使用 Java 反射获取方法 Class

Question

大家好，我是所有这些测试自动化的新手，正在尝试按照教程学习，但我一直在尝试运行这段代码。

我遇到异常

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

不知道有什么问题，因为我正在学习教程，所以我认为一切正常。

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 1

问题是您永远不会向您的 method[] 数组中填充任何内容。在构造函数中，数组将被填充，但它永远不会被调用。因此，尝试在 main 方法中调用构造函数。

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

Answer 2

在这一行中，您需要将 "Test Steps" 更改为 'Sheet1'（或将 Excel sheet 名称更改为 "Test Steps"）：

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

使用 Java 反射获取方法 Class

Get methods using Java Reflection Class

java

reflection

selenium