Realm Java 2.2.0: Build better apps, faster apps

Realm JAVA 2.2.0
Build better apps, faster apps
Author: Doi Thanh Thinh
Savvycom JSC
1Doi Thanh Thinh - Savvycom JSC

SQLite problems
• Queries too slow
• Complex
relationships
• Nest SELECT, JOIN
• Migration

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'

1. What Realm Is
2. Compare and contrast with SQLite
3. Implement Realm
4. Example
Overview

 Realm is a mobile database and a replacement
for SQLite
 Core is written in C++
 Cross platform mobile database
What Realm Is

 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

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)

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

Benchmarks

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

 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;
}

 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

Relationships
N – 1
public class Contact extends
RealmObject {
private Email email;
// Other fields…
}
N - N
public class Contact extends
RealmObject {
public RealmList<Email> emails;
// Other fields…
}
You can use this to model
both one-to-many, and
many-to-many
relationships.

Conditions of Queries
 between(), greaterThan(), lessThan(), greaterThanOrEqualTo() &
lessThanOrEqualTo()
 equalTo() & notEqualTo()
 contains(), beginsWith() & endsWith()
 isNull() & isNotNull()
 isEmpty() & isNotEmpty()

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);

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();
@Override
Dog myPuppy = realm.where(Dog.class).equalTo("age", 1).findFirst();
myPuppy.setAge(2);
}
});
myDog.getAge(); // => 2
Auto-Updating
Auto Update Realtime

Example
public class Person extends
RealmObject {
private String id;
private RealmList<Dog> dogs;
// getters and setters
}
public class Dog extends RealmObject {
private String id;
private String color;
// getters and setters
}

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")
.findAll();
// r2 => [U2]
RealmResults<Person> r2 = realm.where(Person.class)
.equalTo("dogs.name", "Fluffy")
.findAll()
.where()
.findAll();
.where()
.equalTo("dogs.color", "Yellow")
.findAll();

Insert/Update
Asynchronous Transactions:
realm.executeTransactionAsync(new Realm.Transaction() {
@Override
public void execute(Realm bgRealm) {
User user = bgRealm.createObject(User.class);
user.setName("John");
user.setEmail("john@corporation.com");
}
}, new Realm.Transaction.OnSuccess() {
@Override
public void onSuccess() {
// Transaction was a success.
}
}, new Realm.Transaction.OnError() {
@Override
public void onError(Throwable error) {
// Transaction failed and was automatically canceled.
}
});
Avoid blocking the UI thread

Delete
// obtain the results of a query
final RealmResults<Dog> results = realm.where(Dog.class).findAll();
// All changes to data must happen in a transaction
@Override
// remove single match
results.deleteFirstFromRealm();
results.deleteLastFromRealm();
// remove a single object
Dog dog = results.get(5);
dog.deleteFromRealm();
// Delete all matches
results.deleteAllFromRealm();
}
});

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 city
public class City extends RealmObject {
private String city;
private int id;
// getters and setters left out ...
}
// Insert from a string
@Override
realm.createObjectFromJson(City.class, "{ city: "Copenhagen", id: 1 }");
}
}); 23Doi Thanh Thinh - Savvycom JSC

Demo

Resources
Official Site for Realm
https://realm.io/
Realm Full API for Java
http://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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