storage.js

一个简单的AJAX图书展示平台

/*
	Copyright (c) 2004-2006, The Dojo Foundation
	All Rights Reserved.

	Licensed under the Academic Free License version 2.1 or above OR the
	modified BSD license. For more information on Dojo licensing, see:

		http://dojotoolkit.org/community/licensing.shtml
*/

/** 
		FIXME: Write better docs.

		@author Alex Russel, [e-mail]
		@author Brad Neuberg, [e-mail] 
*/
dojo.provide("dojo.storage");
dojo.provide("dojo.storage.StorageProvider");

dojo.require("dojo.lang.*");
dojo.require("dojo.event.*");


/** The base class for all storage providers. */

/** 
	 The constructor for a storage provider. You should avoid initialization
	 in the constructor; instead, define initialization in your initialize()
	 method. 
*/
dojo.storage = function(){
}

dojo.lang.extend(dojo.storage, {
	/** A put() call to a storage provider was succesful. */
	SUCCESS: "success",
	
	/** A put() call to a storage provider failed. */
	FAILED: "failed",
	
	/** A put() call to a storage provider is pending user approval. */
	PENDING: "pending",
	
	/** 
	  Returned by getMaximumSize() if this storage provider can not determine
	  the maximum amount of data it can support. 
	*/
	SIZE_NOT_AVAILABLE: "Size not available",
	
	/**
	  Returned by getMaximumSize() if this storage provider has no theoretical
	  limit on the amount of data it can store. 
	*/
	SIZE_NO_LIMIT: "No size limit",
	
	/** 
	  The namespace for all storage operations. This is useful if
	  several applications want access to the storage system from the same
	  domain but want different storage silos. 
	*/
	namespace: "dojoStorage",
	
	/**  
	  If a function is assigned to this property, then 
	  when the settings provider's UI is closed this
	  function is called. Useful, for example, if the
	  user has just cleared out all storage for this
	  provider using the settings UI, and you want to 
	  update your UI.
	*/
	onHideSettingsUI: null,

	/** 
	  Allows this storage provider to initialize itself. This is called
	  after the page has finished loading, so you can not do document.writes(). 
	*/
	initialize: function(){
	 dojo.unimplemented("dojo.storage.initialize");
	},
	
	/** 
	  Returns whether this storage provider is 
	  available on this platform. 
	
	  @returns True or false if this storage 
	  provider is supported.
	*/
	isAvailable: function(){
		dojo.unimplemented("dojo.storage.isAvailable");
	},
	
	/**
	  Puts a key and value into this storage system.

	  @param key A string key to use when retrieving 
	         this value in the future.
	  @param value A value to store; this can be 
	         any JavaScript type.
	  @param resultsHandler A callback function 
	         that will receive three arguments.
	         The first argument is one of three 
	         values: dojo.storage.SUCCESS,
	         dojo.storage.FAILED, or 
	         dojo.storage.PENDING; these values 
	         determine how the put request went. 
	         In some storage systems users can deny
	         a storage request, resulting in a 
	         dojo.storage.FAILED, while in 
	         other storage systems a storage 
	         request must wait for user approval,
	         resulting in a dojo.storage.PENDING 
	         status until the request
	         is either approved or denied, 
	         resulting in another call back
	         with dojo.storage.SUCCESS. 
  
	  The second argument in the call back is the key name
	  that was being stored.
	  
	  The third argument in the call back is an 
	  optional message that details possible error 
	  messages that might have occurred during
	  the storage process.

	  Example:
	    var resultsHandler = function(status, key, message){
	      alert("status="+status+", key="+key+", message="+message);
	    };
	    dojo.storage.put("test", "hello world", 
	                     resultsHandler);	
	*/
	put: function(key, value, resultsHandler){ 
    dojo.unimplemented("dojo.storage.put");
  },

	/**
	  Gets the value with the given key. Returns null
	  if this key is not in the storage system.
	
	  @param key A string key to get the value of.
	  @returns Returns any JavaScript object type; 
	  null if the key is not
	  present. 
	*/
	get: function(key){
    dojo.unimplemented("dojo.storage.get");
  },

	/**
	  Determines whether the storage has the given 
	  key. 
	
	    @returns Whether this key is 
	             present or not. 
	*/
	hasKey: function(key){
		if (this.get(key) != null)
			return true;
		else
			return false;
	},

	/**
	  Enumerates all of the available keys in 
	  this storage system.
	
	  @returns Array of string keys in this 
	           storage system.
	*/
	getKeys: function(){
    dojo.unimplemented("dojo.storage.getKeys");
  },

	/**
	  Completely clears this storage system of all 
	  of it's values and keys. 
	*/
	clear: function(){
    dojo.unimplemented("dojo.storage.clear");
  },
  
  /** Removes the given key from the storage system. */
  remove: function(key){
  	dojo.unimplemented("dojo.storage.remove");
  },

	/**
	  Returns whether this storage provider's 
	  values are persisted when this platform 
	  is shutdown. 
	
	  @returns True or false whether this 
	  storage is permanent. 
	*/
	isPermanent: function(){
		dojo.unimplemented("dojo.storage.isPermanent");
	},

	/**
	  The maximum storage allowed by this provider.
	
	  @returns Returns the maximum storage size 
	           supported by this provider, in 
	           thousands of bytes (i.e., if it 
	           returns 60 then this means that 60K 
	           of storage is supported).
	    
