persistence.js ============== `persistence.js` is a asynchronous Javascript object-relational mapper library. It can be used both in the web browser and on the server using [node.js](http://nodejs.org). It currently supports 4 types of data stores: * [HTML5 WebSQL database](http://dev.w3.org/html5/webdatabase/), a somewhat controversial part of HTML5 that is supported in Webkit browsers, specifically on mobile devices, including iPhone, Android and Palm's WebOS. * [Google Gears](http://gears.google.com), a browser plug-in that adds a number of feature to the browser, including a in-browser database. * [MySQL](http://www.mysql.com), using the [node-mysql](http://github.com/felixge/node-mysql), node.js module on the server. * In-memory, as a fallback. Keeps the database in memory and is cleaned upon a page refresh (or server restart), unless saved to [localStorage](http://dev.w3.org/html5/webstorage/). There is also an experimental support for [Qt 4.7 Declarative UI framework (QML)](http://doc.trolltech.org/4.7-snapshot/declarativeui.html) which is an extension to JavaScript. For browser use, `persistence.js` has no dependencies on any other frameworks, other than the Google Gears [initialization script](http://code.google.com/apis/gears/gears_init.js), in case you want to enable Gears support. Plug-ins -------- There are a few `persistence.js` plug-ins available that add functionality: * `persistence.search.js`, adds simple full-text search capabilities, see `docs/search.md` for more information. * `persistence.migrations.js`, supports data migrations (changes to the database schema), see `docs/migrations.md` for more information. * `persistence.sync.js`, supports database synchronization with a remote server, see `docs/sync.md` for more information. * `jquery.persistence.js`, adds jQuery integration, including jQuery-mobile ajax request interception and re-routing to persistencejs, see `docs/jquery.md` for more information and `demo/jquerymobile` for a simple demo. A Brief Intro to Async Programming ---------------------------------- In browsers, Javascript and the web page's rendering engine share a single thread. The result of this is that only one thing can happen at a time. If a database query would be performed _synchronously_, like in many other programming environments like Java and PHP the browser would freeze from the moment the query was issued until the results came back. Therefore, many APIs in Javascript are defined as _asynchronous_ APIs, which mean that they do not block when an "expensive" computation is performed, but instead provide the call with a function that will be invoked once the result is known. In the meantime, the browser can perform other duties. For instance, a synchronous database call call would look as follows: var results = db.query("SELECT * FROM Table"); for(...) { ... } The execution of the first statement could take half a second, during which the browser doesn't do anything else. By contrast, the asynchronous version looks as follows: db.query("SELECT * FROM Table", function(results) { for(...) { ... } }); Note that there will be a delay between the `db.query` call and the result being available and that while the database is processing the query, the execution of the Javascript continues. To make this clear, consider the following program: db.query("SELECT * FROM Table", function(results) { console.log("hello"); }); console.log("world"); Although one could assume this would print "hello", followed by "world", the result will likely be that "world" is printed before "hello", because "hello" is only printed when the results from the query are available. This is a tricky thing about asynchronous programming that a Javascript developer will have to get used to. Using persistence.js in the browser =================================== Browser support --------------- * Modern webkit browsers (Google Chrome and Safari) * Firefox (through Google Gears) * Opera * Android browser (tested on 1.6 and 2.x) * iPhone browser (iPhone OS 3+) * Palm WebOS (tested on 1.4.0) * Other browsers supporting `localStorage` (e.g. Firefox) (The following is being worked on:) Internet Explorer is likely not supported (untested) because it lacks `__defineGetter__` and `__defineSetter__` support, which `persistence.js` uses heavily. This may change in IE 9. Setting up ---------- To use `persistence.js` you need to clone the git repository: git clone git://github.com/zefhemel/persistencejs.git To use it you need to copy `lib/persistence.js` to your web directory, as well as any data stores you want to use. Note that the `mysql` and `websql` stores both depend on the `sql` store. A typical setup requires you to copy at least `lib/persistence.js`, `lib/persistence.store.sql.js` and `lib/persistence.store.websql.js` to your web directory. You can then load them as follows: If you want to use the in-memory store (in combination with `localStorage`) you also need the `persistence.store.memory.js` included. Setup your database ------------------- You need to explicitly configure the data store you want to use, configuration of the data store is store-specific. The