design pattern is implemented by Struts2

design pattern is implemented by Struts2

Struts2 interceptors implement the  Interceptor design pattern , which is a behavioral pattern that allows objects to be composed dynamically at runtime. Interceptors in Struts2 provide a way to apply cross-cutting concerns such as logging, validation, and exception handling without modifying the core logic of individual components.

design pattern is implemented by Struts2

Explanation

The Interceptor design pattern allows behavior to be added to an object dynamically. Instead of modifying the object itself, additional functionality is “intercepted” and applied before or after the core operation of the object. This promotes modularity, reusability, and separation of concerns.

Java Example

Below is a simplified example demonstrating the use of interceptors in Struts2.

LoggingInterceptor Example
java
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;

public class LoggingInterceptor extends AbstractInterceptor {
    
    @Override
    public String intercept(ActionInvocation invocation) throws Exception {
        // Pre-processing logic
        System.out.println("Before executing action: " + invocation.getAction().getClass().getName());
        
        // Execute the action or proceed to the next interceptor
        String result = invocation.invoke();
        
        // Post-processing logic
        System.out.println("After executing action: " + invocation.getAction().getClass().getName());
        
        return result;
    }
}

Configuration in struts.xml
xml
<struts>
    <package name="default" extends="struts-default">
        <interceptors>
            <interceptor name="loggingInterceptor" class="com.example.interceptor.LoggingInterceptor"/>
            <!-- Other interceptors -->
        </interceptors>
        
        <action name="helloWorld" class="com.example.action.HelloWorldAction">
            <interceptor-ref name="loggingInterceptor"/>
            <!-- Other interceptors or defaultStack -->
            <result name="success">/success.jsp</result>
        </action>
    </package>
</struts>

Explanation

  • 1.  LoggingInterceptor Class : Implements the AbstractInterceptor class from Struts2. It overrides the intercept method to provide custom pre-processing and post-processing logic.
  • 2.  Configuration in struts.xml : Defines the loggingInterceptor and configures it to intercept the helloWorld action. Multiple interceptors can be configured in a stack (interceptor-stack) to apply a sequence of interceptors to an action.

Benefits of Interceptor Design Pattern in Struts2

  • Modularity : Interceptors encapsulate cross-cutting concerns, promoting modular code.
  • Reusability : Interceptors can be reused across multiple actions without duplicating code.
  • Separation of Concerns : Core business logic remains separate from cross-cutting concerns.
  • Flexibility : Interceptors can be configured globally or on a per-action basis, providing flexibility in application behavior.

Conclusion

Struts2 interceptors implement the Interceptor design pattern, enabling developers to modularize and manage cross-cutting concerns effectively. This pattern enhances code maintainability, reusability, and flexibility in web application development.