Teriyaki Teriyaki - 4 months ago 22
Java Question

Get methods using Java Reflection Class

Hi guys im new to all this test automation stuff and trying to learn following a tutorial but im stuck trying to run this code.

I get an exception

Exception in thread "main" java.lang.NullPointerException
at executionEngine.DriverScript.execute_Actions(DriverScript.java:45)
at executionEngine.DriverScript.main(DriverScript.java:39)


dunno whats wrong as im following a tutorial so i assume everything should be working.

package executionEngine;

import java.lang.reflect.Method;
import config.ActionKeywords;
import utility.ExcelUtils;

public class DriverScript {
//This is a class object, declared as 'public static'
//So that it can be used outside the scope of main[] method
public static ActionKeywords actionKeywords;
public static String sActionKeyword;
//This is reflection class object, declared as 'public static'
//So that it can be used outside the scope of main[] method
public static Method method[];

//Here we are instantiating a new object of class 'ActionKeywords'
public DriverScript() throws NoSuchMethodException, SecurityException{
actionKeywords = new ActionKeywords();
//This will load all the methods of the class 'ActionKeywords' in it.
//It will be like array of method, use the break point here and do the watch
method = actionKeywords.getClass().getMethods();
}

public static void main(String[] args) throws Exception {

//Declaring the path of the Excel file with the name of the Excel file
String sPath = "D://Tools QA Projects//trunk//Hybrid Keyword Driven//src//dataEngine//DataEngine.xlsx";

//Here we are passing the Excel path and SheetName to connect with the Excel file
//This method was created in the last chapter of 'Set up Data Engine'
ExcelUtils.setExcelFile(sPath, "Test Steps");

//Hard coded values are used for Excel row & columns for now
//In later chapters we will use these hard coded value much efficiently
//This is the loop for reading the values of the column 3 (Action Keyword) row by row
//It means this loop will execute all the steps mentioned for the test case in Test Steps sheet
for (int iRow = 1;iRow <= 9;iRow++){
//This to get the value of column Action Keyword from the excel
sActionKeyword = ExcelUtils.getCellData(iRow, 3);
//A new separate method is created with the name 'execute_Actions'
//You will find this method below of the this test
//So this statement is doing nothing but calling that piece of code to execute
execute_Actions();
}
}

//This method contains the code to perform some action
//As it is completely different set of logic, which revolves around the action only,
//It makes sense to keep it separate from the main driver script
//This is to execute test step (Action)
private static void execute_Actions() throws Exception {
//This is a loop which will run for the number of actions in the Action Keyword class
//method variable contain all the method and method.length returns the total number of methods
for(int i = 0;i < method.length;i++){
//This is now comparing the method name with the ActionKeyword value got from excel
if(method[i].getName().equals(sActionKeyword)){
//In case of match found, it will execute the matched method
method[i].invoke(actionKeywords);
//Once any method is executed, this break statement will take the flow outside of for loop
break;
}
}
}
}

Answer

The problem is that you do never fill something into your method[] array. In the constructor, the array would be filled, but it is never called. Therefore, try calling the constructor inside the main method.

public static void main(String[] args) throws Exception {
    new DriverScript();
...