When working with REST Assured to test RESTful APIs, you often need to customize your requests for various reasons, such as adding authentication tokens, setting content types, or implementing logging mechanisms. This is where request filters come into play.

What are Request Filters?

Request filters are hooks that allow you to define common operations that should occur before an API request is sent. They can be utilized to apply global changes to all requests or to modify specific requests, helping to reduce duplication and improve maintainability.

Types of Request Filters

In REST Assured, two types of filters can be beneficial:

1. Pre-filters: These filters are executed before the request is sent to the server. Common use cases include adding headers and modifying the request body.

2. Post-filters: While the primary focus here is on pre-filters, it's worth noting that post-filters can be applied too, allowing operations right after the response is received.

Creating a Request Filter

To create a custom request filter, you need to implement the Filter interface provided by REST Assured. This includes overriding the filter method, where you can define your custom logic.

Here's a simple example:

import io.restassured.filter.Filter;
import io.restassured.filter.FilterContext;
import io.restassured.response.Response;
import io.restassured.specification.RequestSpecification;

public class CustomRequestFilter implements Filter {

    @Override
    public Response filter(RequestSpecification requestSpec, FilterContext ctx) {
        // Add a custom header to the request
        requestSpec.header("Custom-Header", "HeaderValue");

        // Perform logging or additional modifications if necessary
        System.out.println("Request URI: " + requestSpec.getURI());
        
        // Proceed with the request execution
        return ctx.next(requestSpec);
    }
}

Applying the Filter to Your Tests

Once you have created a custom filter, you can apply it to your REST Assured requests. Here’s how to integrate the CustomRequestFilter into a test scenario:

import io.restassured.RestAssured;
import io.restassured.response.Response;
import org.junit.Test;

import static io.restassured.RestAssured.given;

public class ApiTest {

    @Test
    public void testWithCustomRequestFilter() {
        // Register the custom filter
        RestAssured.filters(new CustomRequestFilter());

        // Make a request
        Response response = given()
                                .baseUri("https://api.example.com")
                                .basePath("/endpoint")
                            .when()
                                .get();
        
        // Add assertions for validation
        assert response.getStatusCode() == 200;
    }
}

Using Built-in Filters

REST Assured comes with several built-in filters that you might find useful, such as LoggingFilter, which can be used to log requests and responses easily:

import io.restassured.filter.log.LogDetail;
import io.restassured.filter.log.LoggingFilter;

public class ApiTestWithLogging {

    @Test
    public void testWithLoggingFilter() {
        // Register the logging filter
        RestAssured.filters(new LoggingFilter(LogDetail.ALL));

        // Make a request
        Response response = given()
                                .baseUri("https://api.example.com")
                                .basePath("/endpoint")
                            .when()
                                .get();
        
        // Add assertions for validation
        assert response.getStatusCode() == 200;
    }
}

Chaining Multiple Filters

You can also chain multiple filters together. For instance, if you want to log requests and add a custom header, you can do it as follows:

RestAssured.filters(new CustomRequestFilter(), new LoggingFilter(LogDetail.ALL));

With this setup, every request will pass through both filters, allowing for a clean and organized testing structure.

Implementing request filters in REST Assured is a straightforward process that can significantly streamline your API testing efforts. Whether you want to add custom headers, log requests, or handle authentication, request filters provide a powerful way to customize your testing environment and enhance maintainability.