
            e.printStackTrace();
        }
        return null;
    }

    public static Double getDouble(HttpServletRequest request, String name) {
        String param = getString(request, name);
        if (param == null) {//没传参数
            return null;
        }
        try {
            return Double.parseDouble(param);
        } catch (NumberFormatException e) {//如果参数不是数字格式
            e.printStackTrace();
        }
        return null;
    }
}