Data access object (DAO) in Java

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I was going through a document and I came across a term called DAO. I found out that it is a Data Access Object. Can someone please explain me what this actually is?

I know that it is some kind of an interface for accessing data from different types of sources, in the middle of this little research of mine I bumped into a concept called data source or data source object, and things got messed up in my mind.

I really want to know what a DAO is programmatically in terms of where it is used. How it is used? Any links to pages that explain this concept from the very basic stuff is also appreciated.

The Data Access Object is basically an object or an interface that provides access to an underlying database or any other persistence storage.

That definition from: http://en.wikipedia.org/wiki/Data_access_object

Check also the sequence diagram here: http://www.oracle.com/technetwork/java/dataaccessobject-138824.html

Maybe a simple example can help you understand the concept:

Let's say we have an entity to represent an employee:

public class Employee {

    private int id;
    private String name;


    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

}

The employee entities will be persisted into a corresponding Employee table in a database. A simple DAO interface to handle the database operation required to manipulate an employee entity will be like:

interface EmployeeDAO {

    List<Employee> findAll();
    List<Employee> findById();
    List<Employee> findByName();
    boolean insertEmployee(Employee employee);
    boolean updateEmployee(Employee employee);
    boolean deleteEmployee(Employee employee);

}

Next we have to provide a concrete implementation for that interface to deal with SQL server, and another to deal with flat files, etc.

Data Access Object Pattern, Data Access Object Pattern or DAO pattern is used to separate low level data accessing API or operations from high level business services. StudentDaoImpl is concrete class implementing Data Access Object Interface. Student.java Step 1 : Create Customer domain model java class. Step 2: In an application, the Data Access Object (DAO) is a part of Data access layer. Step 3 : An implementation of CustomerDao interface that persists customers in RDBMS . Step 4 : Customer Schema SQL Class. Step 5 : Let's create some user

Data access object (DAO) in Java, The Data Access Object is basically an object or an interface that provides access to an underlying database or any other persistence storage. The Data Access Object (DAO) pattern is a structural pattern that allows us to isolate the application/business layer from the persistence layer (usually a relational database, but it could be any other persistence mechanism) using an abstract API.

DAO (Data Access Object) is a very used design pattern in enterprise applications. It basically is the module that is used to access data from every source (DBMS, XML and so on). I suggest you to read some examples, like this one:

DAO Example

Please note that there are different ways to implements the original DAO Pattern, and there are many frameworks that can simplify your work. For example, the ORM (Object Relational Mapping) frameworks like iBatis or Hibernate, are used to map the result of SQL queries to java objects.

Hope it helps, Bye!

Data access object, of abstraction and encapsulation object oriented principles. It separates persistence logic is a separate layer called Data access layer which enables application to react safely to change in Persistence mechanism. The data access object in a computer software which is as an object which is responsible for providing abstract interface for communication to a specific form of database. Through the method of mapping, the app is able to call the persistence layer and the DAO then provides a certain type of data operations.

Data Access Object Pattern or DAO pattern is used to separate low level data accessing API or operations from high level business services. Following are the participants in Data Access Object Pattern.

Data Access Object Interface - This interface defines the standard operations to be performed on a model object(s).

Data Access Object concrete class -This class implements above interface. This class is responsible to get data from a datasource which can be database / xml or any other storage mechanism.

Model Object or Value Object - This object is simple POJO containing get/set methods to store data retrieved using DAO class.

Sample code here..

Data Access Object (DAO) design pattern in Java , : it abstracts the retrieval of data from a data resource such as a database. The concept is to "separate a data resource's client interface from its data access mechanism." I was going through a document and I came across a term called DAO. I found out that it is a Data Access Object. Can someone please explain me what this actually is?

I think the best example (along with explanations) you can find on the oracle website : here. Another good tuturial could be found here.

DAO Design Pattern, Data Access Object or DAO design pattern is a popular design pattern to implement persistence layer of Java application. DAO pattern is based on abstraction  The Data Access object is the primary object of this design pattern. This object abstract the data access implementations for the other object to enable transparently access to the database. An example given below which illustrates the Data Access Design Pattern.

Core J2EE Patterns - Data Access Object, Many real-world Java 2 Platform, Enterprise Edition (J2EE) applications need to Use a Data Access Object (DAO) to abstract and encapsulate all access to the​  Data Access Object Pattern or DAO pattern is used to separate low level data accessing API or operations from high level business services. Following are the participants in Data Access Object Pattern. Data Access Object Interface - This interface defines the standard operations to be performed on a model object(s).

Data Access Object Pattern, Data Access Object Pattern or DAO pattern is used to separate low level data Java object in addition to a servlet or helper bean that accesses the data source. Use a Data Access Object (DAO) to abstract and encapsulate all access to the data source. The DAO manages the connection with the data source to obtain and store data. The DAO implements the access mechanism required to work with the data source.

Data Access Object, DAO, Data Access Object, DAO Design Pattern, Java DAO Example, DAO pattern implementation in java, DAO in java, DAO interface, implementation example  Data Access Object Pattern or DAO pattern is used to separate low level data accessing API or operations from high level business services. Following are the participants in Data Access Object Pattern.

Comments
  • hi rami, m really glad thayt you tried explaining me with a very simple exaple, which is what i needed. can you please explain wat you meant with 'concrete implementation' did you mean that we have to next write the definition for the methods by implementing the interface to a class.. ??
  • Yes that's right. Like a class called EmployeeSQLServerDAO which implements the EmployeeDAO interface by providing full implementation for its methods in a way relevant to SQL Server
  • so that is all a DAO is?? it is just a class that WE are writing to access the database. whenever we need a service from the database, we create an object of a DAO use it for database operations and then get rid of the DAO once we get what we want from the database. Am i right?? and may i know the Scope of this DAO concept rami??
  • Yes, The DAO as its name implies is for accessing/updating the underlying storage regarding a certain entity/class. So in the above example we have an employee class/entity which we use a SQL server DB table to persist. The Employee DAO will contain methods to insert/delete/update/select employee(s)
  • @PhilipRego we can certainly have multiple implementations for example a MSSQL server implementation, and another one that uses a CSV file to be used with unit tests.
  • Is it just me or are most Java tutorials and informational sites super old? That tutorial is from 2008! A lot of the top search results on various Java topics are even older.
  • @bergie3000: this pattern is not new.