注意事項(xiàng)

• 本文以華東1（杭州）外網(wǎng)Endpoint為例。如果您希望通過與OSS同地域的其他阿里云產(chǎn)品訪問OSS，請使用內(nèi)網(wǎng)Endpoint。關(guān)于OSS支持的Region與Endpoint的對應(yīng)關(guān)系，請參見OSS訪問域名、數(shù)據(jù)中心、開放端口。

• 本文以從環(huán)境變量讀取訪問憑證為例。如何配置訪問憑證，請參見配置訪問憑證。

• 本文以OSS域名新建OSSClient為例。如果您希望通過自定義域名、STS等方式新建OSSClient，請參見新建OSSClient。

• 要查詢文件，您必須具有oss:GetObject權(quán)限。具體操作，請參見為RAM用戶授權(quán)自定義的權(quán)限策略。

• OSS僅支持查詢CSV文件和JSON文件，不支持查詢其他格式的文件。

示例代碼

以下代碼用于查詢CSV和JSON文件。

import com.aliyun.oss.model.*;
import com.aliyun.oss.OSS;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.OSSClientBuilder;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.InputStreamReader;

/**
 * Examples of create select object metadata and select object.
 *
 */
public class SelectObjectSample {
    // yourEndpoint填寫B(tài)ucket所在地域?qū)?yīng)的Endpoint。以華東1（杭州）為例，Endpoint填寫為https://oss-cn-hangzhou.aliyuncs.com。
    private static String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
    // 填寫B(tài)ucket名稱，例如examplebucket。
    private static String bucketName = "examplebucket";

    public static void main(String[] args) throws Exception {
      
      	// 從環(huán)境變量中獲取訪問憑證。運(yùn)行本代碼示例之前，請確保已設(shè)置環(huán)境變量OSS_ACCESS_KEY_ID和OSS_ACCESS_KEY_SECRET。
        EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
        // 填寫B(tài)ucket所在地域。以華東1（杭州）為例，Region填寫為cn-hangzhou。
        String region = "cn-hangzhou";

        // 創(chuàng)建OSSClient實(shí)例。
        ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
        clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);        
        OSS ossClient = OSSClientBuilder.create()
        .endpoint(endpoint)
        .credentialsProvider(credentialsProvider)
        .clientConfiguration(clientBuilderConfiguration)
        .region(region)               
        .build();
        // 填寫Object完整路徑后，根據(jù)SELECT語句查詢文件中的數(shù)據(jù)。Object完整路徑中不能包含Bucket名稱。
        // 填寫CSV格式的Object完整路徑。
        selectCsvSample("test.csv", ossClient);
        // 填寫JSON格式的Object完整路徑。
        selectJsonSample("test.json", ossClient);
        ossClient.shutdown();
    }

    private static void selectCsvSample(String key, OSS ossClient) throws Exception {
        // 填寫上傳的內(nèi)容。
        String content = "name,school,company,age\r\n" +
                "Lora Francis,School A,Staples Inc,27\r\n" +
                "Eleanor Little,School B,\"Conectiv, Inc\",43\r\n" +
                "Rosie Hughes,School C,Western Gas Resources Inc,44\r\n" +
                "Lawrence Ross,School D,MetLife Inc.,24";

        ossClient.putObject(bucketName, key, new ByteArrayInputStream(content.getBytes()));

        SelectObjectMetadata selectObjectMetadata = ossClient.createSelectObjectMetadata(
                new CreateSelectObjectMetadataRequest(bucketName, key)
                        .withInputSerialization(
                                new InputSerialization().withCsvInputFormat(
                                        // 填寫內(nèi)容中不同記錄之間的分隔符，例如\r\n。
                                        new CSVFormat().withHeaderInfo(CSVFormat.Header.Use).withRecordDelimiter("\r\n"))));
        System.out.println(selectObjectMetadata.getCsvObjectMetadata().getTotalLines());
        System.out.println(selectObjectMetadata.getCsvObjectMetadata().getSplits());

        SelectObjectRequest selectObjectRequest =
                new SelectObjectRequest(bucketName, key)
                        .withInputSerialization(
                                new InputSerialization().withCsvInputFormat(
                                        new CSVFormat().withHeaderInfo(CSVFormat.Header.Use).withRecordDelimiter("\r\n")))
                        .withOutputSerialization(new OutputSerialization().withCsvOutputFormat(new CSVFormat()));
        // 使用SELECT語句查詢第4列，值大于40的所有記錄。
        selectObjectRequest.setExpression("select * from ossobject where _4 > 40");
        OSSObject ossObject = ossClient.selectObject(selectObjectRequest);

        // 讀取內(nèi)容。
        BufferedReader reader = new BufferedReader(new InputStreamReader(ossObject.getObjectContent()));
        while (true) {
            String line = reader.readLine();
            if (line == null) {
                break;
            }
            System.out.println(line);
        }
        reader.close();

        ossClient.deleteObject(bucketName, key);
    }

    private static void selectJsonSample(String key, OSS ossClient) throws Exception {
        // 填寫上傳的內(nèi)容。
        final String content = "{\n" +
                "\t\"name\": \"Lora Francis\",\n" +
                "\t\"age\": 27,\n" +
                "\t\"company\": \"Staples Inc\"\n" +
                "}\n" +
                "{\n" +
                "\t\"name\": \"Eleanor Little\",\n" +
                "\t\"age\": 43,\n" +
                "\t\"company\": \"Conectiv, Inc\"\n" +
                "}\n" +
                "{\n" +
                "\t\"name\": \"Rosie Hughes\",\n" +
                "\t\"age\": 44,\n" +
                "\t\"company\": \"Western Gas Resources Inc\"\n" +
                "}\n" +
                "{\n" +
                "\t\"name\": \"Lawrence Ross\",\n" +
                "\t\"age\": 24,\n" +
                "\t\"company\": \"MetLife Inc.\"\n" +
                "}";

        ossClient.putObject(bucketName, key, new ByteArrayInputStream(content.getBytes()));

        SelectObjectRequest selectObjectRequest =
                new SelectObjectRequest(bucketName, key)
                        .withInputSerialization(new InputSerialization()
                                .withCompressionType(CompressionType.NONE)
                                .withJsonInputFormat(new JsonFormat().withJsonType(JsonType.LINES)))
                        .withOutputSerialization(new OutputSerialization()
                                .withCrcEnabled(true)
                                .withJsonOutputFormat(new JsonFormat()))
                        .withExpression("select * from ossobject as s where s.age > 40"); // 使用SELECT語句查詢文件中的數(shù)據(jù)。

        OSSObject ossObject = ossClient.selectObject(selectObjectRequest);

        // 讀取內(nèi)容。
        BufferedReader reader = new BufferedReader(new InputStreamReader(ossObject.getObjectContent()));
        while (true) {
            String line = reader.readLine();
            if (line == null) {
                break;
            }
            System.out.println(line);
        }
        reader.close();

        ossClient.deleteObject(bucketName, key);
    }
}

相關(guān)文檔

• 關(guān)于查詢文件的完整示例代碼，請參見GitHub示例。

• 關(guān)于查詢文件的API接口說明，請參見SelectObject。