This document discusses how to use GreenDAO, an ORM library for Android, to generate code for database operations. It explains how to create a database schema, generate DAO files, perform CRUD operations like insert, query, and join data from multiple tables. GreenDAO allows mapping Java objects to database tables, provides an API to write queries using query builders, and handles database operations asynchronously on background threads.

1. GreenDAO

2. Code Generation

3. Code Generation

4. Generator Project
1. Create java module
2. Add gradle script
3. Create DB Schema
4. Compile and run

7. Create DB Schema
public static void main(String[] args){
// DB版本號 , 目標 package name
Schema schema = new Schema(1, "com.yanbin.clustering.dao");
createTable(schema);
generateDaoFiles(schema);
}

8. Create Table
private static void createTable(Schema schema){
//一個Entity 對應一個 DB table
Entity point = schema.addEntity("Point");
//add table column
point.addIdProperty();
point.addDoubleProperty("xPos").notNull();
point.addDoubleProperty("yPos").notNull();
}

9. Available Types
1. Boolean
2. Byte
3. Short, Long, Int, Float, Double
4. ByteArray
5. String
6. Date

10. Date Format in GreenDAO
● Not “YYYY-MM-DD HH:MM:SS.SSS”
● Actually It is INTEGER as Unix Time
● Compare greenDAO date with date.
getTime();

11. Generate DAO Files
private static void generateDaoFiles(Schema schema){
try {
DaoGenerator generator = new DaoGenerator();
//建立到指定目錄
generator.generateAll(schema, "../Clustering/app/src/main/java");
} catch (Exception e){
e.printStackTrace();
}
}

13. Android Project

14. Gradle
● build.gradle
dependencies {
...
compile 'de.greenrobot:greendao:1.3.7'
...
}

15. Core classes

16. Get DAO Session
private static final String DB_NAME = "clustering.db";
private DaoSession daoSession;
private DBHelper(Context context) {
DaoMaster.DevOpenHelper helper = new DaoMaster.DevOpenHelper(context, DB_NAME, null);
DaoMaster daoMaster = new DaoMaster(helper.getWritableDatabase());
daoSession = daoMaster.newSession();
}

17. Insert
public class DBHelper {
public PointDao getNoteDao(){
return daoSession.getPointDao();
}
}
-----------------------------------------------------------------------------------------------------------------------------
PointDao pointDao = DBHelper.getInstance(this).getNoteDao();
...
//run on background thread
pointDao.insert(new Point(null, x, y));

18. Insert at Background
1. For not block MainThread
2. Data consistency

19. Insert at Background
1. For not block MainThread
2. Data consistency

20. Insert at Background
1. For not block MainThread
2. Data consistency
GreenDAO will handle this
https://github.
com/greenrobot/greenDAO/blob/master/DaoCore/src/de/greenrobot/dao/Abstra
ctDao.java
line 258

21. Insert at Background
1. For not block MainThread

22. Insert at Background
1. For not block MainThread

23. AsyncSession
public class DBHelper {
private AsyncSession asyncSession;
...
private DBHelper(Context context) {
...
asyncSession = daoSession.startAsyncSession();
}
...
public AsyncSession getAsyncSession(){
return asyncSession;
}
}

24. Async Insert
AsyncSession asyncSession = DBHelper.getInstance(this).getAsyncSession();
asyncSession.insert(new Point(null, x, y));

25. Load By Id, Load All
PointDao pointDao = DBHelper.getInstance(this).getPointDao();
Point point = pointDao.load(pid);
---------------------------------------------------------------------------------------------------
List<Point> points = pointDao.loadAll();

26. Query
public List<Point> getNegXPoints(){
QueryBuilder<Point> queryBuilder = getPointDao().queryBuilder();
queryBuilder.where(PointDao.Properties.XPos.lt(0))
return queryBuilder.list();
}

27. Query
public List<Point> getPosXPoints(){
QueryBuilder<Point> queryBuilder = getPointDao().queryBuilder();
queryBuilder.where(PointDao.Properties.XPos.ge(0))
return queryBuilder.list();
}

