java - 数据表参数为 Null ，导致 NumberFormatException :Null. 有解决方案吗？

Question

我有一个操作注释，它充当 Jquery 数据表的服务器端处理操作。在获取数据表的参数时，我遇到了异常。获取参数的类是:

package com.healthslate.reports.view.actions;

import javax.servlet.http.HttpServletRequest;

public class DataTablesParamUtility {

public static JQueryDataTableParamModel getParam(HttpServletRequest request)
{
    if(request.getParameter("sEcho")!=null || request.getParameter("sEcho")!= "")
    {
        JQueryDataTableParamModel param = new JQueryDataTableParamModel();
        param.sEcho = request.getParameter("sEcho");
        param.sSearch = request.getParameter("sSearch");
        param.sColumns = request.getParameter("sColumns");
        param.iDisplayStart = Integer.parseInt(request.getParameter("iDisplayStart"));
        param.iDisplayLength= Integer.parseInt(request.getParameter("iDisplayLength") );
        param.iColumns = Integer.parseInt( request.getParameter("iColumns") );
        param.iSortingCols = Integer.parseInt( request.getParameter("iSortingCols") );
        param.iSortColumnIndex = Integer.parseInt(request.getParameter("iSortCol_0"));
        param.sSortDirection = request.getParameter("sSortDir_0");
        return param;
    }else
        return null;
    }
}

我在以下位置遇到异常 param.iDisplayStart = Integer.parseInt(request.getParameter("iDisplayStart"));

异常(exception)是:

HTTP Status 500 - null

type Exception report

message null

description The server encountered an internal error that prevented it from fulfilling this request.

exception

java.lang.NumberFormatException: null
    java.lang.Integer.parseInt(Unknown Source)
    java.lang.Integer.parseInt(Unknown Source)
    com.healthslate.reports.view.actions.DataTablesParamUtility.getParam(DataTablesParamUtility.java:16)
    com.healthslate.reports.view.actions.pageVisitReportModifiedAction.serverSideSearch(pageVisitReportModifiedAction.java:78)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    java.lang.reflect.Method.invoke(Unknown Source)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:450)
    com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:289)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:252)
    org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:167)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
    org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:239)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:239)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:191)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:73)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:91)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:252)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
    com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:161)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:193)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:189)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    com.googlecode.s2hibernate.struts2.plugin.interceptors.SessionTransactionInjectorInterceptor.intercept(SessionTransactionInjectorInterceptor.java:181)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    net.bull.javamelody.StrutsInterceptor.intercept(StrutsInterceptor.java:68)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:246)
    org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:563)
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:99)
    org.displaytag.filter.ResponseOverrideFilter.doFilter(ResponseOverrideFilter.java:125)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.35 logs.

Answer 1

当您尝试将非法值转换为 int 值时，会发生

NumberFormatException。在尝试将它们读取为 int 值

之前，您需要检查该值

//Check the `iDisplayStart` parameter is not null 
if(request.getParameter("iDisplayStart")!=null)
//do the conversion if it is not null
param.iDisplayStart = Integer.parseInt(request.getParameter("iDisplayStart"))

注意:iDisplayStart 参数应包含有效值，该值可以解析为 int 值。否则，您将得到 NumberFormatException。您还可以创建一个实用程序方法，该方法获取输入值、验证它并进行转换并返回解析的 int 值。如果实用程序方法中发生任何异常，它将返回一个 int 值，表示失败或错误