store.js

ajax开发实例

dojo.provide("dwr.data.Store");

dojo.declare("dwr.data.Store", null, {
    // Summary: An implementation of all 4 DataStore APIs
    // TODO: Consider support for queryOptions (see fetch)
    // TODO: Consider caching attributes for dojo.data.api.Read.getAttributes
    // Since we're generally going to be storing sets of homogeneous objects
    // we might pass an official attribute list across the wire and cache it
    // TODO: Something more formal about errors in _callback()?
    // TODO: I only discovered from reading the QueryReadStore that the param
    // passed into fetch() is a dojo.data.api.Request. I'm assuming that the same
    // is true for fetchItemByIdentity()
    // TODO: do we need to check that we don't have prototype polution?
    // save() and (maybe) other functions do 'for(a in b) {...}' without checking
    // that b[a] isn't a function.
    // TODO: The logic for the call to onComplete in the callback in simpleFetch
    // is different to our implementation.I thought that I'd followed the spec.
    // Either I can't read, or the author of simpleFetch can't read, wibble.

    // When we need to generate a local $id from a call to newItem()
    autoIdPrefix:"_auto_",

    constructor: function(/*string*/ storeId, /*object*/ params) {
        // Summary: Create a new data store
        // Description: ...
        // storeId: The id of StoreProvider as provided to DWR in
        //          org.directwebremoting.datasync.Directory.register(storeId, store);
        // params: An optional set of customizations to how the data
        //         is fetched from the store. The options are:
        //         - subscribe: The DwrStore implements dojo.data.api.Notification but will
        //         only send updates if subscribe=true. The updates will be sent in a
        //         timely manner iff dwr.engine.setActiveReverseAjax=true.
        if (storeId == null || typeof storeId != "string") {
            throw new Error("storeId is null or not a string");
        }
        var listener = (params && params.subscribe) ? this : null;
        this.dwrCache = new dwr.data.Cache(storeId, listener);

        // Important: you'll need to know this to grok the rest of the file.
        // We store data in a set of entries. What we give to the outside as an
        // 'item' is actually just a string aka the id of each entry.
        // Each entry is:
        // { $id:.., $label:.., data:.., updates:.., isDeleted:.., isDirty:.. }
        // $id and $label have $ prefixes because they are partially exposed
        // - itemId: primary key derivative, set to what the server gives us.
        //   If this entry was loaded from the server then $id == itemId
        // - $id: key that is exposed to the client. different to itemId if this
        //   item came from newItem() when we didn't have time to ask for a new ID
        // - $label: is like java.lang.Object.toString. For more details see
        //   org.directwebremoting.io.Item and dojo.data.api.Read.getLabel
        // - data: is what you would expect DWR to return from Java-Land
        // - updates: data that has been altered locally, but not save()d yet
        // - isDeleted: Has this item been deleted?
        // - isDirty: Has this item been updated?
        // The first 3 are sent from the server, the second 3 are client side only

        // We store items against their itemIds in here. Currently the former is
        // going to grow and grow. When do we need to clear it out?
        this._entries = {};
        this._updated = {};

        // We need to generate unique local ids for newItem();
        this._nextLocalId = 0;

        // Should we check the server for fetchItemByIdentity? I think we don't need to.
        this.fastFetchItemByIdentity = true;

        // If we are doing subscription, we want to pass to the server this by reference not by value
        this.$dwrByRef = true;
    },

    getFeatures: function() {
        // Summary: See `dojo.data.api.Read.getFeatures`
        return {
            'dojo.data.api.Write': true,
            'dojo.data.api.Notification': true,
            'dojo.data.api.Identity': true,
            'dojo.data.api.Read': true
        };
    },

    _getAttributeValue: function(/*string*/ id, /*string*/ attribute, /*anything*/ defaultValue) {
        // Summary: Get the entry as indexed by the given id.
        // id: The id of the item (and hence it's data)
        // attribute: The attribute to look for in the data referenced by id
        // defaultValue: The value to return if the attribute could not be found
        var entry = this._entries[id];
        if (entry == null) throw new Error("non item");
        if (attribute == "$id") return entry.$id;
        if (attribute == "$label") return entry.$label;
        var value = entry.updates[attribute];
        if (value === undefined) value = entry.data[attribute];
        if (value === undefined) value = defaultValue;
        return value;
    },

    getValue: function(/*item*/ id, /*string*/ attribute, /*anything*/ defaultValue) {
        // Summary: See `dojo.data.api.Read.getValue`
        var value = this._getAttributeValue(id, attribute, defaultValue);
        return (dojo.isArray(value)) ? null : value;
    },

