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EventFiringDecorator.java
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EventFiringDecorator.java
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// Licensed to the Software Freedom Conservancy (SFC) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The SFC licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
package org.openqa.selenium.support.events;
import com.google.common.primitives.Primitives;
import org.openqa.selenium.Alert;
import org.openqa.selenium.Beta;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.support.decorators.Decorated;
import org.openqa.selenium.support.decorators.WebDriverDecorator;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;
/**
* This decorator creates a wrapper around an arbitrary {@link WebDriver} instance that notifies
* registered listeners about events happening in this WebDriver and derived objects, such as
* {@link WebElement}s and {@link Alert}.
* <p>
* Listeners should implement {@link WebDriverListener}. It supports three types of events:
* <ul>
* <li>"before"-event: a method is about to be called;</li>
* <li>"after"-event: a method was called successfully and returned some result;</li>
* <li>"error"-event: a method was called and thrown an exception.</li>
* </ul>
* To use this decorator you have to prepare a listener, create a decorator using this listener,
* decorate the original WebDriver instance with this decorator and use the new WebDriver
* instance created by the decorator instead of the original one:
* <pre><code>
* WebDriver original = new FirefoxDriver();
* WebDriverListener listener = new MyListener();
* WebDriver decorated = new EventFiringDecorator(listener).decorate(original);
* decorated.get("http://example.com/");
* WebElement header = decorated.findElement(By.tagName("h1"));
* String headerText = header.getText();
* </code></pre>
* <p>
* The instance of WebDriver created by the decorator implements all the same interfaces as
* the original driver.
* <p>
* A listener can subscribe to "specific" or "generic" events (or both). A "specific" event
* correspond to a single specific method, a "generic" event correspond to any method called in
* a class or in any class.
* <p>
* To subscribe to a "specific" event a listener should implement a method with a name derived from
* the target method to be watched. The listener methods for "before"-events receive the parameters
* passed to the decorated method. The listener methods for "after"-events receive the parameters
* passed to the decorated method as well as the result returned by this method.
* <pre><code>
* WebDriverListener listener = new WebDriverListener() {
* @Override
* public void beforeGet(WebDriver driver, String url) {
* logger.log("About to open a page %s", url);
* }
* @Override
* public void afterGetText(WebElement element, String result) {
* logger.log("Element %s has text '%s'", element, result);
* }
* };
* </code></pre>
* <p>
* To subscribe to a "generic" event a listener should implement a method with a name derived from
* the class to be watched:
* <pre><code>
* WebDriverListener listener = new WebDriverListener() {
* @Override
* public void beforeAnyWebElementCall(WebElement element, Method method, Object[] args) {
* logger.log("About to call a method %s in element %s with parameters %s",
* method, element, args);
* }
* @Override
* public void afterAnyWebElementCall(WebElement element, Method method, Object[] args, Object result) {
* logger.log("Method %s called in element %s with parameters %s returned %s",
* method, element, args, result);
* }
* };
* </code></pre>
* <p>
* There are also listener methods for "super-generic" events:
* <pre><code>
* WebDriverListener listener = new WebDriverListener() {
* @Override
* public void beforeAnyCall(Object target, Method method, Object[] args) {
* logger.log("About to call a method %s in %s with parameters %s",
* method, target, args);
* }
* @Override
* public void afterAnyCall(Object target, Method method, Object[] args, Object result) {
* logger.log("Method %s called in %s with parameters %s returned %s",
* method, target, args, result);
* }
* };
* </code></pre>
* <p>
* A listener can subscribe to both "specific" and "generic" events at the same time. In this case
* "before"-events are fired in order from the most generic to the most specific,
* and "after"-events are fired in the opposite order, for example:
* <pre><code>
* beforeAnyCall
* beforeAnyWebDriverCall
* beforeGet
* // the actual call to the decorated method here
* afterGet
* afterAnyWebDriverCall
* afterAnyCall
* </code></pre>
* <p>
* One of the most obvious use of this decorator is logging. But it can be used to modify behavior
* of the original driver to some extent because listener methods are executed in the same thread
* as the original driver methods.
* <p>
* For example, a listener can be used to slow down execution for demonstration purposes, just
* make a listener that adds a pause before some operations:
* <pre><code>
* WebDriverListener listener = new WebDriverListener() {
* @Override
* public void beforeClick(WebElement element) {
* try {
* Thread.sleep(3000);
* } catch (InterruptedException e) {
* Thread.currentThread().interrupt();
* }
* }
* };
* </code></pre>
* <p>
* Just be careful to not block the current thread in a listener method!
* <p>
* Listeners can't affect driver behavior too much. They can't throw any exceptions
* (they can, but the decorator suppresses these exceptions), can't prevent execution of
* the decorated methods, can't modify parameters and results of the methods.
* <p>
* Decorators that modify the behaviour of the underlying drivers should be implemented by
* extending {@link WebDriverDecorator}, not by creating sophisticated listeners.
