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AsyncReadOnlyTransactionExample.java
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AsyncReadOnlyTransactionExample.java
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/*
* Copyright 2020 Google Inc.
*
* 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 com.example.spanner;
// [START spanner_async_read_only_transaction]
import com.google.api.core.ApiFuture;
import com.google.api.core.ApiFutures;
import com.google.cloud.spanner.AsyncResultSet;
import com.google.cloud.spanner.AsyncResultSet.CallbackResponse;
import com.google.cloud.spanner.AsyncResultSet.ReadyCallback;
import com.google.cloud.spanner.DatabaseClient;
import com.google.cloud.spanner.DatabaseId;
import com.google.cloud.spanner.ReadOnlyTransaction;
import com.google.cloud.spanner.Spanner;
import com.google.cloud.spanner.SpannerException;
import com.google.cloud.spanner.SpannerOptions;
import com.google.cloud.spanner.Statement;
import com.google.common.collect.ImmutableList;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
class AsyncReadOnlyTransactionExample {
static void asyncReadOnlyTransaction()
throws InterruptedException, ExecutionException, TimeoutException {
// TODO(developer): Replace these variables before running the sample.
String projectId = "my-project";
String instanceId = "my-instance";
String databaseId = "my-database";
try (Spanner spanner =
SpannerOptions.newBuilder().setProjectId(projectId).build().getService()) {
DatabaseClient client =
spanner.getDatabaseClient(DatabaseId.of(projectId, instanceId, databaseId));
asyncReadOnlyTransaction(client);
}
}
static void asyncReadOnlyTransaction(DatabaseClient client)
throws InterruptedException, ExecutionException, TimeoutException {
ApiFuture<Void> finished1;
ApiFuture<Void> finished2;
ExecutorService executor = Executors.newFixedThreadPool(2);
try (ReadOnlyTransaction transaction = client.readOnlyTransaction()) {
try (AsyncResultSet resultSet =
transaction.executeQueryAsync(
Statement.of("SELECT SingerId, AlbumId, AlbumTitle FROM Albums"))) {
finished1 =
resultSet.setCallback(
executor,
new ReadyCallback() {
@Override
public CallbackResponse cursorReady(AsyncResultSet resultSet) {
try {
while (true) {
switch (resultSet.tryNext()) {
case OK:
System.out.printf(
"%d %d %s%n",
resultSet.getLong(0), resultSet.getLong(1), resultSet.getString(2));
break;
case DONE:
return CallbackResponse.DONE;
case NOT_READY:
return CallbackResponse.CONTINUE;
default:
throw new IllegalStateException();
}
}
} catch (SpannerException e) {
System.out.printf("Error in callback: %s%n", e.getMessage());
return CallbackResponse.DONE;
}
}
});
}
try (AsyncResultSet resultSet =
transaction.executeQueryAsync(
Statement.of("SELECT SingerId, FirstName, LastName FROM Singers"))) {
finished2 =
resultSet.setCallback(
executor,
new ReadyCallback() {
@Override
public CallbackResponse cursorReady(AsyncResultSet resultSet) {
try {
while (true) {
switch (resultSet.tryNext()) {
case OK:
System.out.printf(
"%d %s %s%n",
resultSet.getLong(0),
resultSet.getString(1),
resultSet.getString(2));
break;
case DONE:
return CallbackResponse.DONE;
case NOT_READY:
return CallbackResponse.CONTINUE;
default:
throw new IllegalStateException();
}
}
} catch (SpannerException e) {
System.out.printf("Error in callback: %s%n", e.getMessage());
return CallbackResponse.DONE;
}
}
});
}
}
ApiFutures.allAsList(ImmutableList.of(finished1, finished2)).get(60L, TimeUnit.SECONDS);
executor.shutdown();
}
}
//[END spanner_async_read_only_transaction]