dao

问题 I need to execute several sql clauses, inserts, updates and delete for example. How to use a transaction in Access to bind them together? DAO is preferred. like: BeginTrans Excute SQL_1 Excute SQL_2 ..... CommitTrans Thanks! 回答1: If you use DAO, you can use the BeginTrans and CommitTrans methods of the global DBEngine object: Dim db As Database Set db = CurrentDb DBEngine.BeginTrans db.Execute SQL_1 db.Execute SQL_2 ... DBEngine.CommitTrans 回答2: Here is a more complete skeleton... Dim ws As

问题 Having studied Java at school I am quite familiar with the DAO-pattern(Data access object). However at work I use .NET. In .NET there is often talk about the DAL(Data Access Layer). To me their purpose seems quite similar. So the question is are DAO and DAL basically the same thing? Is the term DAL only made up so it wouldn't be mixed up with Data Access Objects? 回答1: The Data Access Layer (DAL) is the layer of a system that exists between the business logic layer and the persistence /

问题 I know that Hibernate implements ORM (Object Relational Mapping), what type of mapping does JDBC implement? Does it implement DAO? I don't totally understand how/if DAO is related to JDBC...? 回答1: DAO isn't a mapping. DAO stands for Data Access Object. It look something like this: public interface UserDAO { public User find(Long id) throws DAOException; public void save(User user) throws DAOException; public void delete(User user) throws DAOException; // ... } For DAO, JDBC is just an

问题 Closed . This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 2 years ago . As I mention in the title, I'm interested to know what you (as experienced developers) think about the use of the DAO pattern, specifically within a web application. What advantages have you found and what consequences of its use have you disliked? 回答1: The problems with DAOs

问题 I am trying to create a check constraint on an access (jet?) table. So, I open the .mdb file with access, go into queries->create query in design view, type esc, then menu->view->query and finally type create table X ( a number, check (a > 20) ) but access thinks that I have a "syntax error in field definition". However, I don't think so. Therefore my question: is it possible to create a check constraint with access. If so: how. Additionally, I'd like to create the constraint with dao/vba,

问题 Use annotation in dao @Repository("testDao") public class TestDaoImpl extends JdbcDaoSupport implements BaseDao{ @Override public Object addObject(String sqlid, Object obj) { // TODO Auto-generated method stub return null; } Caused by: java.lang.IllegalArgumentException: 'dataSource' or 'jdbcTemplate' is required I do not want to use ： <bean id="termsDao" class="com.manage.base.dao.impl.TestDaoImpl"> <property name="jdbcTemplate" ref="jdbcTemplate"/> </bean> this code set in xml， and

问题 Does anyone have a good example for how to do a findByExample in JPA that will work within a generic DAO via reflection for any entity type? I know I can do it via my provider (Hibernate), but I don't want to break with neutrality... Seems like the criteria API might be the way to go....but I am not sure how to handle the reflection part of it. 回答1: Actually, Query By Example (QBE) has been considered for inclusion in the JPA 2.0 specification but is not included, even if major vendors

问题 My problem is as follows. I need a class that works as a single point to a database connection in a web system, so to avoid having one user with two open connections. I need it to be as optimal as possible and it should manage every transaction in the system. In other words only that class should be able to instantiate DAOs. And to make it better, it should also use connection pooling! What should I do? 回答1: You will need to implement a DAO Manager . I took the main idea from this website,

问题 Before writing the question I read the following references: Factory Method Vs Abstract Factory Abstract Factory vs Factory Method (scope) Abstract Factory, Factory Method, Builder Factory, Abstract Factory and Factory Method Differences between Abstract Factory Pattern and Factory Method I see that many like me have had difficulty "grasping" the concrete differences between Abstract Factory and Factory Pattern. I'm not familiar with the design patterns, I came across this example http://www

问题 It is often useful to have a field in a DAO whose value comes from a Java enumeration. A typical example is a login DAO where you usually have a field that characterises the user as "NORMAL" or "ADMIN". In Hibernate, I would use the following 2 objects to represent this relationship in a (semi-)typesafe way: class User { String username; String passwd; UserType type; } class UserType { private enum Type {ADMIN, NORMAL}; private String type; //Setters/Getters for Hibernate public void setType