Client API. The Codename One framework your app is built on: this runs on the device, not in a backend.

public interface Dao<T>

Runtime contract a build-time-generated @Entity data access object implements. Application code rarely references Dao by name – the typed dao is reached through EntityManager.dao(EntityClass.class).

All methods throw IOException for the same reasons com.codename1.db does: the underlying SQLite driver propagates IO failures, locking failures, and constraint violations through IOException.

Methods

public abstract Class<T> type()The entity class this dao handles.
public abstract String tableName()The SQL table name.
public abstract void attach(Database db)Connects this dao to a Database instance.
public abstract void createTable() throws IOExceptionCREATE TABLE IF NOT EXISTS ....
public abstract void dropTable() throws IOExceptionDROP TABLE IF EXISTS ....
public abstract void insert(T entity) throws IOExceptionINSERT INTO ....
public abstract T save(T entity) throws IOExceptionStores entity and answers the instance that holds what the database decided: inserted when its auto-increment key is still unassigned or no row has its key, updated otherwise.
public abstract void update(T entity) throws IOExceptionUPDATE ... WHERE id = ?.
public abstract void delete(T entity) throws IOExceptionDELETE ... WHERE id = ?.
public abstract T findById(Object id) throws IOExceptionSELECT ... WHERE id = ?.
public abstract List<T> findAll() throws IOExceptionSELECT * FROM ....
public abstract List<T> find(String where, Object... params) throws IOExceptionFree-form WHERE clause; where is appended verbatim after WHERE and params fills the ? placeholders.

Method details

type

public abstract Class<T> type()
The entity class this dao handles.

tableName

public abstract String tableName()
The SQL table name. Defaults to the simple class name; an explicit @Entity(table="...") wins.

attach

public abstract void attach(Database db)
Connects this dao to a Database instance. Called by EntityManager.dao(Class); the same dao is reused for the lifetime of the entity manager.

createTable

public abstract void createTable() throws IOException
CREATE TABLE IF NOT EXISTS .... Idempotent.

Throws

IOException

dropTable

public abstract void dropTable() throws IOException
DROP TABLE IF EXISTS ....

Throws

IOException

insert

public abstract void insert(T entity) throws IOException
INSERT INTO .... When the entity has an auto-increment @Id, the generated id is written back into the instance via SELECT last_insert_rowid().

Throws

IOException

save

public abstract T save(T entity) throws IOException

Stores entity and answers the instance that holds what the database decided: inserted when its auto-increment key is still unassigned or no row has its key, updated otherwise.

For an ordinary entity the answer is entity itself. A record cannot have its generated key written into it, so for one the answer is a copy that carries the key – the instance to keep.

Throws

IOException

update

public abstract void update(T entity) throws IOException
UPDATE ... WHERE id = ?.

Throws

IOException

delete

public abstract void delete(T entity) throws IOException
DELETE ... WHERE id = ?.

Throws

IOException

findById

public abstract T findById(Object id) throws IOException
SELECT ... WHERE id = ?. Returns null when no row matches.

Throws

IOException

findAll

public abstract List<T> findAll() throws IOException
SELECT * FROM .... Returns every row mapped to an instance of the entity class.

Throws

IOException

find

public abstract List<T> find(String where, Object... params) throws IOException

Free-form WHERE clause; where is appended verbatim after WHERE and params fills the ? placeholders.

users.find("age > ? AND city = ?", 18, "Berlin");

Throws

IOException