Developer guide: implementing a generic DAO interface

[qualidafial]

package com.app;

public interface CrudDao<T, ID> {
    @SqlUpdate
    @UseClasspathSqlLocator
    void insert(T entity);

    @SqlQuery
    @UseClasspathSqlLocator
    T getById(ID id);

    @SqlQuery
    @UseClasspathSqlLocator
    List<T> list();

    @SqlUpdate
    @UseClasspathSqlLocator
    void update(T entity);

    @SqlUpdate
    @UseClasspathSqlLocator
    void delete(ID id);
}

@RegisterBeanMapper(Contact.class)
public interface ContactDao extends CrudDao<Contact, Long> {}

@RegisterBeanMapper(Account.class)
public interface AccountDao extends CrudDao<Account, UUID> {}

In this example, SQL is loaded from files on the classpath, depending on the method called and which DAO subclass is used.

• com/app/ContactDao/insert.sql
• com/app/ContactDao/getById.sql
• com/app/ContactDao/list.sql
• com/app/ContactDao/update.sql
• com/app/ContactDao/delete.sql
• com/app/AccountDao/insert.sql
• com/app/AccountDao/getById.sql
• com/app/AccountDao/list.sql
• com/app/AccountDao/update.sql
• com/app/AccountDao/delete.sql

Note that @UseClasspathSqlLocator is repeated on every method instead of once on the CrudDao type. This is because right now, we only look for annotations on the SQL object type itself, and not supertypes (see #438). If a DAO subtype overrides a method from a supertype, we only look at the annotations present in the subtype.

In the future we may change this to look for annotations in the supertype, in which case we can update this example.

[qualidafial]

Tracked in #956