WebSQL store (which includes Google Gears support) is configured as follows: persistence.store.websql.config(persistence, 'yourdbname', 'A database description', 5 * 1024 * 1024); The first argument is always supposed to be `persistence`. The second in your database name (it will create it if it does not already exist, the third is a description for you database, the last argument is the maximum size of your database in bytes (5MB in this example). The in-memory store --------------------------------------- The in-memory store is offered as a fallback for browsers that do not support any of the other supported stores (e.g. WebSQL or Gears). In principal, it only keeps data in memory, which means that navigating away from the page (including a reload or tab close) will result in the loss of all data. A way around this is using the `persistence.saveToLocalStorage` and `persistence.loadFromLocalStorage` functions that can save the entire database to the [localStorage](http://dev.w3.org/html5/webstorage/), which is persisted indefinitely (similar to WebSQL). If you're going to use the in-memory store, you can configure it as follows: persistence.store.memory.config(persistence); Then, if desired, current data can be loaded from the localStorage using: persistence.loadFromLocalStorage(function() { alert("All data loaded!"); }); And saved using: persistence.saveToLocalStorage(function() { alert("All data saved!"); }); Drawbacks of the in-memory store: * Performance: All actions that are typically performed by a database (sorting, filtering), are now all performed in-memory using Javascript. * Limited database size: Loading and saving requires serialization of all data from and to JSON, which gets more expensive as your dataset grows. Most browsers have a maximum size of 5MB for `localStorage`. * Synchronous behavior: Although the API is asynchronous, all persistence actions will be performed synchronously on the main Javascript thread, which may make the browser less responsive. Schema definition ----------------- A data model is declared using `persistence.define`. The following two definitions define a `Task` and `Category` entity with a few simple properties. The property types are based on [SQLite types](http://www.sqlite.org/datatype3.html), specifically supported types are (but any SQLite type is supported): * `TEXT`: for textual data * `INT`: for numeric values * `BOOL`: for boolean values (`true` or `false`) * `DATE`: for date/time value (with precision of 1 second) * `JSON`: a special type that can be used to store arbitrary [JSON](http://www.json.org) data. Note that this data can not be used to filter or sort in any sensible way. If internal changes are made to a `JSON` property, `persistence.js` may not register them. Therefore, a manual call to `anObj.markDirty('jsonPropertyName')` is required before calling `persistence.flush`. Example use: var Task = persistence.define('Task', { name: "TEXT", description: "TEXT", done: "BOOL" }); var Category = persistence.define('Category', { name: "TEXT", metaData: "JSON" }); var Tag = persistence.define('Tag', { name: "TEXT" }); The returned values are constructor functions and can be used to create new instances of these entities later. It is possible to create indexes on one or more columns using `EntityName.index`, for instance: Task.index('done'); Task.index(['done', 'name']); These indexes can also be used to impose unique constraints : Task.index(['done', 'name'],{unique:true}); Relationships between entities are defined using the constructor function's `hasMany` call: // This defines a one-to-many relationship: Category.hasMany('tasks', Task, 'category'); // These two definitions define a many-to-many relationship Task.hasMany('tags', Tag, 'tasks'); Tag.hasMany('tasks', Task, 'tags'); The first statement defines a `tasks` relationship on category objects containing a `QueryCollection` (see the section on query collections later) of `Task`s, it also defines an inverse relationship on `Task` objects with the name `category`. The last two statements define a many-to-many relationships between `Task` and `Tag`. `Task` gets a `tags` property (a `QueryCollection`) containing all its tags and vice versa, `Tag` gets a `tasks` property containing all of its tasks. The defined entity definitions are synchronized (activated) with the database using a `persistence.schemaSync` call, which takes a callback function (with a newly created transaction as an argument), that is called when the schema synchronization has completed, the callback is optional. persistence.schemaSync(); // or persistence.schemaSync(function(tx) { // tx is the transaction object of the transaction that was // automatically started }); There is also a migrations plugin you can check out, documentation can be found in [persistence.migrations.docs.md](migrations/persistence.migrations.docs.md) file. Mix-ins ------- You can also define mix-ins and apply them to entities of the model. A mix-in definition is similar to an entity definition, except using `defineMixin` rather than just `define`. For example: var Annotatable = persistence.defineMixin('Annotatable', { lastAnnotated: "DATE" }); You can define relationships between mix-in and entities. For example: // A normal entity var Note = persistence.define('Note', { text: "TEXT" }); // relationship between a mix-in and a normal entity Annotatable.hasMany('notes', Note, 'annotated'); Once you have defined a mix-in, you can apply it to any entity of your model, with the `Entity.is(mixin)` method. For example: Project.is(Annotatable); Task.is(Annotatable); Now, your `Project` and `Task` entities have an additional `lastAnnotated` property. They also have a one to many relationship called `notes` to the `Note` entity. And you can also traverse the reverse relationship from a `Note` to its `annotated` object. Note that `annotated` is a polymorphic relationship as it may yield either a `Project` or a `Task` (or any other entity which is `Annotatable'). Note: Prefetch is not allowed (yet) on a relationship that targets a mixin. In the example above you cannot prefetch the `annotated` relationship when querying the `Note` entity. Notes: this feature is very experimental at this stage. It needs more testing. Support for "is a" relationships (classical inheritance) is also in the works. Creating and manipulating objects --------------------------------- New objects can be instantiated with the constructor functions. Optionally, an object with initial property values can be passed as well, or the properties may be set later: var task = new Task(); var category = new Category({name: "My category"}); category.metaData = {rating: 5}; var tag = new Tag(); tag.name = "work"; Many-to-one relationships are accessed using their specified name, e.g.: task.category = category; One-to-many and many-to-many relationships are access and manipulated through the `QueryCollection` API that will be discussed later: task.tags.add(tag); tasks.tags.remove(tag); tasks.tags.list(tx, function(allTags) { console.log(allTags); }); Persisting/removing objects --------------------------- Similar to [hibernate](http://www.hibernate.org), `persistence.js` uses a tracking mechanism to determine which objects' changes have to be persisted to the database. All objects retrieved from the database are automatically tracked for changes. New entities can be tracked to be persisted using the `persistence.add` function: var c = new Category({name: "Main category"}); persistence.add(c); for ( var i = 0; i < 5; i++) { var t = new Task(); t.name = 'Task ' + i; t.done = i % 2 == 0; t.category = c; persistence.add(t); } Objects can also be removed from the database: persistence.remove(c); All changes made to tracked objects can be flushed to the database by using `persistence.flush`, which takes a transaction object and callback function as arguments. A new transaction can be started using `persistence.transaction`: persistence.transaction(function(tx) { persistence.flush(tx, function() { alert('Done flushing!'); }); }); For convenience, it is also possible to not specify a transaction or callback, in that case a new transaction will be started automatically. For instance: persistence.flush(); // or, with callback persistence.flush(function() { alert('Done flushing'); }); Note that when no callback is defined, the flushing still happens asynchronously. __Important__: Changes and new objects will not be persisted until you explicitly call `persistence.flush()`. The exception to this rule is using the `list(...)` method on a database `QueryCollection`, which also flushes first, although this behavior may change in the future. Dumping and restoring data -------------------------- The library supports two kinds of dumping and restoring data. `persistence.dump` can be used to create an object containing a full dump of a database. Naturally, it is adviced to only do this with smaller databases. Example: persistence.dump(tx, [Task, Category], function(dump) { console.log(dump); }); The `tx` is left out, a new transaction will be started for the operation. If the second argument is left out, `dump` defaults to dumping _all_ defined entities. The dump format is: {"entity-name": [list of instances], ...} `persistence.load` is used to restore the dump produced by `persistence.dump`. Usage: persistence.load(tx, dumpObj, function() { alert('Dump restored!'); }); The `tx` argument can be left out to automatically start a new transaction. Note that `persistence.load` does not empty the database first, it simply attempts to add all objects to the database. If objects with, e.g. the same ID already exist, this will fail. Similarly, `persistence.loadFromJson` and `persistence.dumpToJson` respectively load and dump all the database's data as JSON strings. Entity constructor functions ---------------------------- The constructor function returned by a `persistence.define` call cannot only be used to instantiate new objects, it also has some useful methods of its own: * `EntityName.all([session])` returns a query collection containing all persisted instances of that object. The `session` argument is optional and only required when `persistence.js` is used in multi-session mode. * `EntityName.load([session], [tx], id, callback)` loads an