    getValues: function(/*item*/ id, /*string*/ attribute) {
        // Summary: See `dojo.data.api.Read.getValues`
        var value = this._getAttributeValue(id, attribute, []);
        return (dojo.isArray(value)) ? value : [ value ];
    },

    getAttributes: function(/*item*/ id) {
        // Summary: See `dojo.data.api.Read.getAttributes`
        var entry = this._entries[id];
        if (entry == null) throw new Error("non item passed to getAttributes()");
        var attributes = [ '$id', '$label' ];
        for (var attributeName in entry.data) {
            if (typeof entry.data[attributeName] != "function") {
                attributes.push(attributeName);
            }
        }
        return attributes;
    },

    hasAttribute: function(/*item*/ id, /*string*/ attribute) {
        // Summary: See `dojo.data.api.Read.hasAttribute`
        var value = this._getAttributeValue(id, attribute, undefined);
        return value !== undefined;
    },

    containsValue: function(/*item*/ id, /*string*/ attribute, /*anything*/ value) {
        // Summary: See `dojo.data.api.Read.containsValue`
        var test = this._getAttributeValue(id, attribute, undefined);
        return test == value;
    },

    isItem: function(/*anything*/ something) {
        // Summary: See `dojo.data.api.Read.isItem`
        return dojo.isString(something) && this._entries[something] != null;
    },

    isItemLoaded: function(/*anything*/ something) {
        // Summary: See `dojo.data.api.Read.isItemLoaded`
        var entry = this._entries[something];
        return entry != null && entry.data != null;
    },

    loadItem: function(/*object*/ keywordArgs) {
        // Summary: See `dojo.data.api.Read.loadItem`
        // We're not doing lazy loading at this level.
        return true;
    },

    fetch: function(/*object*/ request) {
        // Summary: See `dojo.data.api.Read.fetch`
        request = request || {};
        var store = this;
        var scope = request.scope || dojo.global;

        if (request.queryOptions != null) {
            console.log("queryOptions is not currently supported by DwrStore");
        }

        var region = {
            count: request.count,
            start: request.start,
            query: request.query,
            sort: request.sort
        };

        var callbackObj = {
            callback: function(matchedItems) {
                var aborted = false;
                var originalAbort = request.abort;
                request.abort = function() {
                    aborted = true;
                    if (dojo.isFunction(originalAbort)) {
                        originalAbort.call(request);
                    }
                };

                dojo.forEach(matchedItems.viewedMatches, store._importItem, store);

                if (dojo.isFunction(request.onBegin)) {
                    request.onBegin.call(scope, matchedItems.totalMatchCount, request);
                }

                if (dojo.isFunction(request.onItem)) {
                    dojo.forEach(matchedItems.viewedMatches, function(entry) {
                        if (!aborted) {
                            request.onItem.call(scope, entry.$id, request);
                        }
                    });
                }

                if (dojo.isFunction(request.onComplete) && !aborted) {
                    if (dojo.isFunction(request.onItem)) {
                        request.onComplete.call(scope, null, request);
                    }
                    else {
                        var all = [];
                        dojo.forEach(matchedItems.viewedMatches, function(entry) {
                            all.push(entry.$id);
                        });
                        request.onComplete.call(scope, all, request);
                    }
                }
            },

            errorHandler: function(msg, ex) {
                if (dojo.isFunction(request.onError)) {
                    request.onError(ex);
                }
            }
        };

        this.dwrCache.viewRegion(region, callbackObj);

        return request;
    },

    close: function(/*dojo.data.api.Request*/ request) {
        // Summary: See `dojo.data.api.Read.close`
        this._entries = {};
        this._updated = {};
        this.dwrCache.unsubscribe({
            exceptionHandler:function(msg, ex) {
                console.error(ex);
            }
        });
    },

    getLabel: function(/*item*/ id) {
        // Summary: See `dojo.data.api.Read.getLabel`
        // org.directwebremoting.io.Item exposes Object#toString as a label on
        // our items if the data implements ExposeToStringToTheOutside.
        return this._getAttributeValue(id, "$label");
    },

    getLabelAttributes: function(/*item*/ id) {
        // Summary: See `dojo.data.api.Read.getLabelAttributes`
        if (!this.isItem(id)) throw new Error("non item passed to getLabelAttributes()");
        return [ "$label" ];
    },

    getIdentity: function(/*item*/ id) {