feat(gax): add ResumableUploadClient.startUpload() and supporting types

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/resumable/ResumableUploadClient.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.google.api.gax.resumable;
+
+import com.google.api.core.InternalApi;
+import com.google.api.gax.rpc.UnaryCallable;
+import org.jspecify.annotations.NullMarked;
+
+/** Client interface for executing low-level resumable upload operations. */
+@NullMarked
+@InternalApi
+public interface ResumableUploadClient {
+
+  /** Returns a {@link UnaryCallable} to initiate a resumable upload session. */
+  UnaryCallable<StartUploadRequest, ResumableUploadSession> startUploadCallable();
+}

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/resumable/ResumableUploadSession.java

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+/*
+ * Copyright 2026 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.google.api.gax.resumable;
+
+import com.google.api.core.InternalApi;
+import com.google.auto.value.AutoValue;
+import org.jspecify.annotations.NullMarked;
+
+/** Represents the session metadata returned after starting a resumable upload. */
+@NullMarked
+@InternalApi
+@AutoValue
+public abstract class ResumableUploadSession {
+
+  private static final long DEFAULT_CHUNK_GRANULARITY = 1L;
+
+  /** Returns the server-provided URL to which data uploads are directed. */
+  public abstract String getUploadUrl();
+
+  /**
+   * Returns the server-mandated chunk granularity in bytes.
+   *
+   * <p>When specified by the server (via {@code X-Goog-Upload-Chunk-Granularity}), intermediate
+   * upload chunks must have a size and offset that are an exact multiple of this value (the final
+   * chunk may be smaller). If not specified by the server, this defaults to 1 byte, indicating no
+   * alignment or granularity requirements apply.
+   *
+   * @return the chunk granularity in bytes
+   */
+  public abstract long getChunkGranularity();
+
+  /**
+   * Creates a {@link ResumableUploadSession} with the specified upload URL and default chunk
+   * granularity.
+   *
+   * @param uploadUrl the upload session URL
+   * @return a new {@link ResumableUploadSession} instance
+   */
+  public static ResumableUploadSession create(String uploadUrl) {
+    return create(uploadUrl, DEFAULT_CHUNK_GRANULARITY);
+  }
+
+  /**
+   * Creates a {@link ResumableUploadSession} with the specified upload URL and chunk granularity.
+   *
+   * @param uploadUrl the upload session URL
+   * @param chunkGranularity the chunk granularity in bytes; if &le; 0, 1 is used to indicate no
+   *     alignment or granularity requirements apply.
+   * @return a new {@link ResumableUploadSession} instance
+   */
+  public static ResumableUploadSession create(String uploadUrl, long chunkGranularity) {
+    return new AutoValue_ResumableUploadSession(
+        uploadUrl, chunkGranularity > 0 ? chunkGranularity : DEFAULT_CHUNK_GRANULARITY);
+  }
+}

sdk-platform-java/gax-java/gax/src/main/java/com/google/api/gax/resumable/StartUploadRequest.java

@@ -0,0 +1,106 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.google.api.gax.resumable;
+
+import com.google.api.core.InternalApi;
+import com.google.auto.value.AutoValue;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableMap;
+import java.util.List;
+import java.util.Map;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+/** Request parameters for initiating a resumable upload session. */
+@NullMarked
+@InternalApi
+@AutoValue
+public abstract class StartUploadRequest {
+
+  /** Returns the URL path to append to the service endpoint. */
+  public abstract String getPath();
+
+  /** Returns the optional initial JSON request payload. */
+  @Nullable
+  public abstract String getJsonPayload();
+
+  /** Returns the query parameters for the initiation request. */
+  public abstract Map<String, List<String>> getQueryParams();
+
+  public abstract Builder toBuilder();
+
+  public static Builder newBuilder() {
+    return new AutoValue_StartUploadRequest.Builder().setQueryParams(ImmutableMap.of());
+  }
+
+  /**
+   * Convenience factory for creating a {@link StartUploadRequest} with only a target path.
+   *
+   * @param path the resource upload path
+   * @return a new {@link StartUploadRequest} instance
+   */
+  public static StartUploadRequest create(String path) {
+    return newBuilder().setPath(path).build();
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder {
+    public abstract Builder setPath(String path);
+
+    public abstract Builder setJsonPayload(@Nullable String jsonPayload);
+
+    public abstract Builder setQueryParams(Map<String, List<String>> queryParams);
+
+    abstract @Nullable Map<String, List<String>> getQueryParams();
+
+    abstract @Nullable String getPath();
+
+    abstract StartUploadRequest autoBuild();
+
+    public StartUploadRequest build() {
+      if (getPath() != null && getPath().startsWith("/")) {
+        setPath(getPath().substring(1));
+      }
+
+      Map<String, List<String>> params = getQueryParams();
+      if (params != null && !params.isEmpty()) {
+        ImmutableMap.Builder<String, List<String>> mapBuilder = ImmutableMap.builder();
+        for (Map.Entry<String, List<String>> entry : params.entrySet()) {
+          mapBuilder.put(entry.getKey(), ImmutableList.copyOf(entry.getValue()));
+        }
+        setQueryParams(mapBuilder.build());
+      } else {
+        setQueryParams(ImmutableMap.of());
+      }
+
+      return autoBuild();
+    }
+  }
+}

sdk-platform-java/gax-java/gax/src/test/java/com/google/api/gax/resumable/ResumableUploadSessionTest.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+package com.google.api.gax.resumable;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+class ResumableUploadSessionTest {
+
+  private static final String UPLOAD_URL = "https://storage.googleapis.com/upload/session/12345";
+
+  @Test
+  void create_withUploadUrl_setsDefaultChunkGranularityToOneByte() {
+    ResumableUploadSession session = ResumableUploadSession.create(UPLOAD_URL);
+
+    assertThat(session.getUploadUrl()).isEqualTo(UPLOAD_URL);
+    assertThat(session.getChunkGranularity()).isEqualTo(1L);
+  }
+
+  @Test
+  void create_withExplicitChunkGranularity_preservesGranularity() {
+    long customChunkGranularity = 256 * 1024L;
+
+    ResumableUploadSession session =
+        ResumableUploadSession.create(UPLOAD_URL, customChunkGranularity);
+
+    assertThat(session.getUploadUrl()).isEqualTo(UPLOAD_URL);
+    assertThat(session.getChunkGranularity()).isEqualTo(customChunkGranularity);
+  }
+
+  @ParameterizedTest
+  @ValueSource(longs = {0L, -1L, -100L})
+  void create_withNonPositiveChunkGranularity_normalizesToOneByte(long invalidGranularity) {
+    ResumableUploadSession session = ResumableUploadSession.create(UPLOAD_URL, invalidGranularity);
+
+    assertThat(session.getChunkGranularity()).isEqualTo(1L);
+  }
+}