dao

I have a table with 11 columns, but I need to get only 2 of them in my application, I'm using spring/hibernate/DAO combination. For now I have a domain class which includes all 11 fields, and mapping file which maps all 11 columns in table. How do I use get just 2 of them not all? Either: Use projections - Pro: nothing to add - Con: Not typesafe (the result is a List of rows where each row is an Object[]) : select f.foo, f.bar from FatEntity f Use a constructor expression in the SELECT clause (the specified class is not required to be an entity or to be mapped to the database) - Pro: typesafe

I have a DAO class with many methods that have a lot of repeated code along the lines of: - public void method1(...) { Connection conn = null; try { //custom code here } catch (SQLException e) { LOG.error("Error accessing the database.", e); throw new DatabaseException(); } catch (QueryNotFoundException e) { LOG.error("Error accessing the database.", e); throw new DatabaseException(); } finally { if (conn != null) connectionPool.returnConnection(conn); } public void method2(...) { Connection conn = null; try { //different custom code here } catch (SQLException e) { LOG.error("Error accessing

I've JPA entities and need to perform logic with them. Until now a huge static database class did the job. It's ugly because every public interface method had an private equivalent that used the EntityManager, to perform transactions. But I could solve that having a static em too! However i'm wondering if that's an appropriate design, especially as the class is responsible for many things. Not surprisingly, the code i found online of real projects was not easy to understand (i might then as well remeain with my code). The code here is easy to understand, although maybe over generic? Anyway, on

I am using Room architecture component for persistence. I have created generic DAO interface to avoid boilerplate code. Room Pro Tips But my code doesn't compile saying "Error:(21, 19) error: Type of the parameter must be a class annotated with @Entity or a collection/array of it." for the Generic class T. interface BaseDao<T> { @Insert(onConflict = OnConflictStrategy.REPLACE) void insert(T... entity); @Update void update(T entity); @Delete void delete(T entity); } @Dao public abstract class ReasonDao implements BaseDao<ReasonDao> { @Query("SELECT * from Reason") abstract public List<Reason>

Is there a difference between the DAO pattern and the Data Mapper pattern? Is DAO just one of doing Data Mapper? I wouldn't actually call DAO a "pattern". As I see it, DAO is pretty much what it is -- a Data Access Object", which encapsulates the details of accessing a persistent data store and generally speaking has nothing to do with the database: interface IBlogDaoService { Blog GetBlog(long id); void SaveBlog(Blog blog); } It's clear that implementations can use either DB (in which case it's quite logical to use a Data Mapper), or simple XML file storage mechanism. The Data Mapper on the