ParametersInterceptor in struts2

ParametersInterceptor in struts2

In Struts2, the ParametersInterceptor is primarily responsible for mapping HTTP request parameters to corresponding properties of Java Bean objects used as action classes. This interceptor plays a crucial role in automating the data binding process, ensuring that incoming request parameters are correctly populated into the action class properties.

ParametersInterceptor in struts2

ParametersInterceptor

The  ParametersInterceptor  intercepts incoming requests and performs the following tasks:

  • 1.  Parameter Mapping : It maps request parameters to corresponding Java Bean properties based on naming conventions (e.g., username parameter maps to setUsername(String username) method in the action class).
  • 2.  Type Conversion : It converts request parameter values from strings to the appropriate Java types (e.g., String, int, Date) based on the data type of the action class properties.
  • 3.  Validation : It applies validation rules defined in the action class using validation annotations or XML configurations.

Java Example

Let’s illustrate how the ParametersInterceptor works in a simple Struts2 action class.

Example Action Class
java
package com.example.action;

import com.opensymphony.xwork2.ActionSupport;

public class LoginAction extends ActionSupport {

    private String username;
    private String password;

    @Override
    public String execute() throws Exception {
        // Business logic to authenticate user
        return SUCCESS;
    }

    // Getters and setters for username and password
    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

Explanation :

  • LoginAction.java : This action class defines username and password properties with corresponding getter and setter methods.
  • When a request is made to the LoginAction with parameters username and password, the ParametersInterceptor intercepts the request, automatically populates these properties based on the request parameters.

Configuration in struts.xml
xml
<struts>
    <package name="default" namespace="/" extends="struts-default">
        <action name="login" class="com.example.action.LoginAction" method="execute">
            <result name="success">/welcome.jsp</result>
            <result name="input">/login.jsp</result>
        </action>
        <!-- Other action configurations -->
    </package>
</struts>

Explanation :

The action configuration in struts.xml maps the login action to the LoginAction class. When a request is made to /login with username and password parameters, the ParametersInterceptor ensures these parameters are mapped to the corresponding properties in the LoginAction class.

Benefits

  • Automation : ParametersInterceptor automates the process of mapping request parameters to action class properties, reducing boilerplate code and manual data binding efforts.
  • Consistency : Ensures consistent data binding and type conversion based on naming conventions and property types defined in the action class.
  • Integration : Seamlessly integrates with Struts2 validation framework, allowing validation rules to be applied to incoming parameters.

Conclusion

The ParametersInterceptor in Struts2 plays a pivotal role in handling data binding between HTTP request parameters and action class properties. It simplifies the development process by automating parameter mapping and type conversion, ensuring that action classes receive correctly populated data from incoming requests.