Align filter pipeline with main filter chain and harden immutability

Author: viktorlindell12

src/main/java/org/example/server/ConfigurableFilterPipeline.java

@@ -8,19 +8,25 @@
 import java.util.ArrayList;
 import java.util.Comparator;
 import java.util.List;
+import java.util.Objects;
 import java.util.function.BiConsumer;
 
 public class ConfigurableFilterPipeline {
 
     private final List<FilterRegistration> registrations;
 
     public ConfigurableFilterPipeline(List<FilterRegistration> registrations) {
-        this.registrations = registrations;
+        this.registrations = List.copyOf(
+                Objects.requireNonNull(registrations, "registrations must not be null")
+        );
     }
 
     public HttpResponseBuilder execute(HttpRequest request,
                                        BiConsumer<HttpRequest, HttpResponseBuilder> terminalHandler) {
 
+        Objects.requireNonNull(request, "request must not be null");
+        Objects.requireNonNull(terminalHandler, "terminalHandler must not be null");
+
         List<FilterRegistration> globalRegs = new ArrayList<>();
         List<FilterRegistration> routeRegs = new ArrayList<>();
 

src/main/java/org/example/server/FilterRegistration.java

@@ -3,12 +3,17 @@
 import org.example.filter.Filter;
 
 import java.util.List;
+import java.util.Objects;
 
 public record FilterRegistration(
         Filter filter,
         int order,
         List<String> routePatterns
 ) {
+    public FilterRegistration {
+        filter = Objects.requireNonNull(filter, "filter must not be null");
+        routePatterns = routePatterns == null ? null : List.copyOf(routePatterns);
+    }
 
     public boolean isGlobal() {
         return routePatterns == null || routePatterns.isEmpty();