particular object from the database by id or returns `null` if it has not been found. * `EntityName.findBy([session], [tx], property, value, callback)` searches for a particular object based on a property value (this is assumed to be unique), the callback function is called with the found object or `null` if it has not been found. * `EntityName.index([col1, col2, ..., colN], options)` creates an index on a column of a combination of columns, for faster searching. If options.unique is true, the index will impose a unique constraint on the values of the columns. And of course the methods to define relationships to other entities: * `EntityName.hasMany(property, Entity, inverseProperty)` defines a 1:N or N:M relationship (depending on the inverse property) * `EntityName.hasOne(property, Entity)` defines a 1:1 or N:1 relationship Entity objects -------------- Entity instances also have a few predefined properties and methods you should be aware of: * `obj.id`, contains the identifier of your entity, this is a automatically generated (approximation of a) UUID. You should never write to this property. * `obj.fetch(prop, callback)`, if an object has a `hasOne` relationship to another which has not yet been fetched from the database (e.g. when `prefetch` wasn't used), you can fetch in manually using `fetch`. When the property object is retrieved the callback function is invoked with the result, the result is also cached in the entity object itself. * `obj.selectJSON([tx], propertySpec, callback)`, sometime you need to extract a subset of data from an entity. You for instance need to post a JSON representation of your entity, but do not want to include all properties. `selectJSON` allows you to do that. The `propertySpec` arguments expects an array with property names. Some examples: * `['id', 'name']`, will return an object with the id and name property of this entity * `['*']`, will return an object with all the properties of this entity, not recursive * `['project.name']`, will return an object with a project property which has a name property containing the project name (hasOne relationship) * `['project.[id, name]']`, will return an object with a project property which has an id and name property containing the project name (hasOne relationship) * `['tags.name']`, will return an object with an array `tags` property containing objects each with a single property: name Query collections ----------------- A core concept of `persistence.js` is the `QueryCollection`. A `QueryCollection` represents a (sometimes) virtual collection that can be filtered, ordered or paginated. `QueryCollection`s are somewhate inspired by [Google AppEngine's Query class](http://code.google.com/appengine/docs/python/datastore/queryclass.html). A `QueryCollection` has the following methods: * `filter(property, operator, value)` Returns a new `QueryCollection` that adds a filter, filtering a certain property based on an operator and value. Supported operators are '=', '!=', '<', '<=', '>', '>=', 'in' and 'not in'. Example: `.filter('done', '=', true)` * `or(filter)` Returns a new `QueryCollection` that contains items either matching the filters specified before calling `or`, or the filter represented in the argument. The `filter` argument is of a `Filter` type, there are three types of filters: - `persistence.PropertyFilter`, which filters on properties (internally called when `filter(...)` is used. Example: `new persistence.PropertyFilter('done', '=', true)` - `persistence.AndFilter`, which is passed two filter objects as arguments, both of which should be true. Example: `new persistence.AndFilter(new persistence.PropertyFilter('done', '=', true), new persistence.PropertyFilter('archived', '=', true))` - `persistence.OrFilter`, which is passed two filter objects as arguments, one of which should be true. Example: `new persistence.OrFilter(new persistence.PropertyFilter('done', '=', true), new persistence.PropertyFilter('archived', '=', true))` * `and(filter)` same as `or(filter)` except that both conditions should hold for items to be in the collection. * `order(property, ascending)` Returns a new `QueryCollection` that will order its results by the property specified in either an ascending (ascending === true) or descending (ascending === false) order. * `limit(n)` Returns a new `QueryCollection` that limits the size of the result set to `n` items. Useful for pagination. * `skip(n)` Returns a new `QueryCollection` that skips the first `n` results. Useful for pagination. * `prefetch(rel)` Returns a new `QueryCollection` that prefetches entities linked through relationship `rel`, note that this only works for one-to-one and many-to-one relationships. * `add(obj)` Adds object `obj` to the collection. * `remove(obj)` Removes object `obj` from the collection. * `list([tx], callback)` Asynchronously fetches the results matching the formulated query. Once retrieved, the callback function is invoked with an array of entity objects as argument. * `each([tx], eachCallback)` Asynchronously fetches the results matching the formulated query. Once retrieved, the `eachCallback` function is invoked on each element