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() throwsIOException`	`CREATE TABLE IF NOT EXISTS ...`.
`public abstract void dropTable() throwsIOException`	`DROP TABLE IF EXISTS ...`.
`public abstract void insert(T entity) throwsIOException`	`INSERT INTO ...`.
`public abstract void update(T entity) throwsIOException`	`UPDATE ... WHERE id = ?`.
`public abstract void delete(T entity) throwsIOException`	`DELETE ... WHERE id = ?`.
`public abstract T findById(Object id) throws IOException`	`SELECT ... WHERE id = ?`.
`public abstract` `List<T> findAll() throws IOException`	`SELECT * FROM ...`.
`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.

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

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