fix: Register text/html as default body mapper; resolve mapper by media type

src/main/java/com/retailsvc/http/OpenApiServer.java

@@ -366,6 +366,7 @@ private static Map<String, TypeMapper> resolveBodyMappers(
       LinkedHashMap<String, TypeMapper> out = new LinkedHashMap<>();
       out.put("application/x-www-form-urlencoded", new FormTypeMapper());
       out.put("text/plain", new TextTypeMapper());
+      out.put("text/html", new TextTypeMapper());
       out.putAll(userSupplied);
       if (!out.containsKey(JSON)) {
         TypeMapper fallback = tryLoadGsonMapper();

src/main/java/com/retailsvc/http/TypeMapper.java

@@ -3,9 +3,9 @@
 /**
  * Reads and writes request/response bodies for a specific media type. Registered on {@link
  * OpenApiServer.Builder#bodyMapper(String, TypeMapper)} keyed by media type. The library ships
- * built-in mappers for {@code application/x-www-form-urlencoded} and {@code text/plain}; an {@code
- * application/json} mapper must be supplied by the caller or auto-detected via Gson on the
- * classpath.
+ * built-in mappers for {@code application/x-www-form-urlencoded}, {@code text/plain}, and {@code
+ * text/html}; an {@code application/json} mapper must be supplied by the caller or auto-detected
+ * via Gson on the classpath.
  */
 public interface TypeMapper {
 

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

@@ -77,7 +77,8 @@ private void renderBytes(
   }
 
   private byte[] serialize(Object body, String contentType) {
-    TypeMapper mapper = mappers.get(contentType.toLowerCase(Locale.ROOT));
+    String mediaType = ContentTypeHeader.mediaType(contentType);
+    TypeMapper mapper = mappers.get(mediaType.toLowerCase(Locale.ROOT));
     if (mapper == null) {
       throw new IllegalStateException("No TypeMapper registered for " + contentType);
     }

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

@@ -4,9 +4,10 @@
 import java.nio.charset.StandardCharsets;
 
 /**
- * Built-in {@link TypeMapper} for {@code text/plain}. Reads decode bytes using the charset declared
- * on {@code Content-Type} (default UTF-8). Writes return {@code String.valueOf(value)} encoded as
- * UTF-8.
+ * Built-in {@link TypeMapper} for textual media types (e.g. {@code text/plain}, {@code text/html}).
+ * Media-type-agnostic — only the {@code charset} parameter on the {@code Content-Type} header is
+ * read. Reads decode bytes using that charset (default UTF-8). Writes return {@code
+ * String.valueOf(value)} encoded as UTF-8.
  */
 public final class TextTypeMapper implements TypeMapper {
 

src/test/java/com/retailsvc/http/ExtraHandlersIT.java

@@ -57,6 +57,29 @@ void specHandlerServesClasspathResource() throws Exception {
     }
   }
 
+  @Test
+  void textHtmlResponseIsSerializedByDefaultMapper() throws Exception {
+    RequestHandler html =
+        req -> Response.of(200, "<h1>hi</h1>").withContentType("text/html; charset=UTF-8");
+
+    try (var s =
+            newBuilder().spec(spec).handlers(Map.of()).port(0).extraRoute("/page", html).build();
+        var client = httpClient()) {
+
+      var req =
+          HttpRequest.newBuilder()
+              .uri(URI.create("http://localhost:" + s.listenPort() + "/page"))
+              .GET()
+              .build();
+      var resp = client.send(req, BodyHandlers.ofString());
+
+      assertThat(resp.statusCode()).isEqualTo(200);
+      assertThat(resp.headers().firstValue("Content-Type"))
+          .hasValueSatisfying(v -> assertThat(v).startsWith("text/html"));
+      assertThat(resp.body()).isEqualTo("<h1>hi</h1>");
+    }
+  }
+
   @Test
   void extraHandlerExceptionFlowsThroughExceptionHandler() throws Exception {
     RequestHandler boom =