added rate limiter and improved payment start entity

src/main/java/com/billpaymentservice/bbps/config/RateLimitingFilter.java

@@ -0,0 +1,116 @@
+package com.billpaymentservice.bbps.config;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import jakarta.servlet.FilterChain;
+import jakarta.servlet.ServletException;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.springframework.core.annotation.Order;
+import org.springframework.stereotype.Component;
+import org.springframework.web.filter.OncePerRequestFilter;
+import com.billpaymentservice.bbps.util.BBPSConstant;
+import com.billpaymentservice.bbps.dto.ResponseModel;
+
+import io.github.resilience4j.ratelimiter.RateLimiter;
+import io.github.resilience4j.ratelimiter.RateLimiterRegistry;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+@Component
+@Order(1)
+public class RateLimitingFilter extends OncePerRequestFilter {
+
+    private final RateLimiterRegistry rateLimiterRegistry;
+	private static final Logger LOGGER = LoggerFactory.getLogger(RateLimitingFilter.class);
+
+    // Har MID ke liye alag limiter
+    private final Map<String, RateLimiter> limiterCache = new ConcurrentHashMap<>();
+
+    private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();
+
+    public RateLimitingFilter(RateLimiterRegistry rateLimiterRegistry) {
+        this.rateLimiterRegistry = rateLimiterRegistry;
+    }
+
+    @Override
+    protected void doFilterInternal(HttpServletRequest request,
+                                    HttpServletResponse response,
+                                    FilterChain filterChain)
+            throws ServletException, IOException {
+        String mid = request.getHeader("mid");
+        if(mid == null) {
+			mid = "GLOBAL";
+		}
+        
+        // Validate MID
+        if (mid == null || mid.isBlank()) {
+            response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
+            response.setContentType("application/json");
+
+            ResponseModel<Object> apiResponse = new ResponseModel<>("mid cannot be null or blank", "FAILURE", HttpServletResponse.SC_BAD_REQUEST, null);
+            response.getWriter().write(OBJECT_MAPPER.writeValueAsString(apiResponse));
+            return;
+        }
+
+        try {
+            RateLimiter rateLimiter = limiterCache.computeIfAbsent(
+                    mid,
+                    key -> rateLimiterRegistry.rateLimiter("default")
+            );
+
+            // Rate limit check
+            if (!rateLimiter.acquirePermission()) {
+
+                // Prefer existing constant if it maps to 429, otherwise fallback to literal 429
+                int tooManyRequestsStatus =429;
+
+                response.setStatus(tooManyRequestsStatus);
+                response.setContentType("application/json");
+
+                ResponseModel<Object> apiResponse = new ResponseModel<>("Rate limit exceeded for MID: " + mid, "FAILURE", tooManyRequestsStatus, null);
+                response.getWriter().write(OBJECT_MAPPER.writeValueAsString(apiResponse));
+                return;
+            }
+
+            // Proceed with the chain and catch downstream exceptions to return consistent model
+            try {
+                filterChain.doFilter(request, response);
+            } catch (Exception ex) {
+                LOGGER.error("Unhandled exception in filter chain for MID: {}", mid, ex);
+                if (!response.isCommitted()) {
+                    response.reset();
+                    response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
+                    response.setContentType("application/json");
+                    ResponseModel<Object> apiResponse = new ResponseModel<>("Internal server error", "FAILURE", HttpServletResponse.SC_INTERNAL_SERVER_ERROR, null);
+                    response.getWriter().write(OBJECT_MAPPER.writeValueAsString(apiResponse));
+                }
+            }
+
+        } catch (Exception e) {
+            LOGGER.error("Error while rate limiting request", e);
+            if (!response.isCommitted()) {
+                response.reset();
+                response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
+                response.setContentType("application/json");
+                ResponseModel<Object> apiResponse = new ResponseModel<>("Internal server error", "FAILURE", HttpServletResponse.SC_INTERNAL_SERVER_ERROR, null);
+                response.getWriter().write(OBJECT_MAPPER.writeValueAsString(apiResponse));
+            }
+            return;
+        }
+    }
+
+    @Override
+    protected boolean shouldNotFilter(HttpServletRequest request) {
+
+        String path = request.getRequestURI();
+
+        return path.startsWith("/swagger")
+            || path.startsWith("/v3/api-docs")
+            || path.startsWith("/actuator");
+    }
+}

src/main/java/com/billpaymentservice/bbps/util/BBPSConstant.java

@@ -130,6 +130,7 @@ public class BBPSConstant extends BBPS_RESPONSE_COD_CONSTANT {
 	public static final int HTTP_OK_INT = 200;
 	public static final int HTTP_NOT_FOUND = 404;
 	public static final int HTTP_INTERNAL_SERVER_ERROR = 500;
+	public static final int HTTP_TO_MANY_REQUEST=429;
 
 	// Response and helper keys
 	public static final String HTTP_SERVICE_ERROR_PREFIX = "HttpService Error";