1. greenDAO
Kewang

2. Agenda
● SQL syntax
● SQLite @ Android
● ORM
● greenDAO

3. SQL syntax

4. SELECT
● SELECT Persons.LastName, Persons.FirstName,
Orders.OrderNo FROM Persons INNER JOIN
Orders ON Persons.P_Id=Orders.P_Id ORDER BY
Persons.LastName
● SELECT * FROM Persons WHERE LastName
BETWEEN 'Hansen' AND 'Pettersen'
● SELECT Customer,OrderDate,SUM(OrderPrice)
FROM Orders GROUP BY Customer,OrderDate

5. INSERT
● INSERT INTO Persons (P_Id, LastName, FirstName)
VALUES (5, 'Tjessem', 'Jakob')
● INSERT INTO Persons VALUES (4,'Nilsen', 'Johan',
'Bakken 2', 'Stavanger')

6. UPDATE
● UPDATE Persons SET Address='Nissestien 67',
City='Sandnes' WHERE LastName='Tjessem' AND
FirstName='Jakob'
● UPDATE Persons SET Address='Nissestien 67',
City='Sandnes'

7. DELETE
● DELETE FROM Persons WHERE
LastName='Tjessem' AND FirstName='Jakob'

8. SQLite @ Android

9. 4 components
● SQLiteOpenHelper
● SQLiteDatabase
● SQLiteQueryBuilder
● Cursor

10. SQLiteOpenHelper
A helper class to manage database
creation and version management.

11. SQLiteDatabase + SQLiteQueryBuilder
delete * 1
append * 3
insert * 3
replace(update) * 4
open * 5
query * 15

12. Oh my god, I'm a professional DBA!!!

13. Never mind, we have......
execSQL * 2
db.execSQL("CREATE TABLE IF NOT EXISTS person (personid integer primary
key autoincrement, name varchar(20), age INTEGER)");

14. and
rawQuery * 4
db.rawQuery("select count(*) from person", null);

15. Cursor
Recordsets returned by a query

16. Cursor
getDataType * 16
movePosition * 6
isXXX * 6

17. Sample code - Controller
datasource = new CommentsDataSource(this);
datasource.open();
List<Comment> values = datasource.getAllComments();
ArrayAdapter<Comment> adapter = new
ArrayAdapter<Comment>(this,
android.R.layout.simple_list_item_1, values);
open

18. Sample code - Controller
String[] comments = new String[] { "Cool", "Very nice",
"Hate it" };
int nextInt = new Random().nextInt(3);
comment = datasource.createComment(comments[nextInt]);
adapter.add(comment);
insert

19. Sample code - Controller
if (getListAdapter().getCount() > 0) {
comment = (Comment) getListAdapter().getItem(0);
datasource.deleteComment(comment);
adapter.remove(comment);
}
delete

20. Sample code - Model
@Override
public void onCreate(SQLiteDatabase database) {
database.execSQL("create table " + TABLE_COMMENTS +
"(" + COLUMN_ID + " integer primary key autoincrement, "
+ COLUMN_COMMENT + " text not null);");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion,
int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_COMMENTS);
onCreate(db);
}

21. Sample code - Model
public Comment createComment(String comment) {
ContentValues values = new ContentValues();
values.put("comment", comment);
long id = database.insert("comments", null, values);
Cursor cursor = database.query("comments", allColumns,
"_id" + " = " + id, null, null, null, null);
cursor.moveToFirst();
cursor.close();
return cursorToComment(cursor);
}

22. Sample code - Model
public void deleteComment(Comment comment) {
long id = comment.getId();
database.delete("comments", "_id" + " = " + id, null);
}

23. Sample code - Model
private Comment cursorToComment(Cursor cursor) {
Comment comment = new Comment();
comment.setId(cursor.getLong(0));
comment.setComment(cursor.getString(1));
return comment;
}

24. Sample code - Model
public List<Comment> getAllComments() {
List<Comment> comments = new ArrayList<Comment>();
Cursor cursor = database.query("comments", allColumns,
null, null, null, null, null);
cursor.moveToFirst();
while (!cursor.isAfterLast()) {
comments.add(cursorToComment(cursor));
cursor.moveToNext();
}
cursor.close();
return comments;
}

25. No better choice ?

26. ORM
Object-relational mapping

28. Record maps to Java Object

29. Rails sample

30. We use SQLite @ Android
OrmLite
greenDAO

31. greenDAO

32. Architecture

33. Structure

34. How to use...
private void initDatabase() {
helper = new DaoMaster.DevOpenHelper(this, NAME, null);
master = new DaoMaster(helper.getWritableDatabase());
session = master.newSession();
cityDao = session.getCityDao();
townDao = session.getTownDao();
storeDao = session.getStoreDao();
}

35. How to use...
cityDao.insert(new City(1L, "台北市"));
storeDao._queryTown_Stores(townId).isEmpty()
town =
townDao.queryBuilder().where(TownDao.Properties.Name.eq(
"新莊區"), TownDao.Properties.CityId.eq(5)).unique();

36. At first, generate code to use it.
public static void main(String[] args) {
schema = new Schema(4, "tw.kewang.smile319.model");
addCity();
addTown();
addStore();
new DaoGenerator().generateAll(schema, "../Prj/src-gen");
}

37. At first, generate code to use it.
private static void addTown() {
Entity town = schema.addEntity("Town");
town.addIdProperty().columnName("id");
town.addStringProperty("name").notNull();
town.addDoubleProperty("latitude");
town.addDoubleProperty("longitude");
Property cityId =
town.addLongProperty("cityId").notNull().getProperty();
ToMany cityToTowns = city.addToMany(town, cityId);
cityToTowns.setName("towns");
}

38. What is generator ?

39. Generator contains...
● A schema at least
● A schema has many entities (models)
● A entity has many property (data type, not null,
autoincrement, index......etc.)
● 2 entities have a relationship (optional)
● Project has a leader
● Leader belongs to a project

40. QueryBuilder
● whereXXX
● joinXXX
● orderXXX
● listXXX
● uniqueXXX
● or, and
● limit, offset, count

41. FAQ

42. 1. Why use generator ?

43. Typically, annotation & reflection
BUT
1.can't compiler check
2.reflection is very slow @ Android

44. 2. Why use greenDAO ?

45. Speed up !
1.generator instead of reflection
2.refine SQLiteCursor
3.custom LongHashMap @ LUT

46. 3. What about OrmLite ?

48. References
● http://greendao-orm.com/
● https://github.com/greenrobot/greenDAO
● http://www.slideshare.net/droidcon/green-dao

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