New convenience HttpHandler

[Ethan McCue]

My first thought is that if you are computing the string maybe you'd want
to look at the request. Or set a header for content type.

I'm not going to push hard until valhalla is at least in preview (+ we've
already talked it to death) but a Body abstraction would probably
solve your use-case more robustly than yet another method there.

exchange -> exchange.sendResponse(200, Body.of("example"));

On Mon, Apr 28, 2025 at 5:28 AM Pavel Rappo <pavel.rappo at gmail.com> wrote:

> I'm using HttpServer to implement an HTTP probe [^1] that provides
> application state at the time of probing. I find that convenience
> handlers provided by HttpHandlers are insufficient for my use case. I
> also find that implementing a custom HttpHandler is tricky without the
> help of documentation.
>
> Perhaps my use case is typical enough so that HttpHandlers could
> provide a new convenience handler. That handler would send a
> dynamically supplied string, rather than a static string. If you also
> find it useful, I'd appreciate it if we could discuss it. Before I
> create a JBS issue, please have a look at this crude patch to see if
> it makes sense to you in principle. Thanks.
>
> [^1]:
> https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/
>
> diff --git
> a/src/jdk.httpserver/share/classes/com/sun/net/httpserver/HttpHandlers.java
> b/src/jdk.httpserver/share/classes/com/sun/net/httpserver/HttpHandlers.java
> index 03642033914..987de0ede5d 100644
> ---
> a/src/jdk.httpserver/share/classes/com/sun/net/httpserver/HttpHandlers.java
> +++
> b/src/jdk.httpserver/share/classes/com/sun/net/httpserver/HttpHandlers.java
> @@ -25,9 +25,11 @@
>
>  package com.sun.net.httpserver;
>
> +import java.io.OutputStream;
>  import java.nio.charset.StandardCharsets;
>  import java.util.Objects;
>  import java.util.function.Predicate;
> +import java.util.function.Supplier;
>
>  /**
>   * Implementations of {@link com.sun.net.httpserver.HttpHandler
> HttpHandler}
> @@ -140,28 +142,60 @@ public static HttpHandler
> handleOrElse(Predicate<Request> handlerTest,
>       * @throws NullPointerException     if headers or body are null
>       */
>      public static HttpHandler of(int statusCode, Headers headers,
> String body) {
> +        Objects.requireNonNull(body);
> +        return of(statusCode, headers, () -> body);
> +    }
> +
> +    /**
> +     * Returns an {@code HttpHandler} that sends a response
> comprising the given
> +     * {@code statusCode}, {@code headers}, and {@code body}.
> +     *
> +     * <p> This method creates a handler that reads and discards the
> request
> +     * body before it sets the response state and sends the response.
> +     *
> +     * <p> {@code headers} are the effective headers of the response. The
> +     * response <i>body bytes</i> are a {@code UTF-8} encoded byte
> sequence of
> +     * a string, which is supplied by {@code bodySupplier}
> immediately after the request body is read. The response headers
> +     * {@linkplain HttpExchange#sendResponseHeaders(int, long) are sent}
> with
> +     * the given {@code statusCode} and the body bytes' length (or {@code
> -1}
> +     * if the body is empty). The body bytes are then sent as response
> body,
> +     * unless the body is empty, in which case no response body is sent.
> +     *
> +     * @param statusCode a response status code
> +     * @param headers a headers
> +     * @param bodySupplier a supplier for the response body string
> +     * @return a handler
> +     * @throws IllegalArgumentException if statusCode is not a positive
> 3-digit
> +     *                                  integer, as per rfc2616, section
> 6.1.1
> +     * @throws NullPointerException     if headers or body are null
> +     */
> +    public static HttpHandler of(int statusCode, Headers headers,
> Supplier<String> bodySupplier) {
>          if (statusCode < 100 || statusCode > 999)
>              throw new IllegalArgumentException("statusCode must be
> 3-digit: "
>                      + statusCode);
>          Objects.requireNonNull(headers);
> -        Objects.requireNonNull(body);
> +        Objects.requireNonNull(bodySupplier);
>
>          final var headersCopy = Headers.of(headers);
> -        final var bytes = body.getBytes(StandardCharsets.UTF_8);
>
>          return exchange -> {
>              try (exchange) {
> -                exchange.getRequestBody().readAllBytes();
> +
> exchange.getRequestBody().transferTo(OutputStream.nullOutputStream());
> // discard
>                  exchange.getResponseHeaders().putAll(headersCopy);
> -                if (exchange.getRequestMethod().equals("HEAD")) {
> -
> exchange.getResponseHeaders().set("Content-Length",
> Integer.toString(bytes.length));
> -                    exchange.sendResponseHeaders(statusCode, -1);
> -                }
> -                else if (bytes.length == 0) {
> -                    exchange.sendResponseHeaders(statusCode, -1);
> +                var body = bodySupplier.get();
> +                if (body == null) {
> +                    exchange.sendResponseHeaders(500, -1); //
> Internal Server Error
>                  } else {
> -                    exchange.sendResponseHeaders(statusCode,
> bytes.length);
> -                    exchange.getResponseBody().write(bytes);
> +                    final var bytes =
> body.getBytes(StandardCharsets.UTF_8);
> +                    if (exchange.getRequestMethod().equals("HEAD")) {
> +
> exchange.getResponseHeaders().set("Content-Length",
> Integer.toString(bytes.length));
> +                        exchange.sendResponseHeaders(statusCode, -1);
> +                    } else if (bytes.length == 0) {
> +                        exchange.sendResponseHeaders(statusCode, -1);
> +                    } else {
> +                        exchange.sendResponseHeaders(statusCode,
> bytes.length);
> +                        exchange.getResponseBody().write(bytes);
> +                    }
>                  }
>              }
>          };
> diff --git
> a/test/jdk/com/sun/net/httpserver/simpleserver/HttpHandlersTest.java
> b/test/jdk/com/sun/net/httpserver/simpleserver/HttpHandlersTest.java
> index 85d271e44fa..d64fa03740f 100644
> --- a/test/jdk/com/sun/net/httpserver/simpleserver/HttpHandlersTest.java
> +++ b/test/jdk/com/sun/net/httpserver/simpleserver/HttpHandlersTest.java
> @@ -81,7 +81,7 @@ public void testNull() {
>          final var headers = new Headers();
>          final var body = "";
>          assertThrows(NPE, () -> HttpHandlers.of(200, null, body));
> -        assertThrows(NPE, () -> HttpHandlers.of(200, headers, null));
> +        assertThrows(NPE, () -> HttpHandlers.of(200, headers, (String)
> null));
>      }
>
>      @Test
>
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