	           If this provider can not determine 
	           it's maximum size, then 
	           dojo.storage.SIZE_NOT_AVAILABLE is 
	           returned; if there is no theoretical
	           limit on the amount of storage 
	           this provider can return, then
	           dojo.storage.SIZE_NO_LIMIT is 
	           returned
	*/
	getMaximumSize: function(){
    dojo.unimplemented("dojo.storage.getMaximumSize");
  },

	/**
	  Determines whether this provider has a 
	  settings UI.
	
	  @returns True or false if this provider has 
	           the ability to show a
	           a settings UI to change it's 
	           values, change the amount of storage
	           available, etc. 
	*/
	hasSettingsUI: function(){
		return false;
	},

	/**
	  If this provider has a settings UI, it is 
	  shown. 
	*/
	showSettingsUI: function(){
	 dojo.unimplemented("dojo.storage.showSettingsUI");
	},

	/**
	  If this provider has a settings UI, hides
	  it.
	*/
	hideSettingsUI: function(){
	 dojo.unimplemented("dojo.storage.hideSettingsUI");
	},
	
	/** 
	  The provider name as a string, such as 
	  "dojo.storage.FlashStorageProvider". 
	*/
	getType: function(){
		dojo.unimplemented("dojo.storage.getType");
	},
	
	/**
	  Subclasses can call this to ensure that the key given is valid in a
	  consistent way across different storage providers. We use the lowest
	  common denominator for key values allowed: only letters, numbers, and
	  underscores are allowed. No spaces. 
	*/
	isValidKey: function(keyName){
		if (keyName == null || typeof keyName == "undefined")
			return false;
			
		return /^[0-9A-Za-z_]*$/.test(keyName);
  }
});




/**
	Initializes the storage systems and figures out the best available 
	storage options on this platform.
*/
dojo.storage.manager = new function(){
	this.currentProvider = null;
	this.available = false;
	this.initialized = false;
	this.providers = new Array();
	
	// TODO: Provide a way for applications to override the default namespace
	this.namespace = "dojo.storage";
	
	/** Initializes the storage system. */
	this.initialize = function(){
		// autodetect the best storage provider we can provide on this platform
		this.autodetect();
	}
	
	/**
	  Registers the existence of a new storage provider; used by subclasses
	  to inform the manager of their existence. 
	
	  @param name The full class name of this provider, such as 
	  "dojo.storage.browser.Flash6StorageProvider".
	  @param instance An instance of this provider, which we will use to
	  call isAvailable() on. 
	*/
	this.register = function(name, instance) {
		this.providers[this.providers.length] = instance;
		this.providers[name] = instance;
	}
	
	/**
	  Instructs the storageManager to use 
	  the given storage class for all storage requests.
	    
	  Example:
	    
	  dojo.storage.setProvider(
	         dojo.storage.browser.IEStorageProvider)
	*/
	this.setProvider = function(storageClass){
	
	}
	
	/** 
	  Autodetects the best possible persistent
	  storage provider available on this platform. 
	*/
	this.autodetect = function(){
		if(this.initialized == true) // already finished
			return;
			
		// go through each provider, seeing if it can be used
		var providerToUse = null;
		for(var i = 0; i < this.providers.length; i++) {
			providerToUse = this.providers[i];
			if(providerToUse.isAvailable()){
				break;
			}
		}	
		
		if(providerToUse == null){ // no provider available
			this.initialized = true;
			this.available = false;
			this.currentProvider = null;
			dojo.raise("No storage provider found for this platform");
		}
			
		// create this provider and copy over it's properties
		this.currentProvider = providerToUse;
	  	for(var i in providerToUse){
	  		dojo.storage[i] = providerToUse[i];
		}
		dojo.storage.manager = this;
		
		// have the provider initialize itself
		dojo.storage.initialize();
		
		this.initialized = true;
		this.available = true;
	}
	
	/** Returns whether any storage options are available. */
	this.isAvailable = function(){
		return this.available;
	}
	
	/** 
	 	Returns whether the storage system is initialized and
	 	ready to be used. 
	*/
	this.isInitialized = function(){
		// FIXME: This should _really_ not be in here, but it fixes a bug
		if(dojo.flash.ready == false){
			return false;
		}else{
			return this.initialized;
		}
	}

	/**
	  Determines if this platform supports
	  the given storage provider.
	
	  Example:
			
	  dojo.storage.manager.supportsProvider(
	    "dojo.storage.browser.InternetExplorerStorageProvider");
	*/
	this.supportsProvider = function(storageClass){
		// construct this class dynamically
		try{
			// dynamically call the given providers class level isAvailable()
			// method
			var provider = eval("new " + storageClass + "()");
			var results = provider.isAvailable();
			if(results == null || typeof results == "undefined")
				return false;
			return results;
		}catch (exception){
			dojo.debug("exception="+exception);
			return false;
		}
	}

	/** Gets the current provider. */
	this.getProvider = function(){
		return this.currentProvider;
	}
	
	/** 
	  The storage provider should call this method when it is loaded and
	  ready to be used. Clients who will use the provider will connect
	  to this method to know when they can use the storage system:
	
	  dojo.connect(dojo.storage.manager, "loaded", someInstance, 
	               someInstance.someMethod);
	*/
	this.loaded = function(){
	}
}