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;
                }
            }
        }
 }

回答1:

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();
...

回答2:

In this line you need to change "Test Steps" to 'Sheet1' (or change the Excel sheet name to "Test Steps"):

ExcelUtils.setExcelFile(sPath, "Test Steps");