Green dao

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

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);
}

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();
}

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

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();

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();
}
}

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

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();
}

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));

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

2. Data consistency
GreenDAO will handle this
https://github.
com/greenrobot/greenDAO/blob/master/DaoCore/src/de/greenrobot/dao/Abstra
ctDao.java
line 258

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

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

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

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

Query
public List<Point> getPosXPoints(){
queryBuilder.where(PointDao.Properties.XPos.ge(0))
}

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

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;
}

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

Query
public List<Point> getNegPoints(){
queryBuilder.where(PointDao.Properties.XPos.lt(0), PointDao.Properties.YPos.lt(0))
.orderAsc(PointDao.Properties.XPos);
}

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

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

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

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

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

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

Green dao

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