Realm JAVA 2.2.0

Build better apps, faster apps

Author: Doi Thanh Thinh

Savvycom JSC

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SQLite problems

• Queries too slow

• Complex

relationships

• Nest SELECT, JOIN

• Migration

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SQLite problems No-SQL SQLite

A

B

D

G

C

FE

Realm.getA().getC().getF();

SELECT user.name, user.email

FROM user

INNER JOIN shop ON user.id =

shop.userid INNER JOIN city ON

user.cityid = city.id WHERE user.name =

'the flash'

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1. What Realm Is

2. Compare and contrast with SQLite

3. Implement Realm

4. Example

Overview

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Realm is a mobile database and a replacement

for SQLite

Core is written in C++

Cross platform mobile database

What Realm Is

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Advantages

Faster than SQLite

Support in-memory database

Custom migrating

The Realm file can be stored encrypted on disk by standard AES-256

encryption

Missing Features

Auto-incrementing ids

Compoud primary keys

Features

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Prerequisites

• Do not support Java outside of Android at the moment

• Android Studio >= 1.5.1

• A recent version of the Android SDK

• JDK version >=7

• Support all Android versions since API Level 9 (Android

2.3 Gingerbread & above)

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Benchmarks

Faster than SQLite (up to 10x speed up over raw SQLite )

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Benchmarks

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Benchmarks

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Step 1: Add the following class path dependency to the project level

build.gradle file.

buildscript {

repositories {

jcenter()

}

dependencies {

classpath "io.realm:realm-gradle-plugin:2.2.0"

}

}

Step 2: Apply the realm-android plugin to the top of application level

build.gradle file. apply plugin: 'realm-android'

Installation

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Models: Realm model classes are created by extending the RealmObject base class.

public class User extends RealmObject {

private String name;

private int age;

@Ignore

private int sessionId;

// Standard getters & setters generated by your IDE…

public String getName() { return name; }

public void setName(String name) { this.name = name; }

public int getAge() { return age; }

public void setAge(int age) { this.age = age; }

public int getSessionId() { return sessionId; }

public void setSessionId(int sessionId) { this.sessionId = sessionId; }

}

Implement Realm

Custom methods:public boolean hasLongName() {

return name.length() > 7;}

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Field types:

Supports the following field types:

boolean, byte, short, int, long, float, double, String, Date and byte[].

The boxed types Boolean, Byte, Short, Integer, Long, Float and Double

@Required: used to tell Realm to enforce checks to disallow null values

@Ignore: a field should not be persisted to disk

@PrimaryKey : a primary key field

@Index will add a search index to the field

Implement Realm: Types fields

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Relationships

N – 1

public class Contact extendsRealmObject {

private Email email;

// Other fields…

}

N - N

public class Contact extendsRealmObject {

public RealmList<Email> emails;

// Other fields…

}

You can use this to model both one-to-many, and

many-to-many relationships.

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Conditions of Queries

between(), greaterThan(), lessThan(), greaterThanOrEqualTo() &

lessThanOrEqualTo()

equalTo() & notEqualTo()

contains(), beginsWith() & endsWith()

isNull() & isNotNull()

isEmpty() & isNotEmpty()

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RealmResults<User> r = realm.where(User.class)

.greaterThan("age", 10) //implicit AND

.beginGroup()

.equalTo("name", "Peter")

.or()

.contains("name", "Jo")

.endGroup()

.findAll();

Conditions of Queries

RealmResults<User> result = realm.where(User.class).findAll();

result = result.sort("age"); // Sort ascending

result = result.sort("age", Sort.DESCENDING);

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Insert

Realm myRealm = Realm.getInstance(this);

Person person2 = new Person();

person2.setId("U2");

person2.setName("John");

myRealm.beginTransaction();

// copy the object to realm. Any further changes must happen on realmPerson

Person realmPerson = myRealm.copyToRealm(person2);

myRealm.commitTransaction();

Dog dog1 = myRealm.createObject(Dog.class);

// Set its fields

dog1.setId("A");

dog1.setName("Fido");

dog1.setColor("Brown");

myRealm.commitTransaction(); 17Doi Thanh Thinh - Savvycom JSC

realm.executeTransaction(new Realm.Transaction() {

@Override

public void execute(Realm realm) {

Dog myDog = realm.createObject(Dog.class);

myDog.setName("Fido");

myDog.setAge(1);

}

});

Dog myDog = realm.where(Dog.class).equalTo("age", 1).findFirst();

realm.executeTransaction(new Realm.Transaction() {

@Override

public void execute(Realm realm) {

Dog myPuppy = realm.where(Dog.class).equalTo("age", 1).findFirst();

myPuppy.setAge(2);

}

});

myDog.getAge(); // => 2

Auto-Updating

Auto Update Realtime

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Example

public class Person extendsRealmObject {

private String id;

private String name;

private RealmList<Dog> dogs;

// getters and setters

}

public class Dog extends RealmObject {

private String id;

private String name;

private String color;

// getters and setters

}

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Example// persons => [U1,U2]RealmResults<Person> persons = realm.where(Person.class)

.equalTo("dogs.color", "Brown")

.findAll();

// r1 => [U1,U2]RealmResults<Person> r1 = realm.where(Person.class)

.equalTo("dogs.name", "Fluffy")

.equalTo("dogs.color", "Brown")

.findAll();

// r2 => [U2]RealmResults<Person> r2 = realm.where(Person.class)

.equalTo("dogs.name", "Fluffy")

.findAll()

.where()

.equalTo("dogs.color", "Brown")

.findAll();

.where()

.equalTo("dogs.color", "Yellow")

.findAll();20Doi Thanh Thinh - Savvycom JSC

Insert/Update

Asynchronous Transactions:realm.executeTransactionAsync(new Realm.Transaction() {

@Overridepublic void execute(Realm bgRealm) {

User user = bgRealm.createObject(User.class);user.setName("John");user.setEmail("john@corporation.com");

}}, new Realm.Transaction.OnSuccess() {

@Overridepublic void onSuccess() {

// Transaction was a success.}

}, new Realm.Transaction.OnError() {@Overridepublic void onError(Throwable error) {

// Transaction failed and was automatically canceled.}

});

Avoid blocking the UI thread

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Delete

// obtain the results of a queryfinal RealmResults<Dog> results = realm.where(Dog.class).findAll();

// All changes to data must happen in a transactionrealm.executeTransaction(new Realm.Transaction() {

@Overridepublic void execute(Realm realm) {

// remove single matchresults.deleteFirstFromRealm();results.deleteLastFromRealm();

// remove a single objectDog dog = results.get(5);dog.deleteFromRealm();

// Delete all matchesresults.deleteAllFromRealm();

}});

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JSON

• It is possible to add RealmObjects represented as JSON directly to Realm .

they are represented as a String, a JSONObject or an InputStream

• Single object is added through Realm.createObjectFromJson()

• lists of objects are added using Realm.createAllFromJson().

// A RealmObject that represents a citypublic class City extends RealmObject {

private String city;private int id;// getters and setters left out ...

}

// Insert from a stringrealm.executeTransaction(new Realm.Transaction() {

@Overridepublic void execute(Realm realm) {

realm.createObjectFromJson(City.class, "{ city: \"Copenhagen\", id: 1 }");}

});23Doi Thanh Thinh - Savvycom JSC

Demo

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Resources

Official Site for Realmhttps://realm.io/

Realm Full API for Javahttp://realm.io/docs/java/latest/api/

Realm Browser:https://github.com/realm/realm-cocoa/tree/master/tools/RealmBrowser

Github:https://github.com/thinhdt/DemoRealm

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