Do not switch to chunked encoding in webclient when the length is known (helidon-io#10828)

* Do not switch to chunked encoding in webclient when the length is known a priori.
* If chunked encoding is explicitly requested, we must honor it even if content length is set too.

Author: spericas

jersey/tests/connector/src/test/java/io/helidon/jersey/connector/ConnectorContentLengthTest.java

@@ -0,0 +1,101 @@
+/*
+ * Copyright (c) 2025 Oracle and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.helidon.jersey.connector;
+
+import java.io.UncheckedIOException;
+import java.util.NoSuchElementException;
+
+import io.helidon.http.Header;
+import io.helidon.http.HeaderNames;
+import io.helidon.http.Status;
+import io.helidon.webserver.WebServer;
+import io.helidon.webserver.http.HttpRules;
+import io.helidon.webserver.http.ServerRequest;
+import io.helidon.webserver.http.ServerResponse;
+import io.helidon.webserver.testing.junit5.ServerTest;
+import io.helidon.webserver.testing.junit5.SetUpRoute;
+
+import jakarta.ws.rs.ProcessingException;
+import jakarta.ws.rs.client.Client;
+import jakarta.ws.rs.client.ClientBuilder;
+import jakarta.ws.rs.client.Entity;
+import jakarta.ws.rs.core.MediaType;
+import jakarta.ws.rs.core.Response;
+import org.glassfish.jersey.client.ClientConfig;
+import org.junit.jupiter.api.Test;
+
+import static org.hamcrest.CoreMatchers.instanceOf;
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+@ServerTest
+class ConnectorContentLengthTest {
+    // must be larger than 8KB used by Jersey for writing
+    private static final String LARGE_ENTITY = "A".repeat(128 * 1024);
+
+    private final String baseURI;
+    private final Client client;
+
+    ConnectorContentLengthTest(WebServer webServer) {
+        baseURI = "http://localhost:" + webServer.port();
+        ClientConfig config = new ClientConfig();
+        config.connectorProvider(HelidonConnectorProvider.create());       // use Helidon's provider
+        client = ClientBuilder.newClient(config);
+    }
+
+    @SetUpRoute
+    static void routing(HttpRules rules) {
+        rules.post("/largeEntity", ConnectorContentLengthTest::largeEntity);
+    }
+
+    static void largeEntity(ServerRequest request, ServerResponse response) {
+        try {
+            Header header = request.headers().get(HeaderNames.CONTENT_LENGTH);
+            request.content().as(String.class);     // consume entity
+            response.status(Status.OK_200).send(header.getString());
+        } catch (NoSuchElementException e) {
+            response.status(Status.BAD_REQUEST_400).send();
+        }
+    }
+
+    @Test
+    public void testLargeEntity() {
+        try (Response response = client.target(baseURI)
+                .path("largeEntity")
+                .request()
+                .header("Content-Length", LARGE_ENTITY.length())
+                .post(Entity.entity(LARGE_ENTITY, MediaType.TEXT_PLAIN_TYPE))) {
+            assertThat(response.getStatus(), is(200));
+            String entity = response.readEntity(String.class);
+            assertThat(entity, is(String.valueOf(LARGE_ENTITY.length())));
+        }
+    }
+
+    @Test
+    public void testLargeEntityBadLength() {
+        try (Response response = client.target(baseURI)
+                .path("largeEntity")
+                .request()
+                .header("Content-Length", LARGE_ENTITY.length() + 1)    // incorrect
+                .post(Entity.entity(LARGE_ENTITY, MediaType.TEXT_PLAIN_TYPE))) {
+            assertThat(response.getStatus(), is(200));
+            String entity = response.readEntity(String.class);
+            assertThat(entity, is(String.valueOf(LARGE_ENTITY.length())));
+        } catch (ProcessingException e) {
+            assertThat(e.getCause(), instanceOf(UncheckedIOException.class));        // bad length
+        }
+    }
+}

webclient/http1/src/main/java/io/helidon/webclient/http1/Http1CallOutputStreamChain.java

@@ -241,6 +241,17 @@ public void write(byte[] b, int off, int len) throws IOException {
                 throw new IOException("Output stream already closed");
             }
 
+            // if not chunked and length known, write directly checking length at close
+            if (!chunked && contentLength > 0) {
+                if (!whenSent.isDone()) {
+                    sendPrologueAndHeader();
+                    noData = false;
+                }
+                writeContent(BufferData.create(b, off, len));
+                return;
+            }
+
+            // if length not known, try to optimize for single write
             if (!chunked) {
                 if (firstPacket == null) {
                     BufferData first = BufferData.create(len - off);
@@ -279,6 +290,11 @@ public void close() throws IOException {
                     ctx.log(LOGGER_REQ_ENTITY, System.Logger.Level.TRACE, "send data%n%s", terminating.debugDataHex());
                 }
                 writer.write(terminating);
+            } else if (contentLength > 0) {
+                if (contentLength != bytesWritten) {
+                    throw new IOException("Content length is set to " + contentLength
+                                                  + ", but the number of bytes written was " + bytesWritten);
+                }
             } else {
                 headers.remove(HeaderNames.TRANSFER_ENCODING);
                 if (noData) {