步驟 2：測試與分類帳的連線 - Amazon Quantum 賬本數據庫（AmazonQLDB）

本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

步驟 2：測試與分類帳的連線

重要

支援結束通知：現有客戶將能夠使用 Amazon，QLDB直到 2025 年 7 月 31 日終止支援為止。有關更多詳細信息，請參閱將 Amazon QLDB 分類帳遷移到 Amazon Aurora 郵政. SQL

在此步驟中，您確認可以QLDB使用交易資料API端點連接到 Amazon 中的vehicle-registration分類帳。

若要測試與分類帳的連線

  1. 複查下列程式 (ConnectToLedger.java)，此程式會建立與vehicle-registration分類帳的資料階段作業連線。

    2.x
    /*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial;

import java.net.URI;
import java.net.URISyntaxException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import software.amazon.awssdk.auth.credentials.AwsCredentialsProvider;
import software.amazon.awssdk.services.qldbsession.QldbSessionClient;
import software.amazon.awssdk.services.qldbsession.QldbSessionClientBuilder;
import software.amazon.qldb.QldbDriver;
import software.amazon.qldb.RetryPolicy;

/**
 * Connect to a session for a given ledger using default settings.
 * <p>
 * This code expects that you have AWS credentials setup per:
 * http://docs.aws.amazon.com/java-sdk/latest/developer-guide/setup-credentials.html
 */
public final class ConnectToLedger {
    public static final Logger log = LoggerFactory.getLogger(ConnectToLedger.class);
    public static AwsCredentialsProvider credentialsProvider;
    public static String endpoint = null;
    public static String ledgerName = Constants.LEDGER_NAME;
    public static String region = null;
    public static QldbDriver driver;

    private ConnectToLedger() {
    }

    /**
     * Create a pooled driver for creating sessions.
     *
     * @param retryAttempts How many times the transaction will be retried in
     * case of a retryable issue happens like Optimistic Concurrency Control exception,
     * server side failures or network issues.
     * @return The pooled driver for creating sessions.
     */
    public static QldbDriver createQldbDriver(int retryAttempts) {
        QldbSessionClientBuilder builder = getAmazonQldbSessionClientBuilder();
        return QldbDriver.builder()
                             .ledger(ledgerName)
                             .transactionRetryPolicy(RetryPolicy
                                   .builder()
                                   .maxRetries(retryAttempts)
                                   .build())
                             .sessionClientBuilder(builder)
                             .build();
    }

    /**
     * Create a pooled driver for creating sessions.
     *
     * @return The pooled driver for creating sessions.
     */
    public static QldbDriver createQldbDriver() {
        QldbSessionClientBuilder builder = getAmazonQldbSessionClientBuilder();
        return QldbDriver.builder()
            .ledger(ledgerName)
            .transactionRetryPolicy(RetryPolicy.builder()
                                               .maxRetries(Constants.RETRY_LIMIT).build())
            .sessionClientBuilder(builder)
            .build();
    }

    /**
     * Creates a QldbSession builder that is passed to the QldbDriver to connect to the Ledger.
     *
     * @return An instance of the AmazonQLDBSessionClientBuilder
     */
    public static QldbSessionClientBuilder getAmazonQldbSessionClientBuilder() {
        QldbSessionClientBuilder builder = QldbSessionClient.builder();
        if (null != endpoint && null != region) {
            try {
                builder.endpointOverride(new URI(endpoint));
            } catch (URISyntaxException e) {
                throw new IllegalArgumentException(e);
            }
        }
        if (null != credentialsProvider) {
            builder.credentialsProvider(credentialsProvider);
        }
        return builder;
    }

    /**
     * Create a pooled driver for creating sessions.
     *
     * @return The pooled driver for creating sessions.
     */
    public static QldbDriver getDriver() {
        if (driver == null) {
            driver = createQldbDriver();
        }
        return driver;
    }


    public static void main(final String... args) {
        Iterable<String> tables = ConnectToLedger.getDriver().getTableNames();
        log.info("Existing tables in the ledger:");
        for (String table : tables) {
            log.info("- {} ", table);
        }
    }
}
    注意

    • 若要在分類帳上執行資料作業，您必須建立QldbDriver類別的執行環境，以連線至特定分類帳。這與您在上一個步驟中用來建立分類帳的用AmazonQLDB戶端不同的用戶端物件。先前的用戶端僅用於執行中列出的管理API作業Amazon QLDB API 參考。

    • 首先，創建一個QldbDriver對象。建立此動因時，您必須指定分類帳名稱。

      然後，您可以使用此驅動程式的execute方法來執行 PartiQL 陳述式。

    • 您可以選擇性地指定異動例外的重試次數上限。該execute方法會自動重試樂觀並發控制（OCC）衝突和其他常見的瞬態異常，直到這個可配置的限制。預設值為 4。

      如果達到限制後交易仍然失敗，則驅動程序拋出異常。如需進一步了解，請參閱了解 Amazon 中的驅動程序的重試政策 QLDB。

    1.x
    /*
 * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial;

import com.amazonaws.auth.AWSCredentialsProvider;
import com.amazonaws.client.builder.AwsClientBuilder;
import com.amazonaws.services.qldbsession.AmazonQLDBSessionClientBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import software.amazon.qldb.PooledQldbDriver;
import software.amazon.qldb.QldbDriver;
import software.amazon.qldb.QldbSession;
import software.amazon.qldb.exceptions.QldbClientException;