28. Query
public List<Point> getNegPoints(){
QueryBuilder<Point> queryBuilder = getPointDao().queryBuilder();
queryBuilder.where(
queryBuilder.and(PointDao.Properties.XPos.lt(0), PointDao.Properties.YPos.lt
(0)))
.orderAsc(PointDao.Properties.XPos);
return queryBuilder.list();
}

29. QueryBuilder
/**
* Adds the given conditions to the where clause using an logical AND. To create new conditions, use the properties
* given in the generated dao classes.
*/
public QueryBuilder<T> where(WhereCondition cond, WhereCondition... condMore) {
whereCollector.add(cond, condMore);
return this;
}

30. QueryBuilder
/**
* Adds the given conditions to the where clause using an logical AND. To create new conditions, use the properties
* given in the generated dao classes.
*/
public QueryBuilder<T> where(WhereCondition cond, WhereCondition... condMore) {
whereCollector.add(cond, condMore);
return this;
}

31. Let’s Look Closer...

32. WhereCollector
void appendWhereClause(StringBuilder builder, String tablePrefixOrNull, List<Object>
values) {
ListIterator<WhereCondition> iter = whereConditions.listIterator();
while (iter.hasNext()) {
if (iter.hasPrevious()) {
builder.append(" AND ");
}
WhereCondition condition = iter.next();
condition.appendTo(builder, tablePrefixOrNull);
condition.appendValuesTo(values);
}
}
https://github.com/greenrobot/greenDAO/blob/master/DaoCore/src/de/greenrobot/dao/query/WhereCollector.java

33. WhereCollector
void appendWhereClause(StringBuilder builder, String tablePrefixOrNull, List<Object>
values) {
ListIterator<WhereCondition> iter = whereConditions.listIterator();
while (iter.hasNext()) {
if (iter.hasPrevious()) {
builder.append(" AND ");
}
WhereCondition condition = iter.next();
condition.appendTo(builder, tablePrefixOrNull);
condition.appendValuesTo(values);
}
}
https://github.com/greenrobot/greenDAO/blob/master/DaoCore/src/de/greenrobot/dao/query/WhereCollector.java

34. Query
public List<Point> getNegPoints(){
QueryBuilder<Point> queryBuilder = getPointDao().queryBuilder();
queryBuilder.where(
queryBuilder.and(PointDao.Properties.XPos.lt(0), PointDao.Properties.YPos.lt
(0)))
.orderAsc(PointDao.Properties.XPos);
return queryBuilder.list();
}

35. Query
public List<Point> getNegPoints(){
QueryBuilder<Point> queryBuilder = getPointDao().queryBuilder();
queryBuilder.where(PointDao.Properties.XPos.lt(0), PointDao.Properties.YPos.lt(0))
.orderAsc(PointDao.Properties.XPos);
return queryBuilder.list();
}

36. Query
public List<Point> getNegPoints(){
QueryBuilder<Point> queryBuilder = getPointDao().queryBuilder();
queryBuilder.where(PointDao.Properties.XPos.lt(0), PointDao.Properties.YPos.lt(0))
.orderAsc(PointDao.Properties.XPos);
return queryBuilder.list();
}

37. List
● List
● LazyList

38. LazyList
LazyList list = queryBuilder.listLazy();
Item item = list.next();
…
list.close();

39. LazyList
LazyList list = queryBuilder.listLazy();
Item item = list.next();
…
list.close();
Must be closed

40. Why?
public class LazyList<E> implements List<E>, Closeable {
private final Cursor cursor;
…
public void close() {
cursor.close();
}
}

41. Raw query
SQLiteDatabase db = daoSession.getDatabase();
Cursor cursor = db.rawQuery("SELECT SUM(x_pos) FROM point WHERE .....", null);

42. Others
● Joins
http://greendao-orm.com/documentation/joins/
● Relations
http://greendao-orm.com/documentation/relations/

43. References
gitbook :
http://bng86.gitbooks.io/android-third-party-/content/greendao.html