Solution to NullPointerException in my TestNG test case - eclipse

Question

I am trying to login Facebook by using multiple sets of login cridential from external excel sheet using TestNG but in between the code what i have written throws:
FAILED: f
java.lang.NullPointerException
at DataDriven.loginRetesting.f(loginRetesting.java:31)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:84)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:714)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:901)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1231)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
at org.testng.TestRunner.privateRun(TestRunner.java:767)
at org.testng.TestRunner.run(TestRunner.java:617)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:334)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:329)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:291)
at org.testng.SuiteRunner.run(SuiteRunner.java:240)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1224)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1149)
at org.testng.TestNG.run(TestNG.java:1057)
at org.testng.remote.RemoteTestNG.run(RemoteTestNG.java:111)
at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:204)
at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:175)
Code:
#Test
public void f() throws Exception{
FileInputStream fi=new FileInputStream("E:\\workspace99\\SeleniumAutomations\\testdata\\LoginData.xls");
Workbook w=Workbook.getWorkbook(fi);
Sheet s=w.getSheet(0);
for (int i = 1; i < 8; i++) {
driver.findElement(By.id("email")).sendKeys(s.getCell(0,i).getContents());
driver.findElement(By.id("pass")).sendKeys(s.getCell(1,i).getContents());
driver.findElement(By.id("u_0_1")).click();
Thread.sleep(1000);
if (selenium.isElementPresent("id=userNavigationLabel")) {
//driver.findElement(By.cssSelector("span.gb_V.gbii")).click();
driver.findElement(By.id("userNavigationLabel")).click();
driver.findElement(By.cssSelector("input.uiLinkButtonInput")).click();
Thread.sleep(1000);
}
else{
System.out.println("invalid cridential");
driver.findElement(By.id("email")).clear();
driver.findElement(By.id("pass")).clear();
}
}
}
I am not able to find out where the problem is? so how to solve it.

Answer 1

For one thing, don't use "throws Exception" in the method declaration. Instead, have a try block inside the method with a "not null assertion".
Keep in mind that you never want to throw typical exceptions in a test method because it will drop you out of the test lifecycle too early and skip your #After phases. An exception thrown in a #Before annotated method will probably cause a SkipAssertion.
So, what you want to do instead is fail assertions. So, if you have a exception condition that occurs sometimes, swallow the exception (don't throw it) and use an assertion to handle it.
For example:
try {
} catch ( NullPointerException e ) {
Assert.assertTrue( "There was an error in blah.", false );
}

Answer 2

Null pointer means, exepected value of variable is null.
Please check the file exists at the specified path "E:\workspace99\SeleniumAutomations\testdata\LoginData.xls" and you get the value correctly from the file.

Answer 3

The stack trace says the issue is line 31 in your code but your snippet does not allow us to work out where line 31 is .
you are calling "selenium.isElementPresent". Could "selenium" be nil?