feat(internal): ExceptionFilter delegates to consumer ExceptionHandler

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: thced

src/main/java/com/retailsvc/http/internal/ExceptionFilter.java

@@ -0,0 +1,28 @@
+package com.retailsvc.http.internal;
+
+import com.retailsvc.http.ExceptionHandler;
+import com.sun.net.httpserver.Filter;
+import com.sun.net.httpserver.HttpExchange;
+import java.io.IOException;
+
+public final class ExceptionFilter extends Filter {
+  private final ExceptionHandler handler;
+
+  public ExceptionFilter(ExceptionHandler handler) {
+    this.handler = handler;
+  }
+
+  @Override
+  public void doFilter(HttpExchange exchange, Chain chain) throws IOException {
+    try {
+      chain.doFilter(exchange);
+    } catch (RuntimeException | IOException t) {
+      handler.handle(exchange, t);
+    }
+  }
+
+  @Override
+  public String description() {
+    return "Exception filter";
+  }
+}

src/test/java/com/retailsvc/http/internal/ExceptionFilterTest.java

@@ -0,0 +1,32 @@
+package com.retailsvc.http.internal;
+
+import com.retailsvc.http.ExceptionHandler;
+import com.retailsvc.http.NotFoundException;
+import com.sun.net.httpserver.Filter;
+import com.sun.net.httpserver.HttpExchange;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+class ExceptionFilterTest {
+  @Test
+  void delegatesToExceptionHandler() throws Exception {
+    HttpExchange ex = Mockito.mock(HttpExchange.class);
+    ExceptionHandler handler = Mockito.mock(ExceptionHandler.class);
+    Filter f = new ExceptionFilter(handler);
+    Filter.Chain chain = Mockito.mock(Filter.Chain.class);
+    Mockito.doThrow(new NotFoundException("x")).when(chain).doFilter(ex);
+    f.doFilter(ex, chain);
+    Mockito.verify(handler).handle(Mockito.eq(ex), Mockito.any(NotFoundException.class));
+  }
+
+  @Test
+  void passThroughOnSuccess() throws Exception {
+    HttpExchange ex = Mockito.mock(HttpExchange.class);
+    ExceptionHandler handler = Mockito.mock(ExceptionHandler.class);
+    Filter f = new ExceptionFilter(handler);
+    Filter.Chain chain = Mockito.mock(Filter.Chain.class);
+    f.doFilter(ex, chain);
+    Mockito.verify(chain).doFilter(ex);
+    Mockito.verifyNoInteractions(handler);
+  }
+}