com.sencha.gxt.data.client.loader.StorageReadProxy.java Source code

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/**
 * Sencha GXT 4.0.0 - Sencha for GWT
 * Copyright (c) 2006-2015, Sencha Inc.
 *
 * licensing@sencha.com
 * http://www.sencha.com/products/gxt/license/
 *
 * ================================================================================
 * Open Source License
 * ================================================================================
 * This version of Sencha GXT is licensed under the terms of the Open Source GPL v3
 * license. You may use this license only if you are prepared to distribute and
 * share the source code of your application under the GPL v3 license:
 * http://www.gnu.org/licenses/gpl.html
 *
 * If you are NOT prepared to distribute and share the source code of your
 * application under the GPL v3 license, other commercial and oem licenses
 * are available for an alternate download of Sencha GXT.
 *
 * Please see the Sencha GXT Licensing page at:
 * http://www.sencha.com/products/gxt/license/
 *
 * For clarification or additional options, please contact:
 * licensing@sencha.com
 * ================================================================================
 *
 *
 * ================================================================================
 * Disclaimer
 * ================================================================================
 * THIS SOFTWARE IS DISTRIBUTED "AS-IS" WITHOUT ANY WARRANTIES, CONDITIONS AND
 * REPRESENTATIONS WHETHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION THE
 * IMPLIED WARRANTIES AND CONDITIONS OF MERCHANTABILITY, MERCHANTABLE QUALITY,
 * FITNESS FOR A PARTICULAR PURPOSE, DURABILITY, NON-INFRINGEMENT, PERFORMANCE AND
 * THOSE ARISING BY STATUTE OR FROM CUSTOM OR USAGE OF TRADE OR COURSE OF DEALING.
 * ================================================================================
 */
package com.sencha.gxt.data.client.loader;

import com.google.gwt.core.client.Callback;
import com.google.gwt.storage.client.Storage;
import com.sencha.gxt.data.shared.loader.DataProxy;
import com.sencha.gxt.data.shared.writer.DataWriter;

/**
 * A {@link DataProxy} that retrieves data from HTML5 browser based storage.
 * 
 * @param <C> the type of load configuration
 */
public class StorageReadProxy<C> implements DataProxy<C, String> {
    private DataWriter<C, String> writer;
    private final Storage storage;

    /**
     * Creates a storage read proxy that retrieves data from HTML5 browser based
     * storage.
     * 
     * @param session true to use session storage, false to use local storage
     */
    public StorageReadProxy(boolean session) {
        this(session ? Storage.getSessionStorageIfSupported() : Storage.getLocalStorageIfSupported());
    }

    /**
     * Creates a storage read proxy that retrieves data from the given HTML5
     * browser based storage.
     * 
     * @param storage the browser based storage
     */
    public StorageReadProxy(Storage storage) {
        assert storage != null : "Storage may not be null";
        this.storage = storage;
    }

    public DataWriter<C, String> getWriter() {
        return writer;
    }

    public void setWriter(DataWriter<C, String> writer) {
        this.writer = writer;
    }

    @Override
    public void load(C loadConfig, Callback<String, Throwable> callback) {
        String key = getKeyFromConfig(loadConfig);
        callback.onSuccess(storage.getItem(key));
    }

    /**
     * Save a value in the HTML5 browser based storage.
     * 
     * @param saveConfig provides the source of the storage key (see
     *          {@link #getKeyFromConfig(Object)}).
     * @param data the value to save, associated with <code>saveConfig</code>
     */
    public void save(C saveConfig, String data) {
        String key = getKeyFromConfig(saveConfig);
        storage.setItem(key, data);
    }

    /**
     * Generates a storage key from the given load config. By default, this is the
     * value returned by the load config's <code>toString</code> method.
     * 
     * @param loadConfig the load config
     * @return the key that associates load config with its storage
     */
    protected String getKeyFromConfig(C loadConfig) {
        if (writer == null) {
            return loadConfig.toString();
        } else {
            return writer.write(loadConfig);
        }
    }

}