What is a Data Access Object (DAO) and How Does it Work in Java?

Understanding Data Access Objects (DAO) in Java

The Data Access Object (DAO) plays a crucial role in Java programming by providing an abstraction for accessing data from various sources, such as databases or persistent storage systems.

What is a DAO Programmatically?

A DAO is an interface or object that encapsulates the logic for accessing and manipulating data from external sources. It defines an API for performing operations like creating, reading, updating, and deleting (CRUD) data.

How is a DAO Used?

A typical DAO implementation consists of two primary components:

1. DAO Interface: Defines the operations available to interact with the underlying data source. It includes methods for retrieving, modifying, and managing data.
2. DAO Implementation: Implements the DAO interface and handles the specific SQL queries or data access code needed to interact with the database.

Example of a DAO

Consider an employee management system where we have an Employee class:

<code class="java">public class Employee {
    private int id;
    private String name;

    // Getters and Setters
}</code>

A corresponding DAO interface could be:

<code class="java">interface EmployeeDAO {
    List<Employee> findAll();
    Employee findById(int id);
    List<Employee> findByName(String name);
    boolean insertEmployee(Employee employee);
    boolean updateEmployee(Employee employee);
    boolean deleteEmployee(int id);
}</code>

For this interface, we would implement a concrete class that handles database interactions specific to the use case, such as using JDBC for SQL Server or Apache Cassandra for NoSQL data.

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