*/
@Beta
public class EventFiringDecorator<T extends WebDriver> extends WebDriverDecorator<T> {
private static final Logger logger = Logger.getLogger(EventFiringDecorator.class.getName());
private final List<WebDriverListener> listeners;
public EventFiringDecorator(WebDriverListener... listeners) {
this.listeners = Arrays.asList(listeners);
}
@Override
public void beforeCall(Decorated<?> target, Method method, Object[] args) {
listeners.forEach(listener -> fireBeforeEvents(listener, target, method, args));
super.beforeCall(target, method, args);
}
@Override
public void afterCall(Decorated<?> target, Method method, Object[] args, Object result) {
super.afterCall(target, method, args, result);
listeners.forEach(listener -> fireAfterEvents(listener, target, method, result, args));
}
@Override
public Object onError(Decorated<?> target, Method method, Object[] args,
InvocationTargetException e) throws Throwable {
listeners.forEach(listener -> {
try {
listener.onError(target.getOriginal(), method, args, e);
} catch (Throwable t) {
logger.log(Level.WARNING, t.getMessage(), t);
}
});
return super.onError(target, method, args, e);
}
private void fireBeforeEvents(WebDriverListener listener, Decorated<?> target, Method method, Object[] args) {
try {
listener.beforeAnyCall(target.getOriginal(), method, args);
} catch (Throwable t) {
logger.log(Level.WARNING, t.getMessage(), t);
}
try {
if (target.getOriginal() instanceof WebDriver) {
listener.beforeAnyWebDriverCall((WebDriver) target.getOriginal(), method, args);
} else if (target.getOriginal() instanceof WebElement) {
listener.beforeAnyWebElementCall((WebElement) target.getOriginal(), method, args);
} else if (target.getOriginal() instanceof WebDriver.Navigation) {
listener.beforeAnyNavigationCall((WebDriver.Navigation) target.getOriginal(), method, args);
} else if (target.getOriginal() instanceof Alert) {
listener.beforeAnyAlertCall((Alert) target.getOriginal(), method, args);
} else if (target.getOriginal() instanceof WebDriver.Options) {
listener.beforeAnyOptionsCall((WebDriver.Options) target.getOriginal(), method, args);
} else if (target.getOriginal() instanceof WebDriver.Timeouts) {
listener.beforeAnyTimeoutsCall((WebDriver.Timeouts) target.getOriginal(), method, args);
} else if (target.getOriginal() instanceof WebDriver.Window) {
listener.beforeAnyWindowCall((WebDriver.Window) target.getOriginal(), method, args);
}
} catch (Throwable t) {
logger.log(Level.WARNING, t.getMessage(), t);
}
String methodName = createEventMethodName("before", method.getName());
int argsLength = args != null ? args.length : 0;
Object[] args2 = new Object[argsLength + 1];
args2[0] = target.getOriginal();
for (int i = 0; i < argsLength; i++) {
args2[i + 1] = args[i];
}
Method m = findMatchingMethod(listener, methodName, args2);
if (m != null) {
callListenerMethod(m, listener, args2);
}
}
private void fireAfterEvents(WebDriverListener listener, Decorated<?> target, Method method, Object res, Object[] args) {
String methodName = createEventMethodName("after", method.getName());
boolean isVoid = method.getReturnType() == Void.TYPE
|| method.getReturnType() == WebDriver.Timeouts.class;
int argsLength = args != null ? args.length : 0;
Object[] args2 = new Object[argsLength + 1 + (isVoid ? 0 : 1)];
args2[0] = target.getOriginal();
for (int i = 0; i < argsLength; i++) {
args2[i + 1] = args[i];
}
if (! isVoid) {
args2[args2.length - 1] = res;
}
Method m = findMatchingMethod(listener, methodName, args2);
if (m != null) {
callListenerMethod(m, listener, args2);
}
try {
if (target.getOriginal() instanceof WebDriver) {
listener.afterAnyWebDriverCall((WebDriver) target.getOriginal(), method, args, res);
} else if (target.getOriginal() instanceof WebElement) {
listener.afterAnyWebElementCall((WebElement) target.getOriginal(), method, args, res);
} else if (target.getOriginal() instanceof WebDriver.Navigation) {
listener.afterAnyNavigationCall((WebDriver.Navigation) target.getOriginal(), method, args,
res);
} else if (target.getOriginal() instanceof Alert) {
listener.afterAnyAlertCall((Alert) target.getOriginal(), method, args, res);
} else if (target.getOriginal() instanceof WebDriver.Options) {
listener.afterAnyOptionsCall((WebDriver.Options) target.getOriginal(), method, args, res);
} else if (target.getOriginal() instanceof WebDriver.Timeouts) {
listener.afterAnyTimeoutsCall((WebDriver.Timeouts) target.getOriginal(), method, args, res);
} else if (target.getOriginal() instanceof WebDriver.Window) {
listener.afterAnyWindowCall((WebDriver.Window) target.getOriginal(), method, args, res);
}
} catch (Throwable t) {
logger.log(Level.WARNING, t.getMessage(), t);
}
try {
listener.afterAnyCall(target.getOriginal(), method, args, res);
} catch (Throwable t) {
logger.log(Level.WARNING, t.getMessage(), t);
}
}
private String createEventMethodName(String prefix, String originalMethodName) {
return prefix + originalMethodName.substring(0, 1).toUpperCase() + originalMethodName.substring(1);
}
private Method findMatchingMethod(WebDriverListener listener, String methodName, Object[] args) {
for (Method m : listener.getClass().getMethods()) {
if (m.getName().equals(methodName) && parametersMatch(m, args)) {
return m;
}
}
return null;
}
private boolean parametersMatch(Method m, Object[] args) {
Class<?>[] params = m.getParameterTypes();
if (params.length != args.length) {
return false;
}
for (int i = 0; i < params.length; i++) {
if (args[i] != null && ! Primitives.wrap(params[i]).isAssignableFrom(args[i].getClass())) {
return false;
}
}
return true;
}
private void callListenerMethod(Method m, WebDriverListener listener, Object[] args) {
try {
m.invoke(listener, args);
} catch (Throwable t) {
logger.log(Level.WARNING, t.getMessage(), t);
}
}
}