OOB: Middleware (Java Support)

Middleware, in this context, refers to components that can process HTTP requests before they reach the intended API endpoint or after they have been processed

You can achieve this in a Spring Boot application using a combination of filters and the RestTemplate to make a request to example.com/log with the payload extracted from the incoming request. Here's a step-by-step guide:

1. Create a filter that intercepts incoming requests.

2. Extract the required information from the request.

3. Construct the payload.

4. Send the payload to example.com/log using RestTemplate.

Step 1: Create a Filter

Create a filter that intercepts incoming requests and processes them.

javaCopy codeimport org.springframework.stereotype.Component;
import org.springframework.web.filter.OncePerRequestFilter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.FilterRegistration;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Component
public class LoggingFilter extends OncePerRequestFilter {

    @Override
    protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) 
            throws ServletException, IOException {
        
        // Proceed with the filter chain
        filterChain.doFilter(request, response);
        
        // After processing the request, you can extract the information and send the log
        LogPayload logPayload = createLogPayload(request, response);
        sendLog(logPayload);
    }

    private LogPayload createLogPayload(HttpServletRequest request, HttpServletResponse response) {
        // Extract necessary information from request and response
        LogPayload logPayload = new LogPayload();
        logPayload.setCollectionId("your-unique-collection-id");
        logPayload.setEnvironment("prod");
        logPayload.setPath(request.getRequestURI());
        logPayload.setIpAddress(request.getRemoteAddr());
        logPayload.setMethod(request.getMethod());
        logPayload.setResponseBody(response.getContentType()); // Adjust as needed
        logPayload.setRequestHeaders(Collections.list(request.getHeaderNames())
            .stream().collect(Collectors.toMap(h -> h, request::getHeader)));
        logPayload.setResponseCode(String.valueOf(response.getStatus()));
        logPayload.setQueryParams(request.getParameterMap());
        logPayload.setResponseError(300); // Example value, adjust as needed
        logPayload.setResponseTime(300); // Example value, adjust as needed
        logPayload.setStatusCode(response.getStatus());
        // Add more fields as needed
        return logPayload;
    }

    private void sendLog(LogPayload logPayload) {
        RestTemplate restTemplate = new RestTemplate();
        String url = "http://example.com/log";
        HttpEntity<LogPayload> requestEntity = new HttpEntity<>(logPayload);
        restTemplate.postForEntity(url, requestEntity, String.class);
    }
}

Step 2: Create the LogPayload Class

This class represents the structure of the payload you want to send.

javaCopy codeimport java.util.Map;

public class LogPayload {
    private String collectionId;
    private String environment;
    private String path;
    private String ipAddress;
    private String method;
    private String responseBody;
    private Map<String, String> requestHeaders;
    private String responseCode;
    private Map<String, String[]> queryParams;
    private int responseError;
    private int responseTime;
    private int statusCode;
    private Map<String, Object> body;

    // Getters and setters
    // ...
}

Step 3: Configure the Filter

Make sure your filter is registered in your Spring Boot application.

javaCopy codeimport org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Bean
    public FilterRegistrationBean<LoggingFilter> loggingFilter(){
        FilterRegistrationBean<LoggingFilter> registrationBean = new FilterRegistrationBean<>();

        registrationBean.setFilter(new LoggingFilter());
        registrationBean.addUrlPatterns("/api/v2/*");

        return registrationBean;
    }
}

Step 4: Handle the Response Body

Since the response body might not be directly accessible after the filter chain, you might need a custom wrapper for the HttpServletResponse to capture it.

javaCopy codeimport javax.servlet.ServletOutputStream;
import javax.servlet.WriteListener;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.PrintWriter;

public class CustomHttpServletResponseWrapper extends HttpServletResponseWrapper {

    private ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
    private PrintWriter writer = new PrintWriter(outputStream);

    public CustomHttpServletResponseWrapper(HttpServletResponse response) {
        super(response);
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        return new ServletOutputStream() {
            @Override
            public void write(int b) throws IOException {
                outputStream.write(b);
            }

            @Override
            public void setWriteListener(WriteListener writeListener) {
                // No-op
            }

            @Override
            public boolean isReady() {
                return true;
            }
        };
    }

    @Override
    public PrintWriter getWriter() throws IOException {
        return writer;
    }

    public byte[] getResponseData() {
        writer.flush();
        return outputStream.toByteArray();
    }
}

Modify your filter to use this wrapper:

javaCopy code@Override
protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) 
        throws ServletException, IOException {
    
    CustomHttpServletResponseWrapper responseWrapper = new CustomHttpServletResponseWrapper(response);
    
    // Proceed with the filter chain
    filterChain.doFilter(request, responseWrapper);
    
    // After processing the request, you can extract the information and send the log
    LogPayload logPayload = createLogPayload(request, responseWrapper);
    sendLog(logPayload);
}