/**
 * Connect to a session for a given ledger using default settings.
 * <p>
 * This code expects that you have AWS credentials setup per:
 * http://docs.aws.amazon.com/java-sdk/latest/developer-guide/setup-credentials.html
 */
public final class ConnectToLedger {
    public static final Logger log = LoggerFactory.getLogger(ConnectToLedger.class);
    public static AWSCredentialsProvider credentialsProvider;
    public static String endpoint = null;
    public static String ledgerName = Constants.LEDGER_NAME;
    public static String region = null;
    private static PooledQldbDriver driver;

    private ConnectToLedger() {
    }

    /**
     * Create a pooled driver for creating sessions.
     *
     * @return The pooled driver for creating sessions.
     */
    public static PooledQldbDriver createQldbDriver() {
        AmazonQLDBSessionClientBuilder builder = AmazonQLDBSessionClientBuilder.standard();
        if (null != endpoint && null != region) {
            builder.setEndpointConfiguration(new AwsClientBuilder.EndpointConfiguration(endpoint, region));
        }
        if (null != credentialsProvider) {
            builder.setCredentials(credentialsProvider);
        }
        return PooledQldbDriver.builder()
                .withLedger(ledgerName)
                .withRetryLimit(Constants.RETRY_LIMIT)
                .withSessionClientBuilder(builder)
                .build();
    }

    /**
     * Create a pooled driver for creating sessions.
     *
     * @return The pooled driver for creating sessions.
     */
    public static PooledQldbDriver getDriver() {
        if (driver == null) {
            driver = createQldbDriver();
        }
        return driver;
    }

    /**
     * Connect to a ledger through a {@link QldbDriver}.
     *
     * @return {@link QldbSession}.
     */
    public static QldbSession createQldbSession() {
        return getDriver().getSession();
    }

    public static void main(final String... args) {
        try (QldbSession qldbSession = createQldbSession()) {
            log.info("Listing table names ");
            for (String tableName : qldbSession.getTableNames()) {
                log.info(tableName);
            }
        } catch (QldbClientException e) {
            log.error("Unable to create session.", e);
        }
    }
}
    注意

    • 若要在分類帳上執行資料作業，您必須建立PooledQldbDriver或QldbDriver類別的執行環境，以連線至特定分類帳。這與您在上一個步驟中用來建立分類帳的用AmazonQLDB戶端不同的用戶端物件。先前的用戶端僅用於執行中列出的管理API作業Amazon QLDB API 參考。

      我們建議您使用，PooledQldbDriver除非您需要使用QldbDriver. 的預設集區大小PooledQldbDriver是工作階段用戶端允許的開啟HTTP連線數目上限。

    • 首先，創建一個PooledQldbDriver對象。建立此動因時，您必須指定分類帳名稱。

      然後，您可以使用此驅動程式的execute方法來執行 PartiQL 陳述式。或者，您可以從此池驅動程序對象手動創建會話，並使用會話的execute方法。會話表示與分類帳的單個連接。

    • 您可以選擇性地指定異動例外的重試次數上限。該execute方法會自動重試樂觀並發控制（OCC）衝突和其他常見的瞬態異常，直到這個可配置的限制。預設值為 4。

      如果達到限制後交易仍然失敗，則驅動程序拋出異常。如需進一步了解，請參閱了解 Amazon 中的驅動程序的重試政策 QLDB。

  2. 編譯並執行ConnectToLedger.java程式，以測試資料階段作業與vehicle-registration分類帳的連線。

覆寫 AWS 區域

範例應用程式會連線到QLDB預設值 AWS 區域，您可以按照先決條件步驟中的說明進行設定設定您的預設 AWS 憑證和區域。您還可以通過修改QLDB會話客戶端構建器屬性來更改區域。

2.x

下列程式碼範例會實體化新QldbSessionClientBuilder物件。

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.qldbsession.QldbSessionClientBuilder;

// This client builder will default to US East (Ohio)
QldbSessionClientBuilder builder = QldbSessionClient.builder()
    .region(Region.US_EAST_2);

您可以使用該region方法QLDB在任何可用的區域中運行代碼。如需完整清 AmazonQLDB，請參閱 AWS 一般參考.

1.x

下列程式碼範例會實體化新AmazonQLDBSessionClientBuilder物件。

import com.amazonaws.regions.Regions;
import com.amazonaws.services.qldbsession.AmazonQLDBSessionClientBuilder;

// This client builder will default to US East (Ohio)
AmazonQLDBSessionClientBuilder builder = AmazonQLDBSessionClientBuilder.standard()
    .withRegion(Regions.US_EAST_2);

您可以使用該withRegion方法QLDB在任何可用的區域中運行代碼。如需完整清 AmazonQLDB，請參閱 AWS 一般參考.

若要在vehicle-registration分類帳中建立表格，請繼續執行步驟 3：建立資料表、索引和範例資料。