Data Access Object (Dao) Pattern Pattern Inward Coffee - Tutorial Example

Data Access Object or DAO pattern pattern is a pop pattern pattern to implement persistence layer of Java application. DAO pattern is based on abstraction together with encapsulation pattern principles together with shields residue of application from whatever alter inwards the persistence layer e.g. alter of database from Oracle to MySQL, alter of persistence engineering scientific discipline e.g. from File System to Database. For example, if yous are authenticating the user using a relational database together with after your companionship wants to role LDAP to perform authentication. If yous are using DAO pattern pattern to access database, it would last relatively prophylactic equally yous solely postulate to brand a alter on Data Access Layer. DAO pattern pattern likewise keeps coupling depression betwixt dissimilar parts of an application. By using DAO pattern pattern your View Layer is completely independent of DAO layer together with solely Service layer has the dependency on it which is likewise abstracted yesteryear using DAO interface.

Btw, DAO or Data Access Object Pattern is non a GOF pattern pattern equally prescribed yesteryear Gang of Four on the classic book, Design Patterns: Elements of Reusable Object-Oriented Software.  It's non 1 of the object oriented pattern pattern only something which arises from the role of Encapsulation. By keeping information access code together, away from concern logic thence that it tin last developed, optimized together with alter without impacting other layers of application e.g. Model together with View layer.

You tin farther use Generics to template your DAO layer. If yous are using Spring thence yous tin leverage JdbcTemplate for performing JDBC calls which relieve a lot of boilerplate coding. Using DAO pattern to access database is 1 of the JDBC best practices to follow.

What is Data Access Object (DAO) pattern inwards Java

In brusk Data Access Object or DAO pattern pattern is a way to trim down coupling betwixt Business logic together with Persistence logic. Application concern logic ofttimes needs domain objects which are persisted inwards either Database, File System or whatever other persistence storage. DAO pattern allows yous to encapsulate code for performing CRUD functioning against persistence from residue of application. Which way whatever alter on persistence logic volition non acquit upon other layers of application which are already tested. DAO pattern enables an application to attain out alongside whatever alter inwards database provider or persistence technology.

In adjacent section, nosotros volition What are the principal benefits of using DAO pattern pattern inwards Java application. If yous are a J2EE developer, yous should read Real World Java EE patterns together with best practices, 1 of the best books to acquire Java EE patterns for experienced Java JEE programmers.

Benefits of using DAO pattern pattern

DAO or Data Access Object pattern pattern is a expert representative of abstraction together with encapsulation object oriented principles. It separates persistence logic is a split layer called Data access layer which enables application to react safely to alter inwards Persistence mechanism. For example, if yous shift from File-based persistence machinery to Database, your alter volition last express to information access layer together with won't impact Service layer or domain Objects. Data Access Object or DAO pattern is pretty much criterion inwards Java application beingness it nitty-gritty Java, spider web application or company application. Following are distich of to a greater extent than benefits of using DAO pattern inwards Java application:

1) DAO pattern pattern allows JUnit test to run faster equally it allows to attain Mock together with avoid connecting to database to run tests. It improves testing because it's tardily to write seek out alongside Mock objects, rather than an Integration seek out alongside the database. In the instance of whatever issue, spell running Unit test, yous solely postulate to cheque code together with non database. Also shields alongside database connectivity together with surround issues.

2) Since DAO pattern is based on interface, it likewise promotes Object oriented pattern regulation "programming for interface than implementation" which results inwards flexible together with character code.

How to role DAO Pattern inwards Java JEE Application

Here is a dainty diagram how to implement Data Access Pattern inwards a Java together with J2EE application. You tin encounter that your DAO classes e.g. AddressDAO, PersonDAO, together with CompanyDAO are accessing database together with populating information into a Contact object.

Influenza A virus subtype H5N1 Client Service is non withdraw accessing these classes instead it is accessing it via a ContactDAO interface together with object are created using ContactDAOFactory degree which returns the DAO implementation based on the database vendor e.g. hither it is returning classes which tin interact alongside HSQL DB. You tin render classes which tin interact alongside Oracle, SQL Server or MySQL database equally well.

DAO pattern pattern Example

In the nitty-gritty of Data Access Object or DAO pattern is a Java interface, which defines a diverse method to perform CRUD functioning e.g. Create, Read, Update, together with Delete. Based on your application back-end engineering scientific discipline yous tin attain dissimilar implementation of this interface e.g. JdbcDAOImpl to connect database using JDBC, HibernateDAOImple to role hibernate or FileDAOImpl if yous are using the File organization for persistence. Service layer which uses this Data Access Object volition role interface to interact alongside Data access layer. Here is how a typical DAO Interface looks like:

public interface AccountDAO{
   public boolean save(Account account);
   public boolean update(Account account);
   public boolean findByAccountNumber(int accountNumber);
   public boolean delete(Account account);

}

it defines diverse methods to perform CRUD operation. Now yous tin attain dissimilar implementation of this AccountDAO interface e.g. JdbcAccountDAOImpl or HibernateAccountDAOImpl. Your JdbcAccountDAOImpl volition role JDBC API or Spring JdbcTemplate along alongside SQL Queries to perform CRUD operations.

That's all on what is Data Access Object or DAO pattern inwards Java together with what are benefits of using DAO pattern inwards Java application. We bring likewise seen a elementary representative of How to implement Data Access Object pattern alongside AccountDAO interface. It's criterion together with 1 of the criterion JDBC practices to role DAO pattern to attain the persistent layer inwards Java application.

Further Learning
What is Decorator pattern pattern inwards Java alongside Example

What is Observer pattern pattern alongside example

When to role Factory pattern pattern inwards Java

How to implement thread-safe Singleton inwards Java

20 pattern pattern interview questions inwards Java - Answered