先看下入口函数
PageFactory.initElements(new AppiumFieldDecorator(mDriver, 5, TimeUnit.SECONDS),
mQQPageObject);
绑定注入容器（QQPageObject）
public static void initElements(FieldDecorator decorator, Object page) {
//获取所有父类
Class proxyIn = page.getClass();
while (proxyIn != Object.class) {
proxyFields(decorator, page, proxyIn);
proxyIn = proxyIn.getSuperclass();
}
}
proxyFields()创建所有字段的代理类
private static void proxyFields(FieldDecorator decorator, Object page, Class proxyIn) {
//获取所有声明的字段
Field[] fields = proxyIn.getDeclaredFields();
for (Field field : fields) {
//获取代理对象
Object value = decorator.decorate(page.getClass().getClassLoader(), field);
if (value != null) {
try {
field.setAccessible(true);
//重新设置字段
field.set(page, value);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
}
}
}
先获取所有字段，再获取字段的代理对象，并重新赋值给注入容器
public Object decorate(ClassLoader ignored, Field field) {
//使用默认的字段包装器
Object result = defaultElementFieldDecoracor.decorate(ignored, field);
if (result != null) {
return result;
}
//Widget包装器
return decorateWidget(field);
}
先通过默认包装器构造代理对象，如果没有再通过widget包装器构造
public Object decorate(ClassLoader loader, Field field) {
//判断类型
if (!(WebElement.class.isAssignableFrom(field.getType())
|| isDecoratableList(field))) {
return null;
}
//创建一个元素定位器
ElementLocator locator = factory.createLocator(field);
if (locator == null) {
return null;
}
//创建一个元素定位器的代理对象
if (WebElement.class.isAssignableFrom(field.getType())) {
return proxyForLocator(loader, locator);
} else if (List.class.isAssignableFrom(field.getType())) {
return proxyForListLocator(loader, locator);
} else {
return null;
}
}
元素定位器的创建时一个多工厂模式创建的 factory.createLocator(field);
来看看factory的来源.我们在第一步PageFactory.initElements()传入了一个AppiumFieldDecorator字段包装器，
public AppiumFieldDecorator(SearchContext context, TimeOutDuration timeOutDuration) {
...省略无关代码....
defaultElementFieldDecoracor = new DefaultFieldDecorator(
//创建了一个具体的元素定位器的工厂
new AppiumElementLocatorFactory(context, timeOutDuration, originalDriver,
new DefaultElementByBuilder(platform, automation))) {
........省略无关代码......
widgetLocatorFactory =
new AppiumElementLocatorFactory(context, timeOutDuration, originalDriver,
new WidgetByBuilder(platform, automation));
}
回到factory创建定位器的 ElementLocator locator = factory.createLocator(field);
@Override public CacheableLocator createLocator(AnnotatedElement annotatedElement) {
......
//构建一个查找元素的方法
By by = builder.buildBy();
if (by != null) {
//创建一个元素定位器实现对象
return new AppiumElementLocator(searchContext, by, builder.isLookupCached(),
customDuration, timeOutDuration, originalWebDriver);
}
return null;
}
builder.buildBy()是如何构建一个查找元素具体方法的？其实builder是一个抽象类，我们是在AppiumFieldDecorator的构造方法中框架自动给创建一个DefaultElementByBuilder对象。buildBy()实现如下
@Override public By buildBy() {
//断言用户使用的注解是否正确，例如AndroidFindBy 与AndroidFindBys不能同时在一个字段上使用
assertValidAnnotations();
//解析用户的注解并创建一个By
//公用注解
By defaultBy = buildDefaultBy();
//不同系统版本的注解解析
By mobileNativeBy = buildMobileNativeBy();
String idOrName = ((Field) annotatedElementContainer.getAnnotated()).getName();
if (defaultBy == null && mobileNativeBy == null) {
defaultBy =
new ByIdOrName(((Field) annotatedElementContainer.getAnnotated()).getName());
mobileNativeBy = new By.ById(idOrName);
return returnMappedBy(defaultBy, mobileNativeBy);
}
......
