Datatable Parameters are Null , causing NumberFormatException:Null. Any Solution?

Question

I have an action annotation which acts as a server side processing action for Jquery data-table. while getting the params of datatable, I m getting an exception. The class for getting params is:

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;
    }
}

I am getting the exception at param.iDisplayStart = Integer.parseInt(request.getParameter("iDisplayStart"));

Exception is :

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

NumberFormatException occurs when you are trying to convert an illegal value to an int value. You need to check the value before you are trying to read them as int value

//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"))

Note: iDisplayStart parameter should contain a valid value, which can be parsed into an int value. otherwise, you will get NumberFormatException. You can also create an utility method which takes the input value, validate it and do the conversion and return the parsed int value. If any exception occurs in the utility method, it will return a int value denoting a failure or error

Answer 2

There is something called as Exception handling. why have you not done that first. Put your code inside a try - catch block and find th exact source of error.

A number format exception occurs when you try to parse a number there instead of a string. Check the following code first and see what value you are getting if its a number or a string and please do exception handling properly otherwise even if your code works perfectly fine that would be your first review comment. atleast from me :)

 request.getParameter("iDisplayStart")