of the result objects. * `forEach([tx], eachCallback)` Alias for `each` * `one([tx], callback)` Asynchronously fetches the first element of the collection, or `null` if none. * `destroyAll([tx], callback)` Asynchronously removes all the items in the collection. __Important__: this does not only remove the items from the collection, but removes the items themselves! * `count([tx], callback)` Asynchronously counts the number of items in the collection. The arguments passed to the `callback` function is the number of items. Query collections are returned by: * `EntityName.all()`, e.g. `Task.all()` * one-to-many and many-to-many relationships, e.g. `task.tags` Example: var allTasks = Task.all().filter("done", '=', true).prefetch("category").order("name", false).limit(10); allTasks.list(null, function (results) { results.forEach(function (r) { console.log(r.name) window.task = r; }); }); Using persistence.js on the server ================================== Installing `persistence.js` on node is easy using [npm](http://npmjs.org): npm install persistencejs Sadly the node.js server environment requires slight changes to `persistence.js` to make it work with multiple database connections: * A `Session` object needs to be passed as an extra argument to certain method calls, typically as a first argument. * Methods previously called on the `persistence` object itself are now called on the `Session` object. An example `node.js` application is included in `test/node-blog.js`. Setup ----- You need to `require` two modules, the `persistence.js` library itself and the MySQL backend module. var persistence = require('persistencejs'); var persistenceStore = persistence.StoreConfig.init(persistence, { adaptor: 'mysql' }); Then, you configure the database settings to use: persistenceStore.config(persistence, 'localhost', 3306, 'dbname', 'username', 'password'); Subsequently, for every connection you handle (assuming you're building a sever), you call the `persistenceStore.getSession()` method: var session = persistenceStore.getSession(); This session is what you pass around, typically together with a transaction object. Note that currently you can only have one transaction open per session and transactions cannot be nested. session.transaction(function(tx) { ... }); Commit and Rollback ------------------- `persistence.js` works in autocommit mode by default. You can override this behavior and enable explicit commit and rollback by passing true as first argument to `persistence.transaction`. You can then use the following two methods to control the transaction: * `transaction.commit(session, callback)` commits the changes. * `transaction.rollback(session, callback)` rollbacks the changes. Typical code will look like: session.transaction(true, function(tx) { // create/update/delete objects modifyThings(session, tx, function(err, result) { if (err) { // something went wrong tx.rollback(session, function() { console.log('changes have been rolled back: ' + ex.message); }); } else { // success tx.commit(session, function() { console.log('changes have been committed: ' result); }); }); }); Explicit commit and rollback is only supported on MySQL (server side) for now. Defining your data model ------------------------ Defining your data model is done in exactly the same way as regular `persistence.js`: var Task = persistence.define('Task', { name: "TEXT", description: "TEXT", done: "BOOL" }); A `schemaSync` is typically performed as follows: session.schemaSync(tx, function() { ... }); Creating and manipulating objects --------------------------------- Creating and manipulating objects is done much the same way as with regular `persistence.js`, except that in the entity's constructor you need to reference the `Session` again: var t = new Task(session); ... session.add(t); session.flush(tx, function() { ... }); Query collections ----------------- Query collections work the same way as in regular `persistence.js` with the exception of the `Entity.all()` method that now also requires a `Session` to be passed to it: Task.all(session).filter('done', '=', true).list(tx, function(tasks) { ... }); Closing the session ------------------- After usage, you need to close your session: session.close(); Bugs and Contributions ====================== If you find a bug, please [report it](https://github.com/zefhemel/persistencejs/issues). or fork the project, fix the problem and send me a pull request. For a list of planned features and open issues, have a look at the [issue tracker](https://github.com/zefhemel/persistencejs/issues). For support and discussion, please join the [persistence.js Google Group](http://groups.google.com/group/persistencejs). Thanks goes to the people listed in `AUTHORS` for their contributions. If you use [GWT](http://code.google.com/webtoolkit/) (the Google Web Toolkit), be sure to have a look at [Dennis Z. Jiang's GWT persistence.js wrapper](http://github.com/dennisjzh/GwtMobile-Persistence) License ======= This work is licensed under the [MIT license](http://en.wikipedia.org/wiki/MIT_License). Support this work ----------------- You can support this project by flattering it: