基于Cucumber搭建BDD框架时遇URL加载异常及空指针问题

问题描述 #

• 触发空指针异常，报错：java.lang.NullPointerException: Cannot invoke "org.openqa.selenium.WebDriver.get(String)" because "this.driver" is null
• Chrome浏览器打开两次，调试发现driver对象为null，URL无法正常打开

问题根源 #

1. driver引用传递错误：步骤类初始化Baseclass和Loginpage时，传入的是未初始化的null值，后续Baseclass中创建的driver实例无法同步到其他类的引用。
2. 重复实例化driver：类之间重复创建Baseclass实例，导致多次初始化ChromeDriver，引发浏览器重复打开。
3. PageFactory初始化时机错误：driver未初始化时就调用PageFactory.initElements，导致页面元素绑定失败，后续操作触发空指针。

修复方案及修改后代码 #

步骤定义文件（steps.java） #

public class steps  {
    
    private WebDriver driver;
    private Baseclass base;
    private Loginpage login;

    public static Logger logfile = LogManager.getLogger(steps.class.getName());
    
    @Given("open chrome browser")
    public void openBrowser() {
        base = new Baseclass();
        driver = base.initiatingDriver(); // 获取初始化后的driver实例
        login = new Loginpage(driver); // 用已初始化的driver创建Loginpage
    }

    @And("Login to application url")
    public void loginAppicaltionUrl()  {
        login.openUrlLogin("https://opensource-demo.orangehrmlive.com/web/index.php/auth/login");
    }

    @And("^enter the valid \"(.*)\"$")
    public void enterValidUsername(String username) {
        login.enteringUsername(username);
    }
    
    @And("^enter valid \"(.*)\"$")
    public void enterValidPassword(String password) {
        login.enteringPassword(password);   
    }
}

Baseclass类 #

public class Baseclass {
    
    private WebDriver driver;
    
    public static Logger logfile = LogManager.getLogger(Baseclass.class.getName());
    public static String parentWindow;

    // 无参构造，避免传入null driver
    public Baseclass() {
    }
    
    public WebDriver initiatingDriver() {
        driver = new ChromeDriver();
        driver.manage().window().maximize();
        PageFactory.initElements(driver, this); // driver初始化完成后再绑定PageFactory
        return driver;
    }

    public void openUrl() throws Throwable{
        driver.get("https://opensource-demo.orangehrmlive.com/web/index.php/auth/login");
        threadsleep(5000);
        logfile.info("Url opened successfully");
    }
    
    public void sendKeysUsingCss(WebElement element,String username) {
        driver.manage().timeouts().implicitlyWait(Duration.ofSeconds(40));
        element.sendKeys(username);
    }

    public void threadsleep(long ms) throws InterruptedException {
        Thread.sleep(ms);
    }
}

Loginpage类 #

public class Loginpage  {                                                     
                                                                              
    private WebDriver driver;                                           
    private Baseclass base;                                                                           
                                                                              
    public Loginpage(WebDriver driver) {                                      
        this.driver = driver;                                                 
        this.base = new Baseclass();
        PageFactory.initElements(driver, this); // 确保driver已初始化再绑定元素
    }                                                                          
                                                                              
    @FindBy(how=How.CSS, using="input[name^='username']")                     
    private WebElement name;                                                  
                                                                              
    @FindBy(how=How.CSS,using="input[name^='password']")                      
    private WebElement passwrd;                                                                                                                      
                                                                              
    public void openUrlLogin(String url) {                                    
        try {                                                                 
            driver.get(url);                                                  
            driver.manage().window().maximize();                              
            base.threadsleep(5000);                                           
            base.logfile.info("Url opened successfully");                     
        } catch (Throwable e) {                                               
            e.printStackTrace();                                              
            System.out.println(e);                                            
            Assert.fail("Url not opened");                                    
        }                                                                      
    }                                                                          
                                                                              
    public void enteringUsername(String username) {                           
        name.sendKeys(username);                                              
    }

    public void enteringPassword(String password) {
        passwrd.sendKeys(password);
    }
}

关键修复说明 #

• 统一driver生命周期：由步骤类集中管理driver的创建，确保所有类共享同一个driver实例，避免null引用。
• 延迟PageFactory初始化：在driver实例化完成后再调用PageFactory.initElements，保证页面元素正确绑定。
• 避免重复创建实例：移除类内部自动创建Baseclass的逻辑，防止多次初始化ChromeDriver导致浏览器重复打开。

内容的提问来源于stack exchange，提问作者guru