}
有了元素定位方式By后就创建AppiumElementLocator给DefaultFieldDecorator包装器使用了，回到DefaultFieldDecorator.decorate()方法
public Object decorate(ClassLoader loader, Field field) {
if (!(WebElement.class.isAssignableFrom(field.getType())
|| isDecoratableList(field))) {
return null;
}
//创建好定位器了
ElementLocator locator = factory.createLocator(field);
if (locator == null) {
return null;
}
//创建定位代理器
if (WebElement.class.isAssignableFrom(field.getType())) {
return proxyForLocator(loader, locator);
} else if (List.class.isAssignableFrom(field.getType())) {
return proxyForListLocator(loader, locator);
} else {
return null;
}
}
创建一个定位代理器
protected WebElement proxyForLocator(ClassLoader loader, ElementLocator locator) {
InvocationHandler handler = new LocatingElementHandler(locator);
WebElement proxy;
proxy = (WebElement) Proxy.newProxyInstance(
loader, new Class[]{WebElement.class, WrapsElement.class, Locatable.class}, handler);
return proxy;
}
这是最核心的动态代理。看看处理器LocatingElementHandler
public class LocatingElementHandler implements InvocationHandler {
private final ElementLocator locator;
public LocatingElementHandler(ElementLocator locator) {
this.locator = locator;
}
public Object invoke(Object object, Method method, Object[] objects) throws Throwable {
WebElement element;
try {
//通过定位器来查找元素
element = locator.findElement();
} catch (NoSuchElementException e) {
if ("toString".equals(method.getName())) {
return "Proxy element for: " + locator.toString();
}
throw e;
}
//如果调用的是getWrappedElement方法则直接返回不代理调用方法
if ("getWrappedElement".equals(method.getName())) {
return element;
}
try {
//再调用元素的真正方法
return method.invoke(element, objects);
} catch (InvocationTargetException e) {
// Unwrap the underlying exception
throw e.getCause();
}
}
}
这样也就是我们在调用WebElement.click()方法的时候回进入到代理器的invoke()方法，先查找到元素，再去真正的执行click()方法。而这个代理器，最后会设置给pageobject的字段。
public static void initElements(FieldDecorator decorator, Object page) {
Class proxyIn = page.getClass();
while (proxyIn != Object.class) {
proxyFields(decorator, page, proxyIn);
proxyIn = proxyIn.getSuperclass();
}
}
private static void proxyFields(FieldDecorator decorator, Object page, Class proxyIn) {
Field[] fields = proxyIn.getDeclaredFields();
for (Field field : fields) {
Object value = decorator.decorate(page.getClass().getClassLoader(), field);
if (value != null) {
try {
field.setAccessible(true);
//把动态代理对象重新设置回来
field.set(page, value);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
}
}
}
}
所以当我们在调用字段的方法时，实际是调用一个代理对象。
再看看代理器是怎么通过被代理对象locator来找元素的。locator.findElement()
从上面的分析locator是一个AppiumElementLocator
public WebElement findElement() {
//如果有缓存则直接用
if (cachedElement != null && shouldCache) {
return cachedElement;
}
try {
WebElement result = waitFor(() ->
//查找元素
searchContext.findElement(by));
if (shouldCache) {
cachedElement = result;
}
return result;
} catch (TimeoutException | StaleElementReferenceException e) {
throw new NoSuchElementException(exceptionMessageIfElementNotFound, e);
}
}
searchContext.findElement(by);其实是通过RemoteWebDriver的findElement(By by) 方法查找,又转移到By方法查找
public WebElement findElement(SearchContext context) {
List allElements = findElements(context);
if (allElements == null || allElements.isEmpty())
throw new NoSuchElementException("Cannot locate an element using "
+ toString());
return allElements.get(0);
}
假如这个By是ById那么转移到ById的findElement()方法中了
@Override
public WebElement findElement(SearchContext context) {
if (context instanceof FindsById)
return ((FindsById) context).findElementById(id);
return ((FindsByXPath) context).findElementByXPath(".//*[@id = '" + id
+ "']");
}
最后还是转移到RemoteWebDriver中
protected WebElement findElement(String by, String using) {
if (using == null) {
throw new IllegalArgumentException("Cannot find elements when the selector is null.");
}
//这里是真正执行网络通信查找控件的方法
Response response = execute(DriverCommand.FIND_ELEMENT,
ImmutableMap.of("using", by, "value", using));
//接收网络返回的WebElement
Object value = response.getValue();
WebElement element;
try {
element = (WebElement) value;
} catch (ClassCastException ex) {
throw new WebDriverException("Returned value cannot be converted to WebElement: " + value, ex);
}
//标识查找的方式
setFoundBy(this, element, by, using);
return element;
}
execute方法就是拼json参数，形成httpRequest请求，通过HttpClient发送请求，
解析返回的HttpResponse，用selenium的Response接收，最终封装成我们需要的WebElement.
总结下：pageobject模式其实就是依赖注入+动态代理实现的，每一个pageobject都可以看成一个注入容器，而我们查找控件的操作看成一个切面，通过动态代理实现AOP切面编程。
QQ图片20180129192831.jpg