java.lang.NullPointerException using page object model in selenium webdirver

Question

I am facing an issue in POM selenium webdriver. This is my code for one class.

package Pages;

import org.openqa.selenium.By;
import org.openqa.selenium.Keys;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;

public class KnowledgeBase {
private static WebDriver driver = null;

public void opening_correlation_explorer()
{
    driver.findElement(By.xpath("//*[@id='warren-nav']/div[2]/ul/li[3]/a")).click();
    driver.findElement(By.xpath("//*[@id='warren-nav']/div[2]/ul/li[3]/ul/li[1]/a")).click();

}

This is my code for another class:

package Pages;

import java.util.concurrent.TimeUnit;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.chrome.ChromeOptions;

public class LoginPage {
    private static WebDriver driver = null;

    public void login()
    {
        System.setProperty("webdriver.chrome.driver", "chromedriver.exe");

        ChromeOptions options = new ChromeOptions();
        options.addArguments("--start-maximized");
        driver = new ChromeDriver(options);
        driver.get("https://www.website.com");

        driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);

        WebElement loginButton = driver.findElement(By.xpath("/html/body/nav/div/a[7]"));
        loginButton.click();

        WebElement Email = driver.findElement(By.xpath("//*[@id='loginform']/div[2]/div[1]/div[1]/input[1]"));
        Email.sendKeys("abc@gmail.com");

        WebElement Password = driver.findElement(By.xpath("//*[@id='loginform']/div[2]/div[1]/div[1]/input[2]"));
        Password.sendKeys("123456");

        WebElement signin_button = driver.findElement(By.xpath("//*[@id='login']"));
        signin_button.click();
    }

}

And I am running a test case where user logs in (from class LoginPage) and then redirects to a new page (from class KnowledgeBase). Test case class is as follows:

package TestCases;

import Pages.KnowledgeBase;
import Pages.LoginPage;

public class correlation_explorer {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        LoginPage user_login = new LoginPage();
        KnowledgeBase correlation = new KnowledgeBase();

        user_login.login();
        correlation.opening_correlation_explorer();

    }

}

In this test case class, I made 2 objects of both classes from which I had to call methods, but when I run this test, only LoginPage class test is run. After that it gives me the following exception.

Exception in thread "main" java.lang.NullPointerException
    at Pages.KnowledgeBase.opening_correlation_explorer(KnowledgeBase.java:20)
    at TestCases.correlation_explorer.main(correlation_explorer.java:18)

Any help will be highly appreciated.

Could you please tell me which line is line 20 on KnowledgeBase.java? There is some variable that is either not being initialized or when you create it with "new Something();" you're getting a null value. For the explanation of NullPointerException, please look here: http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it — George, Sep 01 '15 at 16:33
@GeorgeRappel the first command of opening_correlation_explorer() method is the line no 20 — , Sep 02 '15 at 06:44

score 1 · Answer 1 · answered Sep 02 '15 at 01:49

I didn't notice any initialization for your driver in

public class KnowledgeBase {
private static WebDriver driver = null;

So the NullPointer means your driver in KnowledgeBase is null. I suggest you

Don't initialize WebDriver in a single method. It's unreasonable.
For your process, return a KnowledgeBase type in you LoginPage.login.

Code like following

public static void main(String[] args) {
    Webdriver driver = new ChromDriver();
    //Here I suggest you pass driver to every page Object as their Constructor parameter.
    LoginPage user_login = new LoginPage(driver);

    //in login() method you must return a new KnowledgeBase(driver).
    KnowledgeBase correlation = user_login.login();

    correlation.opening_correlation_explorer();

}

java.lang.NullPointerException using page object model in selenium webdirver

1 Answers1