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/*
 * Copyright 2011 Google Inc.
 *
 * 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.
 */

package com.google.gwt.storage.client;

import com.google.gwt.core.client.GWT;
import com.google.gwt.dom.client.PartialSupport;
import com.google.gwt.event.shared.HandlerRegistration;

/**
 * Implements the HTML5 Storage interface.
 *
 * 

* You can obtain a Storage by either invoking * {@link #getLocalStorageIfSupported()} or * {@link #getSessionStorageIfSupported()}. *

* *

* Experimental API: This API is still under development * and is subject to change. *

* *

* If Web Storage is NOT supported in the browser, these methods return * null. *

* *

* Note: Storage events into other windows are not supported. *

* * *

* This may not be supported on all browsers. *

* * @see W3C Web Storage - * Storage * @see Safari * Client-Side Storage and Offline Applications Programming Guide - * Key-Value Storage * @see Quirksmode.org - * HTML5 Compatibility - Storage * @see Wiki - Quickstart Guide */ // TODO(pdr): Add support for Object values, instead of just Strings. The // Storage API spec specifies this, but browser support poor at the moment. // TODO(pdr): Add support for native events once browsers correctly implement // storage events. @PartialSupport public final class Storage { // Still a separate class to prevent native calls on class load as it my break existing code. private static class StorageSupportDetector { static final boolean localStorageSupported = checkStorageSupport(StorageImpl.LOCAL_STORAGE); static final boolean sessionStorageSupported = checkStorageSupport(StorageImpl.SESSION_STORAGE); // Adapted from modernizr private static native boolean checkStorageSupport(String storage) /*-{ var c = '_gwt_dummy_'; try { $wnd[storage].setItem(c, c); $wnd[storage].removeItem(c); return true; } catch (e) { return false; } }-*/; } static final StorageImpl impl = GWT.create(StorageImpl.class); private static Storage localStorage; private static Storage sessionStorage; /** * Registers an event handler for StorageEvents. * * @see W3C Web * Storage - the storage event * @param handler * @return {@link HandlerRegistration} used to remove this handler */ public static HandlerRegistration addStorageEventHandler( StorageEvent.Handler handler) { return impl.addStorageEventHandler(handler); } /** * Returns a Local Storage. * *

* The returned storage is associated with the origin of the * Document. *

* * @see W3C Web * Storage - localStorage * @return the localStorage instance, or null if Web Storage is * NOT supported. */ public static Storage getLocalStorageIfSupported() { if (localStorage == null && isLocalStorageSupported()) { localStorage = new Storage(StorageImpl.LOCAL_STORAGE); } return localStorage; } /** * Returns a Session Storage. * *

* The returned storage is associated with the current top-level browsing context. *

* * @see W3C Web * Storage - sessionStorage * @return the sessionStorage instance, or null if Web Storage is * NOT supported. */ public static Storage getSessionStorageIfSupported() { if (sessionStorage == null && isSessionStorageSupported()) { sessionStorage = new Storage(StorageImpl.SESSION_STORAGE); } return sessionStorage; } /** * Returns true if the localStorage part of the * Storage API is supported on the running platform. */ public static boolean isLocalStorageSupported() { return StorageSupportDetector.localStorageSupported; } /** * Returns true if the sessionStorage part of the * Storage API is supported on the running platform. */ public static boolean isSessionStorageSupported() { return StorageSupportDetector.sessionStorageSupported; } /** * Returns true if the Storage API (both localStorage and * sessionStorage) is supported on the running platform. */ public static boolean isSupported() { return isLocalStorageSupported() && isSessionStorageSupported(); } /** * De-registers an event handler for StorageEvents. * * @see W3C Web * Storage - the storage event * @param handler */ public static void removeStorageEventHandler(StorageEvent.Handler handler) { impl.removeStorageEventHandler(handler); } // Contains either "localStorage" or "sessionStorage": private final String storage; /** * This class can never be instantiated externally. Use * {@link #getLocalStorageIfSupported()} or * {@link #getSessionStorageIfSupported()} instead. */ private Storage(String storage) { this.storage = storage; } /** * Removes all items in the Storage. * * @see W3C Web * Storage - Storage.clear() */ public void clear() { impl.clear(storage); } /** * Returns the item in the Storage associated with the specified key. * * @param key the key to a value in the Storage * @return the value associated with the given key * @see W3C Web * Storage - Storage.getItem(k) */ public String getItem(String key) { return impl.getItem(storage, key); } /** * Returns the number of items in this Storage. * * @return number of items in this Storage * @see W3C Web * Storage - Storage.length() */ public int getLength() { return impl.getLength(storage); } /** * Returns the key at the specified index. * * @param index the index of the key * @return the key at the specified index in this Storage * @see W3C Web * Storage - Storage.key(n) */ public String key(int index) { return impl.key(storage, index); } /** * Removes the item in the Storage associated with the specified key. * * @param key the key to a value in the Storage * @see W3C * Web Storage - Storage.removeItem(k) */ public void removeItem(String key) { impl.removeItem(storage, key); } /** * Sets the value in the Storage associated with the specified key to the * specified data. * * Note: The empty string may not be used as a key. * * @param key the key to a value in the Storage * @param data the value associated with the key * @see W3C Web * Storage - Storage.setItem(k,v) */ public void setItem(String key, String data) { // prevent the empty string due to a Firefox bug: // bugzilla.mozilla.org/show_bug.cgi?id=510849 assert key.length() > 0; impl.setItem(storage, key, data); } }




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