com.google.gwt.gwtpages.client.applicationpresenter.CompositeLayoutApplicationPresenter.java Source code

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Here is the source code for com.google.gwt.gwtpages.client.applicationpresenter.CompositeLayoutApplicationPresenter.java

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package com.google.gwt.gwtpages.client.applicationpresenter;

import java.util.HashMap;

import com.google.gwt.gwtpages.client.PageRequestSession;
import com.google.gwt.gwtpages.client.Pages;
import com.google.gwt.gwtpages.client.page.ApplicationPresenter;
import com.google.gwt.gwtpages.client.page.LoadedPageContainer;
import com.google.gwt.gwtpages.client.page.PageAttributes;
import com.google.gwt.gwtpages.client.page.parameters.PageParameters;
import com.google.gwt.user.client.ui.HasWidgets;
import com.google.gwt.user.client.ui.RootLayoutPanel;
import com.google.gwt.user.client.ui.Widget;

/**
 * Application presenter which can use several different application presenters
 * based on the page or session attributes. Each known presenter is mapped to a
 * String token and all available presenters are passed as entries into the
 * constructor.
 * 
 * All nested application presenters *must* be layout panels as they will be
 * added to the {@link RootLayoutPanel}
 * 
 * To change the presenter per page, you can either
 * <ul>
 * <li>add a {@link TokenProvider} to the {@link PageAttributes} in a page loader
 * using {@link PageAttributes#put(Class, Object)} with the Class parameter
 * being {@link CompositeLayoutApplicationPresenter.TokenProvider}</li>
 * <li>add a {@link TokenProvider} to the {@link PageRequestSession} in a page request
 * event using {@link PageAttributes#put(Class, Object)} with the Class
 * parameter being {@link CompositeLayoutApplicationPresenter.TokenProvider}</li>
 * </ul>
 * 
 * If no Oracle is set, the default application presenter will be used. Note:
 * you also have the ability to directly set a page token (instead of an
 * implementation of the Oracle) by using the TOKEN_APPLICATION_PRESENTER key
 * with the value of the application presenter token String.
 * 
 * @author Joe Hudson
 */
public class CompositeLayoutApplicationPresenter implements ApplicationPresenter {

    public static final Object PRESENTER_TOKEN_KEY = new Object();
    protected HashMap<String, ApplicationPresenter> index = new HashMap<String, ApplicationPresenter>();
    protected ApplicationPresenter currentPresenter;
    private String defaultToken;

    public CompositeLayoutApplicationPresenter(String defaultToken) {
        this.defaultToken = defaultToken;
    }

    /**
     * Register an application presenter with the provided token
     * 
     * @param token
     *            the token
     * @param applicationPresenter
     *            {@link ApplicationPresenter}
     * @return this for chaining
     */
    public CompositeLayoutApplicationPresenter register(String token, ApplicationPresenter applicationPresenter) {
        index.put(token, applicationPresenter);
        return this;
    }

    public void init(Pages settings) {
        for (ApplicationPresenter presenter : index.values())
            presenter.init(settings);
    }

    public void showPage(LoadedPageContainer page, PageParameters parameters, PageRequestSession session) {
        TokenProvider oracle = session.get(TokenProvider.class, true);
        ApplicationPresenter presenter = null;
        String presenterToken = null;
        if (null == oracle) {
            presenterToken = (String) session.get(PRESENTER_TOKEN_KEY, true);
            if (null == presenterToken) {
                presenterToken = defaultToken;
            }
        } else {
            presenterToken = oracle.getPresenterToken(page, parameters, session);
        }
        if (null != presenterToken)
            presenter = index.get(presenterToken);
        if (null == presenter) {
            if (null == presenterToken)
                throw new NullPointerException("Null presenter token for page '" + page.getPageToken() + "'");
            else
                throw new NullPointerException("No presenter located for token '" + presenterToken + "'");
        }
        if (null == currentPresenter || !currentPresenter.equals(presenter)) {
            if (null != currentPresenter)
                RootLayoutPanel.get().clear();
            RootLayoutPanel.get().add((Widget) presenter.asWidget());
            currentPresenter = presenter;
        }
        try {
            presenter.showPage(page, parameters, session);
        } catch (Throwable t) {
            currentPresenter.clearCurrentPage();
            currentPresenter = null;
            clearCurrentPage();
            if (t instanceof RuntimeException)
                throw (RuntimeException) t;
            else
                throw new RuntimeException(t);
        }
    }

    public void clearCurrentPage() {
        RootLayoutPanel.get().clear();
    }

    public Widget asWidget() {
        return null;
    }

    public interface TokenProvider {
        public String getPresenterToken(LoadedPageContainer page, PageParameters parameters,
                PageRequestSession session);
    }
}