WebDriverWait.java

/*
 * (C) Copyright 2006-2011 Nuxeo SA (http://nuxeo.com/) and others.
 *
 * Licensed 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.
 *
 * Contributors:
 */

package org.openqa.selenium.support.ui;

import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static java.util.concurrent.TimeUnit.SECONDS;

import org.openqa.selenium.NotFoundException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebDriverException;

import com.google.common.base.Function;

/**
 * An implementation of the Wait interface that makes use of WebDriver. The expected usage is in conjunction with the
 * {@link ExpectedCondition} interface.
 * <p>
 * Because waiting for elements to appear on a page is such a common use-case, this class will silently swallow
 * NotFoundException whilst waiting.
 */
public class WebDriverWait implements Wait<WebDriver> {
    private final Clock clock;

    private final WebDriver driver;

    private final long timeOutInMillis;

    private final long sleepTimeOut;

    private static final long DEFAULT_SLEEP_TIMEOUT = 500;

    /**
     * @param driver The WebDriver instance to pass to the expected conditions
     * @param timeOutInSeconds The timeout in seconds when an expectation is called
     */
    public WebDriverWait(WebDriver driver, long timeOutInSeconds) {
        this(new SystemClock(), driver, timeOutInSeconds, DEFAULT_SLEEP_TIMEOUT);
    }

    /**
     * @param clock The clock to use when measuring the timeout
     * @param driver The WebDriver instance to pass to the expected conditions
     * @param timeOutInSeconds The timeout in seconds when an expectation is
     * @param sleepTimeOut The timeout used whilst sleeping. Defaults to 500ms called
     */
    protected WebDriverWait(Clock clock, WebDriver driver, long timeOutInSeconds, long sleepTimeOut) {
        this.clock = clock;
        this.driver = driver;
        this.timeOutInMillis = SECONDS.toMillis(timeOutInSeconds);
        this.sleepTimeOut = sleepTimeOut;
    }

    @Override
    public <T> T until(Function<WebDriver, T> isTrue) {
        long end = clock.laterBy(timeOutInMillis);
        NotFoundException lastException = null;

        while (clock.isNowBefore(end)) {
            try {
                T value = isTrue.apply(driver);

                if (value != null && Boolean.class.equals(value.getClass())) {
                    if (Boolean.TRUE.equals(value)) {
                        return value;
                    }
                } else if (value != null) {
                    return value;
                }
            } catch (NotFoundException e) {
                // Common case in many conditions, so swallow here, but be ready to
                // rethrow if it the element never appears.
                lastException = e;
            }
            sleep();
        }

        throwTimeoutException(
                String.format("Timed out after %d seconds", SECONDS.convert(timeOutInMillis, MILLISECONDS)),
                lastException);

        throw new IllegalStateException("'throwTimeoutException' should have thrown an exception!");
    }

    /**
     * Override this method to throw an exception that is idiomatic for a given test infrastructure. E.g. JUnit4 should
     * throw an {@link AssertionError}
     */
    protected void throwTimeoutException(String message, Exception lastException) {
        throw new TimeoutException(message, lastException);
    }

    private void sleep() {
        try {
            Thread.sleep(sleepTimeOut);
        } catch (InterruptedException e) {
            // restore interrupted status
            Thread.currentThread().interrupt();
            throw new WebDriverException(e);
        }
    }
}