M — Model in MVC, MVP, MVVC in Android（译者注：MVC，MVP，MVVC架构中Model层在Android中的定义） – Artem Zinnatullin https://medium.com/@artem_zin/m-model-from-mvc-mvp-in-android-flow-and-mortar-bd1e50c45395#.82qjulegz

如果你不还了解Model层中的JSON与SQL，或者不能透彻理解Model层的图像模型，这篇文章将带你进一步理解什么是Model层以及为什么Model层独立于其他层。其中“Model layer is solution”部分很好的解释了如何通过面向接口的方式编写测试。

#####Overview:

• Powerful & Simple set of Operations: Put, Get, Delete
• API for Humans: Type Safety, Immutability & Thread-Safety
• Convenient builders with compile-time guarantees for required params. Forget about 6-7 null in queries
• Optional Type-Safe Object Mapping, if you don't want to work with Cursor and ContentValues you don't have to
• No reflection in Operations and no annotations in the core, also StorIO is not ORM
• Every Operation over StorIO can be executed as blocking call or as rx.Observable
• RxJava as first class citizen, but it's not required dependency!
• Reactive: rx.Observable from Get Operation will observe changes in StorIO (SQLite or ContentProvider) and receive updates automatically
• StorIO is replacements for SQLiteDatabase and ContentResolver APIs
• StorIO + RxJava is replacement for Loaders API
• We are working on MockStorIO (similar to MockWebServer) for easy unit testing

#####Why StorIO?

• Open Source -> less bugs
• Documentation, Sample app and Design tests -> less bugs
• StorIO has unit and integration tests -> less bugs
• Simple concept of just three main Operations: Put, Get, Delete -> less bugs
• Almost everything is immutable and thread-safe -> less bugs
• Builders for everything make code much, much more readable and obvious -> less bugs
• StorIO annotated with @NonNull and @Nullable annotations -> less bugs
• Less bugs -> less bugs

####Documentation:

• Why we made StorIO
• StorIO SQLite
• StorIO ContentResolver

Easy ways to learn how to use StorIO -> check out Documentation, Design Tests and Sample App:

• Design tests for StorIO SQLite
• Design tests for StorIO ContentResolver
• Sample App

####Download:

// If you need StorIO for SQLite
compile 'com.pushtorefresh.storio:sqlite:1.7.0'

// If you need StorIO for ContentResolver
compile 'com.pushtorefresh.storio:content-resolver:1.7.0'

// IN StorIO 2.0 we will remove default Scheduling from Rx Operations!
// You'll have to put subscribeOn() manually!

// Notice that RxJava is optional dependency for StorIO,
// So if you need it -> please add it manually.

You can find all releases on Maven Central.

####Some examples

#####Get list of objects from SQLiteDatabase

List<Tweet> tweets = storIOSQLite
  .get()
  .listOfObjects(Tweet.class) // Type safety
  .withQuery(Query.builder() // Query builder
    .table("tweets")
    .where("author = ?")
    .whereArgs("artem_zin") // Varargs Object..., no more new String[] {"I", "am", "tired", "of", "this", "shit"}
    .build()) // Query is immutable — you can save it and share without worries
  .prepare() // Operation builder
  .executeAsBlocking(); // Control flow is readable from top to bottom, just like with RxJava

#####Put something to SQLiteDatabase

storIOSQLite
  .put() // Insert or Update
  .objects(someTweets) // Type mapping!
  .prepare()
  .executeAsBlocking();

#####Delete something from SQLiteDatabase

storIOSQLite
  .delete()
  .byQuery(DeleteQuery.builder()
    .table("tweets")
    .where("timestamp <= ?")
    .whereArgs(System.currentTimeMillis() - 86400) // No need to write String.valueOf()
    .build())
  .prepare()
  .executeAsBlocking();

####Reactive? Observable.just(true)!

#####Get something as rx.Observable and receive updates!

storIOSQLite
  .get()
  .listOfObjects(Tweet.class)
  .withQuery(Query.builder()
    .table("tweets")
    .build())
  .prepare()
  .createObservable() // Get Result as rx.Observable and subscribe to further updates of tables from Query!
  .observeOn(mainThread()) // All Rx operations work on Schedulers.io()
  .subscribe(tweets -> { // Please don't forget to unsubscribe
  	  // Will be called with first result and then after each change of tables from Query
  	  // Several changes in transaction -> one notification
  	  adapter.setData(tweets);
  	}
  );

#####Want to work with plain Cursor, no problems

Cursor cursor = storIOSQLite
  .get()
  .cursor()
  .withQuery(Query.builder() // Or RawQuery
    .table("tweets")
    .where("who_cares = ?")
    .whereArgs("nobody")
    .build())
  .prepare()
  .executeAsBlocking();

####How object mapping works? #####You can set default type mappings when you build instance of StorIOSQLite or StorIOContentResolver

StorIOSQLite storIOSQLite = DefaultStorIOSQLite.builder()
  .sqliteOpenHelper(someSQLiteOpenHelper)
  .addTypeMapping(Tweet.class, SQLiteTypeMapping.<Tweet>builder()
    .putResolver(new TweetPutResolver()) // object that knows how to perform Put Operation (insert or update)
    .getResolver(new TweetGetResolver()) // object that knows how to perform Get Operation
    .deleteResolver(new TweetDeleteResolver())  // object that knows how to perform Delete Operation
    .build())
  .addTypeMapping(...)
  // other options
  .build(); // This instance of StorIOSQLite will know how to work with Tweet objects

You can override Operation Resolver per each individual Operation, it can be useful for working with SQL JOIN.

To save you from coding boilerplate classes we created Annotation Processor which will generate PutResolver, GetResolver and DeleteResolver at compile time, you just need to use generated classes

dependencies {
	// At the moment there is annotation processor only for StorIOSQLite 
	compile 'com.pushtorefresh.storio:sqlite-annotations:insert-latest-version-here'

	// We recommend to use Android Gradle Apt plugin: https://bitbucket.org/hvisser/android-apt
	apt 'com.pushtorefresh.storio:sqlite-annotations-processor:insert-latest-version-here'
}

@StorIOSQLiteType(table = "tweets")
public class Tweet {
	
	// annotated fields should have package-level visibility
	@StorIOSQLiteColumn(name = "author")
	String author;

	@StorIOSQLiteColumn(name = "content")
	String content;

    // please leave default constructor with package-level visibility
	Tweet() {}
}

Annotation Processor will generate three classes in same package as annotated class during compilation:

• TweetStorIOSQLitePutResolver
• TweetStorIOSQLiteGetResolver
• TweetStorIOSQLiteDeleteResolver

You just need to apply them:

StorIOSQLite storIOSQLite = DefaultStorIOSQLite.builder()
  .sqliteOpenHelper(someSQLiteOpenHelper)
  .addTypeMapping(Tweet.class, SQLiteTypeMapping.<Tweet>builder()
    .putResolver(new TweetStorIOSQLitePutResolver()) // object that knows how to perform Put Operation (insert or update)
    .getResolver(new TweetStorIOSQLiteGetResolver()) // object that knows how to perform Get Operation
    .deleteResolver(new TweetStorIOSQLiteDeleteResolver())  // object that knows how to perform Delete Operation
    .build())
  .addTypeMapping(...)
  // other options
  .build(); // This instance of StorIOSQLite will know how to work with Tweet objects

BTW: Here is a class with all types of fields, supported by StorIO SQLite Annotation Processor.

Few tips about Operation Resolvers:

• If your entities are immutable or they have builders or they use AutoValue/AutoParcel -> write your own Operation Resolvers
• If you want to write your own Operation Resolver -> take a look at Default Operation resolvers, they can fit your needs
• Via custom Operation Resolvers you can implement any Operation as you want -> store one object in multiple tables, use custom sql things and so on

API of StorIOContentResolver is same.

####Documentation:

• Why we made StorIO
• StorIO SQLite
• StorIO ContentResolver

Easy ways to learn how to use StorIO -> check out Design Tests and Sample App:

• Design tests for StorIO SQLite
• Design tests for StorIO ContentResolver
• Sample App

####Versioning: Because StorIO works with important things like User data and so on, we use Semantic Versioning 2.0.0 scheme for releases (http://semver.org).

Short example: 1.2.3 -> MAJOR.MINOR.PATCH

• MAJOR version changes when we make incompatible API changes.
• MINOR version changes when we add functionality in a backwards-compatible manner.
• PATCH version changes when we make backwards-compatible bug fixes.

Please read CHANGELOG and check what part of the version has changed, before switching to new version.

####Architecture: StorIOSQLite and StorIOContentResolver — are abstractions with default implementations: DefaultStorIOSQLite and DefaultStorIOContentResolver.

It means, that you can have your own implementation of StorIOSQLite and StorIOContentResolver with custom behavior, such as memory caching, verbose logging and so on or mock implementation for unit testing (we are working on MockStorIO).

One of the main goals of StorIO — clean API for Humans which will be easy to use and understand, that's why StorIOSQLite and StorIOContentResolver have just several methods, but we understand that sometimes you need to go under the hood and StorIO allows you to do it: StorIOSQLite.Internal and StorIOContentResolver.Internal encapsulates low-level methods, you can use them if you need, but please try to avoid it.

####Queries

All Query objects are immutable, you can share them safely.

####Concept of Prepared Operations You may notice that each Operation (Get, Put, Delete) should be prepared with prepare(). StorIO has an entity called PreparedOperation<T>, and you can use them to perform group execution of several Prepared Operations or provide PreparedOperation<T> as a return type of your API (for example in Model layer) and client will decide how to execute it: executeAsBlocking() or createObservable(). Also, Prepared Operations might be useful for ORMs based on StorIO.

You can customize behavior of every Operation via Resolvers: GetResolver, PutResolver, DeleteResolver.

####Rx Support Design Every Operation can be executed as rx.Observable. Get Operations will be automatically subscribed to the updates of the data. Every Observable runs on Schedulers.io() by default, currently we don't offer overloads to pass your Scheduler, feel free to send PRs!

Master branch build status:

Made with love in Pushtorefresh.com by @artem_zin and @nikitin-da