“Programming for interfaces than implementation” is very popular principle in java programming and design pattern. Here I am going to explain some interested facts about interface in java in term of Spring Framework.
Here I am not going to explain that interface is a keyword in java we will focus on beyond the keyword. Actually interface in java is the core part of programming, it is not for hello world type of application, it is using for abstraction and decoupling concept in java. It is simple object oriented term to define contract or rules and abstraction between producer and consumer for applications.
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public class EmployeeRegistrationService { public void saveToRDBMS(Employee employee ) { //save to RDBMS } public void saveToNoSQL(Employee employee ) { //save to NoSQL DB } }
In this case, the EmplyeeRegistrationController should be aware of the concrete implementation of these two functions in EmployeeRegistrationService to use them. Suppose we want to add additional functionality to save the information as JSON is required then you will have to add a new function saveToJson() in the Service class as well as make changes in the Controller. This adds lots of complication to maintenance of our huge application with hundreds of controllers and services. To avoid these complications we could use interface instead of implementation of registration service.
interface EmployeeRegistrationService { void save(Employee employee ); }
Now controller doesn’t care about the concrete implementation of service, it is only aware of this interface, which has a save method.
public class EmployeeServiceRDS implements EmployeeRegistrationService { @Override public void saveToRDBMS(Employee employee ) { //save to RDBMS } } public class EmployeeServiceNoSQL implements EmployeeRegistrationService { @Override public void saveToNoSQL(Employee employee ) { //save to NoSQL DB } }
@Controller Class EmployeeController { @Resource(name="employeeServiceRDS ") EmployeeRegistrationService registrationService ; @RequestMapping("/emp-save") public void saveEmployee(Employee employee) { registrationService.save(employee); } }
This highly reduces the software modification and extension cost. As changes in one layer does not effect other layer and new functionalities are made available to other layer immediately. Thus using interface gives you more power over extending and maintaining your application, utilize abstraction and implement good software development practices.
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