org.openqa.selenium.support.ui.LoadableComponent.java Source code

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Here is the source code for org.openqa.selenium.support.ui.LoadableComponent.java

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//   http://www.apache.org/licenses/LICENSE-2.0
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package org.openqa.selenium.support.ui;

/**
 * Represents any abstraction of something that can be loaded. This may be an entire web page, or
 * simply a component within that page (such as a login box or menu) or even a service. The expected
 * usage is:
 *
 * <pre class="code">
 * new HypotheticalComponent().get();
 * </pre>
 *
 * <p>
 * After the {@link LoadableComponent#get()} method is called, the component will be loaded and
 * ready for use. This is verified using Assert.assertTrue so expect to catch an Error rather than
 * an Exception when errors occur. *
 *
 * @param <T> The type to be returned (normally the subclass' type)
 */
public abstract class LoadableComponent<T extends LoadableComponent<T>> {
    /**
     * Ensure that the component is currently loaded.
     *
     * @return The component.
     * @throws Error when the component cannot be loaded.
     */
    @SuppressWarnings("unchecked")
    public T get() {
        try {
            isLoaded();
            return (T) this;
        } catch (Error e) {
            load();
        }

        isLoaded();

        return (T) this;
    }

    /**
     * When this method returns, the component modeled by the subclass should be fully loaded. This
     * subclass is expected to navigate to an appropriate page should this be necessary.
     */
    protected abstract void load();

    /**
     * Determine whether or not the component is loaded. When the component is loaded, this method
     * will return, but when it is not loaded, an Error should be thrown. This also allows for complex
     * checking and error reporting when loading a page, which in turn supports better error reporting
     * when a page fails to load.
     *
     * <p>
     * This behaviour makes it readily visible when a page has not been loaded successfully, and
     * because an error and not an exception is thrown tests should fail as expected. By using Error,
     * we also allow the use of junit's "Assert.assert*" methods
     *
     * @throws Error when the page is not loaded.
     */
    protected abstract void isLoaded